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Cover of PMC Help

PMC Help

This book contains information on PMC (PubMedCentral), a service of the National Center for Biotechnology Information (NCBI).

PMC is a digital archive of life sciences journal literature that includes the full text of more than three million articles.

PMC also includes final, peer-reviewed author manuscripts by scientists and others who receive research funding from NIH and other funding agencies. For information on submission for NIH-funded manuscripts, please visit the NIH Manuscript Submission System homepage.

PMC provides free access to articles from journals that deposit their content in the archive. Access to the material in PMC is free, but use of the material still is subject to the copyright and/or related license terms of the respective authors or publishers. See the PMC Copyright Notice for more information.

PMC is not a publisher and does not publish journal articles itself. (Find out how journal publishers can participate in PMC).

PMC is managed by the National Center for Biotechnology Information (NCBI) at the U.S. National Library of Medicine (NLM).

Answers to many common questions about PMC are available on the PMC FAQ pages.

This guide is meant to help you use PMC to find and read articles of interest to you.

PMC Quick Start

Using this Quick Start section is the fastest way to begin using PMC.

Browse and download title, ISSN, holding, and embargo information for journals

Visit the PMC Journal List to browse journal titles, ISSNs, holdings, and access and embargo information.

This list can be downloaded in a comma-separated values (CSV) file format by clicking the Download CSV link found on the Journal List page.

Journals added to PMC in the last 60 days can be found by clicking on the New tab.

The Special Collections tab shows a list of publisher programs that have an arrangement with PMC to deposit just selected articles from a set of journals.

How do I search PMC?

From any PMC page, enter the key concept terms for your search into the Search box at the top of the page, and then click Search.

Example
What is the role of mood in sleep disorders? The key concepts terms are “mood” and “sleep disorders”. Enter the following into the Search box, and then click Search
mood sleep disorders

Search by author

In the Search box, enter the author’s full name or their last name followed by initials, without punctuation.

Search by journal name

Enter the journal name or title abbreviation in the Search box, and any additional search terms. It is often helpful to use quotation marks around a journal’s title.

Example
To search for articles about obesity in the journal Preventing Chronic Disease, enter the following in the Search box:
obesity "preventing chronic disease"

Or: click Advanced to use the Advanced Search Builder, and then select Journal from the All Fields menu.

Or: go to the journal list page, and enter the journal title or abbreviation in the Search for journals box.

Search for author manuscripts

To limit your searches to author manuscripts, add the author manuscript filter to your search term(s) using the AND operator, and then click Search.

Example
To search for author manuscripts related to childbirth, enter the following in the Search box:
childbirth AND author manuscript[filter]

You may also enter “author manuscript[filter]” without other search terms to view all author manuscripts in PMC.

If you are a researcher seeking to submit a manuscript, visit the NIH Manuscript Submission homepage.

Can you explain the search results?

PMC search results are displayed in a summary format explained in the illustration below.

Results are initially displayed in order of relevance with 20 results per page. On the search results page you can go directly to the article in 4 different formats (Classic View, PubReader, PDF, and Citation). You can also filter your results according to article type. You can find related data in other NCBI datasets. You can also send your results to a file, email them, or save them using the Clipboard and Collections tools.

Image pmchelp-Image001

Example of Search Results Display

See Customizing Your Search Results Display and Viewing Articles for additional information.

How can I save my search results?

There are several ways to save PMC search results, including saving them to a file, emailing them, using the Clipboard to save results temporarily, and using Collections in My NCBI to save them indefinitely.

For details see Saving and Emailing Results and Searches

I am not finding what I need. How does a PMC search work?

The PMC search program may modify your search terms to enhance your retrieval. Sometimes these changes may not match what you have in mind.

To see how PMC modified your search, consult the Search details box displayed on the results page. Click the “See more…” link for additional information on how the query was translated.

Example
If you search for cystic fibrosis by its abbreviation cf, the cf search retrieves some articles that do not discuss cystic fibrosis. To see why PMC retrieved these articles, review the Search details box to see how PMC translated cf to search for articles about cerebrospinal fluid or cf. See example below.
Image pmchelp-Image002

Search details for search for cf

For additional information, see automatic term mapping.

Why do I get different search results in PubMed and PMC?

Although they are interrelated, PubMed and PMC are two separate and unique resources. PubMed is a database of citations and abstracts for more than 20 million articles.

PMC is an electronic archive of full-text journal articles, offering free access to most of its contents. PMC contains over 3 million articles, most of which have a corresponding citation in PubMed.

For a comprehensive search, it is advisable to search PubMed and PMC separately for the following reasons:

  • PubMed searches only what appears in a PubMed record—citation and abstract. PubMed does not have citations for certain types of PMC material, such as book reviews, that are considered out of scope for PubMed.
  • In addition, some articles published prior to 1966 and added to PMC via the Back Issue Digitization project do not have corresponding citations in PubMed.

Also note that searches in PMC and in PubMed will generate separate search histories. For more information on the connection between PMC and PubMed, visit the PMC FAQs page.

What if I find an error in an article?

Articles in PMC reflect the final published version as provided by the publisher.

If you are the author of an article and find an error, please email the publisher and send a copy (“cc”) of your message to the PMC Help Desk [vog.hin.mln.ibcn@lartnecdembup] .

If you discover other problems with the PMC archive (e.g., an article associated with the incorrect PDF), please send an email to the PMC Help Desk [vog.hin.mln.ibcn@lartnecdembup] with a description of the problem.

