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【简答题】
用波长 l =632.8nm 的平行光垂直入射在单缝上,缝后用焦距 f=50cm 的凸透镜把衍射光会聚于焦平面上。测得中央明条纹的宽度为 3.4mm ,则单缝的宽度 b=___mm 。 ( 结果保留两位有效数据 )
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【判断题】制造直径为 200mm 的轴应选用 45 钢而不应选 42CrMo 钢。 prefix="o" ns="urn:schemas-microsoft-com:office:office" ?xml:namespace>
A.
正确
B.
错误
【简答题】YB32—200 型压力机液压系统由哪些基本回路组成? prefix="o" ns="urn:schemas-microsoft-com:office:office" ?xml:namespace>
【判断题】某种碳钢的牌号是 ZG200-400,那么它是一种铸钢。 ( ) prefix="o" ns="urn:schemas-microsoft-com:office:office" ?xml:namespace>
A.
正确
B.
错误
【简答题】( ) While the hot pot is kept simmering, ingredients are placed into the pot and are cooke d at the tabl e .
【单选题】As concern over Alzheimer's disease grows, more Americans are turning to expensive and potentially unsafe supplements that claim to enhance memory. But prevention of age-related memory loss may be no ...
A.
lose their memory when they grow old.
B.
lose the ability to protect themselves.
C.
result in inflammation and oxidation.
D.
die a few years after the disease is detected.
【单选题】The flowers_in the big pot are sunflowers.
A.
are planted
B.
were planted
C.
plant
D.
planted
【简答题】YB32—200 型液压压力机液压系统工作原理是什么? prefix="o" ns="urn:schemas-microsoft-com:office:office" ?xml:namespace>
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