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   357216篇
  免费   2649篇
  国内免费   880篇
化学   160002篇
晶体学   5451篇
力学   19754篇
综合类   11篇
数学   69379篇
物理学   106148篇
  2020年   1759篇
  2019年   1959篇
  2018年   18740篇
  2017年   19349篇
  2016年   12099篇
  2015年   3739篇
  2014年   3987篇
  2013年   9567篇
  2012年   13481篇
  2011年   27747篇
  2010年   16800篇
  2009年   17226篇
  2008年   22229篇
  2007年   27174篇
  2006年   7205篇
  2005年   13818篇
  2004年   10150篇
  2003年   10026篇
  2002年   7146篇
  2001年   6530篇
  2000年   5187篇
  1999年   3698篇
  1998年   2984篇
  1997年   2876篇
  1996年   2914篇
  1995年   2642篇
  1994年   2491篇
  1993年   2342篇
  1992年   2962篇
  1991年   2866篇
  1990年   2801篇
  1989年   2841篇
  1988年   2865篇
  1987年   2862篇
  1986年   2729篇
  1985年   3469篇
  1984年   3459篇
  1983年   2750篇
  1982年   2864篇
  1981年   2921篇
  1980年   2691篇
  1979年   3045篇
  1978年   3045篇
  1977年   3051篇
  1976年   2932篇
  1975年   2643篇
  1974年   2584篇
  1973年   2585篇
  1972年   1761篇
  1968年   1814篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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   
2.
3.

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   
4.
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   
5.
Journal of Applied Spectroscopy - Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The...  相似文献   
6.
Russian Journal of General Chemistry - Tungstophosphatozincates with the Keggin anion structure Kt5[PW11O39Zn(H2O)]?nH2O, Kt = Rb+, Cs+, (CH3)4N+; (C2H5)4N+ were synthesized. Their...  相似文献   
7.
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial...  相似文献   
8.
Russian Journal of Organic Chemistry - A highly efficient green protocol has been proposed for the synthesis of symmetrical S-aryl arenesulfonothioates by irradiation of N-hydroxy arenesulfonamides...  相似文献   
9.
Optics and Spectroscopy - Optical investigations of crystals of solid solutions NdxGd1 – xCr3(BO3)4, 0.01 ≤ x ≤ 1, have been performed. Absorption spectra in the...  相似文献   
10.
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