Academic Search Complete - a general and multidisciplinary database of more than 8,500 full text periodicals with pdf content going back as far as 1887.
Project Muse - use to find articles in scholarly journals
Provides full-text access to more than 400 scholarly journals in the arts and humanities, social sciences, and mathematics. Coverage varies by publication.
JSTOR - a shared digital library that includes the full text of more than 2,000 academic journals, dating back to the first volume published. Coverage varies depending on the journal title. ---
GreenFILE -- Offers well-researched information covering all aspects of human impact on the environment.