首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   535939篇
  免费   4289篇
  国内免费   1325篇
化学   273526篇
晶体学   7712篇
力学   26255篇
综合类   17篇
数学   69295篇
物理学   164748篇
  2021年   5113篇
  2020年   5555篇
  2019年   6286篇
  2018年   8468篇
  2017年   8611篇
  2016年   11745篇
  2015年   6290篇
  2014年   10558篇
  2013年   23907篇
  2012年   18632篇
  2011年   22141篇
  2010年   16622篇
  2009年   16464篇
  2008年   20997篇
  2007年   20832篇
  2006年   18933篇
  2005年   16937篇
  2004年   15716篇
  2003年   14195篇
  2002年   14118篇
  2001年   14839篇
  2000年   11455篇
  1999年   8841篇
  1998年   7679篇
  1997年   7563篇
  1996年   7041篇
  1995年   6332篇
  1994年   6358篇
  1993年   6111篇
  1992年   6470篇
  1991年   6955篇
  1990年   6655篇
  1989年   6554篇
  1988年   6401篇
  1987年   6209篇
  1986年   5933篇
  1985年   7538篇
  1984年   7893篇
  1983年   6628篇
  1982年   6931篇
  1981年   6450篇
  1980年   6129篇
  1979年   6602篇
  1978年   6850篇
  1977年   6739篇
  1976年   6688篇
  1975年   6392篇
  1974年   6222篇
  1973年   6508篇
  1972年   4762篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
92.
It is shown that the exact solution of the problem of convective heat exchange in a low-Prandtl-number fluid flow (Pr ? 1) can be obtained for a two-dimensional body of arbitrary shape provided that the conformal mapping relating the body contour with a circle is known. By way of example, the Joukowsky airfoil is considered.  相似文献   
93.
A class of Hamiltonian dynamic systems integrated by the variable separation method is considered. The integration for this class is the inversion of an Abel mapping on hyperelliptic curves. We prove that the derivative of the Abel mapping is the Stäckel matrix, which determines a diagonal Riemannian metric and curvilinear orthogonal coordinate systems in a flat space. Lax representations with the spectral parameter are constructed. The corresponding classicalr-matrices are dynamic. It is shown how the class of pointwise canonical transformations can be naturally generalized using the Abel integral reduction theory.  相似文献   
94.
A model kinetic equation is constructed for the transport of a massless Bose gas. This equation is applied to solve the boundary value problem for the transport of radiation in the half-space occupied by a dispersive medium that is in local thermal equilibrium with the radiation. It is shown that the difference in temperature between the dispersive medium and the incident radiation substantially depends on the character of the scattering properties of the particles in the medium. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 111, No. 3, pp. 462–472, June, 1997.  相似文献   
95.
96.
97.
A set theory ZFI′ which does not employ the Law of the Excluded Middle φ ∀ ⊥ φ, for all φ, retians the stock of expressive capacities of the classical set theory ZF, on the one hand, and has many of the features of an effective theory on the other. In the article, a broad class of formulas σ is constructed for which ZF ⊥ σ implies ZFI′ ⊥ σ. This result provides a generalization of Friedman's theorem on AE-arithmetic formulas. Besides, we prove transfer theorems of classical logic for the case of rings; in particular, Hilbert's theorem on zeros and Artin's theorem on ordered fields are extended to the case of regular f-rings, and we bring in appropriate upper bounds for them. Supported by RFFR grant No. 93-012-1027. Translated fromAlgebra i Logika, Vol. 36, No. 3, pp. 282–303, May–June, 1997.  相似文献   
98.
We show that the modified method for finite-dimensional approximation of solutions of Fredholm integral equations of the first kind presented in this paper is more economical than traditional methods for finite-dimensional approximation. Institute of Mathematies, Ukrainian Academy of Science, Kiev. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 49, No. 2, pp. 289–295, February, 1997.  相似文献   
99.
Solutions of the dispersion equations for polariton states in finite one-dimensional crystals of arbitrary length are obtained. The appearance and evolution of the radiative and nonradiative polariton branches are traced as the length varies from two monomers to limiting values, above which the spectrum no longer undergoes significant changes. The dependences of the frequencies and radiative widths on the polariton wave vector are found for various orientations of the dipole moment of the quantum transition. The evolution of superradiance as the length of the crystal increases is traced. Some previously unknown significant features of the polariton spectrum are noted particularly the damping of the branch traditionally termed nonradiative as a consequence of emission from the end faces. Fiz. Tverd. Tela (St. Petersburg) 40, 2136–2140 (November 1998)  相似文献   
100.
A. V. Pomyalov  I. Laulicht  J. Barak 《Physica A》1993,200(1-4):267-277
The microwave subsidiary absorption threshold in tangentially magnetized yttrium-iron-garnet (YIG) films was measured as a function of the static magnetic field, film thickness and decrease in the 0.3–3 μm range is observed. The effect is explained quantitatively by using modified Damon-Eshbach dispersion relations which take into account exchange interactions.

The effect of temperature on hcrit, the smallest threshold field amplitude, in the 250<T< 450 K temperature range can be expressed by an empirical relationship hcrit Ms(T)-1.6 where Ms is the saturation magnetization. This hcrit vs Ms relationship is similar to that obtained for the magnetization dependence of parallel pump thresholds in Li-Ti ferrite compounds.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号