全文获取类型
收费全文 | 10808篇 |
免费 | 737篇 |
国内免费 | 722篇 |
专业分类
化学 | 1717篇 |
晶体学 | 80篇 |
力学 | 788篇 |
综合类 | 130篇 |
数学 | 6328篇 |
物理学 | 3224篇 |
出版年
2023年 | 68篇 |
2022年 | 163篇 |
2021年 | 180篇 |
2020年 | 171篇 |
2019年 | 187篇 |
2018年 | 149篇 |
2017年 | 202篇 |
2016年 | 219篇 |
2015年 | 161篇 |
2014年 | 280篇 |
2013年 | 756篇 |
2012年 | 387篇 |
2011年 | 511篇 |
2010年 | 511篇 |
2009年 | 1005篇 |
2008年 | 1015篇 |
2007年 | 912篇 |
2006年 | 823篇 |
2005年 | 556篇 |
2004年 | 420篇 |
2003年 | 479篇 |
2002年 | 448篇 |
2001年 | 353篇 |
2000年 | 296篇 |
1999年 | 295篇 |
1998年 | 315篇 |
1997年 | 228篇 |
1996年 | 164篇 |
1995年 | 120篇 |
1994年 | 125篇 |
1993年 | 87篇 |
1992年 | 72篇 |
1991年 | 66篇 |
1990年 | 58篇 |
1989年 | 44篇 |
1988年 | 58篇 |
1987年 | 45篇 |
1986年 | 38篇 |
1985年 | 47篇 |
1984年 | 40篇 |
1983年 | 25篇 |
1982年 | 44篇 |
1981年 | 26篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We find exact solutions of the equations of motion for a closed relativistic string that carries a point mass and moves in the space given by the direct product of Minkowski space and a compact manifold (multidimensional torus). We investigate physical characteristics of the system states described by these solutions.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 142, No. 1, pp. 72–82, January, 2005. 相似文献
992.
993.
A novel finite point method is developed to simulate flow problems. The mashes in the traditional numerical methods are supplanted by the distribution of points in the calculation domain. A local interpolation based on the properties of Taylor series expansion is used to construct an approximation for unknown functions and their derivatives. An upwind‐dominated scheme is proposed to efficiently handle the non‐linear convection. Comparison with the finite difference solutions for the two‐dimensional driven cavity flow and the experimental results for flow around a cylinder shows that the present method is capable of satisfactorily predicting the flow separation characteristic. The present algorithm is simple and flexible for complex geometric boundary. The influence of the point distribution on computation time and accuracy of results is included. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
994.
Herbert H.H. Homeier 《Numerical Algorithms》1998,17(3-4):223-239
The stability of a large class of nonlinear sequence transformations is analyzed. Considered are variants of the J transformation [17]. Suitable variants of this transformation belong to the most successful extrapolation algorithms that
are known [20]. Similar to recent results of Sidi, it is proved that the
p
{J} transformations, the Weniger S transformation, the Levin transformation and a special case of the generalized Richardson extrapolation process of Sidi are
S-stable. An efficient algorithm for the calculation of stability indices is presented. A numerical example demonstrates the
validity of the approach.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
995.
996.
The plane problem of steady-state small oscillations of a horizontal cylinder located at the interface between two fluids of different densities and indefinite depth is considered in the linear formulation. Boundary integral equations for the surface source distribution are derived. The behavior of the distributed singularities at points of intersection of the body contour and the interface is investigated. The problem of oscillations of a circular cylinder is solved by the multipole expansion method. The apparent mass and damping coefficients of the radiation problem and the reflection coefficient of the problem of scattering of an impinging wave by a floating body are calculated. 相似文献
997.
张连平 《高校应用数学学报(A辑)》2002,17(3):318-322
本文给出例子,说明离散算子本征投影一致有界推不出其本征幂零一致,有界幂零一致有界也推不出本征幂零的幂一致有界。 相似文献
998.
对武汉大学电波综合观测站于1991年的降雨曲线进行测量,当采样时间为5min时,用单变量雨强时间序列进一步研究了降雨这一大气过程中雨强分维数随时间的变化特性.结果表明,在灾害性降雨天气前后其雨强分维数仍然发生了显著性的改变. 相似文献
999.
A. A. Vladimirov 《Mathematical Notes》2006,79(3-4):342-355
In this paper, we study the problem of the boundary accumulation of a discrete spectrum, which is essential for a boundary-value problem of fourth order arising in the theory of small transverse vibrations in an inhomogeneous viscoelastic rod (a Kelvin—Voigt body). We establish conditions for such an accumulation and its asymptotics, which are expressed in terms of the coefficients defining the problem posed by the differential expression. The results obtained are illustrated by numerical computation data. 相似文献
1000.
双氟取代苯和联苯类液晶化合物的量子化学研究 总被引:1,自引:1,他引:0
运用AM1和PM3两种SCF-MO方法,通过能量梯度全优化计算,给出了对一系列环上双氟取代苯、联苯液晶化合物的稳定几何构型、电子结构和分子基本性质(生成热、偶极矩、前沿分子轨道能级等)。联系有机结构理论进行了分析和讨论。初步阐明了其分子结构与介电各向异性之间的关系,为设计和开发新型液晶分子研究提供了有较大价值的线索。 相似文献