题目内容
对于离心泵的说法：①为了防止发生气缚，启动前需要灌泵；②为了输送达到需要的流量，应在离心泵启动前打开出口阀；③为了防止压出管中的高压液体倒流，停车前应先关闭出口阀；④通过设计回流支路调节流量；⑤理论上只要泵具有足够的机械强度，其压头可达到无穷大，与输送的流量大小无关；⑥为了不发生汽蚀，应控制一定的安装高度。正确的说法是（）
查看答案
搜索结果不匹配？点我反馈
更多问题
Aron Renate---was my best friend.We attended Brough School until I moved away in 1997,then we lost contact.She was redheaded like her mother.Any info pls send to Irene Zuckerbraun at e-mail:lenz2265@sbcglobal.net.What is it（）
Take two tablets with water,followed by one tablet every eight hours,as required.For maximum night-time and early morning relief,take two tablets at bed-time,Do not take more than six tablets in twenty-four hours.Reduce the amount if nervousness,restlessness,or sleeplessness occursIf one cannot sleep,it is suggested that he（）.
各种入侵检测技术中，（）入侵检测技术采用了非集中的系统结构和处理方式，相对于传统的单机IDS具有检测大范围的攻击行为、提高检测准确度、协调响应等优势。
(B)Londoners are great readers.They buy large numbers of newspapers and magazines and of books---especially paperbacks,which are comparatively cheap in spite of ever increasing rises in the cost of printing.They still continue to buy“proper”books,too,printed on good paper and bound between hard covers.There are many streets in London containing shops which specialize in book selling.Perhaps the best known of these is Charring Cross Road in the very heart of London.Here books of all kinds and sizes are to be found,from“the biggest bookshop in the world”to“the tiny,dusty little places which seem to have been left over from Dickens’time.Some of the shops stock or will obtain any kind of books,but many of them specialize in second-hand books,in art books,in foreign books,in books on philosophy,politics or any other various subjects about which books may be written.Although it may be the most convenient place for Londoners to buy books,Charring Cross Road is not the cheapest.For the really cheap second-hand volumes,the collector must turn to Farringdon Road,for example,in the East Central District of London.Here there is nothing as great as bookshops.Instead,the booksellers come along each morning and tip out their sacks of books on to small barrows(流动售货车).And the collectors,some professional,and some just like it,who have been waiting for them,rushed to those dusty places.In places like this one can still,occasionally,pick up for a few pence an old volume that may be worth many pounds. “Londoners are great readers”means that（）.
微信支付 
支付宝支付