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起重机“后退”是指起重机向指挥人员开来()
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参考答案：
举一反三
【多选题】PLC的工作过程主要包括
A.
上电启动
B.
输入刷新
C.
执行用户程序
D.
输出刷新
查看完整题目与答案
【单选题】下列相关实验不能达到预期目的是（　　） 相关实验 预期目的 ① 将SO 2 通入溴水，溴水褪色后加热观察能否恢复原色 验证SO 2 漂白的可逆性 ② 将氯水加入淀粉KI溶液中 验证Cl的非金属性比I强 ③ 在相同温度下，将表面积相同的铝条和镁条投入等体积同浓度的盐酸中，观察产生气泡的速率． 比较同周期金属元素的金属性强弱． ④ 利用电解质溶液的导电性装置，检测AlCl 3 溶液的导电性 证明AlC...
A.
仅①
B.
①④
C.
②③
D.
③④
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【简答题】PLC的主要工作过程的中心内容包括:
查看完整题目与答案
【多选题】How do retroviruses proliferate in host cells?
A.
Like retrotransposons, retroviruses use the enzyme reverse transcriptase to convert RNA into DN The enzyme is encoded by the retroviral genome, and a few molecules of the enzyme are packaged along with the RNA genome in each virus particle. When the single-stranded RNA genome of the retrovirus enters a cell, the reverse transcriptase brought in with it makes a complementary DNA strand to form a DNA/RNA hybrid double helix.
B.
The RNA strand is removed, and the reverse transcriptase (which can use either DNA or RNA as a template) now synthesizes a complementary DNA strand to produce a DNA double helix. This DNA is then inserted, or integrated, into a randomly selected site in the host genome by a virally encoded integrase enzyme. In this integrated state, the virus is latent: each time the host cell divides, it passes on a copy of the integrated viral genome, which is known as a provirus, to its progeny cells.
C.
The next step in the replication of a retrovirus—which can take place long after its integration into the host genome—is the copying of the integrated viral DNA into RNA by a host-cell RNA polymerase, which produces large numbers of single-stranded RNAs identical to the original infecting genome.
D.
These viral RNAs are then translated by the host-cell ribosomes to produce the viral shell proteins, the envelope proteins, and reverse transcriptase—all of which are assembled with the RNA genome into new virus particles.
查看完整题目与答案
【多选题】PLC的工作过程实质上是一个不断循环的顺序扫描过程,其工作的主要过程包括( )
A.
输入采样
B.
执行程序
C.
刷新输出
D.
数据局转换
查看完整题目与答案
【多选题】PLC主要的工作过程包括( )
A.
自诊断
B.
输入扫描
C.
程序执行
D.
输出刷新
查看完整题目与答案
【简答题】American researchers have developed a technique that may become an important tool in fighting virus from attacking its target-cells in the body's defense system．When virus enters the blood，i...
查看完整题目与答案
【简答题】（12分）通过火法冶金炼出的铜是粗铜，含杂质金、银、铁、锌，不适于电器及其他许多工业使用，必须进行电解精炼。 ⑴在精炼铜时，阳极减小的质量与阴极增加的质量是否相等 ▲ （填“是”或“否”）；阳极下面沉积金属的成分主要是 ▲ 。 ⑵在精炼铜的过程中，Cu 2+ 浓度逐渐下降，c(Fe 2+ )、c(Zn 2+ )会逐渐 ▲ ，所以需要定时除去其中的Fe 2+ 、Zn 2+ 。甲同学设计了下列除杂方案...
查看完整题目与答案
【单选题】What occurs when a temperate phage enters a state called lysogeny? ( )
A.
Most viral genes are expressed
B.
The bacterial cell is lysed
C.
Many new viruses are produced
D.
Most normal bacterial functions are turned off.
E.
The virus may become integrated into the host genome.
查看完整题目与答案
【多选题】PLC 主要的工作过程包括( )
A.
自诊断
B.
输入扫描
C.
程序执行
D.
输出刷新
E.
