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| 次要数据来源 | |||
| 次级来源; 第二手来源 | |||
| 二次中子源核 | |||
| 二次文献; 二手资料 | |||
| 二手来源 | |||
| 次级源 | |||
| 二次光源 | |||
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secondary source : 21 phrases in 10 subjects |
| Advertising | 2 |
| Aviation | 2 |
| Commerce | 1 |
| Ecology | 1 |
| Electronics | 3 |
| Explosives and Explosive Ordnance Disposal | 2 |
| Nuclear and fusion power | 2 |
| Rail transport | 1 |
| Space | 2 |
| Technology | 5 |