排序方式: 共有4条查询结果,搜索用时 15 毫秒
1
1.
氮杂环丁烷类化合物是一类重要的饱和四元含氮杂环化合物,不仅是有机合成中的重要原料、中间体及手性助剂或催化剂,也是氨基酸、生物碱及其天然和合成生物活性或药物活性化合物等分子结构中的重要活性单元。因此,发展氮杂环丁烷结构的合成方法非常重要。本文综述了氮杂环丁烷类化合物合成的发展,着重综述了近十年来该类化合物合成方法的进展,主要包括形成C-N键成环、形成C-C键成环、胺催化的亚胺和丙二烯甲酸酯环加成、亚胺和烯烃的光环加成、缩环扩环重排和氮杂环丁-2-酮(β-内酰胺)还原等方法构建氮杂环丁烷结构的新成果。 相似文献
2.
Response of colloidal liquids containing magnetic holes of different volume densities to magnetic field characterized by transmission measurement 下载免费PDF全文
This paper systematically investigates the response of colloidal liquids containing magnetic holes of different volume densities to magnetic field by conventional transmission measurements. It finds that the enhancement in the transmission of such a colloidal liquid under a magnetic field exhibits a strong dependence on the volume density of magnetic holes. A linear increase in the maximum enhancement factor is observed when the volume density of magnetic holes is below a critical level at which a maximum enhancement factor of ~150 is achieved in the near infrared region. Once the volume density of magnetic holes exceeds the critical level, a sharp drop of the maximum enhancement factor to ~2 is observed. After that, the maximum enhancement factor increases gradually till a large volume density of ~9%. By monitoring the arrangement of magnetic holes under a magnetic field, it reveals that the colloidal liquids can be classified into three different phases, i.e., the gas-like, liquid-like and solid-like phases, depending on the volume density of magnetic holes. The response behaviour of colloidal liquids to magnetic field is determined by the interaction between magnetic holes which is governed mainly by their volume density. A phase transition, which is manifested in the dramatic reduction in the maximum enhancement factor, is clearly observed between the liquid-like and solid-like phases. The optical switching operations for colloidal liquids in different phases are compared and the underlying physical mechanisms are discussed. 相似文献
3.
Ⅰ.四川大学分析化学教研室定性实验室的经验关於半微量定性分析实验中硫化氧的来源问题,我们是借硫化碱与硫酸作用获得解决的。当然,这一原理的采用不是新鲜的,但是根据我们的实际情况,这方法对我们说来是比较合适的,下面介绍一下我们的方法,仅供参考,并希批评指正。 相似文献
4.
1