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【单选题】
The word science is heard so often in modern times that almost everybody has some notion of its meaning. The meaning of the term is confusing, but everyone should understand its meaning and objectives. Just to make the explanation as simple as possible, suppose science is defined as classified knowledge. Even in true sciences, distinguishing tact from fiction is not always easy. For this reason great care should be taken to distinguish between beliefs and truths. For example, hypotheses and theories are attempts to explain natural phenomena. From these positions scientists continue to experiment and observe until they are proved. The exact status of any explanation should be clearly labeled to avoid confusion. The objectives of science are primarily the discovery and the subsequent understanding of the unknown. Man cannot be satisfied with recognizing that secrets exist in nature or that questions are unanswerable he must solve them. Toward that end specialists in the field of biology and related fields of interest are directing much of their time and energy. Actually, two basic approaches lead to the discovery of new information. One, aimed at satisfying curiosity, is referred to as pure science. The other is aimed at using knowledge for specific purposes such as improving health, or creating new consumer products. In this case knowledge is put to economic use. Such an approach is referred to as applied science. Sometimes practical-minded people miss the point of pure science in thinking only of its immediate application for economic reward. Chemists responsible for discoveries could hardly anticipated that their findings would one day result in applications of such a practical nature as those directly related to life and death. The discovery of one bit of information opens the door to the discovery of another. However, one should remember that the construction of the microscope had to precede the discovery of the cell. Many scientists dedicating their lives to pure science are not apologetic about ignoring the practical side of their discoveries they know from experience that most knowledge is eventually applied. To define science, we can simply name it as ______.
A.
the study of nature and mankind
B.
an attempt to pose and prove hypotheses and theories
C.
categorized knowledge
D.
the study of unrelated natural phenomena
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【单选题】蛋白质变性后的主要表现是
A.
分子量变小
B.
黏度降低
C.
溶解度降低
D.
不易被蛋白酶水解
【单选题】蛋白质变性后的主要表现是
A.
分子量变小
B.
粘度降低
C.
溶解度降低
D.
不宜被蛋白酶水解
【单选题】蛋白质变性后的主要表现是
A.
分子量变小
B.
生物活性消失
C.
分子量变大
D.
不易被蛋白酶水解
E.
生物活性不变
【单选题】关于卵裂周期特点的描述,下列哪项不正确
A.
对于爪蟾和果蝇,早期的卵裂没有G,和Gz期,只有S和M期
B.
早期胚胎细胞有丝分裂周期短、速度快
C.
哺乳类动物受精卵的发育也遵从相同的规律,卵裂周期也比较短
D.
卵裂的启动实质是卵母细胞减数分裂向有丝分裂转化的过程
E.
卵裂过程中受精卵mRNA可以直接指导蛋白质的翻译,不需要从染色体水平指导蛋白的合成
【简答题】具有司呼吸功能的脏是
【多选题】关于卵裂的特点,下列描述正确的是( )。
A.
有丝分裂,DNA复制迅速。
B.
卵裂球的数量增加,原生质的总量并不增加,甚至还有减少的趋势。
C.
通常卵裂球并非均等分裂,往往较大的一个先分裂,较小的后分裂,造成某瞬间会出现卵裂球为奇数的情况。
D.
兔子的2~8细胞的细胞胚胎的卵裂球具有发育成一个完整胚胎的全能性,绵羊的全能性可保持到8细胞甚至更多的阶段。
E.
发育所需的营养物质来自母体输卵管和子宫。
F.
胚胎发育在透明带内进行。
【单选题】蛋白质变性后的主要表现是()
A.
分子量变小
B.
黏度降低
C.
溶解度降低
D.
不易被蛋白酶水解
E.
溶解度增大
【单选题】具有司呼吸功能的脏是
A.
B.
C.
D.
E.
【单选题】蛋白质变性后的主要表现是
A.
分子量变小
B.
黏度降低
C.
溶解度降低
D.
不易被蛋白酶水解
E.
280nm处光吸收减少
【单选题】蛋白质变性后的主要表现是
A.
相对分子质量变小
B.
粘度降低
C.
溶解度降低
D.
不易被蛋白酶水解
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