This is a great, general database covering many disciplinary fields. This is a wonderful place to start your research before moving on to the more specialized databases in the sciences.
Articles (Research Databases)
Database of citations and abstracts that covers topics including: geology, ecology, geography, and volcanology. Coverage from 1980-present.
A database of citations and abstracts covering geology and geophysics.
This is a great resource for peer-reviewed journal articles in the sciences.