1.** National Literature Center for Philosophy and Social Sciences * *: provides a large number of academic resources for literature retrieval in both Chinese and English, covering various academic journals, degrees, conference papers, etc.

2.** Google Academic * *: Provide global academic literature search service, including periodicals, papers and technical reports.

3.**SCI-Hub**: It is a tool developed by Russian Niuren, and you can download any document magazine. Enter the document title, DOI and other information you want to download, and you can get the real address of the document and browse it online.

4.** Kota Academic * *: A collection of scientific research information, scientific research stations, scientific research assistants, Kota academic navigation and special topics.