排序方式: 共有59条查询结果,搜索用时 15 毫秒
41.
以硬脂酸和聚乙二醇为原料,经酯化后生成聚乙二醇双酯。再经磺化剂氯磺酸的磺化作用下得α-磺基硬脂酸聚乙二醇双酯,加NaOH中和后成盐,形成α-磺基硬脂酸聚乙二醇双酯钠盐。实验结果表明,在催化剂用量为2.0%(基于反应体系的质量分数),酸醇的量比为2.5∶1.0,反应时间为4小时,反应温度140~150℃时,聚乙二醇双酯收率达83%。磺化剂氯磺酸与双酯的量比为2.4∶1.0,反应时间为1小时,反应温度为60~70℃,α-磺基硬脂酸聚乙二醇双酯收率为96%。α-磺基硬脂酸聚乙二醇双酯钠盐的总收率为79.7%。 相似文献
42.
分析了夫琅禾费双矩孔衍射及其特例的光强分布,基于Matlab软件实现了夫琅禾费双矩孔衍射及其特例的计算机仿真.结果表明,夫琅禾费双矩孔衍射的光强分布为两个矩孔衍射的相干叠加结果;仿真图像与实际实验的结果一致,可应用于光学辅助教学等. 相似文献
43.
44.
分析了高等师范院校地理信息系统课程的教学内容、教学方法,对双语教学、案例教学在课程中的实践进行了探讨.并针对"地理信息系统"是一门技术性、实践性很强的新学科的教学特点,对课程的实践教学(包括实验课教学、生产单位实践、国内交流学习、毕业论文及毕业设计等)进行了改革与创新. 相似文献
45.
46.
及万会 《洛阳师范学院学报》2006,25(5):32-34
设P,q为正整数,Lucas序列Un+2=PUn+1+q Un,U1=1,U2=p;Vn+2=PVn+1+q Vn,V0=2,V1=p,本文得到系数为Lucas数孪生幂级数定理与几组孪生恒等式. 相似文献
47.
Jim Stevenson 《Reading and writing》1991,3(3-4):249-269
Genetic influences on reading are investigated in a sample of 285, 13 year old twins. Using a multiple regression procedure, the heritability of disability (h
g
2
) for Reading Recognition was found to be non-significant. However the h
g
2
for spelling disability was found to be 0.58 (P<0.05), after controlling for individual differences in IQ. The twins in this study were an unselected sample from the general population. Therefore it was possible to estimate h
g
2
for differing degrees of severity of disability. These analyses showed that for spelling but not for Reading Recognition or Reading Composite, there were substantial genetic contributions to all levels of disability. For indices of Orthographic Coding there were no significant values of h
g
2
. In contrast measures of Phonological Coding and Homophone Recognition have consistently high values of h
g
2
. More detailed analyses suggested that there were possibly two independent aspects of phonological ability, each influenced by genetic factors. 相似文献
48.
对导线粘连的原因及维护方法进行了分析,提出单独增大粘连档同相双分裂导线子导线间距的维护方法,此维护方法在实际运用中取得了良好的成效中成效良好。 相似文献
49.
50.
英语成对词是一种特殊的习语。笔者从四个方面分析了成对词:它们的结构,内部关系,语言特点以及如何正确应用。并且指出从英语习语当中把英语成对词提取出来进行归纳、分析、比较,使我们对这种特殊的习语有了新的认识和了解,并加强了对英语语言的感受力。因此,有助于对英语的学习和掌握。 相似文献