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   599887篇
  免费   6688篇
  国内免费   1631篇
化学   308161篇
晶体学   9056篇
力学   27837篇
综合类   18篇
数学   80286篇
物理学   182848篇
  2021年   4090篇
  2020年   4641篇
  2019年   4960篇
  2018年   12674篇
  2017年   13187篇
  2016年   12712篇
  2015年   6897篇
  2014年   9568篇
  2013年   23902篇
  2012年   21194篇
  2011年   31319篇
  2010年   20865篇
  2009年   20553篇
  2008年   28211篇
  2007年   30741篇
  2006年   19139篇
  2005年   22391篇
  2004年   18523篇
  2003年   16638篇
  2002年   14964篇
  2001年   15807篇
  2000年   12060篇
  1999年   9453篇
  1998年   7906篇
  1997年   7641篇
  1996年   7543篇
  1995年   6796篇
  1994年   6545篇
  1993年   6373篇
  1992年   7153篇
  1991年   7225篇
  1990年   6890篇
  1989年   6802篇
  1988年   6776篇
  1987年   6691篇
  1986年   6344篇
  1985年   8268篇
  1984年   8490篇
  1983年   6837篇
  1982年   7154篇
  1981年   6995篇
  1980年   6653篇
  1979年   7067篇
  1978年   7336篇
  1977年   7080篇
  1976年   7063篇
  1975年   6584篇
  1974年   6475篇
  1973年   6679篇
  1972年   4581篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
61.
62.
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine...  相似文献   
63.
64.
65.
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
66.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling.  相似文献   
67.
68.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
69.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
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