全文获取类型
收费全文 | 308篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 154篇 |
晶体学 | 1篇 |
力学 | 7篇 |
数学 | 21篇 |
物理学 | 131篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 19篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 16篇 |
2012年 | 19篇 |
2011年 | 10篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 9篇 |
2005年 | 21篇 |
2004年 | 15篇 |
2003年 | 6篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1962年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1937年 | 2篇 |
1887年 | 1篇 |
1886年 | 1篇 |
排序方式: 共有314条查询结果,搜索用时 13 毫秒
1.
We investigate the existence of nontranslation invariant (periodic) density profiles, for systems interacting via translation invariant long-range potentials, as minimizers of local mean field free energy functionals. The existence of a second-order transition from a uniform to a nonuniform density at a specified temperature is proven for a class of model systems. 相似文献
2.
3.
Protein film voltammetry has been employed to define multiple catalytic consequences of proton coupled electron transfer (PCET) in a cytochrome c nitrite reductase. Current-potential profiles reflecting the steady-state rate of nitrite-limited reduction have been defined from pH 4 to 8. Lowering the electrode potential at pH 8 causes the catalytic current to increase and then decrease before it takes a value independent of any further lowering of electrode potential. By comparison, at pH 4, catalysis is initiated at more positive electrode potentials in an approximately sigmoidal fashion with no attenuation of the catalytic rate evident at more negative electrode potentials. The results show that activity is turned on by the coupled transfer of two electrons and one proton to the enzyme. The decreased rate of catalysis at lower electrode potentials under more alkaline conditions shows that this rate attenuation occurs only when reduction is not coupled to compensating protonation(s) of the enzyme. Sites within the enzyme whose reduction and/or protonation may contribute to the definition of these activities are discussed. 相似文献
4.
5.
6.
7.
8.
Sun G Kappl M Pakula T Kremer K Butt HJ 《Langmuir : the ACS journal of surfaces and colloids》2004,20(19):8030-8034
Forces across polymer melts are poorly understood despite their importance for adhesion and fabricating composite materials. Using an atomic force microscope (AFM), this interaction was measured for poly(dimethyl siloxane) (PDMS). The structure of the polymer at the surface changed during the first approximately 10 h. Afterward, short-range attractive forces were observed with short-chain PDMS (M(w) = 4200 g/mol). Using PDMS with a molecular weight (M(w) = 18 000 g/mol) above the entanglement limit, we measured a monotonically decaying repulsive force, which indicates that a quasi-immobilized layer had formed at the solid surface. Due to the small radius of curvature of the tip, forces could be measured in equilibrium. 相似文献
9.
Field SJ Thornton NP Anderson LJ Gates AJ Reilly A Jepson BJ Richardson DJ George SJ Cheesman MR Butt JN 《Dalton transactions (Cambridge, England : 2003)》2005,(21):3580-3586
Protein film voltammetry of Paracoccus pantotrophus respiratory nitrate reductase (NarGH) and Synechococcus elongatus assimilatory nitrate reductase (NarB) shows that reductive activation of these enzymes may be required before steady state catalysis is observed. For NarGH complementary spectroscopic studies suggest a structural context for the activation. Catalytic protein film voltammetry at a range of temperatures has allowed quantitation of the activation energies for nitrate reduction. For NarGH with an operating potential of ca. 0.05 V the activation energy of ca. 35 kJ mol-1 is over twice that measured for NarB whose operating potential is ca. -0.35 V. 相似文献
10.
Novel products from attempted michael addition to 1-methyl-1,2,5,6-tetrahydropyridine-4-carbonitrile
Graeme L. Butt Leslie W. Deady Maureen F. Mackay Maruse Sadek 《Tetrahedron letters》1982,23(43):4485-4488
The reaction of some phenols with the title compound, in the presence of sodium, gives 2-(2-hydroxyaryl_piperidine derivatives. Geometrical isomers have been separated, which differ in having an equatorial (A) or axial (B) cyano group on the piperidine chair (the methyl and aryl groups are equatorial in both forms). The x-ray crystallographic structures of an example of each of A and B are reported and the proton NMR spectra are assigned. 相似文献