Where can I find information on PMC metadata access or high-volume retrieval?

See the OAI-PMH Service page for information and tools for Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH), which discusses access to PMC records, high-volume retrieval, and other related data utilities.

I need further assistance and training.

To contact customer support, email the Help Desk [vog.hin.mln.ibcn@lartnecdembup].

Searching PMC

Searching by author

Enter the author’s full name or last name plus initials, without punctuation, in the Search box and click Search.

Or: click Advanced to use the Advanced Search Builder, and then select Author from the All Fields menu.

To search for articles written by the author on a particular topic, enter the terms and author’s name as in the following example:

Example
To search for articles written by Bonnie W. Ramsey about gene therapy for cystic fibrosis patients, enter the following search terms into the Search box:
cystic fibrosis gene therapy ramsey bw

Full author names may be searched for articles published from 2002 forward if the full author name is available in the article. For example, “Joshua Lederberg” or “Garcia Algar, Oscar”.

If you only know the author’s last name, use the author search field tag [au]. For example, brody[au].

More information about author searching:

  • Click Advanced and use the Search Builder. Select Author in the drop-down box and enter an author’s name.
  • Author names are automatically truncated to account for varying initials and designations such as Jr. To turn off the truncation, use double quotes around the author's name with the author search field tag [au]. For example, "smith j" [au].
  • If only the author's last name is entered, use the author search field [au], to find the name in the author field only. For example, cervenak[au]

Searching by journal title

Enter in the Search box one of the following:

Another way to search by journal is to click the Advanced link under the Search box, select Journal from the All Fields drop-down list, and enter the journal title there.

More information about journal searches:

  • Tag your search term by using the search field “[journal]” to limit your search to only the journal title. For example, “gene therapy[journal]”, “scanning [journal]”.
  • Searching with the full journal title or abbreviation is recommended for complete retrieval of indexed items; older articles may not have an ISSN.
  • If a journal title or abbreviation includes a special character (e.g., parentheses, brackets, &), enter the title or abbreviation without the special characters. For example, to search for the journal abbreviation “j hand surg [am]”, enter “j hand surg am”.
  • Searching for a journal will automatically map to the official journal title and the title associated with an alternative title, if one exists. To turn off this automatic mapping enter the journal in double quotes and tag with [journal]. For example, “"science"[journal]”.

Searching by date

Searching by date or date range in the Search box

From the PMC Home page, enter dates into the Search box using the format YYYY/MM/DD [date field], or enter a date range using a colon (:) between each date followed by a date field.

The recognized date fields are:

[pubdate] - date of publication

[epubdate] – electronic publication date

[pmclivedate] – PMC live date

[edate] – Entrez date

[printpubdate] – print publication date

Searching by date using Limits

  • Click on Limits below the Search box.
    • Under Dates, select either one of the pull-down menus for Published in the Last or Added to PMC in the Last
    • These menus include pre-set options for searching articles that became available in PMC in the past 30, 60, 90, 180 days 1 year, etc.
  • The following date fields are also available from the pop-up menu under Search Field Tags:
    • Electronic Publication Date- the date of electronic publication of the article or issue containing the article.
    • PMC Live Date - the date the article entered PMC.
    • Publication Date – the date of publication of the article or issue containing the article.
    • Entrez date
    • Print publication date

See Search field descriptions and tags for more information about these date fields.

Tip: When you start a new search, turn off the Dates limit by clicking on the Reset button

Limits

The Limits feature allows you to refine your search by dates, article types, embargoed articles, author, journal name, and specific search fields.

1.

Click Limits under the Search box at the top of the home page.

2.

On the Limits page, choose any selections from the options available.

3.

If necessary, make changes to the search terms in the Search box or enter a new search.

4.

Click Search.

Note: When Limits are selected a Limits Activated message will display on the results page. To turn off or modify the limits, click Change or Remove and run a new search.

Limit by Dates

Choose a date from the Published in the Last or Added to PMC in the Last menu selections to limit your search results by date.

Limit by Article Type

The article type restricts your search based on the type of material the article represents, such as:

  • Research & Review
  • Articles Cited by Other PMC Articles
  • Author Manuscripts
  • Open Access Articles
  • Corrected or Retracted Articles
  • Digitized Back Issues
  • Articles with Supplementary Material

You can further limit the search by selecting AND, OR, or NOT in the box to the right.

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Example of Limits Page Display

Limit by Embargoed Articles

To include retrieval of articles under embargo, click the box under Embargoed Articles at the top of the Limits page.

Limit by Author

1.

Click on Add Author.

2.

Enter the author’s name in the format of last name followed by initials. Omit punctuation. You will see that the author Search box includes an autocomplete feature.

3.

Click Search.

4.

Click on Clear to undo this option.

Limit by Journal

1.

Click on Add Journal.

2.

Enter the journal name. You will see that the journal Search box includes an autocomplete feature.

3.

Click on Clear to undo this option.

Search Field Tags

Choose a specific search field tag to limit all terms in the Search box to that field.

Filters

Filters automatically group PMC articles into subsets according to certain criteria. Users can use filters to narrow down their search results conveniently.

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Example of Filters Display in My NCBI

For details on using Filters in My NCBI, see Working with Filters in My NCBI Help.

Filters can be used in two ways:

1.

As a search term in the PMC Search box

A filter name, followed by the tag [sb] or [filter], can be entered into the PMC Search box directly. One can also combine the filter name with other search terms.

