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   449764篇
  免费   3660篇
  国内免费   924篇
化学   222152篇
晶体学   6086篇
力学   23209篇
综合类   19篇
数学   61101篇
物理学   141781篇
  2021年   3100篇
  2020年   3428篇
  2019年   4147篇
  2018年   12048篇
  2017年   12625篇
  2016年   10812篇
  2015年   4836篇
  2014年   7413篇
  2013年   16676篇
  2012年   15934篇
  2011年   24737篇
  2010年   16717篇
  2009年   17004篇
  2008年   22030篇
  2007年   24742篇
  2006年   12614篇
  2005年   16077篇
  2004年   12873篇
  2003年   12250篇
  2002年   10541篇
  2001年   10897篇
  2000年   8445篇
  1999年   6215篇
  1998年   5134篇
  1997年   5137篇
  1996年   4947篇
  1995年   4427篇
  1994年   4455篇
  1993年   4128篇
  1992年   4931篇
  1991年   4936篇
  1990年   4821篇
  1989年   4825篇
  1988年   4844篇
  1987年   4836篇
  1986年   4512篇
  1985年   5860篇
  1984年   5974篇
  1983年   4808篇
  1982年   4937篇
  1981年   4967篇
  1980年   4553篇
  1979年   5212篇
  1978年   5224篇
  1977年   5393篇
  1976年   5278篇
  1975年   4852篇
  1974年   4750篇
  1973年   4845篇
  1972年   3511篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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   
2.
Nikolaev  N. N. 《JETP Letters》2022,115(11):639-643
JETP Letters - A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The...  相似文献   
3.
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   
4.
5.

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   
6.
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   
7.
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   
8.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,...  相似文献   
9.
Russian Journal of General Chemistry - A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan,...  相似文献   
10.
Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.  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