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   575822篇
  免费   6292篇
  国内免费   1630篇
化学   279339篇
晶体学   8028篇
力学   29361篇
综合类   14篇
数学   97132篇
物理学   169870篇
  2021年   4017篇
  2020年   4409篇
  2019年   4742篇
  2018年   20399篇
  2017年   20630篇
  2016年   16869篇
  2015年   7177篇
  2014年   9217篇
  2013年   21222篇
  2012年   22228篇
  2011年   36628篇
  2010年   23522篇
  2009年   23764篇
  2008年   31037篇
  2007年   34965篇
  2006年   17141篇
  2005年   21205篇
  2004年   17650篇
  2003年   16437篇
  2002年   13909篇
  2001年   13904篇
  2000年   10700篇
  1999年   8151篇
  1998年   6829篇
  1997年   6518篇
  1996年   6464篇
  1995年   5722篇
  1994年   5598篇
  1993年   5440篇
  1992年   6020篇
  1991年   6090篇
  1990年   5800篇
  1989年   5626篇
  1988年   5648篇
  1987年   5536篇
  1986年   5229篇
  1985年   6736篇
  1984年   6877篇
  1983年   5462篇
  1982年   5539篇
  1981年   5507篇
  1980年   5112篇
  1979年   5489篇
  1978年   5636篇
  1977年   5453篇
  1976年   5426篇
  1975年   4996篇
  1974年   4958篇
  1973年   4989篇
  1972年   3496篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
63.
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   
64.
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   
65.
66.
67.
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   
68.
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   
69.
70.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  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