Let me add Google Scholar is probably the best source in the net. As Tdol mentioned, some of the documents there are subscriptions but one may have access to them via the university or the institute one is searching from. The other thing is that there often is "all
a number versions" link on the right to the title, and following it one may sometimes download the document even if following the main link to the document provides the information that one has no access to it, or just to its abstract. For sure learning the advanced Google Scholar possibilities may be of help.
Cheers,
Nyggus
