PubMed Central is a free database of scientific literature in biomedical and life sciences. It is on the Internet. It grew from the online Entrez PubMed biomedical literature search system. PubMed Central was developed by the U.S. National Library of Medicine (NLM) as an online archive of biomedical journal articles.
All the words in the PubMed Central articles can be read freely. Some publishers, though, do not show their articles for some time after they publish them on paper (usually about six months).
As of September 2004, PubMedCentral, PubMed, and related NLM services had about 1,300 hits every second, and gave 1.3 terabytes of data every day. The Library of Congress and the British Library showed support for the National Library of Medicine (NLM). It has also been popular with journal service providers.