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   629972篇
  免费   5067篇
  国内免费   1634篇
化学   319266篇
晶体学   9241篇
力学   32040篇
综合类   27篇
数学   83011篇
物理学   193088篇
  2021年   5833篇
  2020年   6290篇
  2019年   7173篇
  2018年   9686篇
  2017年   9813篇
  2016年   13577篇
  2015年   7285篇
  2014年   12336篇
  2013年   27943篇
  2012年   21634篇
  2011年   25752篇
  2010年   19419篇
  2009年   19377篇
  2008年   24371篇
  2007年   24128篇
  2006年   21902篇
  2005年   19565篇
  2004年   18337篇
  2003年   16517篇
  2002年   16337篇
  2001年   17517篇
  2000年   13469篇
  1999年   10445篇
  1998年   8979篇
  1997年   8900篇
  1996年   8333篇
  1995年   7468篇
  1994年   7549篇
  1993年   7270篇
  1992年   7829篇
  1991年   8222篇
  1990年   7944篇
  1989年   7857篇
  1988年   7651篇
  1987年   7385篇
  1986年   7111篇
  1985年   9111篇
  1984年   9526篇
  1983年   7959篇
  1982年   8189篇
  1981年   7749篇
  1980年   7326篇
  1979年   7958篇
  1978年   8187篇
  1977年   8163篇
  1976年   8141篇
  1975年   7776篇
  1974年   7570篇
  1973年   7931篇
  1972年   5833篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
A finite-deformation theory is developed to study the mechanics of thin buckled films on compliant substrates. Perturbation analysis is performed for this highly nonlinear system to obtain the analytical solution. The results agree well with experiments and finite element analysis in wavelength and amplitude. In particular, it is found that the wavelength depends on the strain. Based on the accurate wavelength and amplitude, the membrane and peak strains in thin films, and stretchability and compressibility of the system are also obtained analytically.  相似文献   
52.
Current methodologies used for the inference of thin film stress through curvature measurement are strictly restricted to stress and curvature states that are assumed to remain uniform over the entire film/substrate system. These methodologies have recently been extended to a single layer of thin film deposited on a substrate subjected to the non-uniform misfit strain in the thin film. Such methodologies are further extended to multi-layer thin films deposited on a substrate in the present study. Each thin film may have its own non-uniform misfit strain. We derive relations between the stresses in each thin film and the change of system curvatures due to the deposition of each thin film. The interface shear stresses between the adjacent films and between the thin film and the substrate are also obtained from the system curvatures. This provides the basis for the experimental determination of thin film stresses in multi-layer thin films on a substrate.  相似文献   
53.
The chlorination of benzene, toluene, and o-xylene with molecular chlorine in the presence of the phthalocyanine complexes of different structures was studied. The transformations of the catalysts during the reaction were investigated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1644–1647, August, 2008.  相似文献   
54.
55.
The kinetics of unhindered sedimentation of a titanium dioxide suspension (as model dispersed system) was studied, and the effect of the concentration and mode of addition of various formulations based on anionic and cationic acrylamide copolymers on their flocculation properties in aqueous salt (NaCl) solutions was evaluated.  相似文献   
56.
Thermodynamic parameters of reactions of methyl and phenyl isocyanates with a series of compounds were determined by quantum-chemical calculations. The products of these reactions model for various functional groups present in commercial polyurethanes. The thermodynamic stability series for compounds formed from aliphatic and aromatic isocyanates were constructed.  相似文献   
57.
Oximes of 4-(4-pyrazolyl)-3-buten-2-onees obtained by successive reaction of 3-aryl-4-formylpyrazoles with acetone and hydroxylamine at the treatment with iodine suffered an oxidative cyclization yielding 3-aryl-4-(5-isoxazolyl)pyrazoles.  相似文献   
58.
59.
Possibilities of utilization of by-products formed in manufacture of epichlorohydrin are considered. A promising way to utilize wastes from production of epichlorohydrin by synthesis of 2,3-dichloropropene from 1,2,3-trichloropropane is suggested.  相似文献   
60.
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