If your topic is specific to nursing chose CINHAL.
One of two major databases for nursing, providing references to over 1,800 nursing and allied health journal articles in addition to citations for book chapters, nursing dissertations, association publications, educational software, conference proceedings and selected full-text for state nursing journal articles, legal cases, patient education material, research instruments, standards of practice, critical paths, nurse practice acts, drugs, clinical innovations and government publications. References for alternative/complementary medicine, consumer health and health sciences librarianship are also included. Coverage: 1982 - Present. Updates: Monthly. App information
If your question has a psychological concept try PsycINFO.
PsycINFO provides access to international literature in psychology and related disciplines. Unrivaled in its depth of psychological coverage and respected worldwide for its high quality, the database is enriched with literature from an array of disciplines related to psychology such as psychiatry, education, business, medicine, nursing, pharmacology, law, linguistics, and social work. Nearly all records contain nonevaluative summaries, and all records from 1967 to the present are indexed using the Thesaurus of Psychological Index Terms.
If you have a general health question start with PubMed.
PubMed is a web interface that allows you to search MEDLINE, the National Library of Medicine's premier database of citations and abstracts for biomedical research articles. The core subject is medicine, but subject coverage also includes bioethics, biology, chemistry, dentistry, environmental health, genetics, gerontology, health care planning and administration, history of medicine, hospital administration, microbiology, nutrition, nursing (International Nursing Index), physiology, pre-clinical sciences, public health, sports medicine, veterinary medicine and zoology. MEDLINE covers over 4,800 journals published in the United States and 70 other countries. The database contains over 15 million citations dating back to 1950. Coverage is worldwide and updated weekly. Learn more about PubMed at: http://www.nlm.nih.gov/pubs/factsheets/pubmed.html. or Try the Tutorial at: http://www.nlm.nih.gov/bsd/pubmed_tutorial/m1001.html