Google has released Google Scholar, which is designed to enable users to search specifically for scholarly literature, including peer-reviewed papers, theses, books, preprints, abstracts, and technical reports from broad areas of research. Google Scholar can be used to find articles from a variety of academic publishers, professional societies, preprint repositories, and universities, as well as scholarly articles available across the Web.

Google Scholar orders search results by how relevant they are to a user's query and the relevance ranking takes into account the full text of each article as well as the article's author, the publication in which the article appeared, and how often it has been cited in scholarly literature. Google Scholar also analyzes and extracts citations and presents them as separate results, even if the documents they refer to are not online.
(http://scholar.google.com)