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. It was started in 2000.[1][2] As of 2021, it had over 7 million science papers in it.[2]
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).