首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5393篇
  免费   138篇
  国内免费   31篇
化学   3246篇
晶体学   45篇
力学   276篇
数学   1049篇
物理学   946篇
  2023年   33篇
  2022年   99篇
  2021年   103篇
  2020年   85篇
  2019年   103篇
  2018年   66篇
  2017年   74篇
  2016年   179篇
  2015年   154篇
  2014年   158篇
  2013年   302篇
  2012年   348篇
  2011年   342篇
  2010年   221篇
  2009年   198篇
  2008年   305篇
  2007年   328篇
  2006年   273篇
  2005年   259篇
  2004年   279篇
  2003年   209篇
  2002年   207篇
  2001年   61篇
  2000年   49篇
  1999年   61篇
  1998年   55篇
  1997年   60篇
  1996年   73篇
  1995年   56篇
  1994年   49篇
  1993年   43篇
  1992年   46篇
  1991年   38篇
  1990年   35篇
  1989年   24篇
  1988年   46篇
  1987年   35篇
  1986年   25篇
  1985年   55篇
  1984年   42篇
  1983年   46篇
  1982年   46篇
  1981年   44篇
  1980年   36篇
  1979年   33篇
  1978年   25篇
  1977年   18篇
  1976年   18篇
  1975年   17篇
  1974年   18篇
排序方式: 共有5562条查询结果,搜索用时 15 毫秒
1.
We prove that the arithmetic degree of a graded or local ring A is bounded above by the arithmetic degree of any of its associated graded rings with respect to ideal I in A. In particular, if Spec(A) is equidimensional and has an embedded component (i.e., A has an embedded associated prime ideal), then the normal cone of Spec(A) along V(I) has an embedded component too. This extends a result of W. M. Ruppert about embedded components of the tangent cone.Mathematics Subject Classification (2000): Primary 13H15, 13A30; Secondary 13D45, 14Q99  相似文献   
2.
3.
4.
For a given two-dimensional surface μ, we studi invariants for oriented links in μ×[0,1] which generalize the two-variable HOMFLY polynomials when μ is the 2-disk. These invariants are connected to multiparameter quantum groups whose special properties are discussed. Si studiano gli invarianti dei nodi in spazi del tipo μ×[0,1], dove μ è una superficie. Questi invarianti generalizzano gli invarianti di HOMFLY.
(Conferenza tenuta dal Prof. P. Cotta-Ramusino il 16 maggio 1991)  相似文献   
5.
We obtain a precise relation between the Chern–Schwartz–MacPherson class of a subvariety of projective space and the Euler characteristics of its general linear sections. In the case of a hypersurface, this leads to simple proofs of formulas of Dimca–Papadima and Huh for the degrees of the polar map of a homogeneous polynomial, extending these formula to any algebraically closed field of characteristic \(0\), and proving a conjecture of Dolgachev on ‘homaloidal’ polynomials in the same context. We generalize these formulas to subschemes of higher codimension in projective space. We also describe a simple approach to a theory of ‘polynomial Chern classes’ for varieties endowed with a morphism to projective space, recovering properties analogous to the Deligne–Grothendieck axioms from basic properties of the Euler characteristic. We prove that the polynomial Chern class defines homomorphisms from suitable relative Grothendieck rings of varieties to \(\mathbb{Z }[t]\).  相似文献   
6.
We consider the generalization of the classical P||Cmax problem (assign n jobs to m identical parallel processors by minimizing the makespan) arising when the number of jobs that can be assigned to each processor cannot exceed a given integer k. The problem is strongly NP-hard for any fixed k > 2. We briefly survey lower and upper bounds from the literature. We introduce greedy heuristics, local search and a scatter search approach. The effectiveness of these approaches is evaluated through extensive computational comparison with a depth-first branch-and-bound algorithm that includes new lower bounds and dominance criteria.  相似文献   
7.
We prove that there is no functorial universal finite type invariant for braids in Σ×I if the genus of Σ is positive. To cite this article: P. Bellingeri, L. Funar, C. R. Acad. Sci. Paris, Ser. I 338 (2004).  相似文献   
8.
Some authors claim that reporting the best result obtained by a stochastic algorithm in a number of runs is more meaningful than reporting some central statistic. In this short note, we analyze and refute the main argument brought in favor of this statement.  相似文献   
9.
Dopo aver dato una definizione di parte convessa di un gruppo topologico, si stabilisce una condizione affinchè il condominio di una misura sia convesso.  相似文献   
10.
In this paper we study a Ginzburg–Landau model which describes the behaviour of a superconducting material including thermal effects. We extend the traditional formulation of the problem, by introducing the temperature as an additional state variable. Accordingly, together with the Gor’kov–Eliashberg system, we introduce an evolution equation for the absolute temperature. We examine in detail the case which allows only variations of the concentration of superconducting electrons and of the temperature, neglecting the electromagnetic field. For this problem existence and uniqueness of the solution are shown. Finally we analyze the asymptotic behaviour of the solutions, proving that the system possesses a global attractor.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号