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Term | 术语 | Definition | 定义 |
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free wave | 自由波
| See WAVE. | 一种产生作用力停止作用后仍然继续存在的波，与由连续作用力产生和保持的强迫波相反。水面上的自由波是由突然的冲击推力而引发的，此后它仅受摩擦力、水域大小、水介质的扩散特性影响。大多数海洋表面波除潮汐波外均为自由波。参见oscillation（震荡波）。 |
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freezing | NULL | See FROST. | NULL |
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freezing point | 冰点
| Temperature of solidification of a liquid in given conditions. | 在一定的环境中，液体变成固体所要求的最低限度的温度。 |
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frequency | 频率
| The number of VIBRATIONS or CYCLES in unit time. | 单位时间内的振动次数或者周期数。 |
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frequency: extremely high (EHF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency: high (HF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency: low (LF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency: medium (MF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency: natural | 固有频率，自然频率
| The lowest resonant FREQUENCY of a body or system. | 物体或系统的最低谐振频率。 |
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frequency: radio | 无线电频率 | Any FREQUENCY at which electromagnetic RADIATION of energy is useful for communication. Radio frequencies are usually classed as very low, b... more | 无线电通信中，电磁波的有效辐射频率。无线电频率通常分为：甚低频（30千赫以内）、低频（30-300千赫）、中频（300-3000千赫）、高频（3-30兆赫）、甚高频（30-300兆赫）、特高频（300-3000兆赫）、超高频（3000-30000兆赫）、极高频（30000-300... more |
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frequency: resonant | 谐振（共振）频率
| Any FREQUENCY at which a body or system vibrates more readily. | 物体或系统的固有振动频率。 |
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frequency: super high (SHF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency: ultra high (UHF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency: very high (VHF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency: very low (VLF) | NULL | See FREQUENCY: RADIO. | NULL |
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frequency band | 波段、频带
| See BAND OF FREQUENCY. | 参见band of frequency（频带）。 |
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frequency channel | 频道
| See CHANNEL. | 频谱中适合某一使用特定发射类别播送的一个连续部分。 |
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frequency modulation | 调频
| See MODULATION. | 对正弦载波的角度调制。调制波的瞬时频率与载波频率的差值，与调制波（幅度）瞬时值成正比。 |
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frequency of soundings | 测深密度 | See DENSITY OF SOUNDINGS. | 参见density of soundings（测深密度）。 |
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freshet | 淡水区，暴涨，山洪
| An area of comparatively fresh water at or near the MOUTH of a STREAM flowing into the SEA. A FLOOD or overflowing of a RIVER caused by hea... more | 位于流入海的河口附近的淡水区。由于大雨或者冰雪融化而引起的洪水或者河水流量过大。 |