Funding for this research was provided by:
National Natural Science Foundation of China (81673146)
Text and Data Mining valid from 2020-04-08
Received: 24 September 2019
Accepted: 19 March 2020
First Online: 8 April 2020
Ethics approval and consent to participate
: The study protocol was approved by the Peking University Institutional Review Committee. The ethical approval project identification code is IRB00001052–16071. This study was conducted according to the guidelines of the Declaration of Helsinki. All participants signed informed consent form before participating in the study.
: Not applicable.
: The authors declare that they have no competing interests.