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   448208篇
  免费   3982篇
  国内免费   1220篇
化学   224249篇
晶体学   6822篇
力学   21212篇
综合类   5篇
数学   61388篇
物理学   139734篇
  2020年   2749篇
  2019年   3084篇
  2018年   11566篇
  2017年   12284篇
  2016年   9548篇
  2015年   4643篇
  2014年   5985篇
  2013年   16256篇
  2012年   15771篇
  2011年   25795篇
  2010年   16331篇
  2009年   16281篇
  2008年   22855篇
  2007年   25866篇
  2006年   12856篇
  2005年   17800篇
  2004年   13642篇
  2003年   12531篇
  2002年   10562篇
  2001年   11680篇
  2000年   8822篇
  1999年   6767篇
  1998年   5284篇
  1997年   5371篇
  1996年   5133篇
  1995年   4743篇
  1994年   4600篇
  1993年   4465篇
  1992年   5178篇
  1991年   5290篇
  1990年   4988篇
  1989年   4924篇
  1988年   4950篇
  1987年   4849篇
  1986年   4596篇
  1985年   6077篇
  1984年   6214篇
  1983年   5094篇
  1982年   5369篇
  1981年   5159篇
  1980年   4980篇
  1979年   5310篇
  1978年   5611篇
  1977年   5349篇
  1976年   5481篇
  1975年   4980篇
  1974年   5061篇
  1973年   5414篇
  1972年   3402篇
  1971年   2648篇
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
41.
42.
43.
44.
The European Physical Journal Special Topics - The removal of suspended particles from the interior of a thermocapillary liquid bridge via a finite-particle-size effect restricting the particle...  相似文献   
45.
46.
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   
47.
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   
48.
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   
49.
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   
50.
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