A Science Search Engine

Scirus is a science-specific search engine on the Internet for searching more than 415 million science-related pages. According to their site, Scirus helps you quickly locate scientific information on the Web:

• Filters out non-scientific sites. For example, if you search on REM, Google finds the rock group - Scirus finds information on sleep, among other things
• Finds peer-reviewed articles such as PDF and PostScript files, which are often invisible to other search engines.
• Searches the most comprehensive combination of web information, preprint servers, digital archives, repositories and patent and journal databases. Scirus goes deeper than the first two levels of a Web site, thereby revealing much more relevant information.