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【单选题】
在介质中,由于微粒的热运动而产生的质量迁移现象,主要是由于密度差引起的,这种现象称为( )A.
数量极移动
B.
扩散现象
C.
细胞悬浮
D.
分离沉降
E.
重力场作用
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举一反三
【单选题】My brother _______ while he _______ his bicy c le and h u rt himself
A.
f ell , was riding
B.
fell , is riding
C.
had fallen, rode
D.
had fallen. was riding
【单选题】A man has genotype A1A2 G1G2 (one each of the A1 and A2 alleles of gene A, and one each of the G1 and G2 alleles of gene G) The A and G loci are on different chromosomes. What gametes will a single me...
A.
2 of A1A2, 2 of G1G2
B.
1 of A1A1, 1 of A1G1, 1 of A2G1, 1 of G1G2
C.
1 of A1, 1 of A2, 1 of G1, 1 of G2
D.
1 of A1G1, 1 of A1G2, 1 of A2G1, 1 of A2G2
E.
None of the above
【单选题】A man has genotype A1A2 G1G2. (one each of the A1 and A2 alleles of gene A, one each of the G1 and G2 alleles of gene G ) The A and G loci are on difference chromosomes. What gametes will many meioses...
A.
1/2 A1A2, 1/2 G1G2
B.
1/4 A1A1, 1/4 A1G1, 1/4 A2G1, 1/4 G1G2
C.
1/4 A1, 1/4 A2, 1/4 G1, 1/4 G2
D.
1/4 A1G1, 1/4 A1/G2, 1/4 A2G1, 1/4 A2G2
E.
None of the above
F.
More information is needed
【简答题】根的初生木质部发育方式是（），而茎的初生木质部的发育方式是（）。
【单选题】A man has genotype A1A1, G1G2. (He has two copies of the A1 allele of gene A, one copy each of the G1 and G2 alles of gene G). The A and G genes are on different chromosomes. What gametes will a singl...
A.
2 of A1A1, 2 of G1G2
B.
1 of A1A1, 1 of A1G1, 1 of A1G2, 1 of G1G2
C.
2 of A1G1, 2 of A1G2
D.
2 of A1, 1 of G1A2, 1 of G2
E.
None of the above
F.
More information is needed
【简答题】轴的直径为30mm,材料为低碳钢,F=500N,M=100Nm受力如图,(1)确定轴的危险点,并画出危险点的应力状态;(2)求出轴危险点的主应力;(3)按第三强度理论计算其相当应力。
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