研究人员还表示,在佩特里培养皿中的脑细胞前体可以发育成神经元.The researchers also showed that the progenitors mature into neurons in Petri dishes.植树细胞中丙氨酸和亮氨酸 、 缬氨酸的主要前体是丙酮酸.In plant cells the principal precursor of alanine , as well as leucine and v...
He stopped at the mailbox and dropped the letter in.他在邮筒前停了下来,把信投了进去.He stuck down the envelope and dropped it into the mailbox.他把信封粘好后便投进邮筒.He then dropped both the fire and the ice into the mailbox.他把冰和火一起投进了邮筒....