Google: “With Google Patents, you can search and read the full text of patent grants and applications from around the world. If you’re looking for prior art, you can use the integrated Prior Art Finder tool and Google Scholar documents to find patent and non-patent prior art, all in one interface. You can still access the old Google Patents and the Prior Art Finder.
What patents are available? Google Patents includes patent applications and grants from the USPTO, EPO, WIPO, DPMA, CIPO and SIPO. Patents without English full text are machine-translated to English, so you can search foreign patent documents using only English keywords. If you check “Include non-patent literature”, it also searches documents from Google Scholar (minus legal opinions and citation-only results). Scholar classifications – Documents from Google Scholar have been classified with Cooperative Patent Classification (CPC) codes using a machine-classification model, to make it easier to search non-patent literature in a patent searching context.”