The CINAHL database (Cumulative Index to Nursing and Allied Health) covers nursing, allied health, biomedical and consumer health journals, publications of the American Nursing Association, and the National League for Nursing.
It's also a great database to find articles written by nurses.
Healthcare professionals sometimes use the PICO or PICOT format to develop keywords for searching of clinical questions where:
P - Patient or Population
I - Intervention
C - Comparison
O - Outcome
T - Time (sometimes included)
For more information about forming and using a PICO question to search, please see the American Journal of Nursing article below.