Examples

a.

Find all author manuscripts in PMC: Author manuscript [filter] or Author manuscript [sb])

b.

Search for articles on Cancer that are also Open Access: Open Access [filter] AND Cancer

2.

Select in My NCBI

Filters can also be selected in the Search Filters function in My NCBI. After they are created, filters will be listed at the top of the right side of the search results page, under Filter your results. These can be selected divide your search result into subsets according the filter properties. Currently, up to five custom filters can be activated at any one time.

Stopwords

PMC searches use the same stopwords that are used in PubMed. See PubMed Stopwords for more information.

Using the Advanced Search Builder

Click Advanced under the Search box to go to the Advanced Search Builder.

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Example of Advanced Search Builder Display

Searching by a specific field

For example, to search by author, select Author from the All Fields menu, and then enter an author’s name. The name will automatically display in the Search box. To search by journal, select Journal from the All Fields menu, and enter a journal name.

To search for other fields in a article, use the All Fields pull-down menus to select a field before entering a term in the search Builder box.

Note that the default Boolean operator is AND; if desired, choose OR or NOT from the pull-down menu. PMC processes all Boolean operators from left to right.

Note that you may also search a specific field without using the Advanced Search Builder, by adding the search field name to a term, enclosed in square brackets (Search Field Descriptions and Tags). Case and spacing do not matter.

Browsing the index of terms

The Advanced Search Builder Show index list provides an alphabetical display of all terms in each PMC search field. You can browse by all fields or within a specific field such as, for example, “MeSH Subheading”.

1.

Click Advanced and use the Builder to select a search field from the All Fields menu.

2.

Click Show index list.

3.

The index displays an alphabetical list of search terms and the number of results for each term. Click Previous 200 or Next 200 to move within the index.

4.

Scroll until you find a term and then highlight it to add it to the Search box.

You can select multiple items from the index list, and the Builder will automatically join the terms with the OR operator.

Combining searches using History

Searches can be combined or used in subsequent searches using the search number from Advanced search History.

1.

Click Advanced.

2.

In the History list, click Add to move the search to the Builder.

3.

Alternatively, click the search number to display additional options to add the search to the Builder, including Boolean operators OR or NOT. Other menu options include:

  • Delete from history
  • Show search results
  • Show search details
  • Save in My NCBI
4.

Add additional search terms in the Builder.

5.

Click Search.

More information about the History:

  • The history will be lost after 8 hours of inactivity.
  • Click Clear history to delete all searches from history.
  • PMC will move a search statement number to the top of the History if a new search is the same as a previous search.
  • History search numbers may not be continuous because some numbers are assigned to intermediate processes, such as displaying a result in another format.
  • The maximum number of searches available in History is 100. Once the maximum number is reached, PMC will remove the oldest search from history and add the most recent search.
  • A separate history will be retained for each database, although the search numbers will be assigned sequentially for all databases.
  • The history feature uses browser cookies. To use this feature, your web browser must be set to accept cookies.
  • Results in the Clipboard are represented by the search number #0, which may be used in searches. For example, to limit the results you have collected in the clipboard to author manuscripts, use the following search: “#0 AND author manuscript [filter]”. This does not change or replace the Clipboard contents.

Displaying the Search Details

The PMC search program may modify or add additional search terms to your search to optimize retrieval.

See the Search details box on the results page to view your search as it was translated using automatic term mapping and search rules.

More information about Search details:

  • Click on See more… to see the Query Translation used to run the search.
    • To edit the search in the Query Translation box, add or delete terms and then click the Search button just below the box.
    • Click URL to display the current search as a URL to bookmark for future use. Searches created by combining History numbers should not be saved using the URL feature, because the history numbers are not persistent
  • The Result link is the total number of results for the search.
  • Translations details how each term was translated using PMC's search rules and syntax

User query shows the search terms as you entered them in the query box and whether there were any syntax errors in the query.

Searching for a phrase

PMC does not perform adjacency searching. However, many phrases are recognized by the MeSH Translation Table used in PMC's automatic term mapping feature. For example, if you enter “influenza in birds, PMC recognizes this phrase as a MeSH concept. If a phrase is not recognized, you can instruct PMC to bypass automatic term mapping and search for a phrase using the formats outlined below.

Examples

More information about phrase searching:

  • If you use a hyphen or quotes and the phrase is not found, the hyphen or quotes are ignored and the phrase is processed using automatic term mapping. Phrases may appear in a PMC article but not be in the phrases index.
  • When you enter your search terms as a phrase (using quotation marks), PMC will not perform automatic term mapping, which includes expansion of MeSH terms. For example, "health planning" will include results that are indexed to the MeSH term, Health Planning, but will not include the more specific terms, e.g., Health Care Rationing, Health Care Reform, Health Plan Implementation, etc., that are included with the automatic MeSH mapping.

Truncating search terms

To search for all terms that begin with a word, enter the word followed by an asterisk (*). For example,

Example
flavor*
finds terms that begin with the root term flavor, such as flavored, flavorful, flavoring, etc.

More information about truncation:

  • PMC searches for the first 600 variations of a truncated term. If a truncated term (e.g., “tox*”) produces more than 600 variations, PMC displays a warning message to lengthen the root word to search for all endings.
  • Truncation turns off automatic term mapping and the automatic expansion of a MeSH term. For example, “heart attack*” will not map to the MeSH term “Myocardial Infarction” or include any of the more specific terms, e.g., “Myocardial Stunning”;
    “Shock”, or “Cardiogenic”.
  • Truncating a word in a multi-word query may result in an unexpected phrase search. For example, the search fetus infection* maternal will treat fetus infection* as a phrase.
  • Truncation stops at the end of a term, that is, it does not process beyond a space.

