| Closed Access | Embargo | Metadata Only Access | Open Access | Restricted | Unknown | Total | |
|---|---|---|---|---|---|---|---|
| Total | 567 | 3 | 1875 | 2145 | 489 | 480 | |
| 2025 | - | - | - | 7 | 3 | - | 10 |
| 2024 | - | 1 | - | 87 | 14 | - | 102 |
| 2023 | 2 | - | 5 | 88 | 39 | - | 134 |
| 2022 | - | - | 13 | 174 | 61 | 6 | 254 |
| 2021 | 8 | 1 | 15 | 263 | 55 | 4 | 346 |
| 2020 | 11 | 1 | 12 | 187 | 58 | 5 | 274 |
| 2019 | 22 | - | 21 | 213 | 47 | 14 | 317 |
| 2018 | 3 | - | 32 | 91 | 39 | 5 | 170 |
| 2017 | 6 | - | 26 | 84 | 25 | 3 | 144 |
| 2016 | 16 | - | 25 | 145 | 10 | 15 | 211 |
| 2015 | 53 | - | 25 | 119 | 18 | 53 | 268 |
| 2014 | 63 | - | 158 | 155 | 17 | 44 | 437 |
| 2013 | 41 | - | 109 | 118 | 21 | 54 | 343 |
| 2012 | 36 | - | 108 | 126 | 13 | 44 | 327 |
| 2011 | 45 | - | 163 | 121 | 9 | 51 | 389 |
| 2010 | 10 | - | 228 | 56 | 11 | 29 | 334 |
| 2009 | 5 | - | 162 | 20 | 4 | 18 | 209 |
| 2008 | 10 | - | 182 | 12 | 6 | 20 | 230 |
| 2007 | 13 | - | 189 | 10 | 4 | 23 | 239 |
| 2006 | 14 | - | 155 | 7 | 4 | 24 | 204 |
| 2005 | 11 | - | 146 | 12 | 5 | 35 | 209 |
| 2004 | 14 | - | 9 | 11 | 5 | 11 | 50 |
| 2003 | 15 | - | 5 | 7 | 2 | 1 | 30 |
| 2002 | 16 | - | 10 | 6 | - | 2 | 34 |
| 2001 | 13 | - | 10 | 9 | 2 | 3 | 37 |
| 2000 | 18 | - | 8 | 5 | 1 | 2 | 34 |
| 1999 | 10 | - | 8 | - | 2 | 1 | 21 |
| 1998 | 18 | - | 14 | 1 | 4 | 3 | 40 |
| 1997 | 10 | - | 1 | 2 | 3 | 6 | 22 |
| 1996 | 19 | - | 6 | 1 | 1 | 2 | 29 |
| 1995 | 15 | - | 5 | 3 | - | - | 23 |
| 1994 | 10 | - | 3 | 1 | 1 | - | 15 |
| 1993 | 13 | - | 3 | 2 | 2 | 2 | 22 |
| 1992 | 7 | - | 2 | 1 | 1 | - | 11 |
| 1991 | 4 | - | 11 | - | 2 | - | 17 |
| 1990 | 8 | - | 3 | 1 | - | - | 12 |
| 1989 | 5 | - | 1 | - | - | - | 6 |
| 1988 | 3 | - | - | - | - | - | 3 |
| 1987 | - | - | 2 | - | - | - | 2 |