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   538991篇
  免费   6167篇
  国内免费   1951篇
化学   270515篇
晶体学   7681篇
力学   26693篇
综合类   11篇
数学   85255篇
物理学   156954篇
  2021年   3170篇
  2020年   3593篇
  2019年   3780篇
  2018年   14210篇
  2017年   13888篇
  2016年   12802篇
  2015年   5915篇
  2014年   7721篇
  2013年   21417篇
  2012年   19703篇
  2011年   29534篇
  2010年   18154篇
  2009年   18407篇
  2008年   24172篇
  2007年   26458篇
  2006年   18086篇
  2005年   17270篇
  2004年   16100篇
  2003年   14829篇
  2002年   13638篇
  2001年   14561篇
  2000年   11312篇
  1999年   8876篇
  1998年   7197篇
  1997年   7070篇
  1996年   6979篇
  1995年   6347篇
  1994年   5969篇
  1993年   5777篇
  1992年   6423篇
  1991年   6278篇
  1990年   5994篇
  1989年   5675篇
  1988年   5950篇
  1987年   5695篇
  1986年   5392篇
  1985年   7567篇
  1984年   7789篇
  1983年   6335篇
  1982年   6845篇
  1981年   6815篇
  1980年   6517篇
  1979年   6642篇
  1978年   6802篇
  1977年   6780篇
  1976年   6767篇
  1975年   6495篇
  1974年   6363篇
  1973年   6586篇
  1972年   4002篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Fluorescence - This report describes a combined immunofluorescence and fluorescence viability stain applied as one staining solution for rapid detection of live Legionella...  相似文献   
2.
Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 105 ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma.  相似文献   
3.
Yang  T. L.  Kao  C. L.  Kuo  C. E.  Yeh  H. C.  Li  W. J.  Li  H. T.  Chen  C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the...  相似文献   
4.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
5.
6.
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial...  相似文献   
7.

A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.

  相似文献   
8.
Theoretical and Mathematical Physics - Dynamic systems acting on the plane and possessing the Wada property have been observed. There exist only two topological types, symmetric and antisymmetric,...  相似文献   
9.
Sun  J.  Yuan  H. 《Experimental Mechanics》2021,61(3):565-580
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients...  相似文献   
10.
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