反应物进行催化裂化的先决条件是()。A.油气分子在催化剂表面进行化学反应 B.反应产

题型:单项选择题

问题:

反应物进行催化裂化的先决条件是()。

A.油气分子在催化剂表面进行化学反应

B.反应产物分子自催化剂表面脱附

C.原料油气扩散到催化剂表面,并被其吸附

D.反应产物分子从催化剂表面扩散出来

考点:催化裂化装置操作工高级催化裂化装置操作工高级催化裂化装置操作工题库
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安健环文化宣示设置区域:(1)门口:();(2)办公楼:();(3)为安全通告栏内容。

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《灵枢·天年》篇认为人生十岁,五脏始定,血气已通,其气在下,故()

A.好趋

B.好步

C.好转

D.好走

E.好坐

题型:单项选择题

前列腺增生症被确定,患者对是否会变为前列腺癌及引起尿毒症表示关注。应告知他:

A.目前尚可安心但需定期检查

B.应用了药物治疗就不必担心了

C.只要能尿出来就不必担心发生尿毒症

D.目前必须手术

E.摘除了前列腺就可预防前列腺癌的发生

题型:单项选择题

阅读理解。

     Harvard researchers have created a tough, low-cost, biodegradable (可生物降解的) material

inspired by insects' hard outer shells. The material's inventors say it has a number of possible uses and

someday could provide a more environmentally friendly alternative to plastic. The material, made from

shrimp (虾) shells and proteins produced from silk, is called "shrilk." It is thin, clear, flexible and strong.

     A major benefit of the material is its biodegradability. Plastic's toughness and flexibility represented a

revolution in materials science during the 1950s and '60s. Decades later, however, plastic's very

durability (耐用性) is raising questions about how appropriate it is for one-time products such as plastic

bags, or short-lived consumer goods, used in the home for a few years and then cast into a landfill where

they will degrade for centuries. What is the point of making something that lasts 1,000 years?

     Shrilk not only will degrade in a landfill, but its basic components are used as fertilizer (肥料), and so

will enrich the soil.

     Shrilk has great potential, the inventors said. Materials from which it is made are plentiful in nature,

found in everything ranging from shrimp shells, insect bodies to living plants. That makes shrilk low cost,

and its mass production possible should it be used for products demanding a lot of material.

     Work on shrilk is continuing in the lab. The inventors said the material becomes flexible when wet, so

they're exploring ways to use it in wet environments. They're also developing simpler production

processes, which could be used for non-medical products, like for computer cases and other products

inside the home. They're even exploring combining it with other materials, like carbon fibers, to give it

new properties.

1. Paragraph 1 of the passage is mainly about shrilk's _________.

A. remarkable design

B. interesting name

C. major features

D. basic elements

2. What has become a concern about plastic?

A. Using it properly.

B. Producing it cheaply.

C. Developing its properties quickly.

D. Evaluating its contributions fairly.

3. According to the inventors, shrilk has great potential partly because _________.

A. it can help plastic degrade

B. it can be found in living things

C. its mass production has been realized

D. its raw materials are abundant in nature

4. What are the inventors doing in the lab?

A. Replacing carbon fibers with shrilk.

B. Testing shrilk's use in wet conditions.

C. Making shrilk out of used household goods.

D. Improving shrilk's flexibility for medical purposes.

5. Which of the following can be the best title for the passage? 

A. Recent Progress in Environmental Protection

B. Benefits of Insects in Scientific Research

C. The Harm of One-time Products

D. A Possible Alternative to Plastic

题型:单项选择题

由体育本身的固有特点所决定,()是体育最本质的功能。

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