试 | | 3%淀粉溶 | 2%α-淀粉酶溶 | 1 min 后用碘液检 |
1 | 50 ℃ | 2 mL | 1 mL | 溶液呈棕黄色 |
2 | 55 ℃ | 2 mL | 1 mL | 溶液呈棕黄色 |
3 | 60 ℃ | 2 mL | 1 mL | 溶液呈棕黄色 |
注:溶液呈棕黄色即表示没有检测出淀粉以下改进措施中可行的是 ( )。
A. 将实验温度改为 0 ℃、55 ℃、100 ℃
B. 将淀粉溶液体积改为 4 mL
C. 将 α-淀粉酶溶液浓度改为 3%
D. 将碘液改为斐林试剂
下图示意北京市 2018 年、 2019 年空气质量 “ 成绩单 ” 。据此回答下题。
下列说法正确的是( )
①四项污染物均达到国家标准。
②四项污染物的浓度均有所下降,二氧化硫年均浓度最低。
③空气质量持续改善,趋势向好。
④四项污染物中降幅最大的污染物类型为二氧化硫。
⑤除二氧化硫达标外,其他三项污染物均未达标,大气质量改善进程仍然艰巨。
A . ①②③ B . ①③⑤ C . ②③⑤ D . ①②④
材料 农奴制改革前,俄国出口商品主要包括粮食、亚麻、兽皮、皮货、木材等,粮食占出口额的35%以上;进口商品主要为工业品,即工厂所需的机器和设备、颜料、皮棉、煤。从1822年起,俄国对进口商品实行高关税,对外国商品的输入进行限制,农奴制改革后,俄国的出口结构中,农产品仍然占最大份额,粮食占出口额一半以上,主要出口英国,由于工业急需金属、机器和设备,俄国降低了保护关税税率,使进口机器的支出由1861~1865年的730万卢布增加到1876~1880年的4680万卢布。到90年代,与改革前相比,俄国对外贸易额增加2倍以上。
——摘编自(苏)B.T.琼图洛夫等编《苏联经济史》
(1)根据材料,概括俄国农奴制改革前后对外贸易的变化。
(2)根据材料并结合所学知识,简析对外贸易发生变化的原因。
For the past five years, Paula Smith, a historian of science, has devoted herself to re-creating long-forgotten techniques. While doing research for her new book, she came across a 16th-century French manuscript(手稿)consisting of nearly 1,000 sets of instructions, covering subjects from tool making to finding the best sand.
The author's intention remains as mysterious(神秘)as his name; he may have been simply taking notes for his own records. But Smith was struck mainly by the fact that she didn't truly grasp any of the skills the author described. "You simply can't get an understanding of that handwork by reading about it," she says.
Though Smith did get her hands on the best sand, doing things the old-fashioned way isn't just about playing around with French mud. Reconstructing the work of the craftsmen(工匠)who lived centuries ago can reveal how they viewed the world, what objects filled their homes, and what went on in the workshops that produced them. It can even help solve present-day problems: In 2015, scientists discovered that a 10th-century English medicine for eve problems could kill a drug-resistant virus.
The work has also brought insights for museums, Smith says. One must know how on object was made in order to preserve it. What's more, reconstructions might be the only way to know what treasures looked like before time wore them down. Scholars have seen this idea in practice with ancient Greek and Roman statues. These sculptures were painted a rainbow of striking colours. We can't appreciate these kinds of details without seeing works of art as they originally appeared-something Smith believes you can do only when you have a road map.
Smith has put the manuscript's ideas into practice. Her final goal is to link the worlds of art and science back together: She believes that bringing the old recipes to life can help develop a kind of learning that highlights experimentation, teamwork, and problem solving.
Back when science—then called “the new philosophy”—took shape, academics looked to craftsmen for help in understanding the natural world. Microscopes and telescopes were invented by way of artistic tinkering(修补), as craftsmen experimented with glass to better bend light.
If we can rediscover the values of hands-on experience and craftwork, Smith says, we can marry the best of our modern insights with the handiness of our ancestors.
38.How did Smith, feel after reading the French manuscript?
A.Confused about the technical terms.
B.Impressed with its detailed instructions.
C.Discouraged by its complex structure.
D.Shocked for her own lack of hand skills.
39.According to Smith, the reconstruction work is done mainly to _____________.
A.restore old workshops B.understand the craftsmen
C.improve visual effects D.inspire the philosophers
40.Why does the author mention museums?
A.To reveal the beauty of ancient objects.
B.To present the findings of old science.
C.To highlight the importance of antiques.
D.To emphasise the values of hand skills.
41.Which would be the best title for this passage?
A.Craftsmen Set the Trends for Artists
B.Craftsmanship Leads to New Theories
C.Craftsmanship Makes Better Scientists
D.Craftsmen Reshape the Future of Science
如图1是横放的洋葱根尖结构示意图,A、B、C分别表示根尖上三个部位的细胞结构;图2表示一段时间后根尖的生长状况。据图回答下列问题:
(1)根尖中生长素相在A与B之间的运输方向是 ,这种运输方式属于 (填“主动运输”或“被动运输”)。
(2)为了探究图2中D侧生长速度快于E侧主要是由于细胞体积的增大还是由于细胞数目的增多,可将此处制成临时装片进行对比观察。
①将制好的临时装片置于显微镜下观察,无论使用低倍显微镜还是高倍显微镜都不能找到处于分裂期的细胞,原因是 。
②若两侧细胞的大小基本相同,则弯曲生长主要是由于 ;若 ,则弯曲生长主要是由于 。