已选分类
工学
单选题______ retain their fluid state when exposed to oxygen, but when squeezed into thin joints that block the oxygen, they set up into hard, strong adhesives. A) Hot-melt adhesives B) Loss-of solvent adhesives C) Anaerobic adhesives D) Two-part mix adhesives
单选题在fcc、bcc和hcp三种单晶材料中，形变时各向异性行为最显著的是______。
单选题灰口铸铁，为获得高的耐磨性，应选用( )。 A．孕育处理 B．正火 C．表面淬火
单选题Which concept of the materials cycle has been LEAST AFFECTED by recent trends? A) Concern for the entire cycle that includes effects of harmful by-products and unrecycled old products B) Ability to design materials to meet ever-increasing demands of technology rather than use off-the shelf materials C) Need for a more highly educated workforce to support new manufacturing techniques D) Desire to achieve the maximum properties from any given materials
单选题共晶层片(α+β)共在特定过冷度下生长时，扩散所消耗的驱动力约为______。
单选题在合金非平衡凝固中将会产生各种成分偏析，其中最难消除的偏析是______。
单选题在低碳钢的应力一应变曲线中出现上屈服点和下屈服的的现象，可用______解释。
单选题______ is a homogeneous mixture of chemically distinct substances that forms a phase. The components (substances) lose their individual identities. A) Alloy B) Solute C) Solution D) Solvent
单选题Hollow products (barrels, bottles, tanks) can be produced through ______. A．extrusion B．blowing molding C．compression molding D．calendering
单选题In terms of modulus, which order (from low to high) is correct as far as glass, carbon, and Kevlar fibers are concerned? A．Kevlar fiber, glass fiber, graphite fiber B．Glass fiber, Kevlar fiber, graphite fiber C．Graphite fiber, glass fiber, Kevlar fiber
单选题在MgO离子化合物中，最可能取代Mg2+的阳离子是(已知各离子的半径分别为Mg2+：0.066nm，Ca2+：0.099nm，Li+：0.066nm，Fe2+：0.074nm)______。
单选题a≠b≠c，α=β=γ=90°的晶体属于 晶系。
a．立方 b．六方 c．四方 d．正交
单选题在A-B二元固溶体中，当A-B对的能量小于A-A和B-B对的平均能量，该固溶体最易形成为______。
单选题Thermoplastic plastics are generally best for which of the following type of service conditions? A) impact B) creep resistance C) chemical exposure D) flammability
单选题体型高分子不可能出现______。
单选题在单元系的p(压强)-T(温度)相图内，当高温相向低温度相转变时体积收缩，则根据Clausius-Clapeyron方程，______。
单选题Which statement about fiber loading is not correct? A．the amount of reinforcement in a composite material B．is expressed in volume fraction C．a factor influencing the composite D．the strength of the composite is inversely proportional to the volume fraction of fiber present
单选题______ provides the substrate for CD-ROMs because they possess excellent optical properties as well as hardness and toughness. A．Polystyrene (PS) foam B．Polycarbonates (PC) C．Polyvinyl chloride (PVC) D．Polyethylene (PE)
单选题两平行螺型位错，当伯氏矢量同向时，其相互作用力______。
单选题The coordination number for the atoms in the fcc unit cell is______. A) 2 B) 6 C) 8 D) 12