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   1299497篇
  免费   29567篇
  国内免费   7690篇
化学   644573篇
晶体学   14646篇
力学   74080篇
综合类   103篇
数学   239709篇
物理学   363643篇
  2021年   13326篇
  2020年   15870篇
  2019年   16010篇
  2018年   12687篇
  2016年   27659篇
  2015年   20685篇
  2014年   30269篇
  2013年   74068篇
  2012年   36687篇
  2011年   32959篇
  2010年   36653篇
  2009年   39135篇
  2008年   32833篇
  2007年   28368篇
  2006年   34607篇
  2005年   27316篇
  2004年   28535篇
  2003年   27208篇
  2002年   28351篇
  2001年   26585篇
  2000年   23784篇
  1999年   22028篇
  1998年   20785篇
  1997年   20353篇
  1996年   19062篇
  1995年   18448篇
  1994年   17955篇
  1993年   17478篇
  1992年   17201篇
  1991年   17531篇
  1990年   16777篇
  1989年   16802篇
  1988年   16439篇
  1987年   16467篇
  1986年   15346篇
  1985年   21894篇
  1984年   23279篇
  1983年   19407篇
  1982年   21154篇
  1981年   20399篇
  1980年   19715篇
  1979年   19937篇
  1978年   21295篇
  1977年   20932篇
  1976年   20656篇
  1975年   19380篇
  1974年   18973篇
  1973年   19576篇
  1972年   14060篇
  1967年   12473篇
排序方式: 共有10000条查询结果,搜索用时 218 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