作用 中 心 : 23 phrases in 15 subjects |
Agriculture | 3 |
Automobiles | 1 |
Aviation | 5 |
Bridge construction | 1 |
Business | 1 |
Earth sciences | 1 |
Economy | 1 |
Electronics | 1 |
Engineering geology | 1 |
General | 1 |
Name of organization | 1 |
Space | 3 |
Sports | 1 |
Technology | 1 |
United States | 1 |