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【单选题】
. 双绞线由两条相互绝缘的导线绞合而成,下列关于双绞线的叙述,不正确的是
A.
它既可以传输模拟信号,也可以传输数字信号
B.
安装方便,价格较低
C.
不易受外部干扰,误码率较低
D.
通常只用作建筑内局域网的通信介质
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参考答案：
举一反三
【简答题】在主视图上能看到物体的长和高,在俯视图上能看到物体的( ) 和( ) ,在左视图上能看到物体的( ) 和( ).
查看完整题目与答案
【单选题】The signal sequence for export from the nucleus is ____________________________.
A.
-Met-Glu-Glu-Leu-Ser-Gln-Ala-Leu-Ala-Ser-Ser-Phe-
B.
-Met-Glu-Glu-Leu-Ser-Gln-Ala-Leu-Ala-Ser-Ser-Tyr-
C.
-Met-Glu-Glu-Leu-Ser-Glu-Ala-Leu-Ala-Ser-Ser-Phe-
D.
-Met-Glu-Glu-Lys-Ser-Gln-Ala-Leu-Ala-Ser-Ser-Phe-
查看完整题目与答案
【简答题】如图，小华家的住宅楼AB与北京奥运会主体育场鸟巢隔水相望且能看到鸟巢的最高处CD，两建筑物的底部在同一水平面上，视野开阔，但不能直接到达，小华为了测量鸟巢的最大高度CD，只能利用所在住宅楼的地理位置．现在小华仅有的测量工具是皮尺和测角仪（皮尺可测量长度，测角仪可测量仰角、俯角），请你帮助小华设计一个测量鸟巢的最大高度的方案． （1）要求写出测量步骤和必需的测量数据（用字母表示）并画出测量图形（测角...
查看完整题目与答案
【单选题】What is one function of a signal sequence?
A.
to direct an mRNA molecule into the cisternal space of ER
B.
to bind RNA polymerase to DNA and initiate transcription
C.
to terminate translation of the messenger RNA
D.
to attach ribosomes synthesizing secretory proteins to the ER
查看完整题目与答案
【单选题】美国直接插手 ( ), 阻挠中国人民完成祖国统一大业 , 致使海峡两岸的中国人至今仍处于分离状态。
A.
台湾问题
B.
朝核问题
C.
香港问题
D.
澳门问题
查看完整题目与答案
【多选题】How is a double-pass transmembrane protein with an internal ER signal sequence retained in the lipid bilayer?
A.
In some transmembrane proteins, an internal, rather than an N-terminal, signal sequence is used to start the protein transfer; this internal signal sequence, called a start-transfer sequence, is never removed from the polypeptide.
B.
This arrangement occurs in some transmembrane proteins in which the polypeptide chain passes back and forth across the lipid bilayer. In these cases, hydrophobic signal sequences are thought to work in pairs: an internal start-transfer sequence serves to initiate translocation, which continues until a stop-transfer sequence is reached; the two hydrophobic sequences are then released into the bilayer, where they remain as membrane-spanning α helices.
C.
In complex multipass proteins, in which many hydrophobic α helices span the bilayer, additional pairs of start- and stop-transfer sequences come into play: one sequence reinitiates translocation further down the polypeptide chain, and the other stops translocation and causes polypeptide release, and so on for subsequent starts and stops.
D.
In this way, multipass membrane proteins are stitched into the lipid bilayer as they are being synthesized, by a mechanism resembling the workings of a sewing machine.
查看完整题目与答案
【单选题】The typical sorting signal on a protein is a continuous stretch of amino acid sequence, typically ________ amino acids long. This signal sequence is often (but not always) removed from the finished pr...
A.
10–30
B.
10–60
C.
15–40
D.
15–60
查看完整题目与答案
【单选题】由于石灰浆硬化时（ ），以及硬化强度低等特点，所以不宜单独使用。
A.
吸水性大
B.
需水量大
C.
体积收缩大
D.
体积膨胀大
查看完整题目与答案
【多选题】下列各项中,应按照“生活服务业”计算缴纳增值税的是( )。
A.
出租文化场所
B.
经营网吧
C.
经营音乐茶座
D.