Combining search terms with Boolean operators (AND, OR, NOT)

Enter Boolean operators in uppercase characters to combine or exclude search terms:

More information about using Boolean operators:

Boolean operators must be used when combining tagged search terms as follows: search term [tag] BOOLEAN OPERATOR search term [tag]. (See Search field descriptions and tags for more information about search tags.)

In a multi-word search, PMC will use automatic term mapping to identify concepts. For example, for the search air bladder fistula, the PMC program will search "air bladder" as a phrase. If you do not want this automatic phrase search, enter each term separated by the Boolean operator AND, e.g., air AND bladder AND fistula.

Searching in a specific field or index

To search a specific field in an article (e.g., author, title, journal, etc.) and bypass the automatic term mapping, tag the search term by following it with the appropriate search tag.

Searching for author manuscripts

You may also enter author manuscript [filter] without other search terms to view all author manuscripts in PMC.

You may also use Limits to search for author manuscripts.

1.

Click Limits.

2.

Click in the Author Manuscripts box under the Article Type options.

3.

Add any other search terms or choose any other selections on the page in order to limit your search.

4.

Click Search.

Note: If you are a researcher seeking to submit a manuscript, visit the NIH Manuscript Submission homepage.

Customizing Your Search Results Display

PMC search results initially display in a summary format with 20 results per page sorted by relevance.

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Example of Search Results Display

Changing the Default Display Settings

Use Display Settings to:

  • Change the result format
  • Change the number of items per page
  • Change the sort order for your search results
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Changing Default Display Settings

Sorting your search results

The default sort order for search results is based on an algorithm that analyzes the full text of every PMC article that contains any of your search terms. For a given search query, "weight" is calculated for each article depending on how many search terms are found, which fields they are found in, and the size of the article. Although recently-published articles are given more weight, this is not a major sorting factor.

You may change the sort order for search results using the Display Settings pull-down menu to select a different sort by setting:

  • Default Order
  • Publication Date
  • Journal
  • PMC Live Date

Saving and Emailing Results and Searches

PMC offers a wide variety of methods to save search results.

Send to Options

Use the Send to dropdown in order to:

  • Save results to a file
  • Send results by e-mail
  • Save results temporarily in your Clipboard
  • Save results permanently in MyNCBI Collections
Image pmchelp-Image007

Send to Menu Options

Send to File

  • In your search results, use the result check boxes to select results. You may move to other pages to continue your selections. If you do not make any selections, PMC will save the entire retrieval.
  • From the Send to pull-down menu, select File. Then select a format and a sort order, and click Create file.
  • Your Web browser will prompt you to save the PMC search results to a file on your computer.
More information about saving results to a file:
  • Saving a large retrieval may take several minutes.
  • The default for the Send to File feature is to save the entire retrieval unless you select specific results. For example, if you use the Send to File feature on a screen displaying 1-20 items of 2,356, your saved file will contain all 2,356 results.

Send to E-mail

  • In your search results, use the check boxes to select results. To email all results displayed on the page, do not make any selections.
  • From Send to, select E-mail.
  • Choose selections for Format, Sort by, or Number to send.
  • Enter an email address. You may also enter a message that will be included in the e-mail.
  • Click E-mail. The system returns you to your results page and displays a message confirming that the email message was sent.

You may use My NCBI to setup an automatic emailing of search updates.

Your PMC results will be sent from the NCBI automatic mail server, sent by Entrez [vog.hin.mln.ibcn@ydobon] Do not reply to this message. This is not a functioning customer service email address.

You may email up to 200 items at a time to a single email address.

Send to Clipboard

The Clipboard gives you a place to collect selected results from one or several searches. The Clipboard will be lost after 8 hours of inactivity on PMC or on any of the other Entrez databases.

If you want to store results indefinitely, then you should use My NCBI Collections .

To add results to the Clipboard:

  • In your search results, use the check boxes to select results. You may move to other pages to continue your selections. To save all of your results, leave all of the check boxes unchecked.
  • From the Send to pull-down menu, select Clipboard.
  • To view your selections, click the Clipboard items link.

To delete results from the Clipboard:

  • While viewing the contents of the clipboard, check individual items, and then click Remove selected items
  • To delete all items from the Clipboard, do not select any items, click Remove all items.
More information about the Clipboard:
  • The maximum number of items that can be placed in the Clipboard is 500. If you select Clipboard from the Send to menu without selecting results using the check box, PMC will add all (up to 500 results) of your search results to the Clipboard.
  • Adding the same article to the Clipboard multiple times will not result in duplicate entries in the Clipboard.
  • PMC uses cookies to add your selections to the Clipboard. For you to use this feature, your Web browser must be set to accept cookies.
  • Results in the Clipboard are represented by the search number #0, which may be used in Boolean search statements. For example, to limit the results you have collected in the Clipboard to author manuscripts, use the following search: “#0 AND author manuscript [filter]”. This does not affect or replace the Clipboard contents.

Send to Collections

My NCBI saves searches and results and features an option to automatically update and email search results from your saved searches. My NCBI includes additional features for highlighting search terms, storing an email address, filtering search results, and setting LinkOut, document delivery service, and outside tool preferences.

