全文获取类型
收费全文 | 13871篇 |
免费 | 959篇 |
国内免费 | 624篇 |
专业分类
化学 | 1671篇 |
晶体学 | 49篇 |
力学 | 5437篇 |
综合类 | 111篇 |
数学 | 5505篇 |
物理学 | 2681篇 |
出版年
2024年 | 27篇 |
2023年 | 163篇 |
2022年 | 217篇 |
2021年 | 237篇 |
2020年 | 367篇 |
2019年 | 251篇 |
2018年 | 286篇 |
2017年 | 352篇 |
2016年 | 417篇 |
2015年 | 346篇 |
2014年 | 654篇 |
2013年 | 1091篇 |
2012年 | 561篇 |
2011年 | 798篇 |
2010年 | 644篇 |
2009年 | 830篇 |
2008年 | 775篇 |
2007年 | 790篇 |
2006年 | 700篇 |
2005年 | 613篇 |
2004年 | 577篇 |
2003年 | 554篇 |
2002年 | 501篇 |
2001年 | 484篇 |
2000年 | 399篇 |
1999年 | 406篇 |
1998年 | 352篇 |
1997年 | 309篇 |
1996年 | 255篇 |
1995年 | 257篇 |
1994年 | 198篇 |
1993年 | 163篇 |
1992年 | 197篇 |
1991年 | 145篇 |
1990年 | 136篇 |
1989年 | 76篇 |
1988年 | 51篇 |
1987年 | 56篇 |
1986年 | 24篇 |
1985年 | 52篇 |
1984年 | 51篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1971年 | 1篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
21.
L. C. Lew Yan Voon C. Galeriu M. Willatzen 《Physica E: Low-dimensional Systems and Nanostructures》2003,18(4):547-549
We argue that the two-dimensional elliptic quantum dot problem with finite barrier cannot be exactly solved, contrary to a recent assertion (van den Broek and Peeters, Physica E 11 (2001) 345. We also prove it explicitly by numerically calculating the correct energy spectrum. 相似文献
22.
We present a practical polynomial-time algorithm for computing the
zeta function of a Kummer curve over a finite field of small
characteristic. Such algorithms have recently been obtained using a
method of Kedlaya based upon Monsky–Washnitzer cohomology, and are of
interest in cryptography. We take a different approach.
The problem is reduced to that of computing the L-function
of a multiplicative character sum. This latter task is achieved via a
cohomological formula based upon the work of Dwork and Reich. We show,
however, that our method and that of Kedlaya are very closely related.Dedicated to the memory of Gian-Carlo Rota 相似文献
23.
LiuYuqi LiZhigang YahYakun 《Acta Mechanica Solida Sinica》2004,17(1):58-64
By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM. 相似文献
24.
The paper presents a new formulation of the integral boundary element method (BEM) using subdomain technique. A continuous approximation of the function and the function derivative in the direction normal to the boundary element (further ‘normal flux’) is introduced for solving the general form of a parabolic diffusion‐convective equation. Double nodes for normal flux approximation are used. The gradient continuity is required at the interior subdomain corners where compatibility and equilibrium interface conditions are prescribed. The obtained system matrix with more equations than unknowns is solved using the fast iterative linear least squares based solver. The robustness and stability of the developed formulation is shown on the cases of a backward‐facing step flow and a square‐driven cavity flow up to the Reynolds number value 50 000. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
25.
26.
27.
In this work, the effect of flexibility on the trajectory of a planar two-link manipulator is studied using integrated computer-aided design/analysis (CAD/CAE) procedures. The solid models and finite element models of the parts of the manipulator are created by using the CAD/CAE software I-DEAS. The assembly is defined, and knowing the payload and the end point trajectory, the velocities and accelerations of the parts, joint forces and driving torques are calculated using the rigid body dynamics. All the time dependent nodal forces acting on the parts including distributed gravity and inertia forces are created in files with the I-DEAS program file format. The finite element vibration analysis of the parts is performed by I-DEAS. The end point vibrations and the deviations from the rigid-body trajectory are analyzed for different types of end point acceleration curves. A circular trajectory is considered as an example. It is observed that the precision of the manipulator can be increased by testing different end point acceleration curves without changing the trajectory and the duration of the end point work. The procedure explained in this work can be used for this purpose successfully. 相似文献
28.
Riad Hassani Patrick Hild Ioan Ionescu 《Mathematical Methods in the Applied Sciences》2004,27(1):47-67
We consider the Signorini problem with Coulomb friction in elasticity. Sufficient conditions of non‐uniqueness are obtained for the continuous model. These conditions are linked to the existence of real eigenvalues of an operator in a Hilbert space. We prove that, under appropriate conditions, real eigenvalues exist for a non‐local Coulomb friction model. Finite element approximation of the eigenvalue problem is considered and numerical experiments are performed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
29.
美式期权定价中非局部问题的有限元方法 总被引:2,自引:1,他引:1
在本文中 ,我们关心的是美式期权的有限元方法 .首先 ,根据 [4 ]我们对所讨论的问题引进一个新奇的实用的方法 ,它涉及到对原问题重新形成准确的数学公式 ,使得数值解的计算可以在非常小的区域上进行 ,从而该算法计算速度快精度高 .进而 ,我们利用超逼近分析技术得到了有限元解关于 L2 -模的最优估计 . 相似文献
30.
关于具有给定Sylow子群正规化子的有限群Ⅱ 总被引:1,自引:0,他引:1
本文在有限可解群中解决了:任意m-秩≤2的子群闭的局部群系具有性质:“如果群G的非单位Sylow子群的正规化子属于,则群G也属于的一个充分必要条件. 相似文献