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   1411913篇
  免费   32110篇
  国内免费   9729篇
化学   718510篇
晶体学   15074篇
力学   76989篇
综合类   242篇
数学   248521篇
物理学   394416篇
  2021年   13827篇
  2020年   16420篇
  2019年   16532篇
  2018年   15225篇
  2017年   13569篇
  2016年   29455篇
  2015年   21554篇
  2014年   31182篇
  2013年   75582篇
  2012年   43612篇
  2011年   44064篇
  2010年   40644篇
  2009年   42326篇
  2008年   41883篇
  2007年   38452篇
  2006年   41645篇
  2005年   35296篇
  2004年   34907篇
  2003年   32055篇
  2002年   32460篇
  2001年   32782篇
  2000年   27544篇
  1999年   23936篇
  1998年   21705篇
  1997年   21113篇
  1996年   19634篇
  1995年   18913篇
  1994年   18445篇
  1993年   17953篇
  1992年   18363篇
  1991年   18503篇
  1990年   17695篇
  1989年   17683篇
  1988年   17312篇
  1987年   17234篇
  1986年   16200篇
  1985年   22650篇
  1984年   23763篇
  1983年   19752篇
  1982年   21411篇
  1981年   20602篇
  1980年   19926篇
  1979年   20394篇
  1978年   21589篇
  1977年   21277篇
  1976年   21066篇
  1975年   19753篇
  1974年   19435篇
  1973年   19889篇
  1972年   14415篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Radioanalytical and Nuclear Chemistry - Eco-friendly and low-cost composite, amidoxime-functionalized microcrystalline cellulose/mesoporous silica (MCC/MS-AO), were synthesized by...  相似文献   
2.
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   
3.
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   
4.
5.
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   
6.
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   
7.
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   
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