DEPATISnet is a service of the the German Patent and Trademark Office. Available via a German or English interface, it provides access to the fulltext of all German patents from 1877 forward.
Espacenet is a gateway to over 100 million patent documents from the countries of the European Patent Organization, the European Patent Office, the World Intellectual Property Organization (WIPO), and numerous other non-European countries including the U.S. and Cananda. The entire database, covering all countries, may be searched; or individual countries may be selected and searched. A translation feature is available.
From the USPTO, the Gobal Patent Search Network provides access to Chinese patent documents in English or Chinese from 2008 to 2011. It covers published applications, granted patents, and utility models.
Google Patents covers patents and patent applications from 17 patent offices, including the U.S. (back to 1790), European, China, Japan, Korea, WIPO, Germany, Russia, U.K., and France.
The Interactive Patent Coverage Map displays known patent search systems for countries selected.
From the World Intellectual Property Organization (WIPO), PatentScope provides searching for patents and patent application from several countries. All countires can be searched together or countries can be selected and searched.
From the U.S. Patent and Trademark Office, it links to U.S. government and worldwide patent, copyright, and intellectual property offices.
From the Intellectual Property Office of Singapore, SurfIP provides simultaneous access to several patent sources, including the European Patent Office, the UK Patent Office, the World Intellectual Property Organisation (WIPO), the Japan IPDL, China Patent Infonet, and the USPTO.