What are the ways to obtain invalid patents?

The ways to obtain invalid patents are: (1) The way to obtain invalid patents is 1, and the invalid patents are obtained through CD-ROM. China invalid patent CD-ROM database officially published by Patent Literature Publishing House stores about 250,000 invalid patent information. It is an important library for China Intellectual Property Office to retrieve invalid patent information of related disciplines since 1 April, 9851. 2. Obtaining invalid patents through the Internet, searching China National Intellectual Property Administration through the computer network, entering the website and clicking on the China patent literature database will lead to invalid patent literature for people to choose to use. 3. Obtaining Invalid Patents from Conventional Channels Obtaining Invalid Patents from Printed Patent Documents China Patent Index, Patent Bulletin and Patent Description. Among them, the first two are retrieval tools, and the latter patent specification is a document, reflecting the full text of invalid patents. 4. Establishing characteristic databases of invalid patents University libraries can establish several characteristic databases of invalid patents according to the needs of key subjects and disciplines of the school, and provide services online to realize the enjoyment of invalid patent literature resources. 5. The acquisition of invalid patents abroad is generally searched by wpi and wpa from two ways: subject and classification. It can also be searched through the patent index of ca. You can also search the foreign patent databases including the full texts of American patents, ep patents and wo patents through the Internet, and verify the obtained information through the China patent database to confirm whether these foreign patents have applied for China patents and whether they have expired, so as to obtain a number of relevant foreign invalid patents.