Scitopia.org

scitopia.org is a search engine devoted to science and technology. It was created by "15 leading science and technology societies":

Searching for a better way to help researchers quickly get to the quality content they need, these society publishers developed a gateway to the research most cited in scholarly work and patents. Scitopia.org searches the entire electronic libraries of the leading voices in major science and technology disciplines and provides relevant results, without the noise of other Internet search engines. More than three million documents, including peer-reviewed journal content and technical conference papers, spanning 150 years of science and technology can be searched through the site.

But to get the full text of the articles you find you'll have to be a member of one of the societies or pay per view.