| Closed Access | Embargo | Metadata Only Access | Open Access | Restricted | Total | |
|---|---|---|---|---|---|---|
| Total | 1 | 6 | 1767 | 6723 | 6023 | |
| 9999 | - | - | - | 5 | - | 5 |
| 2024 | - | 2 | 6 | 107 | 18 | 133 |
| 2023 | - | 2 | 18 | 406 | 66 | 492 |
| 2022 | - | 2 | 45 | 423 | 102 | 572 |
| 2021 | - | - | 23 | 370 | 97 | 490 |
| 2020 | - | - | 20 | 328 | 94 | 442 |
| 2019 | - | - | 38 | 413 | 93 | 544 |
| 2018 | - | - | 28 | 355 | 77 | 460 |
| 2017 | - | - | 49 | 255 | 163 | 467 |
| 2016 | - | - | 48 | 296 | 200 | 544 |
| 2015 | - | - | 38 | 296 | 213 | 547 |
| 2014 | - | - | 43 | 143 | 373 | 559 |
| 2013 | - | - | 40 | 139 | 363 | 542 |
| 2012 | - | - | 64 | 81 | 279 | 424 |
| 2011 | - | - | 68 | 84 | 299 | 451 |
| 2010 | - | - | 59 | 102 | 300 | 461 |
| 2009 | - | - | 43 | 125 | 262 | 430 |
| 2008 | - | - | 58 | 146 | 250 | 454 |
| 2007 | - | - | 119 | 136 | 365 | 620 |
| 2006 | - | - | 67 | 136 | 268 | 471 |
| 2005 | - | - | 29 | 143 | 238 | 410 |
| 2004 | - | - | 35 | 193 | 204 | 432 |
| 2003 | - | - | 74 | 140 | 177 | 391 |
| 2002 | - | - | 70 | 113 | 120 | 303 |
| 2001 | - | - | 100 | 122 | 107 | 329 |
| 2000 | - | - | 69 | 131 | 84 | 284 |
| 1999 | 1 | - | 75 | 86 | 94 | 256 |
| 1998 | - | - | 95 | 103 | 99 | 297 |
| 1997 | - | - | 11 | 71 | 77 | 159 |
| 1996 | - | - | 20 | 52 | 92 | 164 |
| 1995 | - | - | 22 | 100 | 71 | 193 |
| 1994 | - | - | 15 | 99 | 68 | 182 |
| 1993 | - | - | 19 | 68 | 50 | 137 |
| 1992 | - | - | 22 | 82 | 62 | 166 |
| 1991 | - | - | 13 | 72 | 56 | 141 |
| 1990 | - | - | 9 | 62 | 55 | 126 |
| 1989 | - | - | 30 | 81 | 51 | 162 |
| 1988 | - | - | 20 | 93 | 50 | 163 |
| 1987 | - | - | 15 | 61 | 44 | 120 |
| 1986 | - | - | 10 | 94 | 43 | 147 |
| 1985 | - | - | 31 | 39 | 59 | 129 |
| 1984 | - | - | 14 | 40 | 53 | 107 |
| 1983 | - | - | 20 | 42 | 42 | 104 |
| 1982 | - | - | 16 | 41 | 10 | 67 |
| 1981 | - | - | 20 | 34 | 15 | 69 |
| 1980 | - | - | 6 | 25 | 30 | 61 |
| 1979 | - | - | 5 | 21 | 19 | 45 |
| 1978 | - | - | 3 | 19 | 18 | 40 |
| 1977 | - | - | 4 | 28 | 9 | 41 |
| 1976 | - | - | 1 | 21 | 5 | 27 |
| 1975 | - | - | 4 | 25 | 9 | 38 |
| 1974 | - | - | - | 21 | 6 | 27 |
| 1973 | - | - | 3 | 22 | 3 | 28 |
| 1972 | - | - | 4 | 8 | 1 | 13 |
| 1971 | - | - | 3 | 2 | 4 | 9 |
| 1970 | - | - | 1 | 4 | 2 | 7 |
| 1969 | - | - | - | 1 | 2 | 3 |
| 1968 | - | - | 1 | 2 | - | 3 |
| 1967 | - | - | - | 1 | - | 1 |
| 1965 | - | - | - | 1 | - | 1 |
| 0 | - | - | 4 | 14 | 12 | 30 |