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   434807篇
  免费   4406篇
  国内免费   1071篇
化学   234380篇
晶体学   7183篇
力学   18974篇
综合类   19篇
数学   47157篇
物理学   132571篇
  2019年   3908篇
  2018年   4964篇
  2017年   5035篇
  2016年   7423篇
  2015年   4557篇
  2014年   7272篇
  2013年   18507篇
  2012年   13540篇
  2011年   16591篇
  2010年   11790篇
  2009年   11624篇
  2008年   15255篇
  2007年   15336篇
  2006年   14337篇
  2005年   12946篇
  2004年   11903篇
  2003年   10902篇
  2002年   10614篇
  2001年   12306篇
  2000年   9468篇
  1999年   7282篇
  1998年   6102篇
  1997年   6077篇
  1996年   5733篇
  1995年   5373篇
  1994年   5424篇
  1993年   5017篇
  1992年   6015篇
  1991年   5923篇
  1990年   5816篇
  1989年   5689篇
  1988年   5850篇
  1987年   5716篇
  1986年   5413篇
  1985年   7116篇
  1984年   7364篇
  1983年   6038篇
  1982年   6194篇
  1981年   6188篇
  1980年   5998篇
  1979年   6252篇
  1978年   6551篇
  1977年   6530篇
  1976年   6439篇
  1975年   5923篇
  1974年   5939篇
  1973年   6042篇
  1972年   4239篇
  1968年   3574篇
  1967年   3560篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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   
2.
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   
3.
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   
4.
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   
5.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
6.
7.
Chemistry of Natural Compounds - O- and N-propylamino-derivatives of betulin and betulonic acid oxime and methyl ester were synthesized. Their antitumor activity against a panel of 60 human cancer...  相似文献   
8.
9.

The aim of this study is to develop and validate a sensitive and specific stability-indicating reversed-phase high-performance liquid chromatographic (RP-HPLC) method for the quantitative determination of Sugammadex sodium together with its process and possible degradation impurities. The pKa value is 2.82. The chromatographic conditions have been optimized by the Hypersil Gold 250 mm X 4.6 mm, 3 µ RP-18 columns with gradient elution using a mobile phase composed of 0.1% phosphoric acid, acetonitrile, and methanol. The eluents were monitored at 205 nm with a flow rate of 1.0 mL/min with an injection volume of 20 µL. The optimized method produced symmetrical and sharp peaks with good separation between the process and degradation impurities. The forced degradation study was carried out under acid, base, oxidation, and thermal conditions to demonstrate the stability-indicating capability of the method. The method was validated as per the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) Q2 (R1) and showed excellent specificity, precision, linearity, accuracy, and robustness. The developed HPLC method was precise with a value of 0.25%. The relative standard deviation of accuracy represented by the recovery studies ranged between 89.5% and 104.6%. Linearity analyses indicated a correlation coefficient value of greater than 0.996 for Sugammadex and its known impurities. The LOD and LOQ values for Sugammadex ranged from 0.017% to 0.050%, and for its related impurities, they ranged from 0.015% to 0.055%. The stability of the analytical solution was evaluated and was stable for 75 h when stored at 5 °C. No chromatographic interference was observed during the degradation studies and also in the blank chromatogram.

  相似文献   
10.
Fan  K.  Lu  R. S.  Liang  K. K.  Hou  Z. C. 《High Energy Chemistry》2022,56(4):264-269
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was...  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