全文获取类型
收费全文 | 7586篇 |
免费 | 390篇 |
国内免费 | 363篇 |
专业分类
化学 | 498篇 |
晶体学 | 18篇 |
力学 | 2850篇 |
综合类 | 41篇 |
数学 | 3000篇 |
物理学 | 1932篇 |
出版年
2024年 | 9篇 |
2023年 | 89篇 |
2022年 | 117篇 |
2021年 | 116篇 |
2020年 | 217篇 |
2019年 | 135篇 |
2018年 | 161篇 |
2017年 | 189篇 |
2016年 | 232篇 |
2015年 | 238篇 |
2014年 | 409篇 |
2013年 | 791篇 |
2012年 | 244篇 |
2011年 | 475篇 |
2010年 | 395篇 |
2009年 | 500篇 |
2008年 | 453篇 |
2007年 | 449篇 |
2006年 | 393篇 |
2005年 | 282篇 |
2004年 | 324篇 |
2003年 | 249篇 |
2002年 | 222篇 |
2001年 | 170篇 |
2000年 | 142篇 |
1999年 | 151篇 |
1998年 | 165篇 |
1997年 | 132篇 |
1996年 | 97篇 |
1995年 | 85篇 |
1994年 | 87篇 |
1993年 | 85篇 |
1992年 | 96篇 |
1991年 | 97篇 |
1990年 | 60篇 |
1989年 | 44篇 |
1988年 | 35篇 |
1987年 | 44篇 |
1986年 | 21篇 |
1985年 | 43篇 |
1984年 | 33篇 |
1983年 | 21篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有8339条查询结果,搜索用时 171 毫秒
81.
高阶非线性波动方程的有限差分方法 总被引:2,自引:0,他引:2
本文研究一类广泛的高阶非线性波动方程组初边值问题的有限差分格式,用离散泛函分析方法和先验估计的技巧得到了有限差分格式的收敛性。 相似文献
82.
YANG BENFU 《高校应用数学学报(英文版)》1994,9(3):291-297
USINGFINITEGEOMETRIESTOCONSTRUCT3-PBIB(2)DESIGNSAND3-DESIGNS¥YANGBENFU(DepartmentofMathematics,ChengduTeachersCollege,Chengdu... 相似文献
83.
This paper investigates the applicability and accuracy of existing formulation methods in general purpose finite element programs to the finite strain deformation problems. The basic shortcomings in using such programs in these applications are then pointed out and the need for a different type of formulation is discussed. An arbitrary Lagrangian-Eulerian (ALE) method is proposed and a concise survey of ALE formulation is given. A consistent and complete ALE formulation is derived from the virtual work equation transformed to arbitrary computational reference configurations. Differences between the proposed formulations and similar ones in the literature are discussed. The proposed formulation presents a general approach to ALE method. It includes load correction terms and is suitable for rate-dependent and rate-independent material constitutive law. The proposed formulation reduces to both updated Lagrangian and Eulerian formulations as special cases. 相似文献
84.
Axel Kohnert 《Discrete Applied Mathematics》2007,155(11):1451-1457
We construct new linear two-weight codes over the finite field with q elements. To do so we solve the equivalent problem of finding point sets in the projective geometry with certain intersection properties. These point sets are in bijection to solutions of a Diophantine linear system of equations. To reduce the size of the system of equations we restrict the search for solutions to solutions with special symmetries.Two-weight codes can be used to define strongly regular graphs. We give tables of the two-weight codes and the corresponding strongly regular graphs. In some cases we find new distance-optimal two-weight codes and also new strongly regular graphs. 相似文献
85.
86.
87.
We apply the least‐squares finite element method with adaptive grid to nonlinear time‐dependent PDEs with shocks. The least‐squares finite element method is also used in applying the deformation method to generate the adaptive moving grids. The effectiveness of this method is demonstrated by solving a Burgers' equation with shocks. Computational results on uniform grids and adaptive grids are compared for the purpose of evaluation. The results show that the adaptive grids can capture the shock more sharply with significantly less computational time. For moving shock, the adaptive grid moves correctly with the shock. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
88.
Atsushi Yamagami 《Journal of Number Theory》2003,99(1):120-138
In this article, for a residual modular representation defined over an arbitrary finite field, Gouvêa's conjecture which says that the universal deformation ring is isomorphic to a certain Hecke algebra is proven in the unobstructed case. 相似文献
89.
Maxim Braverman Valentin Silantyev 《Transactions of the American Mathematical Society》2006,358(8):3329-3361
We extend the Novikov Morse-type inequalities for closed 1-forms in 2 directions. First, we consider manifolds with boundary. Second, we allow a very degenerate structure of the critical set of the form, assuming only that the form is non-degenerated in the sense of Kirwan. In particular, we obtain a generalization of a result of Floer about the usual Morse inequalities on a manifold with boundary. We also obtain an equivariant version of our inequalities.
Our proof is based on an application of the Witten deformation technique. The main novelty here is that we consider the neighborhood of the critical set as a manifold with a cylindrical end. This leads to a considerable simplification of the local analysis. In particular, we obtain a new analytic proof of the Morse-Bott inequalities on a closed manifold.
90.
激光激发的声表面波为材料表面缺陷的检测提供了有力的工具.针对含缺陷材料在模型边界上的复杂性,建立了基于平面应变的有限元模型并选取了相同厚度但含有不同深度的表面裂痕的单层铝板进行了对比计算,得到了声表面波经过不同深度的表面裂痕时产生的反射及透射信号波形的时域特征.进而引入了基于Wigner-Ville分布理论的时-频分析方法计算裂痕前、后散射的瞬态表面波的能量在时间-频率平面内分布的情形.结果显示:声表面波接近中心频率的某一频率成分在经过深度小于其中心波长的表面缺陷时,随着裂痕深度的增加,对应于该频率的反射系数呈现单调递增的趋势;而透射系数呈现递减的特征,这一结果可以为激光超声检测表面缺陷提供一种定量的表征手段. 相似文献