Open Access Subset

The PMC Open Access Subset some or all openaccess content is a part of the total collection of articles in PMC. Articles in the PMC Open Access Subset are still protected by copyright, but are made available under a Creative Commons or similar license that generally allows more liberal redistribution and reuse than a traditional copyrighted work. Note, however, that the license terms are not identical for all of the articles in this subset. Please refer to the license statement in each article for specific terms of use. We also provide a search-by-license feature, described below, which enables finding articles with specific reuse rights.

Please note the following:

  • The majority of the articles in PMC are subject to traditional copyright restrictions and are not part of this subset. Read the PMC Copyright Notice for more information.
  • The PMC OAI service and the PMC FTP service are the only services that may be used for automated downloading of articles from this open access subset.
  • Systematic retrieval (bulk downloading) of articles through any other automated process is prohibited, even if you are only retrieving articles from this subset.
  • Some journals use the label "open access" for an article that is available free at time of publication, but is still subject to traditional copyright restrictions. Such articles are not part of this subset.

Many of the journals that deposit their complete contents into PMC include some or all their articles in the Open Access subset. In PMC’s Journal List, those that deposit all of their articles into the Open Access subset are marked with the symbol all openaccess content. Those full participation journals that deposit only some of their articles in the Open Access subset are marked with a some openaccess content symbol. In addition to the full participation journals, PMC's archive includes those that are part of PMC's selective deposit program, under which publishers deposit selected articles from a range of their journals. These selective deposit articles almost always are included in the Open Access subset. A complete list of the selective deposit journals can be found under the Special Collections tab of the PMC Journal List.

To preview the articles or get a current count of articles in the OA subset, do a search for open access[filter] in PMC. To programmatically find articles by ID or by date, use the API provided by our OA web service. Please note, however, that you may only use the OAI service or FTP service mentioned below for automated (or bulk) retrieval of articles from the OA subset.

Searching for Articles by License

Searching PMC is described in the PMC Help Manual. Any of the search filters described below can be combined with other search terms, either with the Advanced Search Builder or by typing search expressions directly, to help you find exactly the articles you are interested in.

To restrict your search results to only those articles that are in the OA subset, do a search for "open access[filter]" in PMC.

Additional filters are available for searching articles with certain, specific types of Creative Commons (CC) licenses. For descriptions of these licenses, please see the Creative Commons site, About the Licenses.

The filters are described in the following table.

License type Filter in PMC Filter in PubMed
Any CC license cc license pmc cc license
CC BY (Attribution) cc by license pmc cc by license
CC BY-ND (Attribution, no derivatives) cc by-nd license pmc cc by-nd license
CC BY-NC (Attribution, noncommercial) cc by-nc license pmc cc by-nc license
CC BY-NC-ND (Attribution, noncommercial, no derivatives) cc by-nc-nd license pmc cc by-nc-nd license
CC BY-NC-SA (Attribution, noncommercial, share-alike) cc by-nc-sa license pmc cc by-nc-sa license
CC BY-SA (Attribution, share-alike) cc by-sa license pmc cc by-sa license

If you have a MyNCBI account, you can set it up to display any or all of these filters on every PMC search results page, as described in the MyNCBI Help Manual.

These filters are based on license information which is provided to PMC by publishers and other content providers, as encoded by the machine-readable identifiers in the source XML of each journal article. Please note that, in some cases, there are discrepancies between these machine-readable identifiers and the actual text of the license statements. As of February, 2013, PMC has instituted new rules to help ensure consistency of the tagging of the licenses, which apply to all newly received content. Note, however, that PMC will not retroactively fix any previously submitted content with incorrect license tagging.

Retrieval of Articles

To do automated (or bulk) retrieval of articles from the OA subset, use one of the following services.

Use the OAI service to download XML for the full text of articles in this open access subset.

Use the FTP service to download a complete set of files — XML, images, PDF, and supplementary data files, if any — for articles in this subset. For users who are interested in just the XML, the FTP service also provides archive files containing the XML for all the articles in the open access subset.

Additionally, the OA web service provides an API to allow tools to find articles by ID, or those that have been updated recently.

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Last updated: Mon, 13 Jan 2014