Researchers often look for comprehensive information about a topic -- rather than just taking five articles that look pretty good. They use a technique called nesting which lets them do many searches at once.

For example:
(community or communities) and (Internet or Web or online)

This one keyword search in a periodical index would find articles that had one of the following combinations:

community and Internet
community and Web
community and online
communities and Internet
communities and Web
communities and online

Constructing these searches may take a little longer, but it will save you from creating many searches and remembering what combinations you have already tried.