| Closed Access | Embargo | Metadata Only Access | Open Access | Restricted | Total | |
|---|---|---|---|---|---|---|
| Total | 1 | 5 | 1779 | 6973 | 6230 | |
| 9999 | - | - | - | 7 | 1 | 8 |
| 2024 | - | 2 | 2 | 164 | 38 | 206 |
| 2023 | - | 1 | 16 | 417 | 72 | 506 |
| 2022 | - | 2 | 43 | 436 | 103 | 584 |
| 2021 | - | - | 24 | 383 | 98 | 505 |
| 2020 | - | - | 21 | 351 | 99 | 471 |
| 2019 | - | - | 38 | 425 | 97 | 560 |
| 2018 | - | - | 28 | 364 | 78 | 470 |
| 2017 | - | - | 52 | 265 | 165 | 482 |
| 2016 | - | - | 49 | 304 | 207 | 560 |
| 2015 | - | - | 39 | 308 | 222 | 569 |
| 2014 | - | - | 37 | 150 | 398 | 585 |
| 2013 | - | - | 33 | 146 | 381 | 560 |
| 2012 | - | - | 61 | 89 | 296 | 446 |
| 2011 | - | - | 70 | 85 | 308 | 463 |
| 2010 | - | - | 61 | 109 | 303 | 473 |
| 2009 | - | - | 44 | 129 | 265 | 438 |
| 2008 | - | - | 58 | 145 | 261 | 464 |
| 2007 | - | - | 120 | 138 | 366 | 624 |
| 2006 | - | - | 72 | 140 | 273 | 485 |
| 2005 | - | - | 31 | 146 | 244 | 421 |
| 2004 | - | - | 35 | 195 | 211 | 441 |
| 2003 | - | - | 77 | 144 | 181 | 402 |
| 2002 | - | - | 71 | 113 | 122 | 306 |
| 2001 | - | - | 101 | 127 | 111 | 339 |
| 2000 | - | - | 68 | 134 | 92 | 294 |
| 1999 | 1 | - | 78 | 88 | 102 | 269 |
| 1998 | - | - | 96 | 107 | 103 | 306 |
| 1997 | - | - | 11 | 73 | 79 | 163 |
| 1996 | - | - | 20 | 52 | 93 | 165 |
| 1995 | - | - | 24 | 100 | 71 | 195 |
| 1994 | - | - | 15 | 102 | 69 | 186 |
| 1993 | - | - | 20 | 68 | 50 | 138 |
| 1992 | - | - | 22 | 81 | 65 | 168 |
| 1991 | - | - | 14 | 74 | 56 | 144 |
| 1990 | - | - | 9 | 62 | 55 | 126 |
| 1989 | - | - | 31 | 83 | 51 | 165 |
| 1988 | - | - | 20 | 93 | 50 | 163 |
| 1987 | - | - | 15 | 60 | 45 | 120 |
| 1986 | - | - | 11 | 94 | 46 | 151 |
| 1985 | - | - | 32 | 40 | 61 | 133 |
| 1984 | - | - | 14 | 40 | 54 | 108 |
| 1983 | - | - | 20 | 45 | 42 | 107 |
| 1982 | - | - | 16 | 40 | 10 | 66 |
| 1981 | - | - | 21 | 36 | 15 | 72 |
| 1980 | - | - | 6 | 25 | 31 | 62 |
| 1979 | - | - | 5 | 21 | 19 | 45 |
| 1978 | - | - | 4 | 20 | 18 | 42 |
| 1977 | - | - | 4 | 28 | 9 | 41 |
| 1976 | - | - | 1 | 22 | 5 | 28 |
| 1975 | - | - | 4 | 27 | 9 | 40 |
| 1974 | - | - | - | 23 | 6 | 29 |
| 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 | - | - | 3 | 14 | 12 | 29 |