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【简答题】
与选择性激光烧结工艺类似的还有 和电子束熔化。
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【判断题】金属受到污染后可能引起加工时出现脆性或裂纹,在回用料、焊料中带入微量的铅就会使合金材料受到污染,其它的脆性污染物包括硅、硫和其它低熔点金属,要注意回用料的管理,成分不明确的材料不能随便使用,要先进行分析,检查有无这样的杂质。
A.
正确
B.
错误
【简答题】 第二节 (共 5 小题;每小题 2 分,满分 10 分) 根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。 What does it take to be successful? Many books have been written about the secrets of success. ____16____ Four key qualities st...
【单选题】听力原文: The home is the central focus of most young people's lives in Britain, particularly for those who are still attending school. The majority rely upon their home environment as a place of security...
A.
At school.
B.
At home.
C.
At Youth Clubs.
D.
At Youth Centers.
【简答题】金属材料包括铁、铜、铝等纯金属和合金。 ( 1 )因性能优良,被认为 21 世纪的重要金属材料的是 及其合金(填单质名称); ( 2 )铝具有较好的抗腐蚀性能,是因为铝与空气中氧气反应,其表面生成一层致密的氧化膜,则生成该氧化膜的化学方程式为 ; ( 3 )现代以来,人们对金属的认识不断深入,助推多种新材料的研制与使用。飞机的制造中会使用很多新材料,其中有锂铝合金,在飞机制造中使用该材料不能说明其...
【单选题】听力原文: The home is the central focus of most young people's lives in Britain, particularly for those who are still attending school. The majority rely upon their home environment as a place of security...
A.
At school.
B.
At home.
C.
At Youth Clubs.
D.
At Youth Centers.
【单选题】关于三极管的结构特点,以下说法不正确的为( )
A.
基区很薄
B.
基区掺杂浓度最高
C.
发射区掺杂浓度最高
D.
发射结的结面积小于集电结的结面积
【单选题】一般初产妇开始自觉胎动的时间是在妊娠的第
A.
12-15周
B.
16-20周
C.
22-24周
D.
25-26周
E.
27周以后
【单选题】一般初产妇开始自觉胎动的时间是在妊娠的第
A.
12~15周
B.
18~20周
C.
22~24周
D.
25~26周
E.
27周以后
【单选题】Areas where students have particular difficulty________ have been treated particular care.
A.
by
B.
in
C.
under
D.
with
【简答题】 The qualities that truly ___ Winston Churchill _____ were his determination and his ability to inspire others.
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