You can visit www.sipo.gov.cn through the website of China National Intellectual Property Administration (Patent Office).
Look at this.
Many expired patents can be enjoyed. "Invalid patent does not mean invalid technology". Many invalid patents have high technical content. These technologies enable us to enjoy free lunch and dinner.
Free lunch: patented technology for which the patentee has not paid the annual fee.
The patentee needs to pay the annual patent fee to the state every year to maintain the validity of the patent, but some patentees may forget or fail to pay the annual patent fee on time for various reasons, resulting in the invalidation of the patent.
There is also a free dinner: patented technology whose protection period has expired. The protection of patents has a time limit, and the protection period of invention patents is 20 years; The utility model and appearance are only 10 years old. Some patents are still useful even after the longest protection period. We can use these technologies that have passed the protection period and entered the public domain to enjoy a free dinner.