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   24908篇
  免费   676篇
  国内免费   354篇
化学   16310篇
晶体学   123篇
力学   556篇
综合类   31篇
数学   3935篇
物理学   4983篇
  2022年   185篇
  2021年   210篇
  2020年   247篇
  2019年   261篇
  2018年   228篇
  2017年   180篇
  2016年   505篇
  2015年   469篇
  2014年   594篇
  2013年   1176篇
  2012年   888篇
  2011年   973篇
  2010年   741篇
  2009年   704篇
  2008年   943篇
  2007年   969篇
  2006年   853篇
  2005年   853篇
  2004年   823篇
  2003年   833篇
  2002年   879篇
  2001年   629篇
  2000年   567篇
  1999年   423篇
  1998年   334篇
  1997年   335篇
  1996年   355篇
  1995年   354篇
  1994年   352篇
  1993年   322篇
  1992年   312篇
  1991年   296篇
  1990年   321篇
  1989年   289篇
  1988年   276篇
  1987年   276篇
  1986年   242篇
  1985年   442篇
  1984年   431篇
  1983年   283篇
  1982年   344篇
  1981年   301篇
  1980年   350篇
  1979年   334篇
  1978年   313篇
  1977年   392篇
  1976年   328篇
  1975年   287篇
  1974年   244篇
  1973年   299篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given.  相似文献   
4.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
5.
2-Deoxy-2-iodo-glycosylamides have been prepared from a variety of protected d-glucals by their reaction with N-iodosuccinimide and amides. Benzyl protected 2-iodoamides, when treated with sodium hydride and 15-crown-5, gave stable C1 N-linked 2-glycooxazolines as the major products. Silyl protected 2-iodoamides afforded the C1 O-linked 2-glycooxazolines; presumably by the rearrangement of unstable N-acylaziridine intermediates.  相似文献   
6.
7.
In this paper we generalize recent theoretical results on the local continuation of parameter-dependent non-linear variational inequalities. The variational inequalities are rather general and describe, for example, the buckling of beams, plates or shells subject to obstacles. Under a technical hypothesis that is satisfied by the simply supported beam, we obtain the existence of a continuation of both the solution and the eigenvalue with respect to a local parameter. A numerical continuation method is presented that easily overcomes turning points. Numerical results are presented for the non-linear beam.  相似文献   
8.
9.
This paper analyzes the compromise social choice correspondence derived from the τ-value of digraph games. Monotonicity of this correspondence is shown. A connection between several properties of social choice correspondences based on game theoretical solutions and game theoretical properties of the underlying solutions is given. Applications to several game theoretic solutions are provided.  相似文献   
10.
Poly(pyridine ether)s were prepared in two ways: the polycondensation of silylated 1,1,1‐tris(4‐hydroxyphenyl)ethane (THPE) with 2,6‐difluoropyridine (method A) and the polycondensation of free THPE with 2,6‐dichloropyridine (method B). With method A, the THPE/difluoropyridine feed ratio was varied from 1.0:1.0 to 1.0:1.6. Cycles, bicycles, and multicycles were the main reaction products, and crosslinking was never observed. When ideal stoichiometry was used exclusively, multicycles free of functional groups were obtained. These multicycles were detectable in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra up to B38C76 with a mass of approximately 32,000 Da. With method B, the reaction conditions were varied at a fixed feed ratio to achieve an optimum for the preparation of multicyclic polyethers, but because of the lower reactivity of 2,6‐dichloropyridine, a quantitative conversion was not achieved. The reaction products were characterized with MALDI‐TOF mass spectrometry, viscosity measurements, and size exclusion chromatography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5725–5735, 2004  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