Medline (PubMed)
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed
MEDLINE is the National Library of Medicines' (NLM's) premier bibliographic database covering the fields of medicine, nursing, dentistry, veterinary medicine, the health care system, and the preclinical sciences. MEDLINE contains bibliographic citations and author abstracts from more than 4,800 biomedical journals published in the USA and 70 other countries. The database contains over 12 million citations dating back to the mid 1960s. Coverage is worldwide, but most records are from English-language sources or have English abstracts.
Free medical journals
www.freemedicaljournals.com/
A site dedicated to the promotion of free access to medical journals over the Internet.