全文获取类型
收费全文 | 818篇 |
免费 | 58篇 |
国内免费 | 4篇 |
专业分类
化学 | 710篇 |
晶体学 | 4篇 |
力学 | 8篇 |
数学 | 62篇 |
物理学 | 96篇 |
出版年
2023年 | 17篇 |
2022年 | 13篇 |
2021年 | 30篇 |
2020年 | 38篇 |
2019年 | 27篇 |
2018年 | 23篇 |
2017年 | 18篇 |
2016年 | 30篇 |
2015年 | 38篇 |
2014年 | 26篇 |
2013年 | 44篇 |
2012年 | 72篇 |
2011年 | 84篇 |
2010年 | 34篇 |
2009年 | 18篇 |
2008年 | 61篇 |
2007年 | 61篇 |
2006年 | 62篇 |
2005年 | 44篇 |
2004年 | 41篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1939年 | 1篇 |
1893年 | 1篇 |
排序方式: 共有880条查询结果,搜索用时 15 毫秒
21.
Dr. Samantha A. Orr Dr. Emily C. Border Prof. Philip C. Andrews Dr. Victoria L. Blair 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11876-11882
By exploring lithium–bromide exchange reactivity of aromatic Schiff's bases with tert-butyllithium (tBuLi), we have revealed unprecedented competitive intermolecular and intramolecular cascade annulation pathways, leading to valuable compounds, such as iso-indolinones and N-substituted anthracene derivatives. A series of reaction parameters were probed, including solvent, stoichiometry, sterics and organolithium reagent choice, in order to understand the influences that limit such ring-closing pathways. With two viable reactivity options for the organolithium on the imine; namely, nucleophilic addition or lithium–bromide exchange, a surprising competitive nature was observed, where nucleophilic addition dominated, even under cryogenic conditions. Considering the most commonly used solvents for lithium–bromide exchange, tetrahydrofuran (THF) and diethyl ether (Et2O), contrasting reactivity outcomes were revealed with nucleophilic addition promoted in THF, while Et2O yielded almost double the conversion of cyclic products than in THF. 相似文献
22.
Dr. Francesca Arcudi Dana Emily Westmoreland Prof. Emily Allyn Weiss 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14469-14474
Colloidal quantum dot (QD) photocatalysts have the electrochemical and optical properties to be highly effective for a range of redox reactions. QDs are proven photo-redox catalysts for a variety of reactions in organic solvents but are less prominent for aqueous reactions. Aqueous QD photocatalysts require hydrophilic ligand shells that provide long-term colloidal stability but are not so tight-binding as to prevent catalytic substrates from accessing the QD surface. Common thiolate ligands, which also poison many co-catalysts and undergo photo-oxidative desorption, are therefore often not an option. This paper describes a framework for the design of water-solubilizing ligands that are in dynamic exchange on and off the QD surface, but still provide long-term colloidal stability to CdS QDs. The binding affinity and inter-ligand electrostatic interactions of a bifunctional ligand, aminoethyl phosphonic acid (AEP), are tuned with the pH of the dispersion. The key to colloidal stability is electrostatic stabilization of the monolayer. This work demonstrates a means of mimicking the stabilizing power of a thiolate-bound ligand with a zwitterionic tail group, but without the thiolate binding group. 相似文献
23.
24.
25.
Oxidative Addition of Haloheteroarenes to Palladium(0): Concerted versus SNAr‐Type Mechanism 下载免费PDF全文
Prof. Bert U. W. Maes Dr. Stefan Verbeeck Dr. Tom Verhelst Audrey Ekomié Niklas von Wolff Dr. Guillaume Lefèvre Dr. Emily A. Mitchell Prof. Anny Jutand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(21):7858-7865
The kinetics of the oxidative additions of haloheteroarenes HetX (X=I, Br, Cl) to [Pd0(PPh3)2] (generated from [Pd0(PPh3)4]) have been investigated in THF and DMF and the rate constants have been determined. In contrast to the generally accepted concerted mechanism, Hammett plots obtained for substituted 2‐halopyridines and solvent effects reveal a reaction mechanism dependent on the halide X of HetX: an unprecedented SNAr‐type mechanism for X=Br or Cl and a classical concerted mechanism for X=I. These results are supported by DFT studies. 相似文献
26.
27.
28.
29.
Emily F. Evans Norman J. Lewis Isabelle Kapfer Gregor Macdonald Richard J. K. Taylor 《合成通讯》2013,43(11):1819-1825
A mild and efficient procedure is described for the removal of the tert-butoxycarbonyl (BOC) group using boron trifluoride etherate and molecular sieves in dichloromethane at room temperature. The scope of this procedure is explored for the deprotection of a variety of amines including amino acid derivatives. 相似文献
30.