Using My NCBI Collections, you can save multiple searches grouped by any criteria you want to use.

Note: To use My NCBI, your Web browser must be set to accept cookies.

Click the My NCBI Sign In link, located at the top right of the page header, to sign into My NCBI or register for an account.

Saving searches as RSS (Really Simply Syndication) feeds

PMC does not currently support RSS feeds directly through the PMC search page. However, in PubMed you can create an RSS feed by using a search that restricts retrieval to the PMC subset. For detailed information, see the PubMed Central Subset section of PubMed Help: Searching PubMed .

Creating a URL to bookmark your search

You can create a URL with your search terms that can be bookmarked in your Web browser for future use. Documentation is also available for creating a web link to PubMed.

  • Run a search and then click See more under Search Details.
  • Click URL below the Query Translation box.
  • Bookmark the URL using your Web browser function. You can also copy the URL from the Web browser’s URL address box.

More information about creating a bookmark:

  • Searches created using a search statement number in History (for example, “#1 OR #2 AND human[mh]”) should not be saved using the URL feature, because these search statement numbers are lost when the History expires. You may click on the History numbers to save a search in My NCBI using the drop-down menu.
  • After saving the bookmark, you may want to use your Web browser's edit functions to rename the bookmark.

Viewing Articles

PMC offers multiple ways to view an article or the citation data associated with it, including Classic View, PubReader, ePub, PDF, and Citation.

Classic View

In addition to providing text, tables and figures, the Classic View of an article in PMC offers:

  • Easy-to-spot location for the PMCID
  • Navigation within the article using the Go to link
  • Links to other publications by the article’s authors
  • Links to related articles in PubMed, PMC, and other Entrez databases
Image pmchelp-Image008

Example of Classic View front matter display

Using navigational tools and links to PubMed/Entrez

Click on an author’s name in the front-matter section to see PubMed records for other publications by the article authors.

Use the Related Citations in Pubmed list in the sidebar to view related articles in PubMed.

Also in the sidebar is a Links section, which gives a list of links to other resources in NCBI related to this article, including the PubMed record, and, as applicable, Gene, Protein, Taxonomy and other Entrez databases.

When applicable, the front matter of an article may also contain links to related articles such as:

  • Corrections
  • Retractions
  • Comments
  • Cited by

For editorial or subscription information about a journal, click on the journal banner at the top of the page to visit the journal or publisher website.

PubReader

PubReader is an alternative web presentation to the Classic View that offers another, more reader-friendly way to look at articles in the PMC archive. Designed particularly for enhancing readability on tablet and other small screen devices, PubReader can also be used on desktops and laptops and from multiple web browsers. The view is available for any article that is available in full-text in PMC. You can get to the PubReader view from:

  • search results pages;
  • an issue Table of Contents; or
  • the Formats links in the top right corner of an article page in PMC.
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Example of PubReader View

Learn more about PubReader

Summary/Page Browse display

Many older articles in PMC are viewable in a Summary/Page Browse format (for example, PMC2483210). The full text of these articles is still available in PDF format (as a scanned copy of the original print version). An increasing number of Summary/Page Browse articles include a Selected References section offering links to citation records in PubMed or to other PMC articles.

Citation Exporter View

The Citation Exporter view makes it easy to retrieve either styled citations that you can copy/paste into your manuscripts or download into a format compatible with your bibliographic reference manager software.

When viewing a PMC search results page, each result summary includes a Citation link. When, clicked, this opens a pop-up window that you can use to copy and paste citations formatted in one of three popular styles: AMA (American Medical Association), MLA (Modern Language Association), or APA (American Psychological Association). In addition, the box has links at the bottom that can be used to download the citation information in one of three machine-readable formats, which most bibliographic reference management software can import.

Image pmchelp-Image010

Search Result Showing Citation Link

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Citation Exporter Pop-Up Window

The same citation box can also be invoked from an individual article, either in Classic View (with the Citation link among the list of formats) or the PubReader view, by clicking on the citation information just below the article title in the banner.

These human-readable styled citations and machine-readable formats will be available through a public API. For more information on this and other utilities please subscribe to the pmc-utils-announce mailing list.

Search field descriptions and tags

Search field descriptions and their corresponding tags are listed in the table below. Please note, however, that the following search tags apply only to articles that have been indexed by PubMed/MEDLINE: MeSH Major Topic [MAJR], MeSH Subheadings [SH], MeSH Terms [MH], Grant Number [GR], EC/RN Number [RN], and Supplementary Concept [NM]. Use of these tags will restrict the retrieval of search results to the MEDLINE-indexed subset of PMC.

Abstract [AB]

Includes all words and numbers in the abstract of an article. English language abstracts are taken directly from the published article. If an article does not have a published abstract, PMC does not create one.

Accession [ACCN]

Includes accession numbers from the GenBank sequence database that are cited in PMC articles.

Acknowledgements [ACK]

Includes all words in the acknowledgement section of an article (e.g., “National Institutes of Health[ack]”).

Affiliation [AD]

Includes the institutional affiliation and address (including email address, when available) of the authors of the article as it appears in the journal. This field can be used to search for work done at specific institutions (e.g., "mayo[ad] AND clinic[ad]").

All Fields [ALL]

Includes all searchable PMC fields. However, only terms where there is no match found in one of the Translation tables or Indexes via the automatic term mapping process will be searched in All Fields.

