问题 问答题 简答题

信噪比的定义及影响信噪比的因素是什么?

答案

参考答案:

信噪比的定义是组织信号与附加于组织信号中随机背景信号之比值。它与观察视野(FOV)的平方成正比;与层厚及层间距成正比;与平均次数的平方要成正比;TE愈长则信噪比越低;此外它还与TR、TE、TI、B0强度及线圈种类有关,总之信噪比是一个相当复杂的参数。

单项选择题

2009年是中央应对全球金融危机扩内需、保增长的关键之年,也是四川全面实施灾后恢复重建的重要一年。在政府性项目建设资金大规模投放的带动下,全省固定资产投资需求得到迅速释放,全社会投资快速增长,分月投资基本保持千亿元规模,全年投资总量顺利突破万亿大关,达到12020.73亿元,同比增长58.1%,比2007年翻一番。其中6~12月投资额分别为1297亿元、1003亿元、971亿元、1162亿元、1058亿元、1086亿元、1181亿元,12月当月完成投资额同比增长14.8%。

全省第一产业投资524.6亿元,增长61.7%,占全社会投资的比重较2008年提高0.1个百分点,比2007年提高1.1个百分点。第一产业投资中,农业投资105.7亿元,同比增长63.1%;林业投资53.1亿元,同比增长60.3%;畜牧业投资115.5亿元,同比增长53.6%;农林牧渔服务业投资120.39亿元,同比增长126.5%。

全省第二产业完成投资4592.2亿元,比上年增长48%。第二产业投资中,工业投资持续稳步回升,全年完成投资4482.7亿元,比2008年增长45.6%。工业投资占全社会投资的比重自8月以来,已连续4个月上涨,由8月的36.6%逐步上升到37.3%。

在扩大内需政策的促进下,全省第三产业投资快速增长,全年完成投资6904亿元,增速比同期全社会投资快7.2个百分点,成为拉动全社会投资快速增长的主要动力。交通运输业完成投资1249.3亿元,增长91.4%,快于同期全社会33.3个百分点,其中铁路运输投资发展迅速,全年完成投资267.2亿元,增长1.6倍;居民服务和其他服务业、教育、卫生社会保障和社会福利业、文化体育和娱乐业、公共管理和社会组织等行业投资增速均超过一倍。

2008年,四川省第一产业投资额比2007年增长了约()。

A.65.3%

B.61.8%

C.57.2%

D.68.7%

完形填空

根据短文,把下列句子补充完整。(5分)

One day , Mrs.Wilson took Tracy and Aben shopping . They went to the supermarket in the new shopping center .

“ Why do you buy things here ?” Tracy wanted to know .

“ Because it is cheaper here than the store on the corner ,” Mrs.Wilson said . “ Help me check the price .”

The Wilsons were not rich , so Mrs.Wilson was always careful with her money . She looked carefully at the prices of things .

She bought a lot of things in the supermarket . When they got home , the children said , “We don’t think you saved any money by going to the supermarket .”

“ Of course , I did ,” Mrs.Wilson said , “ Everything was cheaper there .”

“ We know ,”the children said , “But we came home by taxi because we had too much to carry .The taxi fare was more than the money that you saved !”

Mrs.Wilson added everything up . Her children were right .

“ Well done ,” she said . “ Next time we’ll do our shopping near our home .”

小题1:Mrs.Wilson went to the supermarket to _______ things because they are ________ there .

小题2: Mrs.Wilson was always _________ with her money because the Wilsons were ________ .

小题3: Mrs.Wilson’s ______ helped her check the ________ when they were in the supermarket .

小题4: After they did some shopping , Mrs.Wilson and her children went home ______ _______.

小题5: The Wilsons couldn’t walk home because it was too _______ away from the supermarket to their home , and they had too __________ things .