1.coursera (www.coursera.org): provides online courses for top universities and institutions in the world, covering various disciplines. Students can learn by watching video lessons, completing homework and participating in discussions.

2.EDX (www.edx.org): Similar to Coursera, it provides online courses for top universities in the world. Students can choose free courses or paid courses and get corresponding certificates.

3. Khan Academy (www.khanacademy.org): provides free educational resources, including courses in mathematics, science and programming. Students can choose learning content according to their own interests and needs.

4. MitopenCourseware (ocw.mit.edu): MIT provides free online course resources covering various disciplines. Students can freely browse and download course materials for self-study.

5. Google Academic Search (scholar.google.com): A powerful academic search engine can help students find relevant academic papers, research articles and books. Students can use keywords to search and get the full text or quotations of relevant documents.

6. Research Gate (www.researchgate.net): a social networking platform for scientists and researchers, where students can communicate with other researchers, share research results and get feedback.

7. Academy.edu (www.academy.edu): An academic social platform where students can establish contacts with other scholars, share papers and research results, and get peer reviews and suggestions.

8.TEDTALKS (www.ted.com): a platform for bringing together outstanding speakers from various fields. Students can get inspiration, expand their knowledge and think about problems by watching lecture videos.