Author [AU]

To search for an author, enter the last name followed by a space and up to the first two initials followed by a space and, if applicable, a suffix abbreviation. Do not include a period or comma after the last name (e.g., "fauci as or o'brien jc jr"). Initials and suffixes may be omitted when searching.

PMC automatically truncates on an author's name to account for varying initials, e.g., o'brien j [au] will retrieve o'brien ja, o'brien jb, o'brien jc jr, as well as o'brien j. To turn off this automatic truncation, enclose the author's name in double quotes and qualify with [au] in brackets, e.g., "o'brien j"[au] to retrieve just o'brien j.

See Full Author Name [FAU] below for more information on author searching.

Article Body - All Words [ARTICLE]

Includes all words and numbers in the body of an article except for the Abstract and References.

Article Body - Key Terms [KWD]

Includes all key terms in the body of an article except for the Abstract and References.

Digital Object Identifier [DOI]

A unique string that identifies a piece of intellectual property in an online environment. Many publishers assign DOI to their online full text articles.

EC/RN Number [RN]

EC/RN numbers are assigned by:

  • The Food and Drug Administration (FDA) Substance Registration System for Unique Ingredient Identifiers (UNIIs), e.g., Y92OUS2H9B
  • The Enzyme Commission (EC) to designate a particular enzyme, e.g., EC 1.1.1.57
  • The Chemical Abstracts Service (CAS) for Registry Numbers, e.g., 2751-14-6

The EC/RN number search field includes both the Registry Number and the Related Registry Number (available in the NLM MeSH Browser).

Electronic Publication Date [EPUBDAT]

The date of the electronic publication. Dates or date ranges must be entered using the format YYYY/MM/DD [epubdat] (e.g., 1998/04/06 [epubdat]) . The month and day are optional (e.g., 1998 [epubdat] or 1998/03 [epubdat]). To enter a date range, insert a colon (:) between the dates (e.g., 1996:1997 [epubdat] or 1998/01:1998/04 [epubdat]).

Entrez Date [EDAT]

The date the article was added to the PMC database. Search results are displayed in Entrez Date order, i.e., last in, first out.

Figure/Table Caption [CAPT]

Includes all words and numbers in the figure and table captions of an article.

Filter [FILTER]

Technical tags used by PMC to qualify results. These include:

Full Author Name [FAU]

The full author names from all articles for which full names are provided to PMC from the publisher. Full author searching can be entered in natural or inverted order, e.g., “julia s wong” or “wong julia s”. See Author [AU] for more information on author searching.

Grant Number [GR]

The grant number search field includes research grant numbers, contract numbers, or both that designate financial support by agencies of the US PHS (Public Health Service), and other national or international funding sources. The four parts of the grant data are:

1.

number, e.g., LM05545

2.

PHS 2-character grant abbreviation, e.g., LM

3.

institute acronym, e.g., NLM NIH HHS

4.

country, e.g., United States

Each individual grant part can be searched using [gr], e.g., NIH[gr]

More information about NIH grant numbers and tips for searching:

NIH grant numbers, e.g., 5R01CA101211-03, typically have three main parts:

1.

A prefix that indicates the type of grant, e.g., 5R01.

2.

An 8-character serial number consisting of a 2-letter NIH institute/center code and a 6-digit number, e.g., CA101211.

3.

A suffix that includes additional data such as grant year.

To search for an individual NIH grant number, use the 8-character serial number and the [gr] tag (e.g., ca101211[gr]).

Note: For a broader search, use the 2-letter grant code assigned to an agency and the [gr] tag (e.g., ca[gr]). For the broadest search, use the agency abbreviation and the [gr] tag (e.g., nci[gr]). See Grant codes and agency abbreviations used in grant numbers for help determining the agency abbreviation using the grant code.

See also Funding Support and Acknowledgements for additional information.

Issue [IP]

The number of the journal issue in which the article is published.

Journal Title [TA]

The journal title abbreviation, full journal title, or ISSN number (e.g., J Biol Chem, Journal of Biological Chemistry, 0021-9258). If a journal title contains parentheses or brackets, enter the name without the parentheses or brackets, e.g., Proc (Bayl Univ Med Cent) as “Proc Bayl Univ Med Cent”.

The PMC Journal List is available to browse journal titles, holdings and embargo information. Or use the Journals Database look up the full name, abbreviation, and ISSN number of a journal.

MeSH Major Topic [MAJR]

A MeSH term that is one of the main topics discussed in the article. See MeSH Terms below.

MeSH Subheadings [SH]

MeSH Subheadings are used with MeSH terms to help describe more completely a particular aspect of a subject. For example, the drug therapy of asthma is displayed as asthma/drug therapy. See MeSH/Subheading Combinations.

The MeSH Subheading field allows users to "free float" Subheadings, e.g., "hypertension [mh] AND toxicity[sh]".

MeSH Subheadings automatically include the more specific Subheading terms under the term in a search. To turn off this automatic feature, use the search syntax [sh:noexp], e.g., "therapy [sh:noexp]".

In addition, you can enter the MEDLINE two-letter MeSH Subheading abbreviations rather than spelling out the Subheading (e.g., dh[sh] = diet therapy [sh]). See PubMed Help: MeSH Subheadings for a full list of abbreviations.

