Funding for this research was provided by:
National Natural Science Foundation of China (71303011)
Text and Data Mining valid from 2018-10-19
Received: 23 April 2018
Accepted: 7 October 2018
First Online: 19 October 2018
Ethics approval and consent to participate
: Ethical approval is not required for conducting this type of survey in China, because our study and team members have no direct contact with human subjects (reference file # Science and Education Department of Ministry of Health  17# ExternalRef removed). All of the information from institutions or study-related persons was anonymized and de-identified prior to analysis.
: This manuscript does not contain any data from any individual person, so consent for publication is not applicable.
: The authors declare that they have no competing interests.
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