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   1700篇
  免费   69篇
  国内免费   15篇
化学   994篇
晶体学   25篇
力学   57篇
数学   233篇
物理学   330篇
无线电   145篇
  2023年   11篇
  2022年   53篇
  2021年   57篇
  2020年   52篇
  2019年   64篇
  2018年   62篇
  2017年   64篇
  2016年   79篇
  2015年   58篇
  2014年   72篇
  2013年   171篇
  2012年   105篇
  2011年   141篇
  2010年   83篇
  2009年   90篇
  2008年   107篇
  2007年   103篇
  2006年   69篇
  2005年   58篇
  2004年   48篇
  2003年   44篇
  2002年   38篇
  2001年   11篇
  2000年   11篇
  1999年   6篇
  1998年   10篇
  1997年   6篇
  1996年   11篇
  1995年   3篇
  1994年   3篇
  1993年   10篇
  1992年   11篇
  1991年   2篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1987年   8篇
  1986年   6篇
  1985年   6篇
  1984年   10篇
  1983年   3篇
  1981年   5篇
  1980年   5篇
  1979年   3篇
  1977年   2篇
  1975年   4篇
  1974年   3篇
  1970年   1篇
  1967年   1篇
  1936年   1篇
排序方式: 共有1784条查询结果,搜索用时 15 毫秒
61.
In this paper, shooting method and homotopy perturbation technique are applied for the flow analysis of temporal energy transport in a deformation channel with isothermal walls. An incompressible viscous fluid fills the space inside the channel. Analytical and numerical solutions are developed for the momentum and energy equations. The viscous dissipation effects are taken into account. Graphs for pertinent flow parameters are sketched and discussed. Comparison between the analytical and numerical solutions indicates an excellent agreement. It is noticed that behaviors of Prandtl and Eckert numbers on the temperature are qualitatively similar. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
62.
Journal of Thermal Analysis and Calorimetry - This research provides the analysis of an analytical method named Homotopy analysis method which is applied to examine the series solutions/results on...  相似文献   
63.
This work aimed to tune the comprehensive properties of Fe-P-C-based amorphous system through investigating the role of microalloying process on the crystallization behavior,glass forming ability(GFA),soft magnetic features,and mechanical properties.Considering minor addition of elements into the system,it was found that the simultaneous microalloying of Ni and Co leads to the highest GFA,which was due to the optimization of compositional heterogeneity and creation of near-eutectic composition.Moreover,the FeCoNiCuPC amorphous alloy exhibited the best anelastic/viscoplastic behavior under the nanoindentation test,which was owing to the intensified structural fluctuations in the system.However,the improved plasticity by the extra Cu addition comes at the expense of magnetic properties,so that the saturation magnetization of this alloying system is significantly decreased compared to the FeCoPC amorphous alloy with the highest soft magnetic properties.In total,the results indicated that a combination of added elemental constitutes,i.e.,Fe69Co5Ni5Cu1P13C7 composition,provides an optimized state for the comprehensive properties in the alloying system.  相似文献   
64.
Wireless Networks - This paper studies enhancing non-orthogonal multiple access (NOMA) spectral efficiency (SE) through optimizing the assigned power to each NOMA user depending on their channel...  相似文献   
65.
66.
Transition Metal Chemistry - Mixed ligand Ni(II) complexes were synthesized from triphenylphosphine and S-methyl- or S-ethyl-isothiosemicarbazone ligands derived from...  相似文献   
67.
Russian Journal of Electrochemistry - In this study, a new biosensor for amisulpride (ASP) determination is defined. The interaction between ASP and fish sperm double-stranded DNA (FSdsDNA) was...  相似文献   
68.
Transition Metal Chemistry - Three 1,3-dimethylbarbiturate-enamine derivatives and their symmetrical palladium(II) complexes were prepared and characterized by spectroscopic methods. In addition,...  相似文献   
69.
70.
Abstract

A series of novel β-mercapto carbonyl compounds (3a–z), methyl 2-(3-oxo-1,3-diarylpropylthio)acetate, were synthesized and characterized via iodine-catalyzed addition of methyl thioglycolate to chalcones (1a–z).

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.  相似文献   
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