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   1320265篇
  免费   33476篇
  国内免费   10421篇
化学   659152篇
晶体学   14569篇
力学   75733篇
综合类   320篇
数学   242401篇
物理学   371987篇
  2021年   14138篇
  2020年   16711篇
  2019年   16873篇
  2018年   12273篇
  2016年   28387篇
  2015年   21554篇
  2014年   31535篇
  2013年   75927篇
  2012年   38543篇
  2011年   34180篇
  2010年   37249篇
  2009年   39812篇
  2008年   33324篇
  2007年   28486篇
  2006年   35829篇
  2005年   27261篇
  2004年   28943篇
  2003年   27538篇
  2002年   28854篇
  2001年   28475篇
  2000年   24915篇
  1999年   22953篇
  1998年   21482篇
  1997年   21001篇
  1996年   19531篇
  1995年   18917篇
  1994年   18369篇
  1993年   17820篇
  1992年   17791篇
  1991年   17984篇
  1990年   17300篇
  1989年   17276篇
  1988年   16824篇
  1987年   16822篇
  1986年   15676篇
  1985年   22246篇
  1984年   23462篇
  1983年   19552篇
  1982年   21256篇
  1981年   20475篇
  1980年   19761篇
  1979年   20096篇
  1978年   21373篇
  1977年   21068篇
  1976年   20781篇
  1975年   19490篇
  1974年   19122篇
  1973年   19649篇
  1972年   14151篇
  1967年   12598篇
排序方式: 共有10000条查询结果,搜索用时 375 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.
Zhang  Hongchi  Liu  Rui  Li  Hui  Yang  Yang  Zhou  Feng 《Chemistry of Natural Compounds》2022,58(3):541-544
Chemistry of Natural Compounds -  相似文献   
8.
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   
9.
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   
10.
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   
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