| Closed Access | Embargo | Metadata Only Access | Open Access | Restricted | Unknown | Total | |
|---|---|---|---|---|---|---|---|
| Total | 25 | 5 | 1750 | 7383 | 6521 | 1288 | |
| 2025 | - | - | 1 | 1 | - | - | 2 |
| 2024 | - | 2 | 5 | 271 | 58 | - | 336 |
| 2023 | - | 1 | 17 | 442 | 77 | 2 | 539 |
| 2022 | - | 1 | 37 | 464 | 113 | 6 | 621 |
| 2021 | - | - | 23 | 400 | 102 | 5 | 530 |
| 2020 | 1 | 1 | 29 | 361 | 104 | 5 | 501 |
| 2019 | 1 | - | 37 | 429 | 100 | 3 | 570 |
| 2018 | - | - | 29 | 371 | 81 | 1 | 482 |
| 2017 | - | - | 51 | 270 | 168 | 2 | 491 |
| 2016 | 1 | - | 49 | 308 | 212 | 8 | 578 |
| 2015 | - | - | 37 | 320 | 222 | 13 | 592 |
| 2014 | - | - | 38 | 159 | 396 | 13 | 606 |
| 2013 | - | - | 30 | 154 | 391 | 10 | 585 |
| 2012 | - | - | 54 | 97 | 306 | 6 | 463 |
| 2011 | 1 | - | 58 | 95 | 341 | 14 | 509 |
| 2010 | 1 | - | 56 | 121 | 309 | 10 | 497 |
| 2009 | - | - | 43 | 141 | 268 | 12 | 464 |
| 2008 | - | - | 57 | 156 | 273 | 15 | 501 |
| 2007 | 3 | - | 118 | 145 | 368 | 18 | 652 |
| 2006 | - | - | 70 | 163 | 271 | 23 | 527 |
| 2005 | 1 | - | 29 | 156 | 248 | 16 | 450 |
| 2004 | 1 | - | 32 | 210 | 219 | 12 | 474 |
| 2003 | 1 | - | 82 | 157 | 193 | 21 | 454 |
| 2002 | 1 | - | 69 | 136 | 123 | 22 | 351 |
| 2001 | - | - | 102 | 130 | 108 | 53 | 393 |
| 2000 | - | - | 72 | 134 | 101 | 34 | 341 |
| 1999 | 1 | - | 80 | 100 | 112 | 32 | 325 |
| 1998 | - | - | 96 | 108 | 106 | 29 | 339 |
| 1997 | - | - | 11 | 73 | 85 | 15 | 184 |
| 1996 | - | - | 19 | 57 | 98 | 13 | 187 |
| 1995 | - | - | 24 | 100 | 74 | 15 | 213 |
| 1994 | - | - | 15 | 99 | 75 | 17 | 206 |
| 1993 | - | - | 20 | 69 | 54 | 15 | 158 |
| 1992 | - | - | 21 | 82 | 66 | 32 | 201 |
| 1991 | - | - | 14 | 74 | 61 | 21 | 170 |
| 1990 | 5 | - | 9 | 74 | 55 | 10 | 153 |
| 1989 | 1 | - | 32 | 81 | 61 | 41 | 216 |
| 1988 | - | - | 20 | 91 | 58 | 42 | 211 |
| 1987 | - | - | 16 | 61 | 50 | 29 | 156 |
| 1986 | - | - | 11 | 94 | 50 | 48 | 203 |
| 1985 | 1 | - | 32 | 40 | 67 | 54 | 194 |
| 1984 | - | - | 15 | 41 | 62 | 51 | 169 |
| 1983 | - | - | 20 | 45 | 46 | 33 | 144 |
| 1982 | - | - | 15 | 41 | 14 | 59 | 129 |
| 1981 | - | - | 21 | 37 | 17 | 52 | 127 |
| 1980 | 1 | - | 6 | 26 | 41 | 41 | 115 |
| 1979 | - | - | 5 | 21 | 31 | 48 | 105 |
| 1978 | - | - | 4 | 25 | 22 | 40 | 91 |
| 1977 | - | - | 3 | 30 | 12 | 35 | 80 |
| 1976 | 1 | - | 1 | 21 | 12 | 39 | 74 |
| 1975 | 1 | - | 4 | 27 | 8 | 37 | 77 |
| 1974 | 1 | - | - | 25 | 8 | 24 | 58 |
| 1973 | - | - | 3 | 26 | 4 | 18 | 51 |
| 1972 | - | - | 4 | 8 | 2 | 21 | 35 |
| 1971 | - | - | 2 | 2 | 8 | 11 | 23 |
| 1970 | 1 | - | 1 | 6 | 4 | 8 | 20 |
| 1969 | - | - | - | 1 | 5 | 17 | 23 |
| 1968 | - | - | 1 | 2 | 1 | 10 | 14 |
| 1967 | - | - | - | 4 | - | 6 | 10 |
| 1966 | - | - | - | - | - | 1 | 1 |
| 1965 | - | - | - | 1 | - | - | 1 |