低水头电站常采用导叶二段关闭装置是为了降低机组在甩负荷时的()。
参考答案:最大水锤压力
基础训练篇(19)
We are all busy talking about and 1. (use) the Internet, but how many of us know 2. history of the Internet?
Many people are 3. (surprise) when they find that the Internet was not set up in the 1960s.At that time, computers were large 4. expensive. Computer networks didn’t work well. If one computer in the network broke 5. , then the whole network stopped. So a new network system had to be set up. It should be good enough to be used by many different computers. If part of the network was working, information could be sent 6. another part. In this way the computer network system would keep on 7. (work) all the time.
The Internet was only used by the government in the 1960s, but in the early 1970s, universities, hospitals and banks were allowed to use it too. However, computers were still very expensive and the Internet was difficult to use. 8. the start of 1990s, computers became cheaper and easier to use. Scientists had also developed software that made “surfing” the Internet more 9. (convenience).
Today it is easy to get online and it is said that millions of people use the Internet every day. 10. (send) emails is more and more popular among students.
The Internet has now become one of the most important parts of people’s life.
读下图,如果把树苗比喻成民族资本主义,则“夏天”和“新的春天”所描述的历史时期应为 ( )
A 19世纪六七十年代、第一次世界大战时期
B 第一次世界大战期间、新中国成立之初
C 甲午中日战争后、国民政府统治时期
D 甲午中日战争后、新中国成立之初