分享多个可用的scihub英文文献下载网址，以防某些网址被人封禁。
https://sci-hub.se/
https://sci-hub.ee/
https://sci-hub.wf/
https://sci-hub.shop/
https://sci-hub.ren/
https://sci-hub.ru/
https://sci-hub.st/
https://www.scihub.net.cn/