Overview and Size of PubMed Central - PubMed Central (PMC) is a free digital repository for open access scholarly articles in biomedical and life sciences journals. - PMC is developed by the National Center for Biotechnology Information (NCBI). - Submissions to PMC are indexed and formatted for enhanced metadata, medical ontology, and unique identifiers. - Content within PMC can be linked to other NCBI databases and accessed via Entrez search and retrieval systems. - PMC is distinct from PubMed, which is a searchable database of biomedical citations and abstracts. - As of December 2018, PMC contains over 5.2 million articles. - Contributions to PMC come from publishers or authors depositing their manuscripts per the NIH Public Access Policy. - From January 2013 to January 2014, author-initiated deposits exceeded 103,000 papers in a 12-month period. - PMC identifies about 4,000 journals that participate in depositing their content. - Some publishers have embargo periods before releasing articles on PMC.

History and Adoption of PubMed Central - PubMed Central began as E-biomed, proposed by Harold Varmus in May 1999. - The idea was inspired by the use of arXiv for preprints. - The goal of E-biomed was to provide free access to all biomedical research. - The proposal faced opposition from commercial publishers. - The revised PubMed Central proposal received support from publishers and led to the creation of CrossRef and the DOI system. - Launched in February 2000, PMC has grown rapidly. - The NIH Public Access Policy aims to make NIH-funded research freely accessible. - Many publishers are working cooperatively with the NIH to provide free access to their works. - The Consolidated Appropriations Act of 2008 required the NIH to modify its policies. - The adoption of PMC has increased the availability of free access to biomedical research.

Role and Function of PubMed Central - PMC serves as a digital archive of full articles accessible to anyone. - It provides a platform for sharing and discovering biomedical knowledge. - PMC facilitates linking to other resources and databases. - The repository enhances metadata and medical ontology for each article. - PMC is an example of systematic external distribution by a third party.

Technology and Workflow of PubMed Central - Publishers send articles to PubMed Central in XML or SGML format, using various article DTDs. - Received articles are converted to the NLM Archiving and Interchange DTD via XSLT. - Graphics are converted to standard formats and sizes. - Bibliographic citations are parsed and automatically linked to relevant resources. - An in-house indexing system provides search capability and is aware of medical terminology.

Impact and Related Resources of PubMed Central - Reactions to PubMed Central vary among the scholarly publishing community. - Some view PubMed Central as a valuable partner for open access publishing, while others express concerns about diverted traffic and economic consequences. - Public repositories like PubMed Central have been found to draw significant numbers of readers away from journal websites. - Open access papers in certain fields have shown greater research impact. - PubMed Central has received support from libraries, universities, and patient rights organizations. - PMCID is a bibliographic identifier for articles in PubMed Central. - It consists of 'PMC' followed by a string of numbers. - Authors applying for NIH awards must include the PMCID in their application. - Europe PubMed Central, JATS, MEDLINE, PMID, PubMed Central Canada, Redalyc, and SciELO are related resources. - A report by Beck provides insights into PubMed Central as an XML-based archive. - NIHMS Statistics offer information on article deposits. - The official website of PubMed Central is hosted by the National Center for Biotechnology Information. - Various references provide additional information and sources for further reading.