MeSH Terms [MH]

NLM's Medical Subject Headings controlled vocabulary of biomedical terms that is used to describe the subject of each journal article in MEDLINE. MeSH contains more than 23,000 terms and is updated annually to reflect changes in medicine and medical terminology. MeSH terms are arranged hierarchically by subject categories with more specific terms arranged beneath broader terms. Entrez allows you to view this hierarchy and select terms for searching in the MeSH database.

Skilled subject analysts examine journal articles and assign to each the most specific MeSH terms applicable, typically 10 to 12. Applying the MeSH vocabulary ensures that articles are uniformly indexed by subject, whatever the author's words.

Notes on MeSH Terms and Major MeSH Topic search fields:

To search the term only as a MeSH term, it must be tagged using the search field, e.g., [mh] for MeSH Terms or [majr] for MeSH Major Topic. A tagged term is checked against the PMC MeSH translation table and mapped to the appropriate MeSH term. Some concepts may map to two or more MeSH terms. To turn off this mapping, enclose the MeSH term in double quotes and tag with [mh], e.g., "cold"[mh].

MeSH terms are arranged hierarchically by subject categories with more specific terms arranged beneath broader terms. MeSH terms in PMC automatically include the more specific MeSH terms in a search. For more detailed information about MeSH vocabulary including the hierarchical structure, please see the MeSH home page.

MeSH/Subheading Combinations:

To directly attach MeSH subheadings, use the format MeSH Term/Subheading, e.g., “neoplasms/diet therapy”. You may also use the MEDLINE two-letter MeSH subheading abbreviations, e.g., neoplasms/dh. The [mh] tag is not required, however [majr] may be used, e.g., “plants/genetics[majr]”. Only one subheading may be directly attached to a MeSH term.

For a MeSH/Subheading combination, PMC always includes the more specific terms arranged beneath broader terms for the MeSH term and also includes the more specific terms arranged beneath broader subheadings. The broader subheading, or one of its subheadings, will be directly attached to the MeSH term or one of its subheadings. For example, “hypertension/therapy” also retrieves “hypertension/diet therapy”; “hypertension/drug therapy”; “hypertension, malignant/therapy”; “hypertension, malignant/drug therapy”, and so on, as well as “hypertension/therapy”.

To turn off the automatic inclusion of the more specific terms, use the syntax [field:noexp], e.g., hypertension[mh:noexp], or hypertension[majr:noexp], or hypertension/therapy[mh:noexp]. The latter example turns off the more specific terms in both parts, searching for only the one Subheading therapy attached directly to only the one MeSH term hypertension.

MeSH terms can be selected for searching in the drop-down menu in the Advanced Search Builder.

Methods - Key Terms [METH]

Key terms from the methods section of the article abstract.

Organism [ORGN]

Contains the scientific and common names for the organisms in the NCBI taxonomy database that are found in PMC articles. The NCBI taxonomy database only includes species that are represented in the public sequence databases, so many of the organisms mentioned in PMC articles will not be found in this index. To cut down on false hits, matches to scientific names are required to add PMC articles to this index - common names in this field will only retrieve articles that mention the corresponding scientific name.

By default, the PMC organism search is “unexpanded” and does not include more specific terms. The query mammalia[orgn] will only retrieve articles that explicitly mention mammalia. The query mammalia[orgn:exp] will retrieve articles that mention any of the species of mammals.

Organism Unsynonymized [ORGN_NOSYN]

Organism names that are identified as synonyms in the NCBI taxonomy database will retrieve the same set of articles in the PMC Organism index (e.g., "Danio rerio[orgn]" = "Brachydanio rerio[orgn]"). The Organism unsynonymized index will only retrieve articles that use the exact name as given.

Pagination [PG]

Enter only the first page number on which the article appears. The result will display the full pagination of the article, but this field is searchable using only the first page number.

PMC Live Date [PMCDAT]

Date the article was first available in PMC. Dates or date ranges must be entered using the format YYYY/MM/DD, e.g. "1998/04/06 [pmcdat]". The month and day are optional (e.g., "1998 [pmcdat]" or "1998/03 [pmcdat]"). To enter a date range, insert a colon (:) between each date (e.g., "1996:1997[pmcdat]" or "1998/01:1998/04[pmcdat]").

Publication Date [PDAT]

The date that the article was published. Dates or date ranges must be searched using the format YYYY/MM/DD, e.g. "1998/03/06[pdat]". The month and day are optional (e.g., "1998[pdat]" or "1998/03 [pdat]").

To enter a date range, insert a colon (:) between each date (e.g., "1996:1998[pdat]" or "1998/01:1998/04[pdat]").

Use the following format to search X days, months, or years immediately preceding today’s date where X = numeric value:

  • “last X days”[pdat]
  • “last X months”[pdat]
  • “last X year”[pdat]

Note: Journals vary in the way the publication date appears on an issue. Some journals include just the year, whereas others include the year plus month or year plus month plus day. Some journals use the year and season (e.g., Winter 1997). The publication date in the citation is recorded as it appears in the journal. It is recommended that you search only by year (e.g., “1996[pdat]” or “1995:1997[pdat]”). (For articles published electronically and in print on different dates, both dates may be included on the citation prefaced with an “Epub” or “Print” label.)

PubMed ID [PMID]

Unique identifier for the PubMed record for a PMC article.

Reference [REFR]

Includes words and numbers in the titles in an article references section.

Reference Author [REFA]

Includes authors cited in an article references section.

PMC references do not list the full author name. The format to search for a reference author is the same as article Author searching.

Section title [SECT]

Includes words and numbers in an article section title.

