全文获取类型
收费全文 | 7526篇 |
免费 | 2367篇 |
国内免费 | 686篇 |
专业分类
化学 | 715篇 |
晶体学 | 116篇 |
力学 | 1335篇 |
综合类 | 74篇 |
数学 | 780篇 |
物理学 | 7559篇 |
出版年
2024年 | 11篇 |
2023年 | 57篇 |
2022年 | 123篇 |
2021年 | 129篇 |
2020年 | 188篇 |
2019年 | 164篇 |
2018年 | 184篇 |
2017年 | 228篇 |
2016年 | 271篇 |
2015年 | 262篇 |
2014年 | 533篇 |
2013年 | 554篇 |
2012年 | 467篇 |
2011年 | 681篇 |
2010年 | 546篇 |
2009年 | 580篇 |
2008年 | 629篇 |
2007年 | 613篇 |
2006年 | 564篇 |
2005年 | 501篇 |
2004年 | 451篇 |
2003年 | 387篇 |
2002年 | 378篇 |
2001年 | 373篇 |
2000年 | 320篇 |
1999年 | 233篇 |
1998年 | 202篇 |
1997年 | 168篇 |
1996年 | 127篇 |
1995年 | 115篇 |
1994年 | 80篇 |
1993年 | 92篇 |
1992年 | 71篇 |
1991年 | 55篇 |
1990年 | 51篇 |
1989年 | 36篇 |
1988年 | 33篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 921 毫秒
961.
设S和R是环.本文证明了若下述条件之一成立,则S和R具有相同的凝聚维数:(1)S是R的优越扩张;(2)S和MMorita等价.作为上述结果的推论,我们证明了环R和下述环类具有相同的凝聚维数:(i)R上的矩阵环Mn(R);(i)R和有限群G(要求|G|-1∈R)的斜群环;(ii)Smash积R#G*(要求G是有限群且|G|-1∈R,R是G分次环) 相似文献
962.
非相干光作用下的Ce:BaTiO3自泵浦相位共轭镜特性 总被引:1,自引:0,他引:1
地Ce:BaTiO3晶体的自泵浦相位共竟然非相干光作用下自泵浦相位共轭反射率增强的特性进行了研究。实验是在He-Ne激光产生稳态自泵浦相位共轭输出后,用非相干光平行c轴照射来获得这一增强特性的,当水平移动非相干光入射位置,发现有两个区域非相干光作用能使相位共轭反射率增加,本文对此进行了相应的分析和讨论。 相似文献
963.
We consider a model of particle motion in the field of an electromagnetic monopole (in the Coulomb-Dirac field) perturbed by homogeneous and inhomogeneous electric fields. After quantum averaging, we obtain an integrable system whose Hamiltonian can be expressed in terms of the generators of an algebra with polynomial commutation relations. We construct the irreducible representations of this algebra and its hypergeometric coherent states. We use these states to represent the eigenfunctions of the original problem in terms of the solutions of the model ordinary differential equation. We also present the asymptotic approximations of the eigenvalues in the leading term of the perturbation theory, where the degeneration of the spectrum is removed completely.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 142, No. 1, pp. 127–147, January, 2005. 相似文献
964.
965.
966.
We propose a technique for rapid monitoring of single-mode operation of a tunable injection laser, based on analysis of the
fine structure of the power-current characteristic obtained with self-heterodyning, using a Michelson interferometer. The
technique makes it possible to determine the range for single-mode lasing and mode tuning as well as the presence of spurious
optical feedback, and to estimate the coherence length.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 119–123, January–February, 2006. 相似文献
967.
968.
Summary Treated herein is an elastica under a point load. One end of the elastica is fully restrained against translation, and elastically
restrained against rotation, while the other end portion is allowed to slide over a friction support. The considered elastica
problem belongs to the class of large-deflection beam problems with variable deformed arc-lengths between the supports. To
solve the governing nonlinear differential equation together with the boundary conditions, the elliptic integral method has
been used. The method yields closed-form solutions that are expressed in a set of transcendental equations in terms of elliptic
integrals. Using an iterative scheme, pertinent bending results are computed for different values of coefficient of friction,
elastic rotational spring constant and loading position, so that their effects may be examined. Also, these accurate solutions
provide useful reference sources for checking the convergence, accuracy and validity of results obtained from numerical methods
and software for large deflection beam analysis. It is interesting to note that this class of elastica problem may have two
equilibrium states; a stable one and an unstable one.
Received 5 August 1996; accepted for publication 14 February 1997 相似文献
969.
On model substances of Cu-Sn(Pb) solders it is shown by the combined use of several physical analytical methods that the intermetallic compounds formed during the annealing process have a crystalline structure, which can be observed also three-dimensionally by ion etching. Moreover, grain boundaries as well as phases become visible, and it is possible to determine the crystallographic orientation of the individual crystals in the Cu starting material and in the diffusion zones by means of the Kossel technique. As a result of the investigations, conclusions can be drawn with respect to the diffusion process, especially also to the crystallographic structure of the diffusion zones and the dendritic growth.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
970.
The problem of heat transfer in the wall region of a turbulent boundary layer has been investigated. The resonant triad in
the theory of hydrodynamic stability was used to obtain the velocity field induced by the coherent structures in the wall
region of the turbulent boundary layer, while the small scale turbulence was represented by a simple model. By such a new
approach of modeling, the 3-D temperature field is calculated, the mean temperature profile in the wall region and the Nusselt
number characterizing the heat flux, which was found to be in good agreement with the experimental observations are obtained.
The instantaneous temperature field had streaky structures, thus offering a mechanism for their generation found in numerical
simulations.
Project supported by the National Natural Science Foundation of China (Grant No. 19132011). 相似文献