全文获取类型
收费全文 | 177025篇 |
免费 | 14463篇 |
国内免费 | 13807篇 |
专业分类
化学 | 61758篇 |
晶体学 | 2411篇 |
力学 | 12847篇 |
综合类 | 1989篇 |
数学 | 54925篇 |
物理学 | 71365篇 |
出版年
2023年 | 1067篇 |
2022年 | 1581篇 |
2021年 | 2276篇 |
2020年 | 2920篇 |
2019年 | 3298篇 |
2018年 | 3110篇 |
2017年 | 3227篇 |
2016年 | 3433篇 |
2015年 | 2950篇 |
2014年 | 4914篇 |
2013年 | 9016篇 |
2012年 | 5560篇 |
2011年 | 6737篇 |
2010年 | 6572篇 |
2009年 | 12513篇 |
2008年 | 14039篇 |
2007年 | 12678篇 |
2006年 | 11548篇 |
2005年 | 9128篇 |
2004年 | 8449篇 |
2003年 | 8413篇 |
2002年 | 8235篇 |
2001年 | 6589篇 |
2000年 | 6196篇 |
1999年 | 5711篇 |
1998年 | 5018篇 |
1997年 | 4052篇 |
1996年 | 3627篇 |
1995年 | 3920篇 |
1994年 | 3796篇 |
1993年 | 2985篇 |
1992年 | 2551篇 |
1991年 | 1889篇 |
1990年 | 1583篇 |
1989年 | 1363篇 |
1988年 | 1250篇 |
1987年 | 989篇 |
1986年 | 735篇 |
1985年 | 1476篇 |
1984年 | 1169篇 |
1983年 | 771篇 |
1982年 | 1052篇 |
1981年 | 1161篇 |
1980年 | 989篇 |
1979年 | 869篇 |
1978年 | 793篇 |
1977年 | 704篇 |
1976年 | 661篇 |
1974年 | 429篇 |
1973年 | 548篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
21.
22.
23.
Dariusz Marek Adam Domaski Joanna Domaska Jakub Szygua Tadeusz Czachrski Jerzy Klamka 《Entropy (Basel, Switzerland)》2021,23(5)
In this article, a way to employ the diffusion approximation to model interplay between TCP and UDP flows is presented. In order to control traffic congestion, an environment of IP routers applying AQM (Active Queue Management) algorithms has been introduced. Furthermore, the impact of the fractional controller and its parameters on the transport protocols is investigated. The controller has been elaborated in accordance with the control theory. The TCP and UDP flows are transmitted simultaneously and are mutually independent. Only the TCP is controlled by the AQM algorithm. Our diffusion model allows a single TCP or UDP flow to start or end at any time, which distinguishes it from those previously described in the literature. 相似文献
24.
In this work, we present and analyze a mathematical model for tumor growth incorporating ECM erosion, interstitial flow, and the effect of vascular flow and nutrient transport. The model is of phase-field or diffused-interface type in which multiple phases of cell species and other constituents are separated by smooth evolving interfaces. The model involves a mesoscale version of Darcy’s law to capture the flow mechanism in the tissue matrix. Modeling flow and transport processes in the vasculature supplying the healthy and cancerous tissue, one-dimensional (1D) equations are considered. Since the models governing the transport and flow processes are defined together with cell species models on a three-dimensional (3D) domain, we obtain a 3D–1D coupled model. 相似文献
25.
使用Galerkin方法,结合Sobolev空间理论和不等式技巧,给出了广义神经传播方程解的存在唯一性定理,然后利用吸引子存在性定理,采用半群方法证明了方程整体吸引子的存在性. 相似文献
26.
27.
28.
29.
An adaptive tracking design strategy based on quantized state feedback is developed for uncertain nonholonomic mobile robots with unknown wheel slippage effects. All state variables and control torques are assumed to be quantized by the state and input quantizers, respectively, in a network control environment. Thus, the quantized state feedback information is only available for the tracking control design. An approximation-based adaptive controller using quantized states is recursively designed to ensure the robust adaptive tracking against unknown wheel slippage effects where the quantized-states-based adaptive mechanism is derived to compensate for unknown wheel slippage effects, system nonlinearities, and quantization errors. The boundedness of the quantization errors and estimated parameters in the closed-loop system is analyzed by presenting some theoretical lemmas. Based on these lemmas, we prove the uniform ultimate boundedness of closed-loop signals and the convergence of the trajectory tracking error in the presence of wheel slippage effects. Simulations verify the effectiveness of the resulting tracking scheme. 相似文献
30.
Riccardo Adami Ugo Boscain Valentina Franceschi Dario Prandi 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2021,38(4):1095-1113
In this paper we show that, for a sub-Laplacian Δ on a 3-dimensional manifold M, no point interaction centered at a point exists. When M is complete w.r.t. the associated sub-Riemannian structure, this means that Δ acting on is essentially self-adjoint in . A particular example is the standard sub-Laplacian on the Heisenberg group. This is in stark contrast with what happens in a Riemannian manifold N, whose associated Laplace-Beltrami operator acting on is never essentially self-adjoint in , if . We then apply this result to the Schrödinger evolution of a thin molecule, i.e., with a vanishing moment of inertia, rotating around its center of mass. 相似文献