全文获取类型
收费全文 | 380篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 227篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 35篇 |
物理学 | 116篇 |
出版年
2023年 | 3篇 |
2020年 | 4篇 |
2018年 | 6篇 |
2015年 | 10篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 17篇 |
2011年 | 19篇 |
2009年 | 5篇 |
2008年 | 18篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 17篇 |
2004年 | 10篇 |
2003年 | 14篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 18篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1969年 | 3篇 |
1965年 | 3篇 |
1961年 | 2篇 |
1926年 | 2篇 |
1922年 | 2篇 |
排序方式: 共有389条查询结果,搜索用时 17 毫秒
1.
2.
3.
4.
5.
6.
7.
[reaction: see text] Hydrozirconation of alkynes followed by in situ transmetalation to dimethylzinc and 1,2-addition to activated ketones and N-diphenylphosphinoylimines leads to tertiary allylic alcohols and amines in high overall yield. With 8-phenylmenthol as the chiral auxiliary, si-face attack proceeds in good to excellent diastereoselectivities. 相似文献
8.
Peter Wipf Stefan Werner Grace H.C. Woo Corey R.J. Stephenson Maciej A.A. Walczak Claire M. Coleman Leslie A. Twining 《Tetrahedron》2005,61(48):11488-11500
The multi-component condensation of organozirconocene, aldimine and zinc carbenoid was applied to the stereoselective synthesis of cyclopropane amino acid derivatives. These compounds served as scaffolds for the preparation of a 46-member library. The C- and N-termini of the cyclopropane amino acid derivatives were diversified by condensations with ten amines and ten acylating agents, respectively. To improve yields and accelerate library synthesis, most products were prepared under microwave irradiation and purified by polymer-bound scavengers and SPE methodology. All compounds were analyzed by LC-MS and a representative selection was fully characterized. 相似文献
9.
Collisions of I2 in the E electronic state with rare gas atoms result in electronic energy transfer to the D, beta, and D' ion-pair electronic states. Rate constants for each of these channels have been measured when I2 is initially prepared in the J = 55, nu = 1 and 2 levels in the E state. The rate constants and effective hard sphere collision cross sections confirm the trends observed when nu = 0 in the E state is initially prepared: He collisions favor population of the D state, while Ar collisions favor population of the beta state. Final state vibrational level distributions are determined by spectral simulation and are found to be qualitatively consistent with the trends in the Franck-Condon factors. The experimental distributions are also compared to the recent quantum scattering calculations of Tscherbul and Buchachenko. 相似文献
10.
Garcia Ruano JL Alcudia A del Prado M Barros D Maestro MC Fernandez I 《The Journal of organic chemistry》2000,65(10):2856-2862
The addition of the lithium anions derived from (R)- and (S)-methyl and -ethyl p-tolyl sulfoxides to (S)-N-benzylidene-p-toluenesulfinamide provides an easy access route to enantiomerically pure beta-(N-sulfinyl)amino sulfoxides. Stereoselectivity can be achieved when the configurations at the sulfur atoms of the two reagents are opposite (matched pair), thus resulting in only one diastereoisomer, even for the case in which two new chiral centers are created. The N-sulfinyl group primarily controls the configuration of the carbon bonded to the nitrogen, whereas the configuration of the alpha-sulfinyl carbanion seems to be responsible for the level of asymmetric induction, as well as for the configuration of the new stereogenic C-SO carbon in the reactions with ethyl p-tolyl sulfoxides. An efficient method for transforming the obtained beta-(N-sulfinyl)amino sulfoxides into optically pure beta-amino alcohols, based on the stereoselective non-oxidative Pummerer reaction, is also reported. 相似文献