首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7篇
  免费   2篇
化学   5篇
物理学   4篇
  2023年   1篇
  2019年   1篇
  2017年   1篇
  2016年   2篇
  2008年   1篇
  2002年   2篇
  2000年   1篇
排序方式: 共有9条查询结果,搜索用时 15 毫秒
1
1.
有源RLC电路量子化的双波描述   总被引:1,自引:0,他引:1  
吴奇学 《光子学报》2002,31(4):500-503
采用正则变换量子化以及规范变换方案,得到有源RLC电路量子化哈密顿算符及其波函数.引入双波函数描述其量子状态,得到了电荷、电流等物理量的时间演化方程.对有源RLC电路给出更完整的描述.  相似文献   
2.
多块YBaCuO高温超导体在永磁轨道上的悬浮力   总被引:6,自引:3,他引:3  
】报道了多块 YBa Cu O高温超导体块材的不同组合方式在永磁轨道上的磁悬浮力的实验研究结果 ,实验研究证明不同的组合方式对其悬浮力的影响较大。作者分别研究了四块 YBa Cu O高温超导体块材以不同的组合方式在永磁轨道上的悬浮力 ,并进行了分析比较 ,为高温超导磁悬浮车的设计提供了初步的实验依据  相似文献   
3.
均匀电场中D维q变形带电振子的双波描述   总被引:1,自引:0,他引:1       下载免费PDF全文
应用双波理论描述均匀电场中D维q变形带电振子的运动,得到了振子各力学量随时间的演化方程.  相似文献   
4.
Trifluoromethanesulfonic anhydride has been widely used in synthetic organic chemistry, not only for the conversion of various oxygen-containing compounds to the triflates, but also for the electrophilic activation and further conversion of amides, sulfoxides, and phosphorus oxides. In recent years, the utilization of Tf2O as an activator for nitrogen-containing heterocycles, nitriles and nitro groups has become a promising tool for the development of new valuable methods with considerable success. In addition, Tf2O has been used as an efficient radical trifluoromethylation and trifluoromethylthiolation reagent due to the contained SO2CF3 fragment, and significant progress has been made in this area. This review summarizes the recent progress in the applications of Tf2O in the above two aspects, and aims to illustrate the role and potential application of this reagent in organic synthesis.  相似文献   
5.
Two anomalously weak transitions within the 2(3)S_(1)--3(3)P_(J) manifolds in 3He have been identified. Their transition strengths are measured to be 1000 times weaker than that of the strongest transition in the same group. This dramatic suppression of transition strengths is due to the dominance of the hyperfine interaction over the fine-structure interaction. An alternative selection rule based on IS coupling (where the nuclear spin is first coupled to the total electron spin) is proposed. This provides qualitative understanding of the transition strengths. It is shown that the small deviations from the IS coupling model are fully accounted for by an exact diagonalization of the strongly interacting states.  相似文献   
6.
7.
Wang  Liang  Wu  Minghuo  Wang  Qixue  Zhan  Jingjing  Chen  Hongbo 《Chromatographia》2016,79(19):1263-1269

Polyethylenimine (PEI) and 2,4,6,8-tetramethyl-2,4,6,8-tetrakis(propyl glycidyl ether)cyclotetrasiloxane (POSS–epoxy) were used as precursors for the preparation of organic-silica hybrid monolithic columns (PEI–POSS monolith) via epoxy–amine ring-opening polymerization (ROP). The high density of amine groups in PEI provides rich chromatographic interaction sites for the polar or acidic analytes in hydrophilic interaction (HILIC) and weak anion exchange (WAX) mechanisms. The column preparation conditions, such as the porogens, solvent and reaction temperature, were systematically investigated according to the morphology, permeability and column efficiency. The separation mechanisms of HILIC and WAX were evaluated with neutral polar compounds and halogen benzoic acids. Owing to the existence of reactive amine groups on the matrix surface, the PEI–POSS monolith is also an ideal starting material for the preparation of HILIC or strong anionic exchange (SAX) stationary phases by modification. The modification of PEI–POSS monoliths with iodomethane or bromoacetic acid via the nucleophilic substitution reaction could achieve the retention mechanisms of SAX or zwitterionic HILIC, respectively.

  相似文献   
8.
A novel activation of acetonitrile for the construction of cyclobutenones by [2+2] cyclization was developed. Acetonitrile is utilized for the first time as two‐carbon (C2) cyclization building block. The present protocol successfully inhibits the competitive cycloaddition with the C≡N bond of acetonitrile, but enables the in situ formation of an unsaturated carbon–carbon bond and the subsequent cycloaddition as a C2 unit. This chemistry features simple reaction conditions, high chemoselectivities, wide substrate scope, and offers a new and practical approach to cyclobutenones and cyclobuteneimines.  相似文献   
9.
Visible‐light photoredox catalysis has been successfully used in the functionalization of inert C?H bonds including C(sp2)‐H bonds of arenes and C(sp3)‐H bonds of aliphatic compounds over the past decade. These transformations are typically promoted by the process of single‐electron‐transfer (SET) between substrates and photo‐excited photocatalyst upon visible light irradiation (household bulbs or LEDs). Compared with other synthetic strategies, such as the transition‐metal catalysis and traditional radical reactions, visible‐light photoredox approach has distinct advantages in terms of operational simplicity and practicability. Versatile direct functionalization of inert C(sp2)‐H and C(sp3)‐H bonds including alkylation, trifluoromethylation, arylation and amidation, has been achieved using this practical strategy.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号