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【简答题】
细胞学说的创始人是 和 。它的主要内容有1 ;2 ;3 。
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】同步带传动是一种 带传动,是靠带上的齿与带轮上的齿槽的 来传递运动和动力的,工作时带与带轮之间不会产生相对滑动。
【单选题】—He’s seldom asked to speak at the meeting, _ _____ _he_? —_ _____ __, many times.
A.
hasn’t; Yes
B.
has; Yes
C.
is, No
D.
is; Yes
【单选题】Though he failed many times in election, he never lost _____ heart and at last he was elected _____ president of the USA. [ ] A. /; a
B.
a; the
C.
his; the
D.
/; /
【单选题】Though he failed many times in the election, he never lost _______ heart and at last was elected _________President of the USA. A.／；a
B.
a；the
C.
his；the
D.
／；／
【单选题】下列有关带传动表述正确的是( ) A . 420L050 是同步带标记,表示带的长度为 420mm B .同步带传动工作时带与带轮之间不会产生相对滑动,但不能保证精确的传动比 C .同步带传动采用张紧轮,若张紧轮采用与同步带有相同节距的齿形带轮,则张紧轮安装在松边内侧,靠近小带轮处 D .数控机床分段无级高速装置中,电动机通过同步带传动,将动力传至机床主轴
A.
B.
C.
D.
D
【单选题】After he had failed many times, he still said he wouldn ’t _____ the programme.
A.
give up
B.
look up
C.
catch up
【单选题】Though he failed many times in election, he never lost______ heart and at last he was elected_______ President of the USA. A. the ; a
B.
a ; the
C.
his; the
D.
/ ; /
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