Possible topic: polymerase chain reaction
Keywords (the most important words—not and the to for):
“polymerase chain reaction” (enclose in quotation marks words you want to keep together as a phrase)
Begin your search with all of the important terms. If you don't retrieve enough hits to have sufficient, good information on your topic drop a term. If you have too many hits narrow by date, by format (scholarly, publication) or add another term, e.g., dna.
You may need some background information in order to understand the topic. Think of the terms in your topic that need to be defined/explained, e.g.,
What is polymerase chain reaction?
Read a definition and watch an animated description in Access Science, a science encyclopedia:
THERE ARE OTHER REFERENCE SOURCES THAT MIGHT HELP:
Gale Virtual Reference--includes articles from multiple encyclopedias, including an entry on PCR in the Encyclopedia of Espionage, Intelligence, and Security
IF YOU NEED HELP ASK.