PMC FAQs

Below are answers to many of the questions PMC frequently receives. There are separate pages for publisher and author FAQs. If you cannot find an answer to your question, please contact the PMC Help Desk at pubmedcentral@ncbi.nlm.nih.gov.

General Interest FAQs

What is PubMed Central (PMC)?

PubMed Central (PMC) is the U.S. National Institutes of Health (NIH) digital archive of biomedical and life sciences journal literature. Since its inception in 2000, PMC has grown from comprising only two journals, PNAS: Proceedings of the National Academy of Sciences and Molecular Biology of the Cell, to an archive of several million articles from several thousands of journals.

Participation by publishers in PMC is voluntary, although participating journals must meet certain scientific and technical standards. PMC, itself, is not a publisher.

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.

What is the difference between PMC and PubMed?

PubMed is a database of citations and abstracts for more than 26 million articles. PMC is an electronic archive of full-text journal articles, offering free access to its contents. PMC contains more than 3 million articles, most of which have a corresponding entry in PubMed.

PubMed does not have citations for certain types of PMC material, such as book reviews, that are considered out of scope for PubMed. These items constitute a small portion of the total PMC collection and there are no current plans to include them in PubMed. For more details, please see the Fact Sheet titled “MEDLINE, PubMed, and PMC (PubMed Central): How are they different?”

Who operates PMC?

PMC was developed and is operated by the National Center for Biotechnology Information (NCBI), a division of the National Library of Medicine (NLM) at the U.S. National Institutes of Health (NIH).

Does any independent group oversee the operation of PMC?

The PMC National Advisory Committee, established in 1999, provides independent advice on the content and operation of PMC. The Committee is responsible for establishing criteria for groups submitting material to the system, and ensuring that PubMed Central remains responsive to the needs of researchers, publishers, librarians, and the general public. Members of the Committee are appointed by the Director of the National Institutes of Health from the biomedical and information communities as well as the general public.

What journals are currently available in PMC?

See the PMC Journal List for a list of currently available journals.

How current is the material in PMC?

The currency and age of material in PMC varies by journal. Many journals make their content available in PMC as soon as it is published. Others may embargo (delay release of) content in PMC for anywhere from a few months to more than a year after publication. Most journals provide free access to full text in PMC within a year of publication.

How far back in time does the archive reach?

NLM has digitized the earlier print issues of many of the PMC journals in order to provide online access to the complete run of issues of these journals. PMC has material dating back to the 1800s for some journals.

Does PMC contain the complete contents of all the journals that are in its archive?

No. Journals that deposit their articles in PMC fall into one of three categories:

Full Participation: These are journals for which a commitment is made to deposit the complete contents of each issue or volume, starting with a particular volume/issue or publication date. For many full participation journals, PMC has a complete archive going back to the journals first volume and issue.
NIH Portfolio: These are journals for which a commitment is made to deposit all NIH-funded articles as defined by the NIH Public Access Policy, and starting with a particular volume/issue or publication date. The publisher may choose to also deposit other, non-NIH-funded articles for the journal under this agreement.
Selective Deposit: These are journals for which the publisher deposits a selected set of articles to PMC; this category is generally used by publishers for journals which offer a hybrid publishing model, i.e., a traditional subscription-based journal in which selected articles are published as "open access." Collections of these selective deposit journals, often grouped by publisher, are referred to in PMC as Special Collections. A list of Special Collections and the journals in each collection can be found on the PMC Journal List page under the Special Collections tab.

In all three categories, PMC contains a journal's final published version of the respective articles. The PMC Journal List includes information about what content is available from each journal, as well as links to that content. The home page of PMC shows the numbers of full participation, NIH portfolio and selective deposit journals depositing in PMC.

In addition to the articles from these journals, PMC contains author manuscripts of selected articles from several thousand other journals. See Who may contribute to PubMed Central for more information. These manuscripts are accessible via a PMC search or a link from the corresponding PubMed abstract.

How can I find out when PMC adds a new journal to its archive?

On the PMC Journal List page, there is a tab labeled “New”, where you can see the list of all the Full Participation and NIH Portfolio journals added in the last 60 days.

How can I find out about changes to PMC?

News and announcements about PMC can be obtained via the methods below:

PMC-Announce email list: Add your name to the list to be notified by email whenever there important announcements about PMC.

New in PMC Page/RSS feed: Check the New in PMC/RSS feed for recent PMC developments or features.

How is PMC related to PMC International or portable PMC?

PMC International (PMCI) is a collaborative effort between NLM, the publishers whose journal content makes up the PMC archive, and organizations in other countries that share NLM's interest in archiving life sciences literature. The long term goal of PMCI is to create a network of digital archives that can share some or all of their respective locally deposited content with others in the network.

To date, NLM has authorized two PMCI centers, Europe PMC (formerly UKPMC) and PMC Canada. UKPMC became operational in January 2007 and was renamed Europe PMC in November 2012. PMC Canada was launched in October 2009. Both repositories receive their journal content directly from the U.S. PMC archive. PMC Canada accepts manuscripts funded by CIHR and makes them available in both the U.S. PMC and Europe PMC. Europe PMC also accepts and processes author manuscripts of journal articles funded by the Funders group and makes them available to U.S. PMC and PMC Canada.

Portable PMC (pPMC) is a version of the PMC software that has been developed by NCBI to enable PMCI sites to display their content in a presentation style similar to the U.S. PMC site. Read more about PMCI and pPMC.

Are there any restrictions on the use of the material in PMC? Can I download a batch of articles from PMC for research or other purposes?

