Funding for this research was provided by:
the National Natural Science Foundation of China (81670994)
Health and Family Planning Commission Research Project of Heilongjiang Province (2017-135)
Innovative Research Programs for Graduate students of Harbin Medical University (YJSCX2016-31HYD)
Article History
Received: 23 January 2020
Accepted: 9 June 2020
First Online: 3 July 2020
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.