全文获取类型
收费全文 | 6599篇 |
免费 | 652篇 |
国内免费 | 572篇 |
专业分类
化学 | 219篇 |
晶体学 | 4篇 |
力学 | 296篇 |
综合类 | 78篇 |
数学 | 3514篇 |
物理学 | 332篇 |
综合类 | 3380篇 |
出版年
2024年 | 19篇 |
2023年 | 56篇 |
2022年 | 66篇 |
2021年 | 106篇 |
2020年 | 149篇 |
2019年 | 141篇 |
2018年 | 169篇 |
2017年 | 222篇 |
2016年 | 220篇 |
2015年 | 197篇 |
2014年 | 291篇 |
2013年 | 394篇 |
2012年 | 357篇 |
2011年 | 401篇 |
2010年 | 336篇 |
2009年 | 348篇 |
2008年 | 383篇 |
2007年 | 491篇 |
2006年 | 439篇 |
2005年 | 383篇 |
2004年 | 319篇 |
2003年 | 306篇 |
2002年 | 280篇 |
2001年 | 266篇 |
2000年 | 229篇 |
1999年 | 211篇 |
1998年 | 172篇 |
1997年 | 162篇 |
1996年 | 112篇 |
1995年 | 111篇 |
1994年 | 97篇 |
1993年 | 64篇 |
1992年 | 68篇 |
1991年 | 55篇 |
1990年 | 41篇 |
1989年 | 27篇 |
1988年 | 26篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1955年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有7823条查询结果,搜索用时 15 毫秒
11.
具有hollingⅢ类功能反应的非自治捕食系统概周期解 总被引:1,自引:0,他引:1
讨论了一类具有hollingⅢ类功能反应的非自治捕食概周期系统,得到了该系统存在的唯一一致渐近稳定概周期解的充分条件。 相似文献
12.
考虑约束最优化问题:minx∈Ωf(x)其中:f:R^n→R是连续可微函数,Ω是一闭凸集。本文研究了解决此问题的梯度投影方法,在步长的选取时采用了一种新的策略,在较弱的条件下,证明了梯度投影响方法的全局收敛性。 相似文献
13.
By using the quasi-Lyapunov function, some sufficient conditions of global exponential stability for impulsive systems are established, which is the basis for the following discussion. Then, by employing Riccati inequality and Hamilton-Jacobi inequality approach, some sufficient conditions of robust exponential stability for uncertain linear/nonlinear impulsive systems are derived, respectively. Finally, some examples are given to illustrate the applications of the theory. 相似文献
14.
Architecture, engineering, and construction (AEC) global project teamwork is communication intensive and relies heavily on synchronous and asynchronous information and collaboration technologies (ICT). We explore in this paper how an asynchronous ICT, called ThinkTank, reshaped the work practice of design-construction global teams, and how the interaction with this ICT reshaped the purpose and benefits of its use. ThinkTank is a web-based asynchronous collaboration and discussion forum. We introduce the influence diffusion model (IDM) that formalizes the process of identifying the influence of people, messages, and terms mathematically. Discovering who the influence leaders in project teams are can be beneficial and critical from a corporate management perspective, since they can guide or motivate the team towards successful actions and outcomes. We present the ThinkTank-IDM integrated system and its validation with a testbed of 53 AEC global team project archived in ThinkTank over 8 years. 相似文献
15.
Anna L. Mazzucato 《Transactions of the American Mathematical Society》2003,355(4):1297-1364
This paper is devoted to the analysis of function spaces modeled on Besov spaces and their applications to non-linear partial differential equations, with emphasis on the incompressible, isotropic Navier-Stokes system and semi-linear heat equations. Specifically, we consider the class, introduced by Hideo Kozono and Masao Yamazaki, of Besov spaces based on Morrey spaces, which we call Besov-Morrey or BM spaces. We obtain equivalent representations in terms of the Weierstrass semigroup and wavelets, and various embeddings in classical spaces. We then establish pseudo-differential and para-differential estimates. Our results cover non-regular and exotic symbols. Although the heat semigroup is not strongly continuous on Morrey spaces, we show that its action defines an equivalent norm. In particular, homogeneous BM spaces belong to a larger class constructed by Grzegorz Karch to analyze scaling in parabolic equations. We compare Karch's results with those of Kozono and Yamazaki and generalize them by obtaining short-time existence and uniqueness of solutions for arbitrary data with subcritical regularity. We exploit pseudo-differential calculus to extend the analysis to compact, smooth, boundaryless, Riemannian manifolds. BM spaces are defined by means of partitions of unity and coordinate patches, and intrinsically in terms of functions of the Laplace operator.
16.
文章对全球变化教学中使用多媒体教学手段总结了技能技巧和经验;提出了出现问题的处理方法。在全球变化教学中使用多媒体教学手段,能够形象、生动和真实地展示全球各种参数的变化特征。 相似文献
17.
本对于全局优化问题提出一个改进的进化规划算法,该算法以概率p接收基于电磁理论求出合力方向作为随机搜索方向,以概率1-p接收按正态分布产生的随机搜索方向。改进算法不仅克服了传统进化规划算法随机搜索的盲目性,而且保留了传统进化规划算法全局搜索性。本算法应用于几个典型例题,数值结果表明本算法是可行的,有效的。 相似文献
18.
研究了Banach空间中非线性混合型微分-积分方程初值问题u′=f(t,u,Tu,Su),u(0)=x0的整体解,完全没有要求f的任何增性,利用Mnch不动点定理和比较结果得到了初值问题整体解的存在性和唯一解,并且给出了一致收敛于唯一解的迭代序列,改进推广和统一了已有的许多结果. 相似文献
19.
20.
The problem of finding the Euclidean distance between two convex polyhedra can be reduced to the combinatorial optimization problem of finding the minimum distance between their faces. This paper presents a global optimality criterion for this problem. An algorithm (QLDPA) for the fast computation of the distance between convex and bounded polyhedra is proposed as an application of it. Computer experiments show its fast performance, especially when the total number of vertices is large. 相似文献