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   2557篇
  免费   74篇
  国内免费   20篇
化学   1494篇
晶体学   14篇
力学   52篇
数学   449篇
物理学   642篇
  2023年   17篇
  2022年   51篇
  2021年   68篇
  2020年   53篇
  2019年   72篇
  2018年   69篇
  2017年   65篇
  2016年   86篇
  2015年   96篇
  2014年   80篇
  2013年   165篇
  2012年   140篇
  2011年   170篇
  2010年   117篇
  2009年   126篇
  2008年   168篇
  2007年   145篇
  2006年   179篇
  2005年   140篇
  2004年   97篇
  2003年   89篇
  2002年   95篇
  2001年   40篇
  2000年   35篇
  1999年   33篇
  1998年   26篇
  1997年   26篇
  1996年   34篇
  1995年   20篇
  1994年   14篇
  1993年   15篇
  1992年   11篇
  1991年   12篇
  1990年   5篇
  1989年   8篇
  1988年   4篇
  1985年   7篇
  1984年   5篇
  1983年   3篇
  1982年   4篇
  1980年   4篇
  1979年   6篇
  1978年   3篇
  1977年   5篇
  1976年   3篇
  1975年   6篇
  1974年   3篇
  1973年   3篇
  1972年   4篇
  1969年   6篇
排序方式: 共有2651条查询结果,搜索用时 15 毫秒
61.
62.
63.
Novel semiflexible polyazomethines containing chromophoric units into azomethine mesogenic core have been synthesised by condensation of a flexible dialdehyde with mesogenic diamines containing fluorene, antraquinone, pyrimidine, azobenzene and benzophenone. The thermotropic behaviour of the resulting polyazomethines was assessed by differential scanning calorimetry, polarised light microscopy and investigations of the miscibility relations. While the pure polyazomethines showed a birefringent viscous texture difficult to be ascribed, by mixing with a liquid crystal dimer, clear Schlieren or marbled textures were observed, indicating a nematic mesophase. The polymers exhibited violet, blue or yellow light emission.  相似文献   
64.
The three‐dimensional (3D) confinement effect on the microphase‐separated structure of a diblock copolymer was investigated both experimentally and computationally. Block copolymer nanoparticles were prepared by adding a poor solvent into a block copolymer solution and subsequently evaporating the good solvent. The 3D structures of the nanoparticles were quantitatively determined with transmission electron microtomography (TEMT). TEMT observations revealed that various complex structures, including tennis‐ball, mushroom‐like, and multipod structures, were formed in the 3D confinement. Detailed structural analysis, showed that one block of the diblock copolymer slightly prefers to segregate into the particle surface compared with the other block. The observed structures were further elaborated using cell dynamics computer simulation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1702–1709  相似文献   
65.
66.
Abstract

The enantiomeric ratio in non-racemic mixtures of 2-anilino-2-oxo-1,3,2-oxazaphospho-rinane (I) and 3-(α-rnethylbenzyl)-(I)1 enantiomers was determined by measurement of the integral intensity ratio of two 31P-NMR signals, assigned to enantiomers and differentiated due to the effect of statistically controlled associate-diastereoisomerim (scada), 2 when association occurs under conditions of fast exchange.  相似文献   
67.
68.
69.
A new 5,10,15,20-tetrasubstituted porphyrin containing four 6-nitro-1,3,3-trimethylspiro(indolino-2,2-2H-chromene) substituents and its complexes with Zn2+ and Cu2+ ions were prepared and characterized by physicochemical methods of analysis.  相似文献   
70.
The aim of this paper is to establish a well‐posedness result for a boundary value problem of transmission‐type for the standard and generalized Brinkman systems in two Lipschitz domains in , the former being bounded, and the latter, its complement in . As a first step, we establish a well‐posedness result for a transmission problem for the standard Brinkman systems on complementary Lipschitz domains in by making use of the Potential theory developed for such a system. As a second step, we prove our desired result (in L2‐based Sobolev spaces) by using a method based on Fredholm operator theory and the well‐posedness result from the previous step.  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