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   1549篇
  免费   73篇
  国内免费   8篇
化学   793篇
晶体学   12篇
力学   57篇
数学   485篇
物理学   283篇
  2023年   12篇
  2022年   45篇
  2021年   57篇
  2020年   59篇
  2019年   56篇
  2018年   83篇
  2017年   49篇
  2016年   80篇
  2015年   53篇
  2014年   73篇
  2013年   105篇
  2012年   133篇
  2011年   109篇
  2010年   69篇
  2009年   64篇
  2008年   75篇
  2007年   50篇
  2006年   48篇
  2005年   46篇
  2004年   41篇
  2003年   33篇
  2002年   21篇
  2001年   11篇
  2000年   15篇
  1999年   9篇
  1998年   11篇
  1997年   9篇
  1996年   8篇
  1995年   11篇
  1994年   14篇
  1993年   13篇
  1992年   12篇
  1991年   12篇
  1990年   10篇
  1989年   7篇
  1988年   7篇
  1987年   8篇
  1986年   8篇
  1985年   13篇
  1984年   7篇
  1983年   6篇
  1982年   19篇
  1981年   13篇
  1980年   4篇
  1979年   4篇
  1976年   5篇
  1975年   4篇
  1974年   7篇
  1973年   4篇
  1972年   6篇
排序方式: 共有1630条查询结果,搜索用时 250 毫秒
51.
MgO@SiO2 core–shell nanoparticles were manufactured, and a synthetic protocol was developed to prepare MgO nanoparticles where the SiO2 shell thickness was less than 10 nm. The influence of synthesis parameters on the formation of MgO@SiO2 nanoparticles was studied. The fact of a SiO2 shell being formed on the MgO surface was established and the sizes of the thus-prepared MgO@SiO2 nanoparticles were determined by TEM and Fourier-transform IR spectroscopy.  相似文献   
52.
Energy management in buildings is addressed in this paper. The energetic impact of buildings in the current energetic context is first depicted. Then the studied optimization problem is defined as the optimal management of production and consumption activities in houses. A scheduling problem is identified to adjust the energy consumption to both the energy cost and the inhabitant’s comfort. The available flexibilities of the services provided by domestic appliances are used to compute optimal energy plans. These flexibilities are associated to time windows or heating storage abilities. A constraints formulation of the energy allocation problem is given. A derived mixed linear program is used to solve this problem. The energy consumption in houses is very dependent to uncertain data such as weather forecasts and inhabitants’ activities. Parametric uncertainties are introduced in the home energy management problem in order to provide robust energy allocation. Robust linear programming is implemented. Event related uncertainties are also addressed through stochastic programming in order to take into account the inhabitant’s activities. A scenario based approach is implemented to face this robust optimization problem.  相似文献   
53.
The synthesis of two series of semiperfluoroalkyloxyphenyl and perfluoroalkylphenyl β-D-glucopyranosides is described. Their mesomorphic properties are studied by DSC, polarized optical microscopy and X-ray diffraction. All mesophases are identified as smectic A with a bimolecular in-layer arrangement.  相似文献   
54.
55.
A simple and efficient aerobic oxidative dehydrogenation reaction method for the conversion of 2-(alkylthio)-1,4-dihydropyrimidines to 2-(alkylthio)pyrimidines using copper catalyst with no additives, such as an oxidant, acid, or base, has been developed. The reaction was successful with a wide range of 2-(alkylthio)-1,4-dihydropyrimidine substrates.  相似文献   
56.
Archiv der Mathematik - In this paper, our purpose is to give a characterization of a sequentially Cohen–Macaulay module, which was introduced by Stanley (Combinatorics and Commutative...  相似文献   
57.
A new xenicane diterpenoid, 15-deoxy-isoxeniolide-A (1) along with four known compounds 9-deoxy-isoxeniolide-A (2), isoxeniolide-A (3), xeniolide-A (4) and coraxeniolide-B (5) were isolated from the Bornean soft coral Xenia sp. The structures of these metabolites were elucidated on the basis of spectral analysis, NMR and HRESIMS. Compound 5 showed cytotoxic activity against ATL cell line, S1T.  相似文献   
58.
Journal of Radioanalytical and Nuclear Chemistry - To keep the accredited category for the gamma spectrometry test in our laboratory, the efficiency curves of a HPGe detector for soil sample in...  相似文献   
59.
Journal of Nonlinear Science - We prove that if the local second-order structure function exponents in the inertial range remain positive uniformly in viscosity, then any spacetime $$L^2$$ weak...  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