全文获取类型
收费全文 | 485篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
化学 | 358篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 9篇 |
物理学 | 134篇 |
出版年
2022年 | 4篇 |
2021年 | 4篇 |
2019年 | 7篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 15篇 |
2012年 | 17篇 |
2011年 | 17篇 |
2010年 | 15篇 |
2009年 | 22篇 |
2008年 | 21篇 |
2007年 | 15篇 |
2006年 | 22篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 26篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 17篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有508条查询结果,搜索用时 187 毫秒
21.
In general, palladium-carbon (Pd/C) catalyzed hydrogenation of epoxides affords the corresponding primary and secondary alcohols as a mixture. It has been found that the catalytic activity of a Pd/C -ethylenediamine complex catalyst [Pd/C(en)] in the hydrogenolysis of epoxide functions is drastically reduced. Herein we describe a mild and chemoselective method for the hydrogenation of olefin, nitro, and azide functions with retention of the epoxide function. The chemoselectivity was accomplished by using a combination of 5% Pd/C(en) and THF as solvent. A significant drop in the chemoselectivity of the hydrogenation is observed with 5% Pd/C(en) in MeOH. These results reinforce the utility of epoxides as important precursors of alcohols in synthetic chemistry. 相似文献
22.
Organic synthesis using biocatalysts has been developed over many years and is still a prominent area of research. In this context, various hybrid biocatalysts composed of a synthetic metal complex catalyst and a protein scaffold (i.e. “artificial metalloenzymes”) have been constructed. One of the most recent research areas in biocatalysts-mediated synthesis is CC bond/cleavage, the most important type of reaction in organic chemistry. Some of the artificial enzymes were applied to in-cell reactions as well as in vitro systems. The effects of the structural fluctuation in biomacromolecules on their functions have also been realized. This review article includes recent research examples of artificial metalloenzymes used to CC bond formation/cleavage. As a perspective, we also focus on how we apply protein dynamics factor for the creation of new generation artificial metalloenzymes. 相似文献
23.
The binding constants of 1-alkanols with α-cyclodextrin (α-CD) were determined by indirect competitive potentiometry, although potentiometry is usually inapplicable to nonionic compounds. This novel method utilizes competitive binding of 1-alkanol and octyltrimethylammonium bromide (OTAB) to α-CD in aqueous media, where the concentration of free OTAB depending on the competitive binding is monitored with an OTAB-selective electrode. Therefore, the concentration of 1-alkanol is indirectly estimated from the observed electromotive force. The binding constants of 1-propapnol, 1-butanol, 1-hexanol, and 1-octanol with α-CD, obtained by this method, are close to the literature values. The implications and limitations of this indirect competitive potentiometry were discussed. 相似文献
24.
A critical review is presented on the studies of the internal rotation potential function which is indispensable in understanding rotational isomerism from a dynamical point of view. Molecules so far investigated are classified into a few groups to clarify what factors govern the potential function. As an application of these results, the molecular structures of some bicyclic compounds are discussed, where the internal rotation is shown to play an important role. The recent microwave studies on two molecules of fundamental importance in the internal rotation problem, namely ethane and dimethylacetylene, are briefly mentioned. 相似文献
25.
26.
About two hundred Stark resonances of the ν2 and ν5 vibration-rotation bands of CD335Cl, using a 9.4 μm CO2 laser as a source, have been measured. By combining these data with the zero-field microwave spectra the following molecular constants have been determined (with the standard deviations in parentheses):
1 028.67275 (15) | 1 059.96970 (11) | (cm?1) | ||||
78 765.20 (89) | 78 030.21 (109) | (MHz) | ||||
10 805.29 (26) | 10 860.10 (13) | (MHz) | ||||
?25 080.77 (99) | (MHz) | |||||
8 756.0 (43) | (MHz) | |||||
μ | 1.90741 (33) | 1.90607 (36) | (D) | |||
μ(ground state) | 1.90597 (33) | (D) |