PubMed is a database comprising more than 28 million citations for biomedical literature from Medline, life science journals and online books. The PubMed database is provided by the U.S. National Library of Medicine (NLM). A distinctive feature of MEDLINE is that the records are indexed with NLM Medical Subject Headings (MeSH).
PubMed has a great user guide to help you get started with searching and includes answers to frequently asked questions.
Access the User Guide at this link.
AND--OR--NOT
AND searches for both terms smoking AND cancer
OR searches for either term infants OR babies
NOT eliminates the term ulcer NOT pressure
Truncation: Search root of word with *
nurs* finds nurse, nurses, nursing
Phrases searching with quotation marks “small cell carcinoma” will keep words together in results.
MeSH stands for Medical Subject Headings and is an online thesaurus used by PubMed and MEDLINE to index records. MeSH uses standardized and controlled vocabulary; meaning, all articles on a particular subject are assigned a consistent subject heading. Descriptors are arranged in a hierarchical structure. This structure, called the MeSH Tree, descends from the general to the specific. For example, Parkinson Disease is the narrowest subject heading in the Nervous System Diseases hierarchy.