Academic Search Complete is a comprehensive scholarly, multi-disciplinary full-text database. Containing over 8,500 full-text periodicals, this is a good first choice for articles in the Earth Sciences.
JSTOR is a comprehensive archive of full-text scholarly articles and e-books. This database provides selected titles in Astronomy, Geology, and Paleontology.
The Directory of Open Access Journals covers free, full text, quality controlled scientific and scholarly journals. Covers numerous subjects and languages. There are over 3600 journals in the directory.