内外通信
查看完整题目与答案
相关题目：
【多选题】PLC的工作过程主要包括
A.
上电启动
B.
输入刷新
C.
执行用户程序
D.
输出刷新
查看完整题目与答案
【单选题】下列相关实验不能达到预期目的是（　　） 相关实验 预期目的 ① 将SO 2 通入溴水，溴水褪色后加热观察能否恢复原色 验证SO 2 漂白的可逆性 ② 将氯水加入淀粉KI溶液中 验证Cl的非金属性比I强 ③ 在相同温度下，将表面积相同的铝条和镁条投入等体积同浓度的盐酸中，观察产生气泡的速率． 比较同周期金属元素的金属性强弱． ④ 利用电解质溶液的导电性装置，检测AlCl 3 溶液的导电性 证明AlC...
A.
仅①
B.
①④
C.
②③
D.
③④
查看完整题目与答案
【简答题】PLC的主要工作过程的中心内容包括:
查看完整题目与答案
【多选题】How do retroviruses proliferate in host cells?
A.
Like retrotransposons, retroviruses use the enzyme reverse transcriptase to convert RNA into DN The enzyme is encoded by the retroviral genome, and a few molecules of the enzyme are packaged along with the RNA genome in each virus particle. When the single-stranded RNA genome of the retrovirus enters a cell, the reverse transcriptase brought in with it makes a complementary DNA strand to form a DNA/RNA hybrid double helix.
B.
The RNA strand is removed, and the reverse transcriptase (which can use either DNA or RNA as a template) now synthesizes a complementary DNA strand to produce a DNA double helix. This DNA is then inserted, or integrated, into a randomly selected site in the host genome by a virally encoded integrase enzyme. In this integrated state, the virus is latent: each time the host cell divides, it passes on a copy of the integrated viral genome, which is known as a provirus, to its progeny cells.
C.
The next step in the replication of a retrovirus—which can take place long after its integration into the host genome—is the copying of the integrated viral DNA into RNA by a host-cell RNA polymerase, which produces large numbers of single-stranded RNAs identical to the original infecting genome.
D.
These viral RNAs are then translated by the host-cell ribosomes to produce the viral shell proteins, the envelope proteins, and reverse transcriptase—all of which are assembled with the RNA genome into new virus particles.
查看完整题目与答案
【多选题】PLC的工作过程实质上是一个不断循环的顺序扫描过程,其工作的主要过程包括( )
A.
输入采样
B.
执行程序
C.
刷新输出
D.
数据局转换
查看完整题目与答案
【多选题】PLC主要的工作过程包括( )
A.
自诊断
B.
输入扫描
C.
程序执行
D.
输出刷新
查看完整题目与答案
【简答题】American researchers have developed a technique that may become an important tool in fighting virus from attacking its target-cells in the body's defense system．When virus enters the blood，i...
查看完整题目与答案
【简答题】（12分）通过火法冶金炼出的铜是粗铜，含杂质金、银、铁、锌，不适于电器及其他许多工业使用，必须进行电解精炼。 ⑴在精炼铜时，阳极减小的质量与阴极增加的质量是否相等 ▲ （填“是”或“否”）；阳极下面沉积金属的成分主要是 ▲ 。 ⑵在精炼铜的过程中，Cu 2+ 浓度逐渐下降，c(Fe 2+ )、c(Zn 2+ )会逐渐 ▲ ，所以需要定时除去其中的Fe 2+ 、Zn 2+ 。甲同学设计了下列除杂方案...
查看完整题目与答案
【单选题】What occurs when a temperate phage enters a state called lysogeny? ( )
A.
Most viral genes are expressed
B.
The bacterial cell is lysed
C.
Many new viruses are produced
D.
Most normal bacterial functions are turned off.
E.
The virus may become integrated into the host genome.
查看完整题目与答案
【多选题】PLC 主要的工作过程包括( )
A.
自诊断
B.
输入扫描
C.
程序执行
D.
输出刷新
E.
内外通信
查看完整题目与答案
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