Although access to the material in PMC is free, the 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.

You may NOT use any kind of automated process to download articles in bulk from the main PMC site. PMC will block the access of any user who is found to be violating this policy. PMC does have two auxiliary services, the PMC OAI service and the PMC FTP service, that may be used to download certain articles in bulk. The PMC Open Access Subset page explains which articles are available through these services.

What is the PMC Open Access subset? Isn't everything in PMC open access?

The majority of the articles in PMC are subject to traditional copyright restrictions. They are free to access, but they are not Open Access articles in the specialized sense of that term.

The PMC Open Access Subset contains articles that 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. See the PMC Open Access Subset page for more information on how you may retrieve and use these articles.

Who may contribute to PMC?

PMC accepts articles from journals that meet PMC’s scientific, editorial, and technical standards and sign a PMC participation agreement with the National Library of Medicine (NLM). To become a PMC-participating journal, the publisher must submit a formal application after which NLM will review the scientific and editorial quality of the content as well as the technical quality of the journal’s digital files (see Add a Journal to PMC).

In addition to PMC-participating journal content, PMC accepts individual author manuscripts that are deposited via the NIH Manuscript Submission (NIHMS) system or a similar manuscript processing system. This submission route is available only for manuscripts that are covered by the public access policies of approved funding agencies (see Funders and PMC). Author manuscripts in PMC are clearly identified as such.

In 2014, with the approval of the PMC National Advisory Committee, PMC implemented a scientific and editorial quality review procedure whereby expert consultants from outside NLM conduct an independent review of journals seeking to participate in PMC. This was in response to a significant increase in new publishers and journals applying to participate in PMC, many of which are unknown to NLM in terms of quality and publishing practices.

The independent review follows an assessment by NLM that the journal meets NLM’s criteria for its collection, as outlined in the Collection Development Manual. NLM’s Library Operations Division takes the independent reviewers’ opinions into account in making the final decision on a journal’s suitability for inclusion in PMC.

What types of material may be deposited in PMC?

As an archive, PMC strives to collect and preserve everything that is published in a participating journal. It has cover-to-cover digital copies of the early issues of any journal that came into PMC through NLM's Back Issue Digitization Project. For more recent material, which a journal must supply in XML form, PMC accepts any editorial content that can be represented accurately with the Journal Article Tag Suite (JATS) or a compatible DTD. In this context, “editorial content” refers to articles and article-like items, including book reviews, news items and obituaries. PMC also accepts journal cover images and accompanying captions.

At this time, PMC will not accept promotional material for pharmaceutical or other products, even if presented in the form of an article.

In general, a participating journal must deposit the final, published version of an article as it appears on the journal's own web site. However, in the instance where PMC serves as the repository for a funding agency's access program (e.g., NIH Public Access Policy) , PMC will accept an author's final, peer reviewed manuscript of an article. Manuscripts may be deposited via the NIH Manuscript Submission (NIHMS) system in a wide range of electronic word-processing formats. See Who may contribute to PMC?

Does PMC include articles written in languages other than English?

Most of the articles in PMC are written in English. However, a few journals in PMC publish material in more than one language and PMC may display some abstracts or full text articles in another language. See this example.

For those older issues of a journal that were scanned under NLM's digitization program, the PMC archive may also include some articles published exclusively in languages other than English.

NIHMS is also able to process non-English manuscripts submitted to PMC that fall under the NIH Public Access Policy, as long as they are written in Latin scripts. Submissions written in other scripts (e.g., Cyrillic, kanji) cannot be processed by NIHMS.

What is the NIH Public Access Policy?

The NIH Public Access Policy ensures that the public has access to the published results of NIH-funded research. It requires scientists to submit final peer-reviewed journal manuscripts that arise from NIH funds to PMC upon acceptance for publication. The Policy requires that these final peer-reviewed manuscripts be accessible to the public on PMC to help advance science and improve human health.

I want to report a bad link or a typo in a PMC article. What do I do?

To report a problem with an article in PMC, please contact the PMC Help Desk at: pubmedcentral@ncbi.nlm.nih.gov. If you are the author of the article, please see There is a problem with my article in PMC, to whom do I report it?.

What does embargo mean and can I get the article anyway?

When an article is under an embargo it means that there is a delay, as specified by the publisher, between when the article is published and when its full version can be made freely available in PMC. The default embargo or release delay for each journal in PMC can be found under the “Free Access” column on the PMC Journal List and the exact release date for each article under embargo can be found on the table of contents for the issue in which the article appears or in the corresponding PubMed record. To obtain an article prior to its availability in PMC, you will need to get access through the journal publisher or their website directly.

Where can I get permissions to reproduce articles or images?

NLM does not hold the copyright for any of the material in PMC and cannot grant others permission to reuse or reproduce any of it (see PMC Copyright Notice ). Many articles in PMC have a license (e.g., a Creative Commons license) that explicitly allows some degree of reuse or redistribution of the content. The licenses vary in what they allow; you need to determine whether a particular license permits the type of use you want to make. NLM cannot interpret the licenses for you. If an article has standard copyright protection and no special license, or if you are unsure of what the license allows, you should contact the respective journal publisher for permission.

What happens if a journal ceases its participation? Will the existing articles be removed?

PMC does not remove articles that have been deposited into its archive when a journal ceases its participation in PMC. The journal will be designated as “No longer participating” in the Participation Level column on the Journal List and all the material deposited previously remains available. For an example, see this journal.

What is PubReader?

PubReader is an alternative web presentation 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. It was released in 2013. To learn more, see PubReader.

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