Funding for this research was provided by:
the General Program of NSFC (61773300)
the Key Program of Fundamental Research Project of Natural Science of Shaanxi Province, China (2017JZ017)
Text and Data Mining valid from 2019-07-03
First Online: 3 July 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This article does not contain any studies with human participants performed by any of the authors.