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   1397290篇
  免费   36380篇
  国内免费   14061篇
化学   711305篇
晶体学   20878篇
力学   77485篇
综合类   556篇
数学   246670篇
物理学   390837篇
  2021年   14759篇
  2020年   17162篇
  2019年   17462篇
  2018年   13817篇
  2016年   29462篇
  2015年   22540篇
  2014年   32613篇
  2013年   77348篇
  2012年   42477篇
  2011年   40214篇
  2010年   40154篇
  2009年   42409篇
  2008年   38691篇
  2007年   34283篇
  2006年   39990篇
  2005年   32055篇
  2004年   32441篇
  2003年   30316篇
  2002年   31346篇
  2001年   31291篇
  2000年   26742篇
  1999年   23670篇
  1998年   21725篇
  1997年   21600篇
  1996年   21553篇
  1995年   19543篇
  1994年   18987篇
  1993年   18475篇
  1992年   18682篇
  1991年   18838篇
  1990年   18105篇
  1989年   18032篇
  1988年   17580篇
  1987年   17555篇
  1986年   16524篇
  1985年   22925篇
  1984年   24014篇
  1983年   20126篇
  1982年   21748篇
  1981年   20961篇
  1980年   20314篇
  1979年   20632篇
  1978年   21825篇
  1977年   21498篇
  1976年   21242篇
  1975年   19924篇
  1974年   19604篇
  1973年   20064篇
  1972年   14554篇
  1967年   12763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.
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.
Bo  Luo  Gao  Wei  Yu  Yuguo  Chen  Xiaojun 《Nonlinear dynamics》2022,110(1):281-311
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns...  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