全文获取类型
收费全文 | 268541篇 |
免费 | 2065篇 |
国内免费 | 627篇 |
专业分类
化学 | 142541篇 |
晶体学 | 4167篇 |
力学 | 11963篇 |
综合类 | 9篇 |
数学 | 29614篇 |
物理学 | 82939篇 |
出版年
2019年 | 2305篇 |
2018年 | 3121篇 |
2017年 | 3116篇 |
2016年 | 4512篇 |
2015年 | 2675篇 |
2014年 | 4300篇 |
2013年 | 10715篇 |
2012年 | 8109篇 |
2011年 | 9956篇 |
2010年 | 7099篇 |
2009年 | 6902篇 |
2008年 | 9355篇 |
2007年 | 9563篇 |
2006年 | 8908篇 |
2005年 | 8095篇 |
2004年 | 7446篇 |
2003年 | 6755篇 |
2002年 | 6678篇 |
2001年 | 7347篇 |
2000年 | 5668篇 |
1999年 | 4374篇 |
1998年 | 3865篇 |
1997年 | 3856篇 |
1996年 | 3598篇 |
1995年 | 3349篇 |
1994年 | 3507篇 |
1993年 | 3200篇 |
1992年 | 3672篇 |
1991年 | 3671篇 |
1990年 | 3609篇 |
1989年 | 3464篇 |
1988年 | 3576篇 |
1987年 | 3469篇 |
1986年 | 3296篇 |
1985年 | 4372篇 |
1984年 | 4636篇 |
1983年 | 3876篇 |
1982年 | 4010篇 |
1981年 | 3940篇 |
1980年 | 3914篇 |
1979年 | 3882篇 |
1978年 | 4196篇 |
1977年 | 4110篇 |
1976年 | 4175篇 |
1975年 | 3853篇 |
1974年 | 3895篇 |
1973年 | 4052篇 |
1972年 | 2852篇 |
1971年 | 2378篇 |
1970年 | 2178篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Mathematical Notes - 相似文献
972.
In this paper, we proved the global existence and uniqueness of the strong, weak and mild solutions for one-dimensional Burgers equation perturbed by a Poisson form process, a Poisson form and Q-Wiener process with the Dirichlet bounded condition. We also proved the existence of the invariant measure of these models. 相似文献
973.
The paper presents a theoretical-numerical hybrid method for determining the stresses distribution in composite laminates
containing a circular hole and subjected to uniaxial tensile loading. The method is based upon an appropriate corrective function
allowing a simple and rapid evaluation of stress distributions in a generic plate of finite width with a hole based on the
theoretical stresses distribution in an infinite plate with the same hole geometry and material. In order to verify the accuracy
of the method proposed, various numerical and experimental tests have been performed by considering different laminate lay-ups;
in particular, the experimental results have shown that a combined use of the method proposed and the well-know point-stress
criterion leads to reliable strength predictions for GFRP or CFRP laminates with a circular hole.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 531–570, July–August, 2007. 相似文献
974.
G. M. Henkin 《Proceedings of the Steklov Institute of Mathematics》2006,253(1):195-211
A comprehensive answer is given to two related questions: (i) Can continuous functions be approximated by holomorphic ones on Jordan curves in ?n (A.G. Vitushkin, 1964)? (ii) Is any Jordan curve in ?n holomorphically convex (E.L. Stout, 1970)? 相似文献
975.
M. López Granados F. Cabello Galisteo M. Alifanti J.L.G. Fierro 《Applied Surface Science》2006,252(24):8442-8450
This work reports the research carried out by studying aliquots extracted at different axial coordinates from Three Way Catalyst (TWC) monoliths aged under real traffic conditions. Our study focused on the catalytic properties and on several chemical and physical effects caused in the Front and Rear monolith washcoat surfaces by vehicle aging after 60,000 km. Regarding the catalytic properties, all the used aliquots showed poorer activity than their corresponding fresh counterparts. The strongest deactivation was detected for NO and hydrocarbon conversion. CO conversion was less affected and the Rear monolith was as deactivated as the Front one. The characterisation techniques (TXRF, N2 adsorption-desorption isotherms, XRD and H2-TPR) detected - (i) the deposition of P, Zn and Pb; (ii) the formation of CePO4 on account of the Ce from the washcoat; (iii) thermal sintering; (iv) inhibition of the reducibility of Ce oxides - as the main effects brought about by vehicle aging conditions. The deactivation observed at the beginning of the Front monolith was the result of a combination of the former effects. When moving downstream to higher axial coordinates, Pb accumulation and the loss of specific area appeared to be the only probable sources of deactivation. 相似文献
976.
977.
The solution of the problem of magnetic field penetration into a conducting unclosed ellipsoidal sheath in the presence of a conducting thick-walled spherical sheath is reduced to the solution of the integral Fredholm equation of the second kind. The effect of the apex angle of the unclosed ellipsoidal sheath, geometric parameters of the screens, and electrophysical properties of the spherical sheath material on the field attenuation coefficient inside the ellipsoidal sheath is studied numerically. 相似文献
978.
A theory of a low-pressure discharge in a xenon-molecular hydrogen mixture is developed. It is shown that, in such a discharge, at an interelectrode distance of L = 1 cm and a total plasma pressure of p 0 ~ 1 Torr, the density of negative hydrogen ions produced via the dissociative attachment of thermal electrons to vibrationally excited molecules H2 can reach a value as high as NH ? ≥ 1012 cm?3. According to calculations, the electron temperature in discharge operating regimes under study attains T e ≈ 1?2 eV, which corresponds to the maximum of the e-v exchange rate constant of H2 molecules. This ensures a relatively high rate of vibrational pumping of H2 molecules in the discharge. 相似文献
979.
S. V. Usachev A. S. Osipov G. I. Kostrykina T. I. Irkhina N. B. Tantsova E. G. Fedorova 《Russian Journal of Applied Chemistry》2006,79(11):1890-1895
Variation of the molecular structure characteristics and properties of natural and 1,4-cis-polybutadiene rubbers (gel content, molecular weight, degree of branching of macromolecules, viscosity) in the course of their separate and joint mastication in the presence of dibenzoylaminodiphenyl sulfide as mastication accelerator or without it was studied. 相似文献
980.
Julio Penin Santos Fernando J.G. Landgraf Geraldo Caixeta Guimarães 《Journal of magnetism and magnetic materials》2006
The paper describes effect of texture on the anisotropy of magnetic properties and shows that an Epstein strip arrangement including strips cut in a direction 45° to the rolling direction gives property values that are closer to the average values than the traditional RD+TD arrangement. 相似文献