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   35371篇
  免费   9612篇
  国内免费   1404篇
化学   41261篇
晶体学   324篇
力学   439篇
综合类   16篇
数学   1995篇
物理学   2352篇
  2023年   19篇
  2022年   15篇
  2021年   171篇
  2020年   1243篇
  2019年   2603篇
  2018年   1025篇
  2017年   651篇
  2016年   3378篇
  2015年   3543篇
  2014年   3430篇
  2013年   4089篇
  2012年   2949篇
  2011年   2163篇
  2010年   2826篇
  2009年   2813篇
  2008年   2372篇
  2007年   1749篇
  2006年   1452篇
  2005年   1641篇
  2004年   1433篇
  2003年   1319篇
  2002年   2002篇
  2001年   1345篇
  2000年   1270篇
  1999年   359篇
  1998年   49篇
  1997年   43篇
  1996年   27篇
  1995年   14篇
  1994年   21篇
  1993年   15篇
  1992年   8篇
  1990年   21篇
  1989年   13篇
  1988年   10篇
  1987年   10篇
  1986年   12篇
  1985年   30篇
  1984年   25篇
  1983年   17篇
  1982年   20篇
  1981年   24篇
  1980年   17篇
  1979年   19篇
  1978年   22篇
  1977年   16篇
  1976年   23篇
  1975年   10篇
  1974年   11篇
  1960年   7篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
41.
42.
Abstract In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global attractor. More precisely, we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the non-autonomous case by the limiting global attractor. * Project supported by the MIUR-COFIN 2004 research program on “Mathematical Modelling and Analysis of Free Boundary Problems”.  相似文献   
43.
44.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities.  相似文献   
45.
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds.  相似文献   
46.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
47.
Electron beam induced quantitative X-ray mapping has become a very useful characterisation tool for determining the elemental distribution in materials, whether using energy dispersive spectroscopy or wavelength dispersive spectroscopy. The X-ray intensity distributions of the elements from an X-ray map allow us to generate two dimensional and ternary scatter diagrams thus converting spatial information into concentration dimensions, which is an important tool for displaying the spatial relationships of elements or correlated elements (phases) in materials. To best understand how to use this tool, we need to understand the production and features of the scatter diagram. The type of clustering observed in the scatter diagram, whether oval, linear or spherical, can give the major and trace element distributions within phases as well as qualitative and quantitative phase information. This paper demonstrates the generation of scatter diagrams, properties of scatter diagrams, interpretation of scatter diagrams and the advantages of scatter diagrams through the use of examples.  相似文献   
48.
49.
50.
A graph G is N2locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005  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