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   583563篇
  免费   19937篇
  国内免费   3196篇
化学   328523篇
晶体学   7835篇
力学   28701篇
综合类   145篇
数学   72120篇
物理学   169372篇
  2022年   5376篇
  2021年   7742篇
  2020年   10050篇
  2019年   8809篇
  2018年   10927篇
  2017年   9564篇
  2016年   17145篇
  2015年   11700篇
  2014年   15601篇
  2013年   29107篇
  2012年   22351篇
  2011年   23949篇
  2010年   20341篇
  2009年   20048篇
  2008年   22521篇
  2007年   21996篇
  2006年   19476篇
  2005年   17279篇
  2004年   16048篇
  2003年   14442篇
  2002年   14470篇
  2001年   15218篇
  2000年   11695篇
  1999年   9145篇
  1998年   7884篇
  1997年   7717篇
  1996年   7174篇
  1995年   6543篇
  1994年   6477篇
  1993年   6320篇
  1992年   6561篇
  1991年   7034篇
  1990年   6716篇
  1989年   6627篇
  1988年   6477篇
  1987年   6267篇
  1986年   5969篇
  1985年   7527篇
  1984年   7888篇
  1983年   6633篇
  1982年   6949篇
  1981年   6470篇
  1980年   6183篇
  1979年   6680篇
  1978年   6919篇
  1977年   6925篇
  1976年   6919篇
  1975年   6725篇
  1974年   6563篇
  1973年   6687篇
排序方式: 共有10000条查询结果,搜索用时 15 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