Funding for this research was provided by:
National Basic Research Program of China (973 Program) (2016YFD0102000)
National Natural Science Foundation of China (31671675)
Text and Data Mining valid from 2018-05-02
Received: 1 March 2018
Accepted: 20 April 2018
First Online: 2 May 2018
Ethics approval and consent to participate
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.