Google Scholar provides easy access to a lot of full text content paid for by The Library, as well as other scholarly or professional content available freely on the Web. Their Help pages describe more fully what is included in this resource.
With a Google account you can exploit special features in Google Scholar.
Set up a Google Scholar Alert to be automatically notified when new articles are added to Google on topics of interest. Do your search in Google Scholar. Look in the green toolbar for the envelope icon, and click it. New items will be sent to your email account as they are found by Google.
Ever wanted to trace an article’s impact? Google now permits searching within citing articles. Do a Google Scholar search. Click on the "Cited by" link under a citation and select the "Search within articles citing..." checkbox.