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   723843篇
  免费   6335篇
  国内免费   2067篇
化学   365637篇
晶体学   10694篇
力学   36170篇
综合类   20篇
数学   96476篇
物理学   223248篇
  2021年   6536篇
  2020年   7008篇
  2019年   7915篇
  2018年   10610篇
  2017年   10876篇
  2016年   15144篇
  2015年   8548篇
  2014年   14186篇
  2013年   33130篇
  2012年   25484篇
  2011年   30471篇
  2010年   22593篇
  2009年   22540篇
  2008年   28427篇
  2007年   28114篇
  2006年   25780篇
  2005年   22954篇
  2004年   21315篇
  2003年   19125篇
  2002年   18987篇
  2001年   20989篇
  2000年   16027篇
  1999年   12487篇
  1998年   10640篇
  1997年   10407篇
  1996年   9744篇
  1995年   8710篇
  1994年   8655篇
  1993年   8351篇
  1992年   8959篇
  1991年   9504篇
  1990年   9065篇
  1989年   8935篇
  1988年   8553篇
  1987年   8512篇
  1986年   8117篇
  1985年   10362篇
  1984年   10787篇
  1983年   9024篇
  1982年   9314篇
  1981年   8735篇
  1980年   8430篇
  1979年   9039篇
  1978年   9281篇
  1977年   9118篇
  1976年   9046篇
  1975年   8677篇
  1974年   8514篇
  1973年   8810篇
  1972年   6323篇
排序方式: 共有10000条查询结果,搜索用时 15 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