| Closed Access | Embargo | Metadata Only Access | Open Access | Restricted | Unknown | Total | |
|---|---|---|---|---|---|---|---|
| Total | 37 | 5 | 1631 | 9161 | 6124 | 1140 | |
| 2026 | - | - | - | 198 | 23 | - | 221 |
| 2025 | - | 1 | - | 451 | 76 | - | 528 |
| 2024 | - | 3 | - | 459 | 58 | - | 520 |
| 2023 | - | 1 | 18 | 461 | 80 | 2 | 562 |
| 2022 | - | - | 42 | 480 | 115 | 3 | 640 |
| 2021 | - | - | 25 | 419 | 104 | - | 548 |
| 2020 | - | - | 27 | 390 | 92 | 2 | 511 |
| 2019 | 3 | - | 35 | 442 | 96 | 2 | 578 |
| 2018 | 1 | - | 29 | 376 | 77 | - | 483 |
| 2017 | - | - | 51 | 287 | 151 | 2 | 491 |
| 2016 | - | - | 49 | 328 | 198 | 3 | 578 |
| 2015 | - | - | 39 | 335 | 212 | 8 | 594 |
| 2014 | 1 | - | 36 | 214 | 350 | 8 | 609 |
| 2013 | 1 | - | 29 | 225 | 328 | 4 | 587 |
| 2012 | 1 | - | 52 | 167 | 242 | 1 | 463 |
| 2011 | - | - | 55 | 164 | 280 | 11 | 510 |
| 2010 | - | - | 50 | 188 | 257 | 6 | 501 |
| 2009 | - | - | 32 | 211 | 216 | 12 | 471 |
| 2008 | - | - | 45 | 209 | 235 | 15 | 504 |
| 2007 | 2 | - | 103 | 188 | 357 | 9 | 659 |
| 2006 | - | - | 69 | 200 | 254 | 19 | 542 |
| 2005 | 1 | - | 23 | 190 | 233 | 12 | 459 |
| 2004 | - | - | 28 | 241 | 211 | 8 | 488 |
| 2003 | 1 | - | 76 | 181 | 193 | 12 | 463 |
| 2002 | 1 | - | 61 | 149 | 127 | 17 | 355 |
| 2001 | - | - | 94 | 144 | 112 | 49 | 399 |
| 2000 | 3 | - | 70 | 150 | 96 | 24 | 343 |
| 1999 | 3 | - | 74 | 114 | 102 | 34 | 327 |
| 1998 | - | - | 91 | 126 | 98 | 25 | 340 |
| 1997 | - | - | 11 | 82 | 81 | 13 | 187 |
| 1996 | - | - | 18 | 62 | 98 | 10 | 188 |
| 1995 | - | - | 15 | 108 | 75 | 16 | 214 |
| 1994 | 2 | - | 12 | 105 | 74 | 15 | 208 |
| 1993 | 1 | - | 18 | 74 | 52 | 17 | 162 |
| 1992 | 1 | - | 20 | 84 | 70 | 28 | 203 |
| 1991 | 2 | - | 10 | 80 | 61 | 18 | 171 |
| 1990 | 5 | - | 9 | 81 | 49 | 10 | 154 |
| 1989 | 1 | - | 31 | 88 | 60 | 36 | 216 |
| 1988 | 1 | - | 19 | 98 | 55 | 38 | 211 |
| 1987 | - | - | 15 | 67 | 47 | 27 | 156 |
| 1986 | - | - | 11 | 98 | 50 | 44 | 203 |
| 1985 | 1 | - | 32 | 43 | 67 | 51 | 194 |
| 1984 | - | - | 14 | 44 | 66 | 45 | 169 |
| 1983 | - | - | 20 | 47 | 47 | 30 | 144 |
| 1982 | - | - | 17 | 42 | 15 | 56 | 130 |
| 1981 | - | - | 20 | 37 | 19 | 52 | 128 |
| 1980 | 1 | - | 6 | 26 | 43 | 41 | 117 |
| 1979 | - | - | 5 | 21 | 31 | 48 | 105 |
| 1978 | - | - | 4 | 24 | 24 | 40 | 92 |
| 1977 | - | - | 4 | 31 | 12 | 33 | 80 |
| 1976 | 1 | - | 1 | 23 | 12 | 37 | 74 |
| 1975 | 1 | - | 4 | 29 | 10 | 33 | 77 |
| 1974 | 1 | - | - | 25 | 8 | 24 | 58 |
| 1973 | - | - | 3 | 26 | 4 | 18 | 51 |
| 1972 | - | - | 4 | 9 | 2 | 20 | 35 |
| 1971 | - | - | 3 | 2 | 8 | 10 | 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 |
| not yet published | - | - | - | 4 | 1 | - | 5 |