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【判断题】
开关电源的效率一般大于线性稳压电源的效率。A.
正确
B.
错误
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皮皮学刷刷变学霸
举一反三
【单选题】Variation in hfeis influenced by ______
A.
junction temperature and collector current
B.
temperature and base current
C.
bias type and device size
D.
device size and base current
【简答题】工业生产纯碱的工艺流程示意图如下 完成下列填空 （1）粗盐水加入沉淀剂A、B除杂质（沉淀剂A来源于石灰窑厂），写出A、B的化学式。 A_____________B____________ （2）实验室提纯粗盐的实验操作依次为：取样、________、沉淀、_________、__________、冷却结晶、_________、烘干。 （3）工业生产纯碱工艺流程中，碳酸化时产生的现象是_______...
【简答题】（14分）工业生产纯碱的工艺流程示意图如下： 完成下列填空： （1）粗盐水加入沉淀剂A、B除杂质（沉淀剂A来源于石灰窑厂），实验室提纯粗盐的实验操作依次为：取样、溶解、沉淀、____、蒸发、冷却结晶、____、烘干。 （2）工业生产纯碱工艺流程中，碳酸化时产生的现象是____。 碳酸化时没有析出碳酸钠晶体，其原因是 ____。 （3）碳酸化后过滤，滤液D最主要的成分是____（填写化学式），检验这...
【简答题】A) She felt it was tiring. B) She felt it was very nice. C).She thought it took less time. D) She thought it was expensive.
【简答题】A．She was impressed by it. B．It was a waste of money. C．She was amazed it had opened so soon. D．She didn't like it as much as the other wings.
【简答题】A．It was stolen. B．It was given a ticket. C．She couldn't find it. D．She found it towed away by the police.
【单选题】Which of the following are components of a time series analysis? (i)Trend (ii)Seasonal variation (iii)Cyclical variation
A.
(i) and (ii) only
B.
(i) and (iii) only
C.
(ii) and (iii) only
D.
(i), (ii) and (iii)
【简答题】A. She was impressed by it. B. It was a waste of money. C. She was amazed that it had opened so soon. D. She didn't like it as much as the other wings.
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