1, Baidu Library: Baidu Library is a very comprehensive library, providing a large number of documents covering various fields. Its advantages are rich content and clear classification, and users can search for what they need through keywords.

2. Douding.com: Douding.com is also a large-scale document sharing platform, where users can upload and download various types of documents, including office documents, e-books and PPT presentations. It is characterized by high document quality and comprehensive content.