ScienceResearch.com is a free, publicly available Internet web portal allowing access to numerous scientific journals and public science databases. A single query will search thousands of high quality journals and databases, effectively millions of documents, in real-time'
Covers major publishers: Elsevier, Highwire, IEEE, Nature, Taylor & Francis, etc and free journal sources like DOAJ. Full text access to commercial journals requires a subscription or payment. A bit like Google Scholar, but better?!