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LinkOut provides access to a wide range of relevant online resources, directly from Entrez databases. This section provides information on using LinkOut to locate and access these resources.
You can see links that have been assigned to an Entrez record in the LinkOut display. In PubMed, you can also view links as icons.
Note: When you click on LinkOut icons or links in the LinkOut display, you leave PubMed and are directed to the resource at an external site. Please review all use and copyright information on the resource provider’s site before using or distributing their material.
To view the LinkOut display for a single Entrez record, click on the Links menu, located on the right side of the screen (B in the image below). If available for the citation, LinkOut is included in the Links menu (C). To view the LinkOut display for all records retrieved by a search, select LinkOut from the Display drop-down menu (A).
Available resources will vary depending on which links have been assigned to the specific Entrez record.
LinkOut information may also appear within Entrez records. For example, you can see the External Information Resources section in Entrez Taxonomy records. The appearance of links within Entrez records varies according to the database that you are using.
In PubMed the LinkOut full text and supplemental information links are available in the Abstract format only when a single citation is selected. The links are found by expanding the plus sign (+) next to "LinkOut - more resources." When displaying multiple records in the Abstract format the LinkOut information is not available.
The "LinkOut Holdings" link is only included with the LinkOut information if users access PubMed through a URL that includes one of the following parameters: holding=, myncbishare=, or otool=. The "LinkOut Holdings" link leads to an alphabetical list of libraries that offer electronic full text access or hold the print version of the article in their collections.
For additional information about the types of links found in Entrez, please see Database Neighbors and Interlinking in Entrez Help.
You can view links as icons in PubMed’s Abstract display. The icons are supplied by LinkOut providers - external organizations that have submitted linking information for their web-accessible resources. The list of LinkOut providers includes libraries, publishers, research institutes, and a variety of commercial and non-profit organizations.
Three types of LinkOut icons appear in PubMed by default - icons that link to PubMed Central, icons that link to free full text, and icons that link to full text at the publisher’s site. Full text at the publisher’s site may require a subscription to view.
The image below shows a single PubMed citation with two default icons, an icon that links to full text at the publisher’s site and an icon that links to free full text at PubMed Central.
You can customize the icon display by activating icons for a specific provider.
You can customize the icon display to show links provided by your institution or links to a particular online resource, such as a MedlinePlus. Your library may have already set up a customized icon display for your institution. Check your library homepage for a special link to PubMed.
Note: When you click on LinkOut icons or links in the LinkOut-more resources, you leave PubMed and are directed to the resource at an external site. Please review all use and copyright information on the resource provider’s site before using or distributing their material.
In the image below, five icons are displayed. The BMJ.com and PubMed Central icons appear in PubMed automatically (more about default icons ).The icons for MedlinePlus, the National Library of Medicine and the NIH library, have been activated by the user. When users click an icon, they leave PubMed and are directed to the resource at the provider’s site.
To activate provider icons, you can either select the provider(s) as filters in My NCBI or enter PubMed through a special URL that will activate the provider icons. To learn how to select providers as filters, see Setting LinkOut Preferences in My NCBI Help or view the LinkOut Filters Quick Tour (animated tutorial, running time approx. 6 minutes; Macromedia Flash™ Player required to view.)
Instructions for activating icons using a special URL follow. You can also view Displaying LinkOut Icons Using a Special URL (animated tutorial; Macromedia Flash™ Player required to view.)
To activate icons using a special URL, enter PubMed through the following URL:
http://www.ncbi.nlm.nih.gov/pubmed?holding=NameAbbr
Replace NameAbbr with a provider’s LinkOut User Name.
| Example |
|---|
| To display LinkOut icons for MedlinePlus, with user name medplus, enter PubMed through the following URL: |
| http://www.ncbi.nlm.nih.gov/pubmed?holding=medplus |
The holding= parameter can also be appended to www.pubmed.gov.
To activate icons for multiple providers using a special URL, create a URL, as described above. Add additional User Names to the URL, separating the User Names with commas. You can activate icons for as many providers as you like.
| Example |
|---|
| To display LinkOut icons for the LinkOut Demonstration Library, User Name nlmlib, and MedlinePlus, User Name medplus, enter PubMed through the following URL: |
| http://www.ncbi.nlm.nih.gov/pubmed?holding=nlmlib,medplus |
The holding= parameter can also be appended to www.pubmed.gov.
All providers must be LinkOut participants. You can find providers’ LinkOut User Names (NameAbbr) in the following lists of LinkOut Providers:
LinkOut Resource Providers (excluding full-text providers)
When you enter PubMed through a special URL, a cookie is placed on your workstation that instructs PubMed to display the icons until 8 hours of inactivity have passed (more about cookies).
There are two ways locate Entrez records with links to a specific resource. My NCBI can display the records as a filter in the search result, or you can limit an individual search to records with links to a specific resource.
My NCBI includes a filters feature that groups search results by areas of interest. For example, PubMed citations that are available at your library, or Nucleotide records with links to a particular molecular biology database can be grouped, as a filter in the results of Entrez searches. Filters are available in a number of Entrez databases, including PubMed, Nucleotide, and Taxonomy. A complete list of databases in which filters can be displayed is available in My NCBI.
To display Entrez records as a filter in the search result:
Sign in to My NCBI
Click Search Filters in the MyNCBI Table of Contents
Select the desired database from the list of Entrez databases
Browse Filters or Search for Filters for LinkOut providers by name
After finding the provider that you would like to display as a filter, check the box for Add as a Filter. To display the provider’s icon in PubMed, click Add as a link icon. You can select up to five filters for each database in My NCBI
The providers that you selected will be displayed as filters under “Filter your results” as long as you are signed in to My NCBI.
In the following example, the user has selected the National Library of Medicine (nlmlib) as a filter. Notice that the NLM icon is displayed below the abstract and citations available from the NLM library are grouped as a filter.
To learn more about using filters in My NCBI, see the LinkOut Filters Quick Tour (animated tutorial, running time approx. 6 minutes; Macromedia Flash™ Player required to view) or My NCBI Help.
To limit a single search to records with links to a specific resource, enter the following in the search box:
loprovNameAbbr [filter]
Replace NameAbbr with the library’s LinkOut User Name.
This filter will be effective for that search only.
Using the NLM library as an example:
Search PubMed for loprovnlmlib [filter].
This limits the search to holdings included in the NLM library holdings.
This filter can be used as part of any PubMed search.
| Example: Limit a search for “AIDS” to articles available from the NLM Library |
|---|
| aids AND loprovnlmlib [filter] |
NOTE: Limiting your search in this way will not cause the provider’s icon to display. Provider icons must be activated in My NCBI or with a special URL.
PubMed does not include copies of journal articles. Here are some tips for obtaining articles:
Free copies of some articles may be obtained through links in PubMed. To locate these articles more easily, try limiting your search to citations with free full text available.
Note: When you click on LinkOut icons or links in the LinkOut display, you leave PubMed and are directed to the full text at an external site. Please review all use and copyright information on the full-text provider’s site before using or distributing their material.
If you are a health professional or are affiliated with a hospital, university, or other institution, you should check your local medical library, or consider registering for Loansome Doc, an NLM-sponsored document delivery service.
You may also want to check with your local library, or go directly to the publisher.
If you belong to a library, talk to a librarian at your institution about using LinkOut. Your local librarian will be best equipped to help you discover LinkOut resources available through your institution.
Please send comments and suggestions about LinkOut and report broken links to linkout@ncbi.nlm.nih.gov.
