全文获取类型
收费全文 | 11041篇 |
免费 | 911篇 |
国内免费 | 433篇 |
专业分类
化学 | 232篇 |
力学 | 937篇 |
综合类 | 98篇 |
数学 | 9600篇 |
物理学 | 1518篇 |
出版年
2024年 | 12篇 |
2023年 | 93篇 |
2022年 | 105篇 |
2021年 | 173篇 |
2020年 | 253篇 |
2019年 | 247篇 |
2018年 | 265篇 |
2017年 | 289篇 |
2016年 | 303篇 |
2015年 | 222篇 |
2014年 | 386篇 |
2013年 | 1080篇 |
2012年 | 470篇 |
2011年 | 493篇 |
2010年 | 444篇 |
2009年 | 600篇 |
2008年 | 612篇 |
2007年 | 639篇 |
2006年 | 546篇 |
2005年 | 507篇 |
2004年 | 398篇 |
2003年 | 409篇 |
2002年 | 358篇 |
2001年 | 355篇 |
2000年 | 363篇 |
1999年 | 280篇 |
1998年 | 322篇 |
1997年 | 260篇 |
1996年 | 204篇 |
1995年 | 176篇 |
1994年 | 167篇 |
1993年 | 139篇 |
1992年 | 135篇 |
1991年 | 97篇 |
1990年 | 93篇 |
1989年 | 73篇 |
1988年 | 79篇 |
1987年 | 70篇 |
1986年 | 83篇 |
1985年 | 81篇 |
1984年 | 78篇 |
1983年 | 39篇 |
1982年 | 58篇 |
1981年 | 47篇 |
1980年 | 57篇 |
1979年 | 52篇 |
1978年 | 43篇 |
1977年 | 45篇 |
1976年 | 44篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Aiming at training the feed-forward threshold neural network consisting of nondifferentiable activation functions, the approach of noise injection forms a stochastic resonance based threshold network that can be optimized by various gradient-based optimizers. The introduction of injected noise extends the noise level into the parameter space of the designed threshold network, but leads to a highly non-convex optimization landscape of the loss function. Thus, the hyperparameter on-line learning procedure with respective to network weights and noise levels becomes of challenge. It is shown that the Adam optimizer, as an adaptive variant of stochastic gradient descent, manifests its superior learning ability in training the stochastic resonance based threshold network effectively. Experimental results demonstrate the significant improvement of performance of the designed threshold network trained by the Adam optimizer for function approximation and image classification. 相似文献
2.
This paper infers from a generalized Picone identity the uniqueness of the stable positive solution for a class of semilinear equations of superlinear indefinite type, as well as the uniqueness and global attractivity of the coexistence state in two generalized diffusive prototypes of the symbiotic and competing species models of Lotka–Volterra. The optimality of these uniqueness theorems reveals the tremendous strength of the Picone identity. 相似文献
3.
4.
In this article, we construct and analyze a residual-based a posteriori error estimator for a quadratic finite volume method (FVM) for solving nonlinear elliptic partial differential equations with homogeneous Dirichlet boundary conditions. We shall prove that the a posteriori error estimator yields the global upper and local lower bounds for the norm error of the FVM. So that the a posteriori error estimator is equivalent to the true error in a certain sense. Numerical experiments are performed to illustrate the theoretical results. 相似文献
5.
6.
7.
8.
AbstractRealistic stochastic modeling is increasingly requiring the use of bounded noises. In this work, properties and relationships of commonly employed bounded stochastic processes are investigated within a solid mathematical ground. Four families are object of investigation: the Sine-Wiener (SW), the Doering–Cai–Lin (DCL), the Tsallis–Stariolo–Borland (TSB), and the Kessler–Sørensen (KS) families. We address mathematical questions on existence and uniqueness of the processes defined through Stochastic Differential Equations, which often conceal non-obvious behavior, and we explore the behavior of the solutions near the boundaries of the state space. The expression of the time-dependent probability density of the Sine-Wiener noise is provided in closed form, and a close connection with the Doering–Cai–Lin noise is shown. Further relationships among the different families are explored, pathwise and in distribution. Finally, we illustrate an analogy between the Kessler–Sørensen family and Bessel processes, which allows to relate the respective local times at the boundaries. 相似文献
9.
It is believed that there are more fundamental gauge symmetries beyond those described by the Standard Model of particle physics. The scales of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose considering the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
in the space-based interferometer detectors. Our study demonstrates that the GW energy spectrum is reachable by the LISA, Tianqin, Taiji, BBO, and DECIGO experiments only for the case where the spontaneous breaking of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
is triggered by at least two electroweak singlet scalars. 相似文献
10.
M.A. Tawhid 《Journal of Optimization Theory and Applications》2002,113(1):149-164
In this paper, we give some sufficient conditions for the local uniqueness of solutions to nonsmooth variational inequalities where the underlying functions are H-differentiable and the underlying set is a closed convex set/polyhedral set/box/polyhedral cone. We show how the solution of a linearized variational inequality is related to the solution of the variational inequality. These results extend/unify various similar results proved for C
1 and locally Lipschitzian variational inequality problems. When specialized to the nonlinear complementarity problem, our results extend/unify those of C
2 and C
1 nonlinear complementarity problems. 相似文献