Funding for this research was provided by:
National Natural Science Foundation of China (71772193)
Text and Data Mining valid from 2019-11-20
Received: 10 November 2018
Accepted: 4 November 2019
First Online: 20 November 2019
Compliance with Ethical Standards
: All the authors declare that they have no conflict of interest.
: All procedures performed in this study were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in this study.