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PatentScope (WIPO)Growing rapidly- 66+ million patent documents as of December 2017; from 54 regional and national patent offices. Has extensive field search, and JSTOR style proximity search: "electric car"~10
DepatisnetThe German Patent Office's international patent database, including 50 million EPO bibliographic records.* U.S. patents from 1790 (to find X1, search: us1 and choose US000000000001I1 from the list)* Includes plant and design patents
The LensAs of December 2017, includes EPO's "81+ Million documents from nearly 100 jurisdictions". Has some older patents back to 1913. Has free data visualization tools
China (CNIPA) - Register for password accessSearch by publication or application number and date, English title or abstract, International Patent Classification (IPC), applicant, inventor, patent agent, patent agency code, priority number and date, and province or country code. Machine translation is free, but not available for all patents
Japan Platform for Patent Information (J-Plat-Pat)The Japan Patent Office's Patent & Utility Model, Design, and Trademarks databases.
* Click on PAJ - Patent Abstracts of Japan
* Search Applicants, Titles, Abstracts in English
* Search IPC (International Patent Classification)
* Other options include number search and FI/F subject terms
* Click numbers in Index list for drawing and English abstract
* Links to Japanese image full text; machine translation back to about 1994, as of September 2015
Korea (KIPRIS) English searchSimple search of title, abstract, and names; or click the flashing "Smart Search" button to get to detailed search page with many choices and search examples. Titles in results are in Korean and English; full translation is available for a fee
If a source has an unusual combination of names or words/phrases; Google often can find books, reports, and articles that cite it in their bibliographies or notes.
Google Patents full records link to both cited (older) and citing (newer) patents, from about the late 1970s. OCR search, as in Google Books, can sometimes find older ones
