全文获取类型
收费全文 | 333篇 |
免费 | 29篇 |
专业分类
化学 | 281篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 40篇 |
物理学 | 34篇 |
出版年
2023年 | 3篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 26篇 |
2013年 | 22篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 11篇 |
2008年 | 30篇 |
2007年 | 16篇 |
2006年 | 9篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1971年 | 2篇 |
1963年 | 2篇 |
1961年 | 2篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1929年 | 2篇 |
1927年 | 2篇 |
1897年 | 2篇 |
1887年 | 2篇 |
1882年 | 2篇 |
排序方式: 共有362条查询结果,搜索用时 62 毫秒
71.
Mantovanelli IC Rivera EC da Costa AC Maciel Filho R 《Applied biochemistry and biotechnology》2007,137(1-12):817-833
In this work a procedure for the development of a robust mathematical model for an industrial alcoholic fermentation process was evaluated. The proposed model is a hybrid neural model, which combines mass and energy balance equations with functional link networks to describe the kinetics. These networks have been shown to have a good nonlinear approximation capability, although the estimation of its weights is linear. The proposed model considers the effect of temperature on the kinetics and has the neural network weights reestimated always so that a change in operational conditions occurs. This allow to follow the system behavior when changes in operating conditions occur. 相似文献
72.
73.
74.
[structure: see text] An organocatalytic asymmetric alpha-alkylation of aldehydes has recently been shown to provide cyclic aldehydes in high yields and enantioselectivities upon treating substituted acyclic halo-aldehydes with a catalytic amount of 2-methylproline in the presence of 1 equiv of triethylamine. Here, we report a density functional study on the mechanism of this reaction. The crucial step is an intramolecular nucleophilic substitution in the enamine intermediate. The added base accelerates the reaction through the electrostatic activation of the leaving group and affects the stereoselectivity by stabilizing anti and syn transition states to a different extent. On the basis of the computed barriers and transition states, we provide an explanation for the remarkable and unexpected increase in enantioselectivity that is observed when using 2-methylproline instead of proline as the catalyst. Calculated and observed enantiomeric excess values are in good agreement. 相似文献
75.
Bulking up with F: The title reaction proceeds using 1?mol?% of the new perfluoroisopropyl chiral disulfonimide catalyst 1 to deliver several 2,6-disubstituted and 2,5,6-trisubstituted dihydropyrones in good yields and with excellent enantiomeric ratios. The utility of this methodology is illustrated with the first enantioselective synthesis of a potent aromatase inhibitor. 相似文献
76.
Dr. Elmer Ccopa Rivera Dr. Rodney L. Summerscales Dr. Padma P. Tadi Uppala Dr. Hyun J. Kwon 《ChemistryOpen》2020,9(8):854-863
The present study introduces a unified framework combining a mechanistic model with a genetic algorithm (GA) for the parameter estimation of electrochemiluminescence (ECL) kinetics of the Ru(bpy)32+/TPrA system occurring in a smartphone-based sensor. The framework allows a straightforward solution for simultaneous estimation of multiple parameters which can be, otherwise, time-consuming and lead to non-convergence. Model parameters are estimated by achieving a high correlation between the model prediction and the measured ECL intensity from the ECL sensor. The developed model is used to perform a sensitivity analysis (SA), which provides quantitative effects of the model parameters on the concentrations of chemical species involved in the system. The results demonstrate that the GA-based parameter estimation and the SA approaches are effective in analyzing the kinetics of the ECL mechanism. Therefore, these approaches can be incorporated as analysis tools in the ECL kinetics study with practical application in the calibration of mechanistic models for any required sensing condition. 相似文献
77.
Some adducts of the known two-coordinate cadmium disilylamide, Cd[N(SiMe3)2]2, have been studied by 1H, 29Si, and 113Cd nuclear magnetic resonance spectroscopy. The physical and spectral properties of three new Cd(NR2)2 species are also described. 相似文献
78.
79.
80.