全文获取类型
收费全文 | 1491篇 |
免费 | 87篇 |
国内免费 | 37篇 |
专业分类
化学 | 71篇 |
晶体学 | 1篇 |
力学 | 138篇 |
综合类 | 11篇 |
数学 | 1230篇 |
物理学 | 164篇 |
出版年
2023年 | 16篇 |
2022年 | 21篇 |
2021年 | 25篇 |
2020年 | 27篇 |
2019年 | 24篇 |
2018年 | 22篇 |
2017年 | 31篇 |
2016年 | 31篇 |
2015年 | 36篇 |
2014年 | 62篇 |
2013年 | 99篇 |
2012年 | 82篇 |
2011年 | 51篇 |
2010年 | 50篇 |
2009年 | 76篇 |
2008年 | 83篇 |
2007年 | 98篇 |
2006年 | 87篇 |
2005年 | 58篇 |
2004年 | 57篇 |
2003年 | 52篇 |
2002年 | 52篇 |
2001年 | 46篇 |
2000年 | 34篇 |
1999年 | 47篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 25篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 1篇 |
排序方式: 共有1615条查询结果,搜索用时 15 毫秒
151.
A. Montanaro 《Journal of Elasticity》1999,57(1):25-53
By extending the procedure of linearization for constrained elastic materials in the papers by Marlow and Chadwick et al., we set up a linearized theory of constrained materials with initial stress (not necessarily based on a nonlinear theory).
The conditions of propagation are characterized for small-displacement waves that may be either of discontinuity type of any
given order or, in the homogeneous case, plane progressive. We see that, just as in the unconstrained case, the laws of propagation
of discontinuity waves are the same as those of progressive waves. Waves are classified as mixed, kinematic, or ghost. Then we prove that the analogues of Truesdell"s two equivalence theorems on wave propagation in finite elasticity hold for
each type of wave.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
152.
本文基于H∞控制理论研究了传感器和作动器非同位配置情况下,柔性悬臂梁的多模态振动抑制问题。采用频域辨识方法获取低阶名义模型,合理选取加性不确定权函数和性能权函数,将鲁棒H∞控制问题转化为标准H∞控制问题。为了避免H∞控制器设计过程中产生的零极点对消问题,在求解过程中引入区域极点约束。比较了鲁棒H∞控制器和不考虑高阶未建模动态的非鲁棒H∞控制器的控制效果,实验结果表明,设计的鲁棒H∞控制器能够有效抑制柔性梁的前三阶模态振动,而且不会发生溢出问题。 相似文献
153.
In this paper, we consider an optimal control problem of switched systems with input and state constraints. Since the complexity of such constraint and switching laws, it is difficult to solve the problem using standard optimization techniques. In addition, although conjugate gradient algorithms are very useful for solving nonlinear optimization problem, in practical implementations, the existing Wolfe condition may never be satisfied due to the existence of numerical errors. And the mode insertion technique only leads to suboptimal solutions, due to only certain mode insertions being considered. Thus, based on an improved conjugate gradient algorithm and a discrete filled function method, an improved bi-level algorithm is proposed to solve this optimization problem. Convergence results indicate that the proposed algorithm is globally convergent. Three numerical examples are solved to illustrate the proposed algorithm converges faster and yields a better cost function value than existing bi-level algorithms. 相似文献
154.
155.
In this paper, we propose a Bayesian semiparametric mean-covariance regression model with known covariance structures. A mixture model is used to describe the potential non-normal distribution of the regression errors. Moreover, an empirical likelihood adjusted mixture of Dirichlet process model is constructed to produce distributions with given mean and variance constraints. We illustrate through simulation studies that the proposed method provides better estimations in some non-normal cases. We also demonstrate the implementation of our method by analyzing the data set from a sleep deprivation study. 相似文献
156.
本文针对工件间具有链状优先约束和relocation资源约束的极小化加权总完工时间调度优化问题展开研究.针对这一NP难问题,利用relocation约束的性质和贪婪算法的思想,设计了一个多项式近似算法,并证明了当链不可中断,每个链具有相同工件数和工件间具有相同加工时间时,2为该算法的紧界. 相似文献
157.
Adrian Falkowski Leszek Słomiński 《Stochastic Processes and their Applications》2017,127(11):3536-3557
We study the existence, uniqueness and stability of solutions of general stochastic differential equations with constraints driven by semimartingales and processes with bounded -variation. Applications to SDEs with constraints driven by fractional Brownian motion and standard Brownian motion are given. 相似文献
158.
159.
Monika Wolfmayr 《Numerical Methods for Partial Differential Equations》2017,33(2):403-424
In this work, new results on functional type a posteriori estimates for elliptic optimal control problems with control constraints are presented. More precisely, we derive new, sharp, guaranteed, and fully computable lower bounds for the cost functional in addition to the already existing upper bounds. Using both, the lower and the upper bounds, we arrive at two‐sided estimates for the cost functional. We prove that these bounds finally lead to sharp, guaranteed and fully computable upper estimates for the discretization error in the state and the control of the optimal control problem. First numerical tests are presented confirming the efficiency of the a posteriori estimates derived. © 2016 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 403–424, 2017 相似文献
160.
The title problem is given the following explicit solution: =
D
S|D, where the elasticity tensor in the constrained case is the restriction to the constraint subspace D of a corresponding unconstrained elasticity tensor S, followed by composition with the orthogonal projection
D
on D. 相似文献