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   2275篇
  免费   93篇
  国内免费   15篇
化学   1708篇
晶体学   13篇
力学   32篇
综合类   16篇
数学   225篇
物理学   389篇
  2023年   19篇
  2022年   15篇
  2021年   40篇
  2020年   46篇
  2019年   55篇
  2018年   36篇
  2017年   27篇
  2016年   58篇
  2015年   56篇
  2014年   55篇
  2013年   127篇
  2012年   152篇
  2011年   156篇
  2010年   78篇
  2009年   102篇
  2008年   169篇
  2007年   147篇
  2006年   133篇
  2005年   148篇
  2004年   124篇
  2003年   93篇
  2002年   98篇
  2001年   29篇
  2000年   30篇
  1999年   25篇
  1998年   23篇
  1997年   21篇
  1996年   25篇
  1995年   12篇
  1994年   22篇
  1993年   19篇
  1992年   19篇
  1991年   7篇
  1990年   21篇
  1989年   11篇
  1988年   9篇
  1987年   13篇
  1986年   5篇
  1985年   22篇
  1984年   13篇
  1983年   15篇
  1982年   19篇
  1981年   16篇
  1980年   16篇
  1979年   10篇
  1978年   6篇
  1977年   11篇
  1976年   6篇
  1975年   5篇
  1974年   8篇
排序方式: 共有2383条查询结果,搜索用时 0 毫秒
31.
32.
33.
34.
35.
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   
36.
Abstract— Both native blue fluorescent α-crystallin from calf lenses and UV (300 nm)-irradiated blue-fluorescent α-crystallin, when further irradiated with 365 nm-UV light, produce photo-products capable of emitting a new fluorescence at 455 nm. Illumination of the photo-products with 420 nm visible light regenerates the original fluorescence at 420–425 nm. In addition, another fluorescence at 400 nm has also been found in UV (300 nm)-irradiated blue-fluorescent α-crystallin, when exposed to 365 nm-UV light.  相似文献   
37.
Five trimethylene-interrupted methyl octadecadiynoates, C18 delta-2a,-7a; delta-3a,-8a; delta-4a,-9a; delta-5a,-10a and delta-6a,-11a, and the corresponding cis,cis-octadecadienoates were synthesized, and their gas-liquid chromatographic properties were studied on Apiezon L, diethylene glycol succinate polyester and Silac 10C stationary phases. The equivalent chain lengths of these esters have been determined, and the separation of mixtures and the prediction of gas chromatographic behaviour of these isomers are discussed.  相似文献   
38.
Kokubo K  Tochika S  Kato M  Sol Y  Oshima T 《Organic letters》2008,10(15):3335-3338
The AlCl3-catalyzed acetylation of 1,2-hydrophenylated [60]fullerenes, HC60-Ar, proceeded via a sequential manner involving the acetylation at the hydrogenated fullerene carbon, the following intramolecular cyclization with the adjacent aryl group, the facile loss of water, and the second acetylation of the generated indenylidene double bond. However, the similar reaction of the hydrobiphenylated analogue brought about the normal acetylation at the terminal aromatic ring prior to the same sequential reactions as did hydrophenylated fullerenes.  相似文献   
39.
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   
40.
We have determined that a cationic rhodium(I)/BINAP complex catalyzes a [2+2+2] cycloaddition of 1,6-diynes with a protected dehydroamino acid, leading to protected α-amino acids bearing a quaternary carbon center in high yield with high enantioselectivity.  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