金融经纪业务
查看完整题目与答案
【单选题】第4题中杂质限量值为( )
A.
4%
B.
0.4%
C.
2.5%
D.
0.25%
查看完整题目与答案
相关题目：
【简答题】在主视图上能看到物体的长和高,在俯视图上能看到物体的( ) 和( ) ,在左视图上能看到物体的( ) 和( ).
查看完整题目与答案
【单选题】The signal sequence for export from the nucleus is ____________________________.
A.
-Met-Glu-Glu-Leu-Ser-Gln-Ala-Leu-Ala-Ser-Ser-Phe-
B.
-Met-Glu-Glu-Leu-Ser-Gln-Ala-Leu-Ala-Ser-Ser-Tyr-
C.
-Met-Glu-Glu-Leu-Ser-Glu-Ala-Leu-Ala-Ser-Ser-Phe-
D.
-Met-Glu-Glu-Lys-Ser-Gln-Ala-Leu-Ala-Ser-Ser-Phe-
查看完整题目与答案
【简答题】如图，小华家的住宅楼AB与北京奥运会主体育场鸟巢隔水相望且能看到鸟巢的最高处CD，两建筑物的底部在同一水平面上，视野开阔，但不能直接到达，小华为了测量鸟巢的最大高度CD，只能利用所在住宅楼的地理位置．现在小华仅有的测量工具是皮尺和测角仪（皮尺可测量长度，测角仪可测量仰角、俯角），请你帮助小华设计一个测量鸟巢的最大高度的方案． （1）要求写出测量步骤和必需的测量数据（用字母表示）并画出测量图形（测角...
查看完整题目与答案
【单选题】What is one function of a signal sequence?
A.
to direct an mRNA molecule into the cisternal space of ER
B.
to bind RNA polymerase to DNA and initiate transcription
C.
to terminate translation of the messenger RNA
D.
to attach ribosomes synthesizing secretory proteins to the ER
查看完整题目与答案
【单选题】美国直接插手 ( ), 阻挠中国人民完成祖国统一大业 , 致使海峡两岸的中国人至今仍处于分离状态。
A.
台湾问题
B.
朝核问题
C.
香港问题
D.
澳门问题
查看完整题目与答案
【多选题】How is a double-pass transmembrane protein with an internal ER signal sequence retained in the lipid bilayer?
A.
In some transmembrane proteins, an internal, rather than an N-terminal, signal sequence is used to start the protein transfer; this internal signal sequence, called a start-transfer sequence, is never removed from the polypeptide.
B.
This arrangement occurs in some transmembrane proteins in which the polypeptide chain passes back and forth across the lipid bilayer. In these cases, hydrophobic signal sequences are thought to work in pairs: an internal start-transfer sequence serves to initiate translocation, which continues until a stop-transfer sequence is reached; the two hydrophobic sequences are then released into the bilayer, where they remain as membrane-spanning α helices.
C.
In complex multipass proteins, in which many hydrophobic α helices span the bilayer, additional pairs of start- and stop-transfer sequences come into play: one sequence reinitiates translocation further down the polypeptide chain, and the other stops translocation and causes polypeptide release, and so on for subsequent starts and stops.
D.
In this way, multipass membrane proteins are stitched into the lipid bilayer as they are being synthesized, by a mechanism resembling the workings of a sewing machine.
查看完整题目与答案
【单选题】The typical sorting signal on a protein is a continuous stretch of amino acid sequence, typically ________ amino acids long. This signal sequence is often (but not always) removed from the finished pr...
A.
10–30
B.
10–60
C.
15–40
D.
15–60
查看完整题目与答案
【单选题】由于石灰浆硬化时（ ），以及硬化强度低等特点，所以不宜单独使用。
A.
吸水性大
B.
需水量大
C.
体积收缩大
D.
体积膨胀大
查看完整题目与答案
【多选题】下列各项中,应按照“生活服务业”计算缴纳增值税的是( )。
A.
出租文化场所
B.
经营网吧
C.
经营音乐茶座
D.
金融经纪业务
查看完整题目与答案
【单选题】第4题中杂质限量值为( )
A.
4%
B.
0.4%
C.
2.5%
D.
0.25%
查看完整题目与答案
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