http://scholar.google.com

includes PubMed and many online article archives. Does not include
many other important online databases like BioSis, Agricola,
ANTH, etc.

Still, it's a tool worth trying. One issue: most of the links
require payment - limited free content as most academic
articles require subscription or per-article fee payment.
These per-article fees range from $10-50 or more, depending on the greed
of the publisher.

PS as the articles are controlled-access, there is no cache feature.

Tom Billings