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   249869篇
  免费   1673篇
  国内免费   440篇
化学   115846篇
晶体学   3846篇
力学   13084篇
综合类   4篇
数学   38673篇
物理学   80529篇
  2021年   1085篇
  2020年   1285篇
  2019年   1333篇
  2018年   10514篇
  2017年   11374篇
  2016年   6751篇
  2015年   2553篇
  2014年   2636篇
  2013年   6368篇
  2012年   9397篇
  2011年   18777篇
  2010年   11544篇
  2009年   11577篇
  2008年   16485篇
  2007年   19936篇
  2006年   5817篇
  2005年   11931篇
  2004年   8116篇
  2003年   7699篇
  2002年   5619篇
  2001年   5813篇
  2000年   4387篇
  1999年   3194篇
  1998年   2218篇
  1997年   2276篇
  1996年   2301篇
  1995年   2087篇
  1994年   2073篇
  1993年   1854篇
  1992年   2326篇
  1991年   2432篇
  1990年   2265篇
  1989年   2226篇
  1988年   2194篇
  1987年   2206篇
  1986年   2016篇
  1985年   2508篇
  1984年   2530篇
  1983年   2019篇
  1982年   2029篇
  1981年   1871篇
  1980年   1867篇
  1979年   2165篇
  1978年   2253篇
  1977年   2130篇
  1976年   2062篇
  1975年   1939篇
  1974年   1919篇
  1973年   1984篇
  1972年   1288篇
排序方式: 共有10000条查询结果,搜索用时 843 毫秒
21.
22.
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   
23.
24.
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   
25.
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   
26.
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   
27.
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   
28.
29.
30.
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