| Closed Access | Embargo | Open Access | Restricted | Unknown | Total | |
|---|---|---|---|---|---|---|
| Total | 347 | 4 | 1731 | 332 | 2306 | |
| 2023 | 2 | 2 | 32 | 20 | 13 | 69 |
| 2022 | - | - | 140 | 34 | 41 | 215 |
| 2021 | 9 | 1 | 229 | 38 | 32 | 309 |
| 2020 | 16 | 1 | 144 | 35 | 29 | 225 |
| 2019 | 21 | - | 205 | 27 | 49 | 302 |
| 2018 | 2 | - | 49 | 20 | 41 | 112 |
| 2017 | 5 | - | 59 | 12 | 33 | 109 |
| 2016 | 10 | - | 142 | 13 | 38 | 203 |
| 2015 | 38 | - | 121 | 29 | 70 | 258 |
| 2014 | 59 | - | 152 | 22 | 195 | 428 |
| 2013 | 36 | - | 114 | 9 | 173 | 332 |
| 2012 | 28 | - | 116 | 14 | 147 | 305 |
| 2011 | 37 | - | 115 | 13 | 213 | 378 |
| 2010 | 10 | - | 44 | 12 | 259 | 325 |
| 2009 | 5 | - | 14 | 3 | 179 | 201 |
| 2008 | 7 | - | 13 | 8 | 195 | 223 |
| 2007 | 5 | - | 11 | 9 | 208 | 233 |
| 2006 | 9 | - | 8 | 4 | 175 | 196 |
| 2005 | 8 | - | 10 | 9 | 168 | 195 |
| 2004 | 6 | - | 5 | 1 | 10 | 22 |
| 2003 | 1 | - | 3 | - | 3 | 7 |
| 2002 | 4 | - | 1 | - | 5 | 10 |
| 2001 | 2 | - | 1 | - | 4 | 7 |
| 2000 | 3 | - | - | - | 6 | 9 |
| 1999 | - | - | - | - | 4 | 4 |
| 1998 | 2 | - | - | - | 4 | 6 |
| 1997 | 3 | - | 1 | - | 4 | 8 |
| 1996 | 4 | - | - | - | 3 | 7 |
| 1995 | 4 | - | - | - | - | 4 |
| 1994 | 5 | - | 1 | - | 1 | 7 |
| 1993 | 2 | - | 1 | - | 2 | 5 |
| 1992 | 2 | - | - | - | - | 2 |
| 1991 | 1 | - | - | - | 2 | 3 |
| 1990 | 1 | - | - | - | - | 1 |