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【简答题】
原子是由原子核和电子构成的。原子核在原子中所占体积极小，其半径约为原子半径的十万分之一，因此，相对而言，原子里有很大的空间。α微粒是带两个单位正电荷的氦原子。1911年，科学家用一束平行高速运动的α微粒轰击金箔时（金原子的核电荷数为79，相对原子质量为197），发现三种实验现象： （1）有一小部分α微粒改变了原来的运动路径,原因是α微粒途经金原子核附近时，受到斥力而稍微改变了运动方向。 （2）大多数α微粒不改变原来的运动方向，原因是______________________。 （3）极少数α微粒被弹了回来，原因是___________________。
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【简答题】specter giddy ultimately vilified contaminated outstripping proceeded supply indefinitely enhance In previous time, when fresh meat was in short _______, pigeons were kept by many households a...
【简答题】晶体三极管的等效理解。晶体三极管工作在截止状态时,C E 之间相当于开关________(闭合/断开);工作在饱和状态时,C E 之间相当于开关________(闭合/断开);工作在放大状态时,C E 之间相当于________。
【单选题】In the history of the hotel industry, thecharacteristicsoftheinn periodwas that（ ）
A.
the hotel facilities were primitive , and the price was low.
B.
the h otel s o ffered luxury facilities and services , and t he expense was prohibitive.
C.
the h otel s were clean , comfortable , and affordable
D.
famous hotel chains expanded rapidly all over the world .
【单选题】In the history of the hotel industry, thecharacteristicsofthemodern hotel period was that（ ）
A.
t he hotel facilities were Primitive , and the price was low.
B.
the h otel s o ffered luxury facilities and services , and t he expense was prohibitive.
C.
the h otel s were clean , comfortable , and affordable.
D.
f amous hotel chains expand ed rapidly all over the world .
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