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About PMC

PubMed Central® (PMC) is a free full-text archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health's National Library of Medicine (NIH/NLM). In keeping with NLM's legislative mandate to collect and preserve the biomedical literature, PMC is part of the NLM collection, which also includes NLM's extensive print and licensed electronic journal holdings and supports contemporary biomedical and health care research and practice as well as future scholarship.

Available to the public online since 2000, PMC was developed and is maintained by the National Center for Biotechnology Information (NCBI) at NLM.

About the Content

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 articles from thousands of journals. In addition, PMC also contains author manuscripts deposited through the NIH Manuscript Submission System (NIHMS), and preprints collected through the NIH Preprint Pilot.

Graphic showing information about the types of records available in PMC which include preprints, author manuscripts and journal articles and the differences between them, especially highlighting that preprints are not yet peer-reviewed, while author manuscripts and journal articles have been peer reviewed.

The PMC archive contains more than 8 million full-text article records spanning several centuries of biomedical and life science research (late 1700s to present). This content includes articles that have been formally published in a scholarly journal, author manuscripts that have been peer-reviewed and accepted for publication in a journal, and preprint versions of articles that have been made public prior to peer review.

Content is deposited in the PMC archive through collaborations with publishers, societies, research funders, and international organizations. Our Collections page provides an overview of the collections that result from these content collaborations.

For more information on content in PMC, see our Policies page and the PMC Disclaimer.

About the Archive

NLM has a statutory mission to collect, index, preserve, and make available biomedical and health-related literature of the present-day and from the past. As such, PMC is designated to provide permanent access to all of its content, even as technology evolves. (Learn more in the Collection and Preservation Policy of the NLM.)

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PMC makes all content free to read (in some cases, following an embargo period), as NLM believes that the best way to ensure the accessibility and viability of digital material over time is through consistent and active use of the archive. However, free access does not mean that there is no copyright protection (see the PMC Copyright Notice).

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PMC stores content in eXtensible Markup Language (XML), which represents the structure and meaning of a document in a relatively simple and human-readable form. All PMC content is converted to and stored in the NISO Z39.96-2015 JATS XML format. This standard format is the most effective and widely used archival format for journal articles.

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NLM operates the PMC International network, which provides a framework to maintain copies of the PMC corpus in other reliable international archives that share the goals of PMC and operate on the same principles.

Because PMC has the capacity to store and cross reference data from diverse sources in a common format within a central repository, a PMC user can quickly search the entire collection of full-text articles and locate all relevant material. The structure of the PMC archive also supports the integration of the literature with other resources.

Bulk retrieval of files for text mining and other purposes is permitted within certain collections or subsets of the PMC archive. An overview of these subsets of the archive is available at PMC Article Datasets.

About PMC Archive Use

In addition to ensuring the long-term preservation of the scientific literature, PMC provides access to the archive in human- and machine-readable formats. Use of PMC has increased as the archive has grown. Numbers reported below for FY13-FY21 reflect access to the PMC website in the last month of each fiscal year (September). Beginning with FY22, the numbers reflect the weekday average for the entire fiscal year.

Fiscal Year Articles Available Avg. Unique Sessions /
FY23 9,407,149 3.8 million
FY22 8,386,512 3.2 million
FY21 7,383,455 3.1 million
FY20 6,471,176 3.4 million
FY19 5,725,819 2.6 million
FY18 5,107,590 2.4 million
FY17 4,553,343 2.1 million
FY16 4,054,283 1.3 million
FY15 3,623,566 1.2 million
FY14 3,227,379 886,000
FY13 2,859,268 834,000

Last modified: Fri Nov. 3 2023