【简答题】自20世纪90年代以来,芳炔类大环化合物的研究发展十分迅速,具有不同分子结构和几何形状的这一类物质在高科技领域有着十分广泛的应用前景。合成芳炔类大环的一种方法是以苯乙炔( )经过反应得到一系列的芳块类大环化合物,其结构为: (1)上述系列中第1种物质的分子式为__________。 (2)已知上述系列第1至第4种物质的分子直径在1~100nm之间,分别将它们溶解于有机溶剂中,形成的分散系为____...
【单选题】【结构科学】20世纪90年代迅速发展起来的( )是一门集组合数学、合成化学和计算机辅助设计等多学科交叉形成的边缘学科,是快速、准确而经济地产生化学多样性的工程技术。
【单选题】在投影系中直线的投影可由直线上两点的( )投影来确定。
【单选题】Which of the following statements about marketing is TRUE?
A.
It is of little importance when products are standardized
B.
It can help create jobs in the economy by increasing demand for goods and services.
C.
It helps to build a loyal customer base but has no impact on a firm's intangible assets.
D.
It is not needed in an Internet-fueled environment.
E.
It is seldom used by nonprofit organizations.
【判断题】直线的投影可由直线上两点的同面投影来确定。
【判断题】投影可由直线上两点的同面投影来确定。( )
【单选题】Which of the following statements about marketing is true?
A.
It is of little importance when products are standardized.
B.
It can help create jobs in the economy by increasing demand for goods and services.
C.
It helps to build a loyal customer base but has no impact on a firm's intangible assets.
D.
It is more important for bigger organizations than smaller ones.
E.
It is seldom used by nonprofit organizations.
【简答题】产品生命周期是指产品从进入( )到最后被( )的全过程。一般可以分成四个阶段,即( )、( )、( )和( )。
【判断题】直线的各面投影可由直线上两个点的同名投影来确定