全文获取类型
收费全文 | 22013篇 |
免费 | 1659篇 |
国内免费 | 1546篇 |
专业分类
化学 | 4031篇 |
晶体学 | 52篇 |
力学 | 1624篇 |
综合类 | 333篇 |
数学 | 14430篇 |
物理学 | 4748篇 |
出版年
2023年 | 199篇 |
2022年 | 300篇 |
2021年 | 377篇 |
2020年 | 466篇 |
2019年 | 570篇 |
2018年 | 498篇 |
2017年 | 587篇 |
2016年 | 640篇 |
2015年 | 476篇 |
2014年 | 839篇 |
2013年 | 1760篇 |
2012年 | 1012篇 |
2011年 | 1134篇 |
2010年 | 941篇 |
2009年 | 1328篇 |
2008年 | 1391篇 |
2007年 | 1384篇 |
2006年 | 1232篇 |
2005年 | 1019篇 |
2004年 | 860篇 |
2003年 | 864篇 |
2002年 | 842篇 |
2001年 | 706篇 |
2000年 | 688篇 |
1999年 | 595篇 |
1998年 | 574篇 |
1997年 | 541篇 |
1996年 | 413篇 |
1995年 | 304篇 |
1994年 | 278篇 |
1993年 | 232篇 |
1992年 | 207篇 |
1991年 | 158篇 |
1990年 | 146篇 |
1989年 | 117篇 |
1988年 | 137篇 |
1987年 | 113篇 |
1986年 | 85篇 |
1985年 | 147篇 |
1984年 | 164篇 |
1983年 | 88篇 |
1982年 | 149篇 |
1981年 | 143篇 |
1980年 | 95篇 |
1979年 | 90篇 |
1978年 | 90篇 |
1977年 | 62篇 |
1976年 | 56篇 |
1974年 | 27篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
71.
We investigate some topological properties of a normal functorH introduced earlier by Radul which is some functorial compactification of the Hartman-Mycielski construction HM. We prove
that the pair (H X, HMY) is homeomorphic to the pair (Q, σ) for each nondegenerated metrizable compactumX and each denseσ-compact subsetY. 相似文献
72.
One of the most ignored, but urgent and vital challenges confronting society today is the vulnerability of urban areas to extreme events. Current organization of response systems, predominantly based on a command and control model, limits their effectiveness and efficiency. Particularly, in decision‐making processes where a large number of actors may be involved. In this article, a new distributed collaborative decision‐making model is proposed to overcome command and control limitations encountered in stressful, hostile, chaotic, and large‐scale settings. This model was derived by borrowing concepts from the collective decision making of honeybees foraging, a successful process in solving complex tasks within complex settings. The model introduced in this article was evaluated through differential equations, i.e., continuous analysis, and difference equations, i.e., discrete analysis. The most important result found is that the best available option in any large‐scale decision‐making problem can be configured as an attractor, in a distributed and timely manner. We suggest that the proposed model has the potential to facilitate decision‐making processes in large‐scale settings. © 2005 Wiley Periodicals, Inc. Complexity 11:28–38, 2005 相似文献
73.
The Mannich-type reaction of imines with (1-methoxy-2-methylpropenyloxy)trimethylsilane and aza-Diels-Alder reaction of imines with Danishefsky's diene can be carried out in scCO2 in the presence of lithium heptadecafluorooctanesulfonate which offer a way to synthesize β-amino carbonyl compounds and nitrogen-containing six-membered ring compounds under environmentally benign conditions. 相似文献
74.
75.
We introduce extensions of the Mangasarian-Fromovitz and Abadie constraint qualifications to nonsmooth optimization problems with feasibility given by means of lower-level sets. We do not assume directional differentiability, but only upper semicontinuity of the defining functions. By deriving and reviewing primal first-order optimality conditions for nonsmooth problems, we motivate the formulations of the constraint qualifications. Then, we study their interrelation, and we show how they are related to the Slater condition for nonsmooth convex problems, to nonsmooth reverse-convex problems, to the stability of parametric feasible set mappings, and to alternative theorems for the derivation of dual first-order optimality conditions.In the literature on general semi-infinite programming problems, a number of formally different extensions of the Mangasarian-Fromovitz constraint qualification have been introduced recently under different structural assumptions. We show that all these extensions are unified by the constraint qualification presented here. 相似文献
76.
On General Mixed Quasivariational Inequalities 总被引:5,自引:0,他引:5
In this paper, we suggest and analyze several iterative methods for solving general mixed quasivariational inequalities by using the technique of updating the solution and the auxiliary principle. It is shown that the convergence of these methods requires either the pseudomonotonicity or the partially relaxed strong monotonicity of the operator. Proofs of convergence is very simple. Our new methods differ from the existing methods for solving various classes of variational inequalities and related optimization problems. Various special cases are also discussed. 相似文献
77.
Patrick Guidotti 《Mathematische Nachrichten》2004,272(1):32-45
We consider elliptic and parabolic problems in unbounded domains. We give general existence and regularity results in Besov spaces and semi‐explicit representation formulas via operator‐valued fundamental solutions which turn out to be a powerful tool to derive a series of qualitative results about the solutions. We give a sample of possible applications including asymptotic behavior in the large, singular perturbations, exact boundary conditions on artificial boundaries and validity of maximum principles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
78.
The aim of this article is to give some property of continued fraction with matrices arguments, about their convergence and
others applications. At the end of this work, we present a resolution of the Algebraic Riccati Equation by giving an explicit
continued fraction development of its solution.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
79.
Sergue A. Nazarov Maria Specovius‐Neugebauer 《Mathematical Methods in the Applied Sciences》2004,27(13):1507-1544
The approximation of solutions to boundary value problems on unbounded domains by those on bounded domains is one of the main applications for artificial boundary conditions. Based on asymptotic analysis, here a new method is presented to construct local artificial boundary conditions for a very general class of elliptic problems where the main asymptotic term is not known explicitly. Existence and uniqueness of approximating solutions are proved together with asymptotically precise error estimates. One class of important examples includes boundary value problems for anisotropic elasticity and piezoelectricity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
80.
In this paper, a unified approach for analysing finite dimensional approximations to a class of partial differential equations boundary value problems (second‐kind Fredholm differential equations) is introduced. The approach is shown to be general despite of its extremely simple form. In particular, it is expected to be useful in the convergence analysis of finite element methods for solving PDE problems. Three specific examples are presented to illustrate the broad applicability of the approach. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献