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   541664篇
  免费   4238篇
  国内免费   1390篇
化学   269042篇
晶体学   7645篇
力学   25995篇
综合类   17篇
数学   67779篇
物理学   163574篇
综合类   13240篇
  2021年   5054篇
  2020年   5483篇
  2019年   6226篇
  2018年   8425篇
  2017年   8588篇
  2016年   11653篇
  2015年   6202篇
  2014年   10470篇
  2013年   23525篇
  2012年   18615篇
  2011年   22158篇
  2010年   16525篇
  2009年   16318篇
  2008年   20936篇
  2007年   20912篇
  2006年   18974篇
  2005年   17037篇
  2004年   15897篇
  2003年   14299篇
  2002年   14228篇
  2001年   15385篇
  2000年   11912篇
  1999年   9123篇
  1998年   7610篇
  1997年   7487篇
  1996年   6942篇
  1995年   6267篇
  1994年   6275篇
  1993年   6028篇
  1992年   6679篇
  1991年   7122篇
  1990年   6854篇
  1989年   6770篇
  1988年   6577篇
  1987年   6427篇
  1986年   6109篇
  1985年   7674篇
  1984年   7948篇
  1983年   6691篇
  1982年   6911篇
  1981年   6424篇
  1980年   6106篇
  1979年   6744篇
  1978年   6979篇
  1977年   6823篇
  1976年   6754篇
  1975年   6483篇
  1974年   6430篇
  1973年   6547篇
  1972年   4825篇
排序方式: 共有10000条查询结果,搜索用时 7 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.
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   
55.
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   
56.
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   
57.
58.
59.
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