Funding for this research was provided by:
Major Project of the National Social Science Fund of China (19ZDA149)
National Social Science Fund of China (20VYJ039)
Innovative Research Group Project of the National Natural Science Foundation of China (71921003)
Article History
Received: 20 October 2020
Accepted: 19 February 2021
First Online: 2 March 2021
Declarations
:
: Not applicable.
: Not applicable. This analysis is based on search engine data at prefectural level, and no individual information is required.
: The authors declare that they have no competing interests.