PsycINFO, from the American Psychological Association, has many powerful features and searches almost 4,000,000 records. In addition to the basic searches available in most databases it also lets you restrict by age, gender, and type of article -- including systematic reviews and meta analysis.
Combine terms using OR and AND (Boolean Operators) for a more focused search. OR for synonyms, AND to add two concepts.
A very powerful feature of PsycINFO is the ability to restrict your search by the following:
Sometimes you want all forms of the word -- teenager, teenagers, teenaged. Rather than combining with OR, you can use the *.
The asterisk (*) is a powerful feature that can stand in for any number of letters after the root. So anorex* will retrieve anorexia, anorexic, anorexics, etc.
If you want to search on an exact phrase, you can enter it in quotation marks ("anorexia nervosa")
Just a sample... there are more!