Reading about open access in medical libraries (see the post discussing it here) got me interested in the history and workings of PubMed Central (PMC), so I wandered over to the website. PMC was created and is run by the National Center for Biotechnology Information (NCBI), which is a division of the NLM. According to the home and FAQ pages, PubMed Central contains over 3.8 million archived articles from over 5,000 journals. These journals fall into 3 categories. Those that pledge full participation deposit all their articles from every edition into PMC, while journals with selective deposit and NIH portfolio agreements put a portion of the articles they publish into PMC. Pretty much all of the contents of PMC have citations on PubMed, except for things such as book reviews (which are considered out of PubMed’s scope). Although the content offered through PMC doesn’t compare to the more than 26 million articles listed on PubMed, it still is an important source of freely available research and information. You can learn more about it here, or look through the journals that it covers here.