Most of the journals that I cite in class and on the web pages are available through the Ursus index and proxy server at Fogler Library (link below)
These include:
and many others. Many journals not listed in the index can be accessed by prefacing their URL with
http://www.library.umaine.edu/auth/EZProxy/test/authej.asp?url=
Searchinig for papers. Your first approach to finding peer-reviewed science is through PubMed and PubMed Central
SciFinder, the online interface to Chemical Abstracts, is your next best choice. See the Ursus Index.
Using Google and Google Scholar to find scientific papers is fine, although coverage is spotty. But cite the papers you find, not the online source.
BEWARE! Wikipedia and other un-peer-reviewed web sites are not acceptable as support references for your work! Anybody can put anything online! The Flat Earth Society. People who think they've been kidnapped by space aliens (there are three million of 'em in the US).
Citing any of these will result in your problem set or paper being returned immediately for correction. Use the original, peer-reviewed scientific literature only!