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Term | 术语 | Definition | 定义 |
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antenna | 天线
| A conductor or system of conductors for radiating or receiving RADIO WAVES. Also called aerial. | 用于发射或接收无线电波的导体或系统。亦称为aerial（天线）。 |
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antenna: directional | 定向天线
| An ANTENNA for transmitting or receiving SIGNALS in, or from, a given direction. | 按照指定的方向发送或者接收信号的天线。 |
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antenna: omnidirectional | 全向天线
| An ANTENNA having essentially uniform response in AZIMUTH and a directional pattern in ELEVATION. | 在水平方向灵敏度基本相同，在垂直方向具方向性的天线。 |
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antenna: screened | 屏蔽天线 | Any ANTENNA which is screened in some way to counteract disturbances. | 以某种方式加以屏蔽以减少干扰的一种天线。 |
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antenna: unidirectional | 单向天线
| An ANTENNA having a single well-defined direction of maximum radiation intensity or maximum GAIN. | 在一个方向上具有最大辐射密度或最大增益的一种天线。 |
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anthelion | 幻日
| Pure white, rounded spot, but sometimes iridescent or surrounded by coloured rings or arcs, which appears on very rare occasions opposite th... more | 一种纯白色的圆点，但有时呈彩虹色或被彩色环或彩色孤所环绕。在极少情况下，该圆点出现在地平与太阳相对的同一高度上。 |
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anticline | 背斜
| An arch of stratified ROCK in which the LAYERS bend downward in opposite directions from the CREST. | 一种层状拱形岩石，在该拱中岩层自山脊按相反的方向向下弯曲。 |
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anticyclone | 反气旋
| Region of the ATMOSPHERE where the pressure is high relative to the surrounding region at the same LEVEL. It is represented on a SYNOPTIC CH... more | 反气旋指在同一高度上比周围大气气压高的大气区域。一般用等气压线或用额定气压的等高线表示在大气图上，该大气区包含有相当高的气压，亦称high（高压）。 |
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antimeridian | 逆子午线；反面子午线
| The MERIDIAN which is 180 deg of LONGITUDE from a given MERIDIAN. One MERIDIAN with its antimeridian constitute a complete GREAT CIRCLE. | 一条给定子午线加上180°夹角得到的子午线，子午线及其逆子午线构成一个完整的大圆。 |
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antipode(s) | 对映点
| Place(s) on the surface of the EARTH directly opposite to each other. | 在地球表面上正好彼此相对的地点。 |
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antiselena | 幻月
| Luminous PHENOMENON analogous to ANTHELION, the luminary being the MOON. | 类似幻日的发光现象，但发光体是月亮。 |
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anti-trade | 反信风
| Air current with a westerly component which in various subtropical regions of either hemisphere sometimes blows above the TRADE WIND. | 南北两半球亚热带地区的信风上方有时出现的一种向西气流。 |
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aperture: relative | 相对孔径
| For a photographic or telescopic LENS, the ratio of the EQUIVALENT FOCAL LENGTH to the diameter of the ENTRANCE PUPIL. Expressed as f: 4.5; ... more | 对摄像机或望远镜的透镜来说，等效焦距与入射光瞳直径之比，可表示为f:4.5；亦称 f-number（f数），f-stop（光圈级数）或speed of lens（透镜速率）。 |
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aperture of antenna | 天线孔径
| The diameter of a reflector antenna, usually expressed in units of WAVE LENGTH. | 反射器天线的直径，通常采用波长单位表示。 |
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aperture stop | 孔径光阑
| The physical element (such as a DIAPHRAGM, or lens periphery) of an OPTICAL SYSTEM which limits the size of the PENCIL of RAYS traversing th... more | 一种光学系统物理部件（如遮光板或透镜边缘），用于限制透过系统的光线束大小。也称作光圈。
透镜有效部分的直径。 |
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apex | 顶点，脊
| The top, PEAK, or highest point of something, as of a MOUNTAIN. See also VERTEX. | 某种物体（如山）的顶、最高点、峰，如山顶。亦可参见vertex（顶点）。 |
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apex: solar | 太阳向点 | The point of the CELESTIAL SPHERE towards which the SOLAR SYSTEM as a whole is moving. It lies in the CONSTELLATION of Hercules. | 太阳系作为一个整体运行所趋向的天球点。该点位于武仙星座。 |
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aphelion | 远日点
| That orbital point farthest from the SUN when the SUN is the centre of attraction, as opposed to PERIHELION. | 当以太阳为引力中心时，距离太阳最远的轨道点就叫做远日点。与近日点（perihelion）相对。 |
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aphotic | 无光的 | (adj.). Without light. | 形容词，没有光亮。 |
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apochromatic lens | 复消色差透镜
| A LENS that has been corrected for CHROMATIC ABERRATION for at least three colours. | 至少能改正三种颜色色差的透镜。 |