Google Scholar

Google Scholar is a freely-accessible Web search engine that indexes the full text of scholarly literature across an array of publishing formats and disciplines.
Google Scholar allows users to search for digital or physical copies of articles, whether online or in libraries. Google Scholar is relatively quick and easy to use. “Scholarly” searches will appear using the references from “’full-text journal articles, technical reports, preprints, theses, books, and other documents, including selected Web pages that are deemed to be “scholarly.’”