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   225156篇
  免费   3031篇
  国内免费   649篇
化学   125993篇
晶体学   3840篇
力学   8380篇
综合类   15篇
数学   23164篇
物理学   67444篇
  2021年   1894篇
  2020年   2104篇
  2019年   2357篇
  2018年   2635篇
  2017年   2738篇
  2016年   4283篇
  2015年   2840篇
  2014年   4260篇
  2013年   10423篇
  2012年   7927篇
  2011年   9650篇
  2010年   6720篇
  2009年   6654篇
  2008年   8605篇
  2007年   8417篇
  2006年   7960篇
  2005年   7211篇
  2004年   6451篇
  2003年   5880篇
  2002年   5542篇
  2001年   6608篇
  2000年   5037篇
  1999年   3869篇
  1998年   3015篇
  1997年   2969篇
  1996年   2915篇
  1995年   2680篇
  1994年   2575篇
  1993年   2396篇
  1992年   3047篇
  1991年   2905篇
  1990年   2848篇
  1989年   2818篇
  1988年   2834篇
  1987年   2861篇
  1986年   2719篇
  1985年   3460篇
  1984年   3473篇
  1983年   2708篇
  1982年   2833篇
  1981年   2871篇
  1980年   2642篇
  1979年   2960篇
  1978年   2931篇
  1977年   3046篇
  1976年   2881篇
  1975年   2605篇
  1974年   2551篇
  1973年   2523篇
  1972年   1734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.
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within...  相似文献   
6.
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   
7.
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   
8.
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   
9.
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   
10.
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   
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