振荡周 期 : 40 phrases in 14 subjects |
Air defense | 1 |
Architecture | 2 |
Automobiles | 1 |
Aviation | 2 |
Construction | 1 |
Ecology | 1 |
Electric machinery | 3 |
Electronics | 3 |
Information technology | 1 |
Oil / petroleum | 3 |
Physics | 1 |
Rail transport | 1 |
Space | 1 |
Technology | 19 |