The topic is what kind of literature can be retrieved on Wanfang Data Knowledge Service Platform? Documents that can be retrieved on Wanfang Data Knowledge Service Platform include:

1. Academic journals: including Chinese journals and foreign journals.

2. Dissertations: including master's dissertations and doctoral dissertations.

3. Conference papers: including domestic conference papers and international conference papers.

4. Foreign literature: including books, periodicals and conference papers.

5. Patented technology: including domestic patents and international patents.