Useful web

画图¶

https://www.processon.com/apps/5daacbc3e4b0ea86c2b74446

https://app.diagrams.net/ or draw.io

Google patent¶

https://patents.99lb.net/

谷歌图书搜索¶

https://books.google.com.hk/?hl=zh-CN

国内的patent¶

https://www.patentguru.com/cn/keywords/h%E6%AE%B5