If you have more money, use a professional patent search database, such as De Winter Patent Database.
Personally, I use it for free (I am poor ~ ~).
Domestic patent search generally uses SOOPAT website or China National Intellectual Property Administration official website.
Abroad, it is widely used on the website of OTE Bureau. Under special circumstances, search on the website of the patent office of the country where the patent is located.
PS: Websites of foreign patent offices and patent organizations, which you can find in "Home >" in official website and China National Intellectual Property Administration; Literature service > Internet patent retrieval system ".