Funding for this research was provided by:
National Natural Science Foundation of China (81671416)
Text and Data Mining valid from 2019-04-02
Received: 14 August 2018
Accepted: 16 March 2019
First Online: 2 April 2019
Compliance with ethical standards
: We declare no conflict of interest.
: This study was approved by the Institutional Ethics Review Board, Yantai Yuhuangding Hospital affiliated to Qingdao University.