The most comprehensive database for biomedical sciences. The MEDLINE database, which makes up much of PubMed, is also searchable in SciFinder and Web of Science. Use PubMed to find recent publications that haven't yet been added to MEDLINE.
Annual Reviews publishes comprehensive, up-to-date review articles in the life, physical, and social sciences. A great place to look for a comprehensive overview of your research topic, as well as suggestions for further reading.