| Closed Access | Embargo | Metadata Only Access | Open Access | Restricted | Unknown | Total | |
|---|---|---|---|---|---|---|---|
| Total | 405 | 3 | 1774 | 2269 | 935 | 387 | |
| 2025 | - | 1 | 2 | 13 | 4 | - | 20 |
| 2024 | - | - | - | 87 | 16 | - | 103 |
| 2023 | 2 | - | 5 | 92 | 40 | - | 139 |
| 2022 | - | - | 13 | 176 | 61 | 6 | 256 |
| 2021 | 7 | 1 | 15 | 263 | 57 | 4 | 347 |
| 2020 | 11 | 1 | 12 | 189 | 59 | 5 | 277 |
| 2019 | 22 | - | 20 | 216 | 49 | 14 | 321 |
| 2018 | 3 | - | 32 | 91 | 42 | 5 | 173 |
| 2017 | 6 | - | 25 | 88 | 28 | 3 | 150 |
| 2016 | 15 | - | 25 | 145 | 12 | 14 | 211 |
| 2015 | 36 | - | 22 | 138 | 44 | 43 | 283 |
| 2014 | 57 | - | 152 | 158 | 39 | 39 | 445 |
| 2013 | 36 | - | 104 | 123 | 33 | 54 | 350 |
| 2012 | 27 | - | 104 | 128 | 33 | 37 | 329 |
| 2011 | 38 | - | 162 | 122 | 20 | 49 | 391 |
| 2010 | 6 | - | 211 | 66 | 39 | 18 | 340 |
| 2009 | 3 | - | 153 | 29 | 19 | 16 | 220 |
| 2008 | 3 | - | 172 | 16 | 31 | 11 | 233 |
| 2007 | 5 | - | 179 | 18 | 33 | 12 | 247 |
| 2006 | 4 | - | 140 | 17 | 32 | 20 | 213 |
| 2005 | 6 | - | 139 | 19 | 38 | 17 | 219 |
| 2004 | 12 | - | 8 | 17 | 24 | 3 | 64 |
| 2003 | 9 | - | 4 | 8 | 9 | 1 | 31 |
| 2002 | 13 | - | 9 | 9 | 11 | 1 | 43 |
| 2001 | 9 | - | 7 | 12 | 16 | 3 | 47 |
| 2000 | 11 | - | 7 | 9 | 15 | 1 | 43 |
| 1999 | 4 | - | 7 | 3 | 15 | 1 | 30 |
| 1998 | 7 | - | 14 | 1 | 22 | 2 | 46 |
| 1997 | 5 | - | 1 | 3 | 17 | 4 | 30 |
| 1996 | 10 | - | 6 | 1 | 15 | 2 | 34 |
| 1995 | 8 | - | 5 | 4 | 9 | - | 26 |
| 1994 | 8 | - | 3 | 3 | 6 | - | 20 |
| 1993 | 6 | - | 3 | 3 | 10 | 2 | 24 |
| 1992 | 4 | - | 1 | 1 | 8 | - | 14 |
| 1991 | 2 | - | 6 | - | 13 | - | 21 |
| 1990 | 4 | - | 3 | 1 | 5 | - | 13 |
| 1989 | 3 | - | 1 | - | 4 | - | 8 |
| 1988 | 2 | - | - | - | 4 | - | 6 |
| 1987 | - | - | 2 | - | - | - | 2 |
| 1986 | - | - | - | - | 2 | - | 2 |
| 1985 | - | - | - | - | 1 | - | 1 |
| 1984 | 1 | - | - | - | - | - | 1 |