Supplementary Concept [NM]

Includes chemical, protocol or disease terms. Synonyms to the supplementary concepts will automatically map when tagged with [nm]. This field was implemented in mid-1980; however, many chemical names are searchable as MeSH terms before that date.

Text Words [TW]

Includes all words and numbers in the title, abstract and article body, as well as in table and figure captions and in the article reference section.

Title [TI]

Words and numbers included in the title of an article.

Volume [VI]

The number of the journal volume in which an article is published.

Appendix

Automatic term mapping

Untagged terms that are entered in the Search box are matched (in this order) against a MeSH (Medical Subject Headings) translation table, a Journals translation table, the Full Author translation table, and an Author index.

When a match is found for a term or phrase in a translation table the mapping process is complete and does not continue to the next translation table.

PMC MeSH translation table

The PMC MeSH translation table contains:

  • MeSH terms
  • The See-Reference mappings (also known as entry terms) for MeSH terms
  • MeSH Subheadings
  • Terms derived from the Unified Medical Language System (UMLS) that have equivalent synonyms or lexical variants in English
  • Supplementary concept (substance) names and their synonyms

If a match is found in this translation table, the term will be searched as MeSH (which includes the MeSH term and any specific terms indented under that term in the MeSH hierarchy), and in all fields.

For example, if you enter “vitamin c” in the query box, PMC will translate this search to: "ascorbic acid"[MeSH Terms] OR vitamin c[Text Word]

More information about automatic term mapping:

See the Search details to verify how your terms are translated. If you want to report a translation that does not seem accurate for your search topic, please email the information to the PMC Help Desk [vog.hin.mln.ibcn@lartnecdembup]

Journals translation table

The Journals translation table contains:

  • full journal title
  • title abbreviation
  • ISSN number

These will automatically map to the journal abbreviation that is used to search journals in PMC.

For example, if you enter the journal title annals of botany in the PMC Search box and check the Search details you will see it translate to: “"Ann Bot"[Journal] OR "annals of botany"[All Fields]”

Full Author translation table

The Full Author translation table contains full author names from all articles for which full names are provided to PMC from the publisher.

More information about full author searching:
  • A comma following the last name for searching is optional. For some names, however, it is necessary to distinguish which name is the last name by using the comma following the last name, e.g., “james, ryan”.
  • Omit periods after initials and put all suffixes at the end, e.g., vollmer charles jr
  • Initials and suffixes are not required. If you include a middle initial or suffix, you will only retrieve results for articles that were published using the middle initial or suffix.
  • To distinguish author initials that may match a full author name use the [fau] search tag, e.g., “peterson do[fau]”.

Author index

If the term is not found in the above tables, except for Full Author, and is not a single term, PMC checks the author index for a match. When combining multiple authors, to avoid a match with full author names, include initials or use the [au] search tag, e.g., ryan[au] james[au].

If no match is found?

PMC breaks apart the phrase and repeats the above automatic term mapping process until a match is found. PMC ignores stopwords in searches. See PubMed Help: Stopwords for a full list of stopwords.

If there is no match, the individual terms will be combined (with AND) together and searched in all fields.

Cookies

A "cookie" is information stored by a web server on your computer. See the NLM Privacy Policy for additional information.

In the case of PMC, cookies are used to store information about your interactions that may be needed later to perform a particular function.

To use interactive features, you need to enable cookies on your computer. Please consult your browser's Help for information on enabling cookies.

If you have problems using cookie-dependent features of PMC even after enabling cookies, possible reasons may include:

  • Cookies are blocked by your provider or institution. Check with your Internet provider and/or the system administrator at your institution to see if cookies can be accepted.
  • Your computer's date and time settings are incorrect. Check your computer's time settings to ensure that they are correct.

Character Conversions

When running a search that includes special characters (e.g., pound sign, dollar sign), PMC uses certain characters to have specific meaning, whereas others are converted to spaces. (See PubMed Character Conversions for more information.) However, in the abstracts and full text of PMC articles, all characters are represented as accurately as possible

PMC URL Format

PMC’s URL format is consistent with other NCBI sites.

In general, the first URL path segment will identify the resource type. Subsequent path segments identify the specific resource, and sometimes sub-resources. Query string parameters are used to filter or refine results, and to specify the response format.

In many cases, there are multiple URLs that will access the same resource. In these cases, we identify one as the canonical URL (shown bold in the table below), and use of the ancillary URLs will cause a redirect to the canonical one. URLs are relative to http://www.ncbi.nlm.nih.gov/pmc.

Resource typeURL(s)
List of journals/journals/
List of journals matching search/journals/?term=respiratory
A specific journal archive/journals/2/
/journals/domain/pnas/
/journals/jrid/32141/
/journals/issn/1091-6490/
/ivip/1091-6490/
Latest issue/journals/2/latest/
Issue/issues/157490/
/ivip/0021-9738/117/8/
Article full text/articles/PMC2814059/
/articles/2814059.3/
/articles/pmid/20126278/
/articles/doi/10.1371/currents.RRN1147/
/articles/ivip/0021-9738/117/9/2380/
Article PDF/articles/PMC2150930/pdf/f-62-00001.pdf
Figure/articles/PMC2278217/figure/F5/
Table/articles/PMC2278217/table/T1/
Article manuscript/articles/mid/NIHMS20955/
Cited-by list/articles/PMC369838/citedby/
Bookshelf ID: NBK3825
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