Fick第一定律中的负号表示扩散方向与浓度降低方向( )。
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1、从热力学角度看,扩散的真正推动力是由浓度梯度的不同引起的,各组元的原子总是由高浓度扩散到低浓度。( )
A. 对
B. 错
质点按空位扩散结构进行扩散时,空位扩散活化能仅包括空位迁移能。( )
A. 对
B. 错
I' d like to order a table _____four_____this Friday.
A. to; on
B. for; for
C. for; at
D. from;in
The person who pays the bill is usually seated with his ______ to the wall.
A. hand
B. face
C. back
D. head