Directory of Science Search Engines

Astroweb
Astronomy/Astrophysics on the Web.
Biolinks
Primary goal is to provide scientists a search engine that will find pertinent information efficiently.
ChemDex
Over 4000 chemistry links by institute or category.
ChemFinder.com
Can search by chemical name, CAS Number, molecular formula, or molecular weight.
Discovery Channel
Search the site from the TV Channel
Environmental Search
The EnviroLink Network is a non-profit organization/Directory which has been providing access to thousands of online environmental resources since 1991.
Mental Health Net
Home of the oldest & largest online mental health directory guide & community.
Network MAD Search
Ask a science question.
Plants Search
The Plants Database maintains and generates data reports in specialized areas.
Sci Seek
Online Science and Nature resource. Search engine and directory
SciNet
Large directory of science sites.
Web-agri, the agriculture search engine
The first search engine specialized in agriculture.
Why Files
Your source for science behind the news.