2. https://www.academia.edu/
Academia.edu is a social networking website for academics.[4] The platform can be used to share papers, monitor their impact, and follow the research in a particular field. It was launched in September 2008,[5] with 31 million registered users as of January 2016 and over 8 million uploaded texts.[6] Academia.edu was founded by Richard Price, who raised $600,000 from Spark Ventures, Brent Hoberman, and others.[7]
3. http://blog.sciencenet.cn/
科学网（英文：ScienceNet），是由中国科学院、中国工程院和国家自然科学基金委支持的中文综合性科学网站，于2007年1月18日正式上线[1]，目标是构建全球华人科学社区。[2]旗下的科学网博客为实名博客，属科学技术类博客群之一，截止到2010年6月30日20时，开通博客的博主有5553位。[3]
科学网称其在全球科学类中文网站中排名首位。[4]除了科教界以外，社会上发生的大事也经常会在科学网引起广泛讨论。
很多博客文章探讨最新科技动态、中国的科研体制、诺贝尔奖、海归科技人员的人生职业规划、科技人员创业、论文发表等等热门话题。科学网博客还发起有“CN域名杯全国青年科学博客大赛”，“年度人物推荐”等活动。

4. http://stackexchange.com/
Stack Exchange is a network of question-and-answer websites on topics in varied fields, each site covering a specific topic, where questions, answers, and users are subject to a reputation award process. The sites are modeled after Stack Overflow, a Q&A site for computer programmingquestions that was the original site in this network. The reputation system allows the sites to be self-moderating.[6] User contributions are licensed under Creative Commons Attribution-ShareAlike 3.0 Unported.[5]
http://stackexchange.com/sites
All kinds of research areas：Marhmatics；Quantitiive Finance

5. https://www.mendeley.com/
Mendeley is a desktop and web program for managing and sharing research papers, discovering research data and collaborating online. It combines Mendeley Desktop, a PDF and reference management application (available for Windows, OS X and Linux) and Mendeley for Android and iOS, with Mendeley Web, an online social network for researchers.
Mendeley requires the user to store all basic citation data on its servers—storing copies of documents is at the user's discretion. Upon registration, Mendeley provides the user with 2 GB of free web storage space, which is upgradeable at a cost.