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   723687篇
  免费   6337篇
  国内免费   2066篇
化学   365560篇
晶体学   10678篇
力学   36168篇
综合类   20篇
数学   96449篇
物理学   223215篇
  2021年   6537篇
  2020年   7011篇
  2019年   7918篇
  2018年   10615篇
  2017年   10880篇
  2016年   15151篇
  2015年   8549篇
  2014年   14191篇
  2013年   33124篇
  2012年   25487篇
  2011年   30467篇
  2010年   22593篇
  2009年   22542篇
  2008年   28419篇
  2007年   28106篇
  2006年   25761篇
  2005年   22945篇
  2004年   21302篇
  2003年   19110篇
  2002年   18979篇
  2001年   20985篇
  2000年   16021篇
  1999年   12482篇
  1998年   10637篇
  1997年   10404篇
  1996年   9744篇
  1995年   8705篇
  1994年   8651篇
  1993年   8345篇
  1992年   8954篇
  1991年   9500篇
  1990年   9063篇
  1989年   8934篇
  1988年   8553篇
  1987年   8509篇
  1986年   8117篇
  1985年   10362篇
  1984年   10784篇
  1983年   9021篇
  1982年   9310篇
  1981年   8734篇
  1980年   8425篇
  1979年   9038篇
  1978年   9276篇
  1977年   9115篇
  1976年   9041篇
  1975年   8675篇
  1974年   8511篇
  1973年   8808篇
  1972年   6321篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
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   
62.
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   
63.
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   
64.
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   
65.
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   
66.
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   
67.
68.
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   
69.
70.
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