Scientific Report
1961
1
1962
2
1964
1
1966
3
1968
1
1969
3
1970
2
1972
1
1974
1
1976
1
1981
1
1982
2
1984
2
1985
1
1986
4
1987
8
1988
1
1989
3
1990
14
1991
15
1992
11
1993
8
1994
13
1995
11
1996
42
1997
276
1998
133
1999
2,952
2000
4,542
2001
4,782
2002
4,635
2003
4,254
2004
4,705
2005
4,707
2006
4,891
2007
4,467
2008
4,502
2009
4,804
2010
4,881
2011
5,005
2012
5,250
2013
5,675
2014
5,627
2015
5,607
2016
5,641
2017
4,968
2018
4,993
2019
5,242
2020
3,737
2021
5,354
more ...