is an internet search engine for scientific literature with a very large database. Compared to other databases Google Scholar offers less search capabilities. It's possible to set up a personnel profile to get the Google Scholar Citations (created by an unknown algorithm).
provides access to the „Web of Science Core Collection”, a multidisciplinary database covering over 73 million records back to 1900. The Journal Citation Reports (JCR) and the Essential Science Indicators (ESI) are also offered. Tools for analyzing search results and creating citation reports are available.
is a multidisciplinary database produced by Elsevier covering a large selection of scientific, technical, medical, and social sciences journals with more than 69 million records. Tools for analyzing search results and creating citation reports are also available.
is the database of the German Patent and Trade Mark Office (Deutsches Patent- und Markenamt) for online searches on patent publications from around the world. It includes the internal DEPATIS electronic document archive of the office (German patent information system).