全文获取类型
收费全文 | 8965篇 |
免费 | 1426篇 |
国内免费 | 1144篇 |
专业分类
化学 | 6549篇 |
晶体学 | 130篇 |
力学 | 501篇 |
综合类 | 72篇 |
数学 | 1254篇 |
物理学 | 3029篇 |
出版年
2024年 | 16篇 |
2023年 | 182篇 |
2022年 | 233篇 |
2021年 | 289篇 |
2020年 | 334篇 |
2019年 | 333篇 |
2018年 | 285篇 |
2017年 | 308篇 |
2016年 | 467篇 |
2015年 | 469篇 |
2014年 | 581篇 |
2013年 | 683篇 |
2012年 | 840篇 |
2011年 | 861篇 |
2010年 | 573篇 |
2009年 | 539篇 |
2008年 | 587篇 |
2007年 | 484篇 |
2006年 | 490篇 |
2005年 | 445篇 |
2004年 | 358篇 |
2003年 | 268篇 |
2002年 | 246篇 |
2001年 | 207篇 |
2000年 | 153篇 |
1999年 | 225篇 |
1998年 | 149篇 |
1997年 | 117篇 |
1996年 | 126篇 |
1995年 | 127篇 |
1994年 | 97篇 |
1993年 | 63篇 |
1992年 | 60篇 |
1991年 | 59篇 |
1990年 | 70篇 |
1989年 | 47篇 |
1988年 | 31篇 |
1987年 | 22篇 |
1986年 | 28篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1928年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
992.
Dang Hai Nguyen George Yin Chao Zhu 《Stochastic Processes and their Applications》2017,127(10):3135-3158
This work is devoted to switching diffusions that have two components (a continuous component and a discrete component). Different from the so-called Markovian switching diffusions, in the setup, the discrete component (the switching) depends on the continuous component (the diffusion process). The objective of this paper is to provide a number of properties related to the well posedness. First, the differentiability with respect to initial data of the continuous component is established. Then, further properties including uniform continuity with respect to initial data, and smoothness of certain functionals are obtained. Moreover, Feller property is obtained under only local Lipschitz continuity. Finally, an example of Lotka–Volterra model under regime switching is provided as an illustration. 相似文献
993.
Infinite Horizon Controlled Diffusions with Randomly Varying and State-Dependent Discount Cost Rates
Xianggang Lu G. Yin Xianping Guo 《Journal of Optimization Theory and Applications》2017,172(2):535-553
This work focuses on optimal controls of diffusions in an infinite horizon. It has several distinct features in contrast to the existing literature. The discount factor is allowed to be randomly varying and state dependent. The existence and uniqueness of the viscosity solution to the associated Hamilton–Jacobi–Bellman equation are established. The verification theorem is also obtained. Because closed-form solutions are virtually impossible to obtain in most cases, we develop numerical methods. Using the Markov chain approximation methods, numerical schemes are constructed; viscosity solution methods are used to prove the convergence of the algorithm. In addition, examples are given for demonstration purpose. 相似文献
994.
Structure-enforced matrix factorization (SeMF) represents a large class of mathematical models appearing in various forms of principal component analysis, sparse coding, dictionary learning and other machine learning techniques useful in many applications including neuroscience and signal processing. In this paper, we present a unified algorithm framework, based on the classic alternating direction method of multipliers (ADMM), for solving a wide range of SeMF problems whose constraint sets permit low-complexity projections. We propose a strategy to adaptively adjust the penalty parameters which is the key to achieving good performance for ADMM. We conduct extensive numerical experiments to compare the proposed algorithm with a number of state-of-the-art special-purpose algorithms on test problems including dictionary learning for sparse representation and sparse nonnegative matrix factorization. Results show that our unified SeMF algorithm can solve different types of factorization problems as reliably and as efficiently as special-purpose algorithms. In particular, our SeMF algorithm provides the ability to explicitly enforce various combinatorial sparsity patterns that, to our knowledge, has not been considered in existing approaches. 相似文献
995.
当二次等参体元用于分析接触问题时,接触面上节点集中接触力不同号给建立接触判据造成困难。本文建立了由节点集中接触力计算接触面上分布接触力节点值的方法,从而可顺利建立接触判据。此方法已成功应用于工程中的弹性固体接触问题分析,文末给出了一个计算实例。 相似文献
996.
各向异性晶体滑移有限元程序及其应用 总被引:4,自引:1,他引:4
本文全面介绍了各向异性晶体滑移结构强度和蠕变分析有限元程序的原理、功能特点及其在镍基单晶涡轮叶片中的应用实例。 相似文献
997.
尹双增 《应用数学和力学(英文版)》1985,6(6):533-544
The existence of the plastic area around the crack tip is an important factor against thecracking.In this plastic region.the cracking most likely develops in such a direction alongwhich the distance from the existant crack tip to the plastic region edge is the shortest one.Substituting the stress components at the crack tip for a combined cracking into R.Von.Mises equation of yielding condition,the boundary equation of the plastic regionaround the crack tip can be expressed as:where r is the distance from the crack tip to the boundary of plastic region.The direction inwhich the cracking develops can be determined by following conditions:One form of the material failures is the slipping under the action of shear stress.Underthe conditions of complex stress,the octahedral shear stress on a point around the crack tipis here.B devotes the.factor of the octahedral shear stress,which relates to the size. pattern ofcrack and the exerted stress.Its magnitude reflects the strength of the stress field aroundthe c 相似文献
998.
999.
1000.