frequency and time
| standard
| frequency and time | |
| geophys. | 频率与时间 |
| standard | |
| gen. | 水准; 格; 水平; 表均 |
| el. meas.inst. | 测量标准 |
| environ. | 标准 |
| hydroel.st. | 准则; 规格 |
| met. | 样品 |
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| 频率与时间 | |||
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frequency and time : 55 phrases in 15 subjects |