若要将位于显微镜视野左下方的物像移动到视野中央,应往哪个方向移动玻片标本() A

题型:选择题

问题:

若要将位于显微镜视野左下方的物像移动到视野中央,应往哪个方向移动玻片标本(  )

A.右下方

B.左下方

C.右上方

D.左上方

考点:显微镜的构造和使用
题型:选择题
阅读下面短文,请从方框中选出适当的句子填人文中的适当位置,使短文内容完整正确。
     In the United States and Canada, people often invite friends for a meal or a party.
         1     "Would you like to come over for dinner tonight?" "Hey, we are having a party on Friday.
Can you come?" _   2  _ either say thank you and accept (接受), or say sorry and give an excuse
(借口) Sometimes, however( 然而), what people say is like invitation but which are not real invitations.  
For example.  "    3     " "Let's get together for lunch soon."They are not real invitations because they
don't talk about the date or the time.     4     To reply to this, people just say "Sure, that would be great."
or " OK, thank you."_  5      listen carefully.  Is it a real invitation or is the person just being friendly?
So next time you hear what is like an invitation,
Here are the kinds of things people always say.
To reply to an invitation,
They just show that the person is trying to be friendly.
Please come over for a drink sometime.
题型:选择题

细心观察,准确判断,是科学探究的基本素质之一.请根据实际情况填上合适的单位.氢气的密度为0.09______;一个鸡蛋的质量为50______;某变电站高压输电电压为220______.

题型:选择题

蚂蚁是同学们熟悉的昆虫,一到夏天我们就能看到它们忙碌的身影。

(1)蚂蚁有雄蚁、蚁后、工蚁和兵蚁之分,不同成员之间分工合作,共同维持蚁群的生活,这说明蚂蚁具有               行为。研究表明,工蚁发现食物后会迅速返回蚁穴,依靠气味招来许多蚂蚁共同搬运食物,这说明蚂蚁群体之间存在着              

(2)蚂蚁的发育要经过卵、幼虫、          、成虫四个时期,而且幼虫与成虫在形态结构和生活习性上有明显差别,像这样的发育过程称为变态发育中的                       

题型:选择题

三个进程P1、P2、P3互斥使用一个包含N(N>0)个单元的缓冲区。P1每次用produce()生成一个正整数并用put()送入缓冲区某一空单元中;P2每次用getodd()从该缓冲区中取出一个奇数并用countodd()统计奇数个数;P3每次用geteven()从该缓冲区中取出一个偶数并用counteven()统计偶数个数。请用信号量机制实现这三个进程的同步与互斥活动,并说明所定义的信号量的含义。要求用伪代码描述。

题型:选择题

被称为二十世纪最突出贡献的科学家是()

A、康克

B、哈勃

C、霍金

D、拉普拉斯

更多题库