1、剑桥大学
https://www.repository.cam.ac.uk/discover
2、ScienceDirect
https://www.sciencedirect.com/
3、CiteSeerX
http://citeseerx.ist.psu.edu/index
https://www.repository.cam.ac.uk/discover
https://www.sciencedirect.com/
http://citeseerx.ist.psu.edu/index