含一个叁键的炔烃，和氢气充分加成后的产物的结构简式为 此炔烃可能有的结构有（ ） A．1种
Sunday evening，October 30，1938，was peaceful in New York City．Some people were returning home from trip to the countryside，and others were sitting down to dinner．In those days，tele
如图为竖直放置的上细下粗的密闭细管，水银柱将气体分隔成A、B两部分，初始温度相同。使A、B升高相同温度达到稳定后，体积变化量为DVA、DVB，压强
已知数列{an}中，a1=a(a＞2)，对一切n∈N*，an＞0，an+1=.（1）求证：an＞2且an+1＜an;（2）证明a1+a2+…+an＜2(n+a-2).
青泥何盘盘， 。扪参历井仰胁息 ， （李白《蜀道难》）
金属钾晶体为体心立方结构，则在单位晶胞中钾原子的个数是 A． 4 B． 3 C． 2 D． 1
Betty doesn`t have enough money to buy that coat. It`s very ___.The price is too_____.A.high, high B.expensive, expensive C.expensive, high D.high, expensive
用平板划线法或稀释涂布平板法纯化大肠杆菌时 ①可以用相同的培养基 ②都需要使用接种针进行接种 ③都需要在火焰旁进
