Contains more than 35 million citations and abstracts for biomedical and life sciences literature. PubMed links to full-text when they are available.
PubMed was developed and is maintained by the National Center for Biotechnology Information (NCBI), at the U.S. National Library of Medicine (NLM), located at the National Institutes of Health (NIH).
National Guideline Clearinghouse published practice guidelines from a broad spectrum of medical specialities. It was discontinued in 2018 but can still be viewed.