手机通讯是利用电磁波的发射和接收实现信息传递的,电磁波在真空中的传播速度约为__

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问题:

手机通讯是利用电磁波的发射和接收实现信息传递的,电磁波在真空中的传播速度约为______m/s;在真空中电磁波的波速与波长和频率的关系是______.

考点:波速、波长和频率的关系
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       Last Wednesday, Mr Chen took his class   1   the Space Museum. There were many things   2  

 space there. First, the children saw a film about space travel.

       They saw how this space shuttle took off in space and later   3   on the earth again. It was very

exciting and the children felt they were travelling in space   4  .

       After the film, Mr Chen took   5   to see some models of rockets   6   the space shuttle. The models

looked very real, but they were much   7  . Then the children saw some moon rocks, Two   8   landed on

the moon in 1969. They put an American flag there. Then they took some rocks back to the   9  .      

       Before the children left, they also watched a video show about people   10   and working in a space

lab. The people could stay in the space lab for months.

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女性,45岁。临床诊断胆囊结石。既往患肾盂肾炎,术前肾功能检查未见异常。在硬膜外麻醉下行胆囊切除术。术后行硬膜外病人自控镇痛术(PCEA),配方如下:0.15%布比卡因150ml,内含吗啡10mg,氟哌利多5mg。术后第一天出现少尿,排尿困难。

下列哪种局麻药,其pH>7.0().

A.盐酸利多卡因

B.盐酸丁卡因

C.盐酸布比卡因

D.盐酸罗哌卡因

E.碳酸利多卡因

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2014年4月1日,中国物流与采购联合会公共采购分会近日成立,中国公共采购网“()”同时正式上线运行。这是我国第一个全国性的政府采购平台,致力于及时、准确、全面发布采购信息,提供安全、高效、阳光的公共采购服务。据不完全统计,全国公共采购(含政府采购、国企采购、军队采购、高校采购、公益采购等)的市场规模超过20万亿元。

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营养不良时免疫功能低下是

A.白细胞吞噬功能下降

B.补体功能低下

C.T细胞亚群改变

D.体液免疫功能低下

E.免疫功能全面下降

题型:填空题

信噪比定义为摄像机的()的比值。

A、原始图像信号与输出图像信号

B、输出图像信号与原始图像信号

C、图像信号与噪声信号

D、单位为线对,数字越小成像越清晰

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