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   1359829篇
  免费   37011篇
  国内免费   13260篇
化学   685467篇
晶体学   20677篇
力学   76830篇
综合类   431篇
数学   245049篇
物理学   381646篇
  2021年   15344篇
  2020年   17608篇
  2019年   17885篇
  2018年   13451篇
  2016年   29628篇
  2015年   22862篇
  2014年   33059篇
  2013年   77548篇
  2012年   40843篇
  2011年   36592篇
  2010年   38943篇
  2009年   41390篇
  2008年   34949篇
  2007年   29824篇
  2006年   36663篇
  2005年   28201篇
  2004年   29549篇
  2003年   28116篇
  2002年   29270篇
  2001年   28299篇
  2000年   24904篇
  1999年   23104篇
  1998年   21603篇
  1997年   21569篇
  1996年   21768篇
  1995年   19790篇
  1994年   19170篇
  1993年   18555篇
  1992年   18513篇
  1991年   18766篇
  1990年   17971篇
  1989年   17918篇
  1988年   17454篇
  1987年   17442篇
  1986年   16338篇
  1985年   22700篇
  1984年   23929篇
  1983年   20071篇
  1982年   21704篇
  1981年   20935篇
  1980年   20255篇
  1979年   20472篇
  1978年   21740篇
  1977年   21397篇
  1976年   21026篇
  1975年   19710篇
  1974年   19305篇
  1973年   19756篇
  1972年   14266篇
  1967年   12531篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
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   
23.
24.
25.
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   
26.
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   
27.
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   
28.
29.
Cinnamaldehyde (CA), an active ingredient isolated from the traditional Chinese medicine Cortex Cinnamomi, has a wide range of bioactivities. To clarify the distribution characteristics of CA, a selective and sensitive method utilizing gas chromatography–mass spetrometry was initially developed for simultaneously determining the concentration of CA and its metabolite cinnamyl alcohol in rat tissues. Selected ion masses of m/z 131, 105 and 92 were chosen, and separation of the analytes was performed on a DB‐5 ms (30 m × 0.25 mm, 0.25 µm, thickness) capillary column by gas chromatography–mass spectrometry. The calibration curves demonstrated good linearity and reproducibility over the range of 20–2000 and 20–4000 ng/mL for various tissue samples. Recoveries ranged from 86.8 to 107.5%, while intra‐ and interday relative standard deviations were all <11.3%. The analysis method was successfully applied in tissue distribution studies for CA and cinnamyl alcohol. As CA and cinnamyl alcohol may inter‐convert to one another, simultaneous determination of both analytes provides a comparative and accurate data for tissue study. The concentrations of CA and cinnamyl alcohol remaining in spleen were the highest among the main organs, including heart, liver, spleen, lung, kidney and brain. In addition, there was no long‐term accumulation of CA in rat tissues. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
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