The current is the charge flow per unit time. 電流是每單位時(shí)間流動(dòng)的電荷。
Perhaps a key adaptive advantage of the angiosperm is their ability to construct wood with much less expenditure of energy per unit weight. 也許被子植物適應優(yōu)勢的秘訣就在于它們有能力形成每單位重量的木材可支付少得多的能。