更多“在生物体内的下列哪种一种物质还原程度最高（）”相关的问题
一只板的板尾打开向外侧移动，另一只板跟进收拢的原地踏步转向是（）。
A.后端固定原地转向
B.前端固定原地转向
C.左端固定原地转向
D.右端固定原地转向
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坍落度筒提离以后，混凝土拌合物若发生崩坍或一边剪坏现象，则应重新取样另行测定。（）
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如果柱体轴向与某个投影面（），那么在这个投影面上，可反映出柱体轴向侧表面每条素线的实长。
A . 平行
B . 垂直
C . 倾斜
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《清明上河图》是北宋画家（）的风俗画作品。
A.张择端 B.刘松年 C.王希孟 D.马贲
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夜间没有充分的照明，安全规程明确规定（）。
A . 钻机不应远距离行走
B . 钻机应该停止作业
C . 不许移动钻机
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酒花削根的方法，根据（）情况，可采取高削、中削或低削法。
A . A、气候
B . B、土壤肥力
C . C、温度变化
D . D、土质
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元素周期表周期数是（）。
A.5
B.6
C.7
D.18
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第一篇 Immune Functions The immune system is equal incomplexity to the combined intricacies of the brain and nervous system. Thesuccess of the immune system in defending the body relies on a dynamicregulatory com- munication network consisting of millions and millions ofcells. Organized into sets and subsets,these cells pass information back andforth like clouds of bees flying around a hive (蜂巢). The result is a sensitive system of checks andbalances that produces an immune response that is prompt, appropriateeffective, and self-limiting. At the heart of the immunesystem is the ability to distinguish between self and nonself. When im- munedefenders encounter cells or organisms carrying foreign or nonselfmolecules,the immune troops move quickly to eliminate the intruders(入侵者). Virtually everybody cell carries distinctive molecules that identify it as self. The body's immunedefenses do not normally attack tissues that carry a self-marker. Rather,immune cells and other body cells coexist peaceably in s state known asself-toler- ance. When a normally functioning immune system attacks a nonselfmolecule, the system has the abil- ity to"remember" the specifics ofthe foreign body. Upon subsequent encounters with the same species ofmolecules, the immune system reacts accordingly. With the possible exception ofantibodies(抗体)passed during lactation (哺乳期),this so called immune system memory is notinherited. Despite the occurrence of a virus in your family, your immune systemmust "learn" from experience with the many millions of distinctivenonself molecules in the sea of microbes(微生物)in which we live. Learning en- tails producing theappropriate molecules and cells to match up with and counteract each nonselfinvader. Any substance capable oftriggering an immune response is called an antigen(抗原). Antigens are notto be confused with allergens (过敏原), which are most often harmless substances that provoke the immunesystem to set off the inappropriate and harmful response known as allergy. Anantigen can be a virus, a bacterium or even a portion or product of one ofthese organisms. Tissues or cells from another individual also act as antigens;because the immune system recognizes transplanted tissues as foreign, itrejects them. The body will even reject nourishing proteins unless they arefirst brokendown by the digestive system into their primary, nonantigenicbuilding blocks. An antigen announces its for- eignness by means of intricateand characteristic shapes called epitopes(抗原表位) , which protrude(突出) from its surface. Most antigens, even thesimplest microbes, carry several different kinds of epitopes on their surface;some may even carry several hundreds. Some epitopes will be more effective thanothers at stimulating an immune response. Only in abnormal situation does theimmune system wrongly identify self as nonself and execute a misdirected immuneattack. What is used to describe the communication network consisting of cells in theimmune system?A.The immune system's memoryB.Immune troops eliminating intrudersC.Bees flying around a hivD.A sea of microbes
A.B.C.D.TheE.ImmuneF.BeesG.A
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下面那一项不是牵引供电工频单相交流制的主要优点。（）
A.牵引供电系统结构简单 B.牵引供电电压增高 C.交流电力机车的粘着性能和牵引性能良好 D.功率因数接近于1
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出口卖方信贷报审材料除常规的送审材料外，还需包括（ ）。 A．出口方银行与进口商或进口方的银行签订的信贷协议 B．出口许可证或其他证明文件 C．商务合同 D．借款人具有机电产品出口经营权的证明文件 E．出口企业与进口商签订的贸易合同
A.出口方银行与进口商或进口方的银行签订的信贷协议
B.出口许可证或其他证明文件
C.商务合同
D.借款人具有机电产品出口经营权的证明文件
E.出口企业与进口商签订的贸易合同
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