pdf

PDF免费转换网址https://www.gzwork.com/；https://tools.pdf24.org/zh/all-tools

2.证件照换背景网址https://bgsub.cn/

3.小游戏https://www.jxgame.net/

4.北大出版社电子书架https://pup6.yunzhan365.com/bookcase/jmyr/index.html