Order | Subject area | Frequency | Centrality | Starting year |
1 | ENVIRONMENTAL SCIENCES & ECOLOGY | 1429 | 0.06 | 1990 |
2 | AGRICULTURE | 1369 | 0.06 | 1990 |
3 | ENVIRONMENTAL SCIENCES | 1068 | 0.23 | 1990 |
4 | SOIL SCIENCE | 792 | 0.03 | 1990 |
5 | PLANT SCIENCES | 689 | 0.19 | 1990 |
6 | ECOLOGY | 519 | 0.26 | 1991 |
7 | AGRONOMY | 441 | 0.10 | 1990 |
8 | WATER RESOURCES | 334 | 0.11 | 1990 |
9 | GEOLOGY | 226 | 0.09 | 1991 |
10 | GEOSCIENCES, MULTIDISCIPLINARY | 221 | 0.09 | 1991 |
11 | ENGINEERING | 216 | 0.30 | 1992 |
12 | AGRICULTURE, MULTIDISCIPLINARY | 203 | 0.07 | 1990 |
13 | FORESTRY | 166 | 0.03 | 1991 |
14 | ENGINEERING, ENVIRONMENTAL | 146 | 0.03 | 1993 |
15 | MICROBIOLOGY | 141 | 0.07 | 1991 |