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   349000篇
  免费   3929篇
  国内免费   972篇
化学   187449篇
晶体学   6118篇
力学   14510篇
综合类   12篇
数学   37480篇
物理学   108332篇
  2020年   2987篇
  2019年   3303篇
  2018年   3985篇
  2017年   4157篇
  2016年   6312篇
  2015年   3862篇
  2014年   6230篇
  2013年   15880篇
  2012年   11510篇
  2011年   13859篇
  2010年   9971篇
  2009年   9996篇
  2008年   12805篇
  2007年   12620篇
  2006年   11894篇
  2005年   10744篇
  2004年   9847篇
  2003年   8994篇
  2002年   8662篇
  2001年   10415篇
  2000年   7851篇
  1999年   6039篇
  1998年   4902篇
  1997年   4732篇
  1996年   4559篇
  1995年   4236篇
  1994年   4126篇
  1993年   3931篇
  1992年   4783篇
  1991年   4629篇
  1990年   4523篇
  1989年   4519篇
  1988年   4512篇
  1987年   4527篇
  1986年   4292篇
  1985年   5556篇
  1984年   5630篇
  1983年   4636篇
  1982年   4827篇
  1981年   4705篇
  1980年   4461篇
  1979年   4927篇
  1978年   4975篇
  1977年   5037篇
  1976年   4919篇
  1975年   4588篇
  1974年   4523篇
  1973年   4649篇
  1972年   3126篇
  1968年   2788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.
Kinetics and Catalysis - The results of studies in the field of synthesis and characterization of layered double hydroxides (LDHs) obtained using solid-phase reactions are summarized. The effect of...  相似文献   
6.
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the...  相似文献   
7.
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed....  相似文献   
8.
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   
9.
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   
10.
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   
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