医学研究表明:偏硅酸有软化血管的作用,对心脏病、高血压有一定的疗效.偏硅酸中含有

题型:选择题

问题:

医学研究表明:偏硅酸有软化血管的作用,对心脏病、高血压有一定的疗效.偏硅酸中含有硅含有硅、氢、氧三种元素,其中硅的化合价为+4价,则其化学式为 [ ]

A.H2SiO4

B.H2SiO3

C.Na2SiO3

D.SiO2

考点:化学式的写法和意义化合价的求法
题型:选择题

下列运动属于平移的是

A.旋转的风车

B.体育比赛中,运动员跳高的整个过程

C.坐在直线行驶的列车上的乘客

D.游乐场里正在荡秋千的人

题型:选择题

下列关于职业病的特点论述错误的是()。

A.控制职业有害因素可消除和减少发病

B.病因大多是可检测的

C.长期接触职业有害因素即可发病

D.接触同一有害因素的人群中很少只有一个发病

E.早期诊断,及时治疗,预后较好

题型:选择题

通过单独反映筹资活动产生的现金流量,可以了解获得未来收益和现金流量而导致资。源转出的程度,以及以前的资源转出带来的现金流入的信息。( )

题型:选择题

下列

不属于

外部感觉的是

A.视觉
B.听觉
C.味觉
D.触觉
E.运动觉

题型:选择题

Few creatures on earth are as cute as the black lion tamarin, and few have as dramatic a story line. Pug-nosed and diminutive, with a comic fringe of hair, these monkeys dwell in trees in small tracts of forest in southeastern Brazil. Or they did until 1905, when they were declared extinct. No one saw a black lion tamarin again in the wild until 1970. Later, in the 1990s, some Brazilian researchers turned up a small set of isolated, inbred populations scattered over a wide region. Since that time, they have been engineering tamarin migration, doing everything they can to save the world’s most distinctive primates.
Although they are no larger than house cats, tamarins have brains big for their size and a family life organized like our own. They live in groups anchored by an adult male andadult female, along with their offspring. When a mother bears young, she usually produces twins, and although members of the group share in their upbringing, it is most often the father who carries them around in the trees, where the families feed on fruits, insects and bird’s eggs.
Unhappily for the lion tamarins, their tree-bound niche began to disappear after the Portuguese landed in Brazil and began clearing forest to make room for Rio de Janeiro, the settlements and farms. As is the case for so many threatened species, the breakup of their habitat sounded the death knell for tamarins, depriving them of the continuity of forest they require to remain abundant and safe from potential threats in any single vicinity. The animals avoid predators by hardly ever coming down from the trees, so even a narrow logging road through a forest can begin the breakup by preventing them from moving from one patch of forest to another.
A simple solution was to build bridges across roads, allowing the monkeys to move from one forest to another. With some lumber and the researchers’ work, habitats that had been separated became continuous again, improving opportunities for migrating and mating.
The next step was to broaden the distribution of the population. The researchers captured two families of black lion tamarins and moved them to a new forest. After a year, the moves were declared a success: Not only had 80 percent of the tamarins survived, but they had also produced new offspring. So far, so good. The researchers had learned the animals could adjust to the new habitats, even if the insects there tasted a little different or the trees were a slightly different size.
The techniques for saving species in the wild vary. Species with less stringent habitat requirements, like wild turkeys, have been rescued by moving them into new settings as well as outlawing their killing. More challenging to preserve are species that require a lot of land, like elephants, and species that have highly specific requirements for habitat and prey -- like black-footed ferrets. Ultimately, as in all challenges, knowledge is power to save wild species from extinction.

What did the researchers learn from the second step

A.The trees in the new forest were in different size.

B.The insects in the new forest had a different taste.

C.Tamarins could get used to the new environment.

D.Above 80% of tamarins survived.

更多题库