全文获取类型
收费全文 | 179764篇 |
免费 | 778篇 |
国内免费 | 262篇 |
专业分类
化学 | 89711篇 |
晶体学 | 2636篇 |
力学 | 9381篇 |
综合类 | 7篇 |
数学 | 20917篇 |
物理学 | 58152篇 |
出版年
2020年 | 1849篇 |
2019年 | 2292篇 |
2018年 | 3398篇 |
2017年 | 3525篇 |
2016年 | 4159篇 |
2015年 | 1853篇 |
2014年 | 3590篇 |
2013年 | 7052篇 |
2012年 | 5537篇 |
2011年 | 6592篇 |
2010年 | 5517篇 |
2009年 | 5640篇 |
2008年 | 6364篇 |
2007年 | 6327篇 |
2006年 | 5622篇 |
2005年 | 4986篇 |
2004年 | 4822篇 |
2003年 | 4369篇 |
2002年 | 4526篇 |
2001年 | 4999篇 |
2000年 | 3692篇 |
1999年 | 2825篇 |
1998年 | 2607篇 |
1997年 | 2461篇 |
1996年 | 2254篇 |
1995年 | 2051篇 |
1994年 | 2005篇 |
1993年 | 2039篇 |
1992年 | 2073篇 |
1991年 | 2380篇 |
1990年 | 2315篇 |
1989年 | 2384篇 |
1988年 | 2264篇 |
1987年 | 2294篇 |
1986年 | 2125篇 |
1985年 | 2657篇 |
1984年 | 2670篇 |
1983年 | 2317篇 |
1982年 | 2371篇 |
1981年 | 2276篇 |
1980年 | 2078篇 |
1979年 | 2393篇 |
1978年 | 2548篇 |
1977年 | 2639篇 |
1976年 | 2729篇 |
1975年 | 2536篇 |
1974年 | 2468篇 |
1973年 | 2634篇 |
1972年 | 2152篇 |
1971年 | 1973篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
We obtain exponential upper bounds for tails of distributions of generalized L-statistics based on a sample from an exponential distribution. We prove the asymptotic normality of generalized L-statistics based on a sample from the uniform distribution on [0,1] and of L-statistics with decomposed kernels (without any restrictions on the sample distribution type). 相似文献
102.
103.
Lobanovsky L. S. Troyanchuk I. O. 《Journal of Experimental and Theoretical Physics》2003,96(2):331-334
Journal of Experimental and Theoretical Physics - The magnetoresistance effect in the SmCu3Mn4O12 compound with a perovskite-like structure is investigated for the first time. It is found that an... 相似文献
104.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
105.
In basin modelling the thermodynamics of a multicomponent multiphase fluid flux are computationally too expensive when derived from an equation of state and the Gibbs equality constraints. In this article we present a novel implicit molar mass formulation technique using binary mixture thermodynamics. The two proposed solution methods, with and without cross derivative terms between components, are based on a preconditioned Newton‐GMRES scheme for each time‐step with analytical computation of the derivatives. These new algorithms reduce significantly the numerical effort for the computation of the molar masses, and we illustrate the behavior of these methods with numerical computations. Copyright © 2004 John Wiley & Sons Ltd. 相似文献
106.
The glow curve structures for LiF:Mg,Cu,Na,Si TL detectors with various dopant concentrations and sintering temperatures were investigated for the improvement of the glow curve structure and sensitivity of the TL detector. The dopant concentrations were varied over the following ranges: Mg (0–0.25 mol%), Cu (0–0.07 mol%), Na and Si (0–1.5 mol%). With increasing Cu concentration, the intensity of the main peak was intensified and reached a maximum at a concentration of 0.05 mol%. The high-temperature peak was reduced. The dependency of the main peak intensity on the Mg concentration exhibits a sharp maximum at 0.2 mol%. The intensity of the high-temperature peak tends to rise slightly with increasing Mg concentration. It was found that the optimum concentrations of the dopants in the LiF:Mg,Cu,Na,Si TL material are Mg: 0.2 mol%, Cu: 0.05 mol%, Na and Si: 0.9 mol%. The dependency of the main peak intensity on sintering temperature exhibits a very sharp maximum at 830°C. The high-temperature peak was rapidly reduced after 825°C. 相似文献
107.
J. R. Lindle W. W. Bewley I. Vurgaftman J. R. Meyer J. L. Johnson M. L. Thomas W. E. Tennant 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):558
A self-referencing, optical modulation technique was used to measure the negative luminescence efficiencies of an array of mid-wave infrared HgCdTe photodiodes with cutoff wavelength 4.6 μm as a function of sample temperature. The internal efficiency at a wavelength of 4 μm was 93% at 295 K, and nearly independent of temperature in the 240–300 K range. This corresponds to an apparent temperature reduction >50 K at room temperature and >30 K at 240 K. Moreover, the reverse-bias saturation current density was only 0.13 A/cm2. The measured transmission and emission spectra were simulated using empirical HgCdTe absorption formulas from the literature. 相似文献
108.
109.
A. V. Turik A. I. Chernobabov G. S. Radchenko S. A. Turik 《Physics of the Solid State》2004,46(12):2213-2216
Effective complex piezoelectric and dielectric constants of disordered heterogeneous systems, such as statistical mixtures consisting of spheroidal particles of the same orientation but with random distribution in space, are studied. It is found for the first time that, in such systems, there exists giant piezoelectric enhancement accompanied by giant relaxation of piezoelectric coefficients and permittivity. The piezoelectric and dielectric spectra differ considerably from the Debye spectra and have a Cole-Cole character. The dependence of the effects considered on the aspect ratios of the spheroids is investigated. The physical mechanisms responsible for the anomalous behavior of the piezoelectric coefficients and permittivity are considered. 相似文献
110.
A. I. Grachev 《Physics of the Solid State》2004,46(3):442-444
The phenomenology of the photogalvanic effect permits prediction of a number of physical phenomena, the most interesting of which is the galvano-dipolar effect. This effect consists in the appearance of an electric dipole moment in a sample through which an electric current is passed. A possible microscopic mechanism of this phenomenon, which can be realized in centrosymmetric media as well, is considered. 相似文献