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   1274966篇
  免费   29555篇
  国内免费   7612篇
化学   628157篇
晶体学   14164篇
力学   73532篇
综合类   102篇
数学   237770篇
物理学   358408篇
  2021年   13042篇
  2020年   15878篇
  2019年   15995篇
  2016年   27284篇
  2015年   20549篇
  2014年   30259篇
  2013年   74099篇
  2012年   35886篇
  2011年   31334篇
  2010年   35694篇
  2009年   38374篇
  2008年   31172篇
  2007年   26343篇
  2006年   33855篇
  2005年   25642篇
  2004年   27659篇
  2003年   26412篇
  2002年   27836篇
  2001年   26208篇
  2000年   23448篇
  1999年   19487篇
  1998年   18399篇
  1997年   19052篇
  1996年   19035篇
  1995年   18423篇
  1994年   17939篇
  1993年   17437篇
  1992年   17135篇
  1991年   17470篇
  1990年   16701篇
  1989年   16766篇
  1988年   16371篇
  1987年   16400篇
  1986年   15256篇
  1985年   21825篇
  1984年   23206篇
  1983年   19378篇
  1982年   21134篇
  1981年   20368篇
  1980年   19677篇
  1979年   19881篇
  1978年   21271篇
  1977年   20877篇
  1976年   20592篇
  1975年   19284篇
  1974年   18904篇
  1973年   19445篇
  1972年   13977篇
  1968年   12023篇
  1967年   12379篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Experimental and Theoretical Physics - Dzyaloshinskii–Moriya interaction, DMI in short, represents an antisymmetric type of magnetic interactions that favor orthogonal orientation...  相似文献   
2.
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   
3.
4.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using...  相似文献   
5.
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   
6.
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   
7.
Chromatographia - We developed a simple, rapid, ecological RP-HPLC method for the estimation of Pitavastatin (PIT), Fenofibrate (FEN), and their impurities in a novel fixed dose combination. We...  相似文献   
8.
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the...  相似文献   
9.
Automotive proton exchange membrane fuel cell stacks need to meet manufacturer specified rated beginning-of-life (BOL) performance before being assembled into vehicles and shipped off to customers. The process of “breaking-in” of a freshly assembled stack is often referred to as “conditioning.” It has become an intensely researched area especially in automotive companies, where imminent commercialization of fuel cell electric vehicles (FCEVs) demands a short, energy- and cost-efficient, and practical conditioning protocol. Significant advances in reducing the conditioning time from 1 to 2 days to as low as 4h or less, in some cases without the use of additional inert gases such as nitrogen, and with minimal use of hydrogen, and specialized test stations will be discussed.  相似文献   
10.
Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been...  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