全文获取类型
收费全文 | 177篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
化学 | 134篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 14篇 |
物理学 | 36篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 10篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有187条查询结果,搜索用时 15 毫秒
181.
Four types of heterogeneous Pd catalysts (10% Pd/C, 10% Pd/HP20, 0.5% Pd/MS3A, and 0.3% Pd/BN) were applied to the flow hydrogenation to systematically evaluate the appropriate conditions for the reduction of a wide variety of reducible functionalities. The use of 10% Pd/C and 10% Pd/HP20 allowed the hydrogenation of various reducible functionalities by a single-pass of the substrate–MeOH solution through the catalyst cartridge, while 0.5% Pd/MS3A and 0.3% Pd/BN catalyzed a novel chemoselective hydrogenation; only alkene, alkyne, azide, and nitro functionalities could be reduced with other coexisting reducible functionalities intact. 相似文献
182.
Kurita T Hattori K Seki S Mizumoto T Aoki F Yamada Y Ikawa K Maegawa T Monguchi Y Sajiki H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(2):664-673
The Pd/C-catalyzed efficient and regioselective hydrogen-deuterium (H-D) exchange reaction on the benzylic site proceeded in D2O in the presence of a small amount of H2 gas. The use of the Pd/C-ethylenediamine complex [Pd/C(en)] as a catalyst instead of Pd/C led to the efficient deuterium incorporation into the benzylic site of O-benzyl protective groups without hydrogenolysis. These H-D exchange reactions provide a post synthetic and D(2)-gas-free deuterium-labeling method on a wide variety of benzylic sites using D2O as the deuterium source and heterogeneous Pd/C or Pd/C(en) as a reusable heterogeneous palladium catalyst under mild and neutral conditions. 相似文献
183.
Dr. Yoshinari Sawama Yuki Yabe Hiroki Iwata Dr. Yuta Fujiwara Dr. Yasunari Monguchi Prof. Dr. Hironao Sajiki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(51):16436-16442
Deuterium‐labeled sugars can be utilized as powerful tools for the architectural analyses of high‐sugar‐containing molecules represented by the nucleic acids and glycoproteins, and chiral building blocks for the syntheses of new drug candidates (heavy drugs) due to their potential characteristics, such as simplifying the 1H NMR spectra and the stability of C? D bonds compared with C? H bonds. We have established a direct and efficient synthetic method of deuterated sugars from non‐labeled sugars by using the heterogeneous Ru/C‐catalyzed H–D exchange reaction in D2O under a hydrogen atmosphere with perfect chemo‐ and stereoselectivities. The direct H–D exchange reaction can selectively proceed on carbons adjacent to the free hydroxyl groups, and the deuterium labeling of various pyranosides (such as glucose and disaccharides), as well as furanosides, represented by ribose and deoxyribose was realized. Furthermore, the desired number of deuterium atoms can be freely incorporated into selected positions by the site‐selective protection of the hydroxyl groups using acetal‐type protective groups because the deuterium exchange reaction never proceeds on positions adjacent to the protected hydroxyl groups. 相似文献
184.
Toshihide Maejima Yutaka Shimoda Kei Nozaki Shigeki Mori Yoshinari Sawama Yasunari Monguchi Hironao Sajiki 《Tetrahedron》2012,68(6):1712-1722
An efficient copper-mediated C–N coupling reaction between various aryl halides and azido compounds to produce the corresponding aromatic primary amines was established. The present amination is apparently involved in both the reduction of an azido functionality to the corresponding primary amino group and its cross-coupling reaction with aryl halides in a one-pot manner. The present amination could be applied to the synthesis of procaine, a local anesthetic drug. A mechanistic study indicated that 2-aminoethanol could work as a major hydrogen donor and the reaction would proceed without the formation of the intermediary aryl azide. 相似文献
185.
A novel solid-phase 3D metal-organic coordination network catalyst was prepared via self-assembly from PdCl2(CH3CN)2 and a trisphosphine hub with three flexible alkyl-chain linkers. This insoluble network complex efficiently catalyzed the Suzuki-Miyaura reaction under atmospheric conditions in water. This catalyst was reused without loss of catalytic activity. 相似文献
186.
Dr. Fukai Xie Zhan Mao Dr. Dennis P. Curran Hongliang Liang Dr. Wen Dai 《Angewandte Chemie (International ed. in English)》2023,62(39):e202306846
Although the development of radical chain and photocatalytic borylation reactions using N-heterocyclic carbene (NHC)-borane as boron source is remarkable, the persistent problems, including the use of hazardous and high-energy radical initiators or the recyclability and photostability issues of soluble homogeneous photocatalysts, still leave great room for further development in a sustainable manner. Herein, we report a conceptually different approach toward highly functionalized organoborane synthesis by using recoverable ultrathin cadmium sulfide (CdS) nanosheets as a heterogeneous photocatalyst, and a general and mild borylation platform that enables regioselective borylation of a wide variety of alkenes (arylethenes, trifluoromethylalkenes, α,β-unsaturated carbonyl compounds and nitriles), alkynes, imines and electron-poor aromatic rings with NHC-borane as boryl radical precursor. Mechanistic studies and density functional theory (DFT) calculations reveal that both photogenerated electrons and holes on the CdS fully perform their own roles, thereby resulting in enhancement of photocatalytic activity and stability of CdS. 相似文献
187.
Jinhua Chen Shin Hasegawa Hitoshi Ohashi Yasunari Maekawa Masaru Yoshida Ryoichi Katakai Norio Tsubokawa 《Macromolecular rapid communications》2002,23(2):141-144
The impedance effect on the ion transport of lithium chloride through temperature‐ and pH‐sensitive gel membranes was investigated. Both conductance and loss tangent show a relatively high value at temperatures near the lower critical solution temperature (14°C), followed by an abrupt drop with a further rise in temperature. The Figure shows an example of changes in absolute complex conductance (Y ), real conductance (G ), and imaginary conductance (B) for a poly(acryloyl‐L ‐proline methyl ester) gel membrane. 相似文献