全文获取类型
收费全文 | 2175篇 |
免费 | 116篇 |
国内免费 | 72篇 |
专业分类
化学 | 109篇 |
力学 | 372篇 |
综合类 | 9篇 |
数学 | 1368篇 |
物理学 | 505篇 |
出版年
2023年 | 20篇 |
2022年 | 21篇 |
2021年 | 23篇 |
2020年 | 34篇 |
2019年 | 42篇 |
2018年 | 31篇 |
2017年 | 47篇 |
2016年 | 59篇 |
2015年 | 46篇 |
2014年 | 88篇 |
2013年 | 164篇 |
2012年 | 159篇 |
2011年 | 116篇 |
2010年 | 79篇 |
2009年 | 125篇 |
2008年 | 121篇 |
2007年 | 128篇 |
2006年 | 106篇 |
2005年 | 111篇 |
2004年 | 84篇 |
2003年 | 76篇 |
2002年 | 89篇 |
2001年 | 87篇 |
2000年 | 67篇 |
1999年 | 65篇 |
1998年 | 52篇 |
1997年 | 47篇 |
1996年 | 41篇 |
1995年 | 34篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有2363条查询结果,搜索用时 15 毫秒
161.
The hub location problem finds the location of hubs and allocates the other nodes to them. It is widely supposed the network created with the hub nodes is complete in the extensive literature. Relaxation of this basic supposition forms the present work. The model minimizes the cost of the proprietor, including the fixed costs of hubs, hub links and spoke links. Costs of hub and spoke links are contemplated as fixed cost or maintenance cost. Moreover, the model considers routing costs of customers who want to travel from origins to destinations. In this study, we offer a model to the multiple allocations of the hub location problems, under the incomplete hub location-routing network design. This model is easily transformed to other hub location problems using one or more constraints. No network format is dictated on the hub network. We suggest a set of valid inequalities for the formulation. Some lower bounds are developed using a Lagrangian relaxation approach and the valid inequalities. Computational analyses evaluate the performances of the lower bounding implementations and valid inequalities. Furthermore, we explore the effects of several factors on the design and solution time of the problem formulation. 相似文献
162.
For an integrable Tonelli Hamiltonian with d (d?2) degrees of freedom, we show that all of the Lagrangian tori can be destroyed by analytic perturbations which are arbitrarily small in the Cd−δ topology. 相似文献
163.
We introduce the monotone Sokolov property and show that it is dual to monotone retractability in the sense that X is monotonically retractable if and only if Cp(X) is monotonically Sokolov. Besides, a space X is monotonically Sokolov if and only if Cp(X) is monotonically retractable. Monotone retractability and monotone Sokolov property are shown to be preserved by R-quotient images and Fσ-subspaces. Furthermore, every monotonically retractable space is Sokolov so it is collectionwise normal and has countable extent. We also establish that if X and Cp(X) are Lindelöf Σ-spaces then they are both monotonically retractable and have the monotone Sokolov property. An example is given of a space X such that Cp(X) has the Lindelöf Σ-property but neither X nor Cp(X) is monotonically retractable. We also establish that every Lindelöf Σ-space with a unique non-isolated point is monotonically retractable. On the other hand, each Lindelöf space with a unique non-isolated point is monotonically Sokolov. 相似文献
164.
本文改进了有界变差函数的加权Ostrowski型不等式,并给出了其在求积公式中的应用. 相似文献
165.
166.
利用对称空间的对偶性,本文建立局部强凸对称等仿射球之集与某复空间形式中的极小对称Lagrange子流形之集间的对应关系,在自然定义的等价意义下,这是一一对应关系.作为这种对应关系的直接应用,本文用完全不同的方法重新证明胡泽军等人最近建立的一个重要定理.该定理对具有平行Fubini-Pick形式的局部强凸等仿射球进行了完全分类. 相似文献
167.
This paper considers the numerical solution of plane elasticity equations with stochastic Young's modulus and stochastic loads.The stochastic fields are approximated by Karhunen-Loeve expansion and Wiener polynomial chaos expansion along sample paths,and in space continuous Lagrangian finite elements axe used.Error estimates are derived.Numerical experiments are done to verify the theoretical results. 相似文献
168.
为了构造快速求解二次Lagrangian有限元方程的几何多重网格法,在选择二次Lagrangian有限元空间和一系列线性Lagrangian有限元空间分别作为最细网格层和其余粗网格层以及构造一种新限制算子的基础上,提出了一种新的几何多重网格法,并对它的计算量进行了估计.数值实验结果,与通常的几何多重网格法和AMG01法相比,表明了新算法计算量少且稳健性强. 相似文献
169.
The subject of this paper is to study the problem of the approximation of function of two variables by means of Chlodowsky-Taylor polynomials in a rectangular domain. 相似文献
170.
1IntroductionAsurfaceisacompactclosed2-manifold.Theorielltable(non-orielltable)surfaceofgenuskisthespherewitllkhandles(crosscaPs)denotedbySk(Nk).AmapMollSk(Nk)meansthatitsunderlyinggraphnlaybedrownou(embeddedin)itsuchthatllthpairofedgesintersectataninnerpoilltalldeachfaceishomeomorphictothedisc.Amapisrootedifanedgewithadirectiollalongtheedge,alldasideoftl1eedgeisdistinguisl1ed.Tworootedmapsareconsideredtobethesal11eifthereisanisomorphismpreserviIlgtl1erooting.ArootedEuleriall1llapissuchaon… 相似文献