已选分类
工学
单选题钢的渗碳温度范围是( )。 A．600～650℃ B．800～850℃ C．900～950℃ D．1000～1050℃
单选题晶体结构中一切对称要素的集合称为______。 A．对称型 B．点群 C．微观对称的要素的集合 D．空间群
单选题在面心立方晶体结构中，密排面是____。 A．001面 B．011面 C．111面
单选题在扩散系数的热力学关系中，称为扩散系数的热力学因子。在非理想混合体系中：当扩散系数的热力学因子＞0时，扩散结果使溶质______；当扩散系数的热力学因子＜0时，扩散结果使溶质______。
单选题能进行滑移的位错为______。
单选题化学键中既无方向性又无饱和性的为______。
单选题高岭石属于层状硅酸盐结构，其结构特征是______。
单选题高分子链能产生不同构象的根本原因是______。
单选题理想密排六方结构金属的c/a为______。
单选题铸锭凝固时如大部分结晶潜热可通过液相散失时，则固态显微组织主要为______。
单选题A type of harness test that compares a materials hardness to some 10 known minerals arranged in order of hardness. A) Scleroscope (HSc) test B) Mohstest C) Brinellhardnesstest D) Rockwell Hardness test
单选题Which ofthe following statement about hydrogen bonding is NOT correct? A) symmetrical charge distribution B) static electrical attraction between positive and negative charges C) an attraction force between adjacent charges with opposite signs D) the strongest ofthe secondary bonding
单选题熔体是______的混合物。
a．相同聚合度的聚合物和游离碱
b．不同聚合程度的各种聚合物
c．各种低聚物
d．各种高聚物
单选题______ are (is) used to speed sulfur vulcanizing. A) Accelerators and activators B) Carbon black C) Retarders D) Antioxidants
单选题三元系统相图中，若存在有n条界线，则此系统相图中能连接出______条连线。
a．3 b．n-1 c．n d．n+1
单选题Choose the correct statement about the wetting phenomenon. A．A fiber can be properly wetted by a matrix only when the surface energy of matrix is greater than that of the fiber B．A fiber can be properly wetted by a matrix only when the surface energy of matrix is lower that that of the fiber C．A fiber can be properly wetted by a matrix only when the surface energy of matrix is equal to that of the fiber D．It is nothing to do with surface energies of matrix and fiber
单选题点群为Fm3m的晶体结构属于______晶系。
A.等轴
B.六方
C.四方
D.正交
单选题下面关于位错应力场的表述中，正确的是______。
单选题fcc结构中分别在(111)和面上的两个肖克利位错(分别是1/6和1/6)相遇时发生位错反应，将生成______。
单选题Which statement ofelastic modulus is NOT correct? A) Elastic modulus is also known as Youngs modulus B) The higher the magnitude ofelastic modulus the stiffer the material C) Elastic modulus can be measured graphically in the elastic region ofthe stress-strain diagram D) The higher the magnitude of elastic modulus the weaker the interatomic bonding forces