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   1390682篇
  免费   33606篇
  国内免费   10453篇
化学   699666篇
晶体学   15967篇
力学   77301篇
综合类   321篇
数学   248377篇
物理学   393109篇
  2021年   14226篇
  2020年   16790篇
  2019年   16961篇
  2018年   15253篇
  2017年   13884篇
  2016年   29860篇
  2015年   21982篇
  2014年   31792篇
  2013年   76321篇
  2012年   42359篇
  2011年   41312篇
  2010年   40266篇
  2009年   42273篇
  2008年   39182篇
  2007年   35285篇
  2006年   39117篇
  2005年   32391篇
  2004年   32644篇
  2003年   30251篇
  2002年   30832篇
  2001年   31143篇
  2000年   26385篇
  1999年   23610篇
  1998年   21776篇
  1997年   21706篇
  1996年   21700篇
  1995年   19688篇
  1994年   19084篇
  1993年   18559篇
  1992年   18150篇
  1991年   18338篇
  1990年   17552篇
  1989年   17518篇
  1988年   17090篇
  1987年   17078篇
  1986年   15957篇
  1985年   22467篇
  1984年   23662篇
  1983年   19760篇
  1982年   21384篇
  1981年   20574篇
  1980年   19875篇
  1979年   20275篇
  1978年   21527篇
  1977年   21177篇
  1976年   20923篇
  1975年   19629篇
  1974年   19286篇
  1973年   19793篇
  1972年   14270篇
排序方式: 共有10000条查询结果,搜索用时 15 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