动物体的主轴一般与口有密接关系,主轴的一端大都为口。因此把主轴的这一极称为口极。由于左右对称动物的口极也是在身体的前端,所以可称为前极(anterior pole),有时也称为吻极(rostralpole)。在辐射对称的动物,其口极因动物不同,或位于上端,或位于下端中部。与主轴口极相反的一侧称为反口极。在左右对称的动物也称为后极(poste-rior pole)。棘皮动物反口极的自然位置在身体的上方。
为了检查一个卵细胞的染色体是否异常,医生用激光在卵细胞外膜上切一小口,通过这个小口抽取极体及其所含的染色体。
To check an egg for chromosomal abnormalities, doctors use a laser to make a small incision in the outer membrane, which allows them to extract the polar body and the chromosomes it contains.
一百五十七页的长度,这本书极惹人喜爱,很容易坐下来一口气读完。
One hundred fifty-seven pages in length, the book is so winsome that it is easy to read in a single sitting.
语音识别部分由软件编程实现,通过串行口编程进行通信,控制单片机,它成功实现控制发光二极管和语音播放的目的。
The voice recognition part is realized by software programming, the microcontroller is controlled by communicating with serial port, it can successfully realize to control the LED and voice broadcast.
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