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   550102篇
  免费   27757篇
  国内免费   18290篇
化学   290364篇
晶体学   8780篇
力学   28541篇
综合类   37篇
数学   68020篇
物理学   200407篇
  2021年   4585篇
  2020年   5149篇
  2019年   6403篇
  2018年   8172篇
  2017年   8816篇
  2016年   11874篇
  2015年   7851篇
  2014年   11420篇
  2013年   25762篇
  2012年   20694篇
  2011年   25075篇
  2010年   21393篇
  2009年   21705篇
  2008年   21687篇
  2007年   21007篇
  2006年   19682篇
  2005年   18106篇
  2004年   18018篇
  2003年   15787篇
  2002年   15448篇
  2001年   16996篇
  2000年   12973篇
  1999年   10616篇
  1998年   8909篇
  1997年   8703篇
  1996年   8513篇
  1995年   8212篇
  1994年   8286篇
  1993年   8157篇
  1992年   8435篇
  1991年   8199篇
  1990年   7656篇
  1989年   7617篇
  1988年   7539篇
  1987年   6965篇
  1986年   6606篇
  1985年   8123篇
  1984年   8492篇
  1983年   6876篇
  1982年   7450篇
  1981年   7169篇
  1980年   6849篇
  1979年   7060篇
  1978年   7230篇
  1977年   7345篇
  1976年   7692篇
  1975年   6791篇
  1974年   6653篇
  1973年   7123篇
  1972年   5107篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 105 ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma.  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.
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 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   
8.
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   
9.
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   
10.
Journal of Structural Chemistry - Atomic and electronic structures of cyclic organosilicon compound 9,9,10,10-tetraethynyl-9,10-dihydrodisilaanthracene are studied by the density functional theory....  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