名校
1 . 新冠疫情防控常态化,核酸检测应检尽检!核酸检测分析是用荧光定量
法,通过化学物质的荧光信号,对在
扩增进程中成指数级增加的靶标
实时检测,在
扩增的指数时期,荧光信号强度达到阈值时,
的数量
与扩增次数
满足:
,其中
为扩增效率,
为
的初始数量.已知某被测标本
扩增5次后,数量变为原来的10倍,那么该标本的扩增效率
约为( )(参考数据:
,
)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab8a2c4e50f3a0318a3ef4aa89ed4eab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab8a2c4e50f3a0318a3ef4aa89ed4eab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59b98020deb38157a0d38373b6c822a9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab8a2c4e50f3a0318a3ef4aa89ed4eab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59b98020deb38157a0d38373b6c822a9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93d0f3799612b81e85b87241ec8eee68.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3a1a125b0bed298617054c6ed7454816.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1010846eeec6c9da29640f5aa3f8738.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd680d9d3352bfe69d373054ab106a0d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59b98020deb38157a0d38373b6c822a9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59b98020deb38157a0d38373b6c822a9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1010846eeec6c9da29640f5aa3f8738.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ec2c729e6e9d5ecd8d6e06b4ab650bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8941ebf212f8143f98c23b6b6caa1dbe.png)
A.0.369 | B.0.415 | C.0.585 | D.0.631 |
您最近一年使用:0次
2021-02-06更新
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647次组卷
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6卷引用:江苏省南通市海安市2020-2021学年高三上学期期末数学试题
2 . 2020年12月17日凌晨,嫦娥五号返回器携带月球样品在内蒙古四子王旗预定区域安全着陆.嫦娥五号返回舱之所以能达到如此高的再入精度,主要是因为它采用弹跳式返回弹道,实现了减速和再入阶段弹道调整,这与“打水漂”原理类似(如图所示).现将石片扔向水面,假设石片第一次接触水面的速率为
,这是第一次“打水漂”,然后石片在水面上多次“打水漂”,每次“打水漂”的速率为上一次的93%,若要使石片的速率低于
,则至少需要“打水漂”的次数为(参考数据:取
,
)( )
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/28/7291b521-6b89-40ba-8a59-a9b3639b06dd.png?resizew=201)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a1d63db62d47b45ed1abb5ee278ea78a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b652e3a4a2302473d0dcfde9f150fbeb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ab3e25ff3da657f0fc59cf9fd452d0c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6dd66508a563da575c870782054a4f95.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/28/7291b521-6b89-40ba-8a59-a9b3639b06dd.png?resizew=201)
A.4 | B.5 | C.6 | D.7 |
您最近一年使用:0次
2021-01-27更新
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308次组卷
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3卷引用:安徽省阜阳市2020-2021学年高三上学期教学质量统测文科数学试题
名校
3 . 从
到
通信,网络速度提升了
倍.其中,香农公式
是被广泛公认的通信理论基础和研究依据,它表示:在受噪声干扰的信道中,最大信息传递率
取决于信道带宽
、信道内信号的平均功率
、信道内部的高斯噪声功率
的大小,其中
叫做信噪比.根据香农公式,以下说法正确的是__________ .
①若不改变信噪比
,而将信道带宽
增加一倍,则
增加一倍;
②若不改变信道带宽
和信道内信号的平均功率
,而将高斯噪声功率
降低为原来的一半,则
增加一倍;
③若不改变带宽
,而将信噪比
从
提升至
,
增加了
;
④若不改变带宽
,而将信噪比
从
提升至
,
大约增加了
.(参考数据:
)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e1bea758006164d7d614c230243e10e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/47248d88a8876e1177cbd3ba43b11bea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b72ac611ae66b86761e080761d9aabc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b629d0b15ee3a7d3123bd63b722b51fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91edc7e2d4811f5ea6c01284cf00393a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60c91fa27331e9958df48fd5633432e4.png)
①若不改变信噪比
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60c91fa27331e9958df48fd5633432e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91edc7e2d4811f5ea6c01284cf00393a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
②若不改变信道带宽
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91edc7e2d4811f5ea6c01284cf00393a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
③若不改变带宽
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91edc7e2d4811f5ea6c01284cf00393a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60c91fa27331e9958df48fd5633432e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d13d3dba8d3376f684c3ff8c9a10c726.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1d525d7572797092de16f9b4724da7c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e2fa2c62d988b9c016b77a1f4be70e9.png)
④若不改变带宽
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91edc7e2d4811f5ea6c01284cf00393a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60c91fa27331e9958df48fd5633432e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a5fa65d80544936e2ef93ea4fdd8e94.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f4500e95a6c2a77e0ccb418518c3f6c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/030e7e934455277a8f3c7763a3a2226f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0ec074b5edcfb70d7c3a3c9fb17a721e.png)
您最近一年使用:0次
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484次组卷
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3卷引用:北京市石景山区2021届高三上学期数学期末试题
北京市石景山区2021届高三上学期数学期末试题(已下线)专题9.3 期中押题检测卷(考试范围:第1-4章)3(难)【满分计划】2021-2022学年高一数学阶段性复习测试卷(苏教版2019必修第一册)重庆市求精中学2021-2022学年高一上学期第二次月考数学试题