There are several databases that you can use to find articles. Remember that databases will only include journals that are within that particular subject area. For instance, if you are interested in nutrition needs for the elderly, then you would want to use AgeLine. If you want articles on behavioral therapy interventions for anorexia, then you would want to use PsycInfo.
for when you need all terms in a search string included in the articles you retrieve
for when you have more than one way to say the same thing
if either of the terms shows up in articles retrieved it will be a useful article
wild-cards for getting a root word and all of it's endings
for example: nutri* will search for nutrition, nutritious, nutrient, nutritional, etc.