【单选题】单向半波可控整流电路,变压器次级电压为20V,晶闸管可能承受的最大反向电压为( )。
【单选题】单向半波可控整流电路,若变压器次级电压为 u 2 ,则输出平均电压的最大值为 ( ) 。
【单选题】For a successful business, friendly and __________ staff are essential
【单选题】We need someone really _____ who can organize the office and make it run smoothly.
【多选题】优先污染物特点是()
A.
难以降解,在环境中有一定残留水平, 具有生物积累性
【判断题】扩展库pandas中DataFrame对象的drop_duplicates()方法可以用来删除重复的数据。
【单选题】The _____ states that it is usually more efficient to use the government policy tool that acts as directly as possible on the source of the distortion separating private and social benefits or costs.
【单选题】单向半波可控整流电路,若变压器次级电压为 U 2 则输出平均电压的最大值为( )。
【简答题】什么是优先污染物?它们大多具有什么样的特点?