全文获取类型
收费全文 | 1482篇 |
免费 | 36篇 |
国内免费 | 9篇 |
专业分类
化学 | 967篇 |
晶体学 | 5篇 |
力学 | 29篇 |
数学 | 200篇 |
物理学 | 326篇 |
出版年
2020年 | 16篇 |
2019年 | 20篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 20篇 |
2014年 | 15篇 |
2013年 | 41篇 |
2012年 | 75篇 |
2011年 | 58篇 |
2010年 | 47篇 |
2009年 | 35篇 |
2008年 | 84篇 |
2007年 | 66篇 |
2006年 | 57篇 |
2005年 | 67篇 |
2004年 | 42篇 |
2003年 | 55篇 |
2002年 | 42篇 |
2001年 | 30篇 |
2000年 | 30篇 |
1999年 | 32篇 |
1998年 | 24篇 |
1997年 | 16篇 |
1996年 | 20篇 |
1995年 | 22篇 |
1994年 | 20篇 |
1993年 | 24篇 |
1992年 | 13篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 23篇 |
1985年 | 30篇 |
1984年 | 19篇 |
1983年 | 19篇 |
1981年 | 12篇 |
1980年 | 20篇 |
1979年 | 26篇 |
1978年 | 16篇 |
1977年 | 22篇 |
1976年 | 16篇 |
1975年 | 16篇 |
1974年 | 24篇 |
1973年 | 15篇 |
1971年 | 13篇 |
1970年 | 10篇 |
1885年 | 16篇 |
排序方式: 共有1527条查询结果,搜索用时 31 毫秒
101.
102.
103.
104.
M. Diehl Th Feldmann R. Jakob P. Kroll 《The European Physical Journal C - Particles and Fields》2005,39(1):1-39
We present a simple empirical parameterization of the x- and t-dependence of generalized parton distributions at zero skewness, using forward parton distributions as input. A fit to experimental data for the Dirac, Pauli and axial form factors of the nucleon allows us to discuss quantitatively the interplay between longitudinal and transverse partonic degrees of freedom in the nucleon (nucleon tomography). In particular we obtain the transverse distribution of valence quarks at given momentum fraction x. We calculate various moments of the distributions, including the form factors that appear in the handbag approximation to wide-angle Compton scattering. This allows us to estimate the minimal momentum transfer required for reliable predictions in that approach to be around
. We also evaluate the valence contributions to the energy-momentum form factors entering Jis sum rule.Received: 16 September 2004, Revised: 15 October 2004, Published online: 17 December 2004 相似文献
105.
Helen?BarbasEmail author Claus?C?Hilgetag Subhash?Saha Caterina?R?Dermon Joanna?L?Suski 《BMC neuroscience》2005,6(1):32
Background
The neocortical commissures have a fundamental role in functional integration across the cerebral hemispheres. We investigated whether commissural projections in prefrontal cortices are organized according to the same or different rules as those within the same hemisphere, by quantitatively comparing density, topography, and laminar origin of contralateral and ipsilateral projections, labeled after unilateral injection of retrograde tracers in prefrontal areas. 相似文献106.
Florian?Nettesheim Claus?B.?Müller Ulf?Olsson Walter?RichteringEmail author 《Colloid and polymer science》2004,282(8):918-926
We report on the shear induced transition from the L3- to the L-phase studied by means of flow birefringence using the system pentaethyleneglycol monododecylether (C12E5), decane, water. The dependence of the critical shear rate, at which the transition from the isotropic state to the anisotropic takes place, on membrane volume fraction was studied in temperature ramp experiments at different constant shear rates and in isothermal shear ramp experiments. These results are compared with relaxation experiments from the shear aligned state back to the isotropic. For all these experiments power law exponents in the membrane volume fraction between 1.6 and 2.8 were found, which are rather low compared to values of current theories. The values found for the inverse critical shear rate and the decay times from the relaxation experiments differ by four orders of magnitude. 相似文献
107.
A theoretical analysis of an optical fiber photonic-bandgap-based refractometer is presented. The design is based on a quarter-wave reflector with one defect. By modifying both the real and the imaginary parts of the index of refraction of the defects we begin to change either the frequency or the amplitude of the localized optical mode. So we could fabricate a specific optical fiber refractometer by combining all the variables: index of refractive index of the defects and the rest of layers, thickness of the defect, number of layers, etc. to yield a large set of design possibilities, for example, detecting wider or thinner ranges of refractive indices, or controlling the detection accuracy. Some rules for the practical implementation of the refractometer are given. 相似文献
108.
Jacob C Giles GI Giles NM Sies H 《Angewandte Chemie (International ed. in English)》2003,42(39):4742-4758
Sulfur and selenium occur in proteins as constituents of the amino acids cysteine, methionine, selenocysteine, and selenomethionine. Recent research underscores that these amino acids are truly exceptional. Their redox activity under physiological conditions allows an amazing variety of posttranslational protein modifications, metal free redox pathways, and unusual chalcogen redox states that increasingly attract the attention of biological chemists. Unlike any other amino acid, the "redox chameleon" cysteine can participate in several distinct redox pathways, including exchange and radical reactions, as well as atom-, electron-, and hydride-transfer reactions. It occurs in various oxidation states in the human body, each of which exhibits distinctive chemical properties (e.g. redox activity, metal binding) and biological activity. The position of selenium in the periodic table between the metals and the nonmetals makes selenoproteins ideal catalysts for many biological redox transformations. It is therefore apparent that the chalcogen amino acids cysteine, methionine, selenocysteine, and selenomethionine exhibit a unique biological chemistry that is the source of exciting research opportunities. 相似文献
109.
Self-assembled microarrays of attoliter molecular vessels 总被引:1,自引:0,他引:1
Stamou D Duschl C Delamarche E Vogel H 《Angewandte Chemie (International ed. in English)》2003,42(45):5580-5583
110.
Analogues of MKC-442 capable of undergoing Michael addition reactions were synthesised in order to investigate the activity against the HIV-1 mutant (Y181C). An improved activity was postulated on the basis of a possible covalent binding to the mercapto group of Cys181. Lithiation of the C-6 position of 1-ethoxymethyl-5-ethyl-1H-pyrimidine-2,4-dione (5) was followed by reaction with alpha,beta-unsaturated aldehydes and oxidation of the alcohols formed to give the alkenoyl analogues 1a-3a. Analogues 1b-3b containing an allyloxymethyl group in the N-1 position instead of the ethoxymethyl group could not be synthesised due to isomerisation of the allylic group during the metallation reaction. The NMR data for compounds 1a-3a showed a hindered rotation, which was more pronounced for the 6-cyclohexenylcarbonyl derivative 3a than for the propenyl derivatives 1a and 2a. Moderate activity against wild type HIV-1 was observed for the alcohol 8 and the ketones 2a-3a. However, no activity was observed against the Y181C mutant. 相似文献