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   949篇
  免费   37篇
  国内免费   23篇
化学   842篇
晶体学   4篇
力学   20篇
数学   59篇
物理学   84篇
  2024年   4篇
  2023年   7篇
  2022年   29篇
  2021年   37篇
  2020年   64篇
  2019年   55篇
  2018年   81篇
  2017年   40篇
  2016年   73篇
  2015年   54篇
  2014年   72篇
  2013年   127篇
  2012年   68篇
  2011年   75篇
  2010年   52篇
  2009年   47篇
  2008年   43篇
  2007年   29篇
  2006年   9篇
  2005年   13篇
  2004年   6篇
  2003年   7篇
  2002年   6篇
  2001年   3篇
  1999年   1篇
  1994年   1篇
  1991年   1篇
  1986年   1篇
  1985年   3篇
  1976年   1篇
排序方式: 共有1009条查询结果,搜索用时 15 毫秒
211.
212.
An efficient method was developed for the [2 + 3] cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles using nanonickel ferrite (NiFe2O4) as an effective heterogeneous catalyst in dimethylformamide. The main advantages of this method are high yields, simple methodology and easy work‐up. The catalyst can be recovered and reused for several cycles with predictable activity. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
213.
214.
215.
216.
A simple and efficient method has been developed for the synthesis of β-amino alcohols by ring opening of epoxides in the presence of a catalytic amount of H14[NaP5W29MoO110] at room temperature under solvent-free conditions. The reaction works well for both aromatic and aliphatic amines.  相似文献   
217.
Efficient TBHP/R4N+X promoted hydroaroylations of dialkyl azo-1,2-dicarboxylates with methyl arenes, aldehydes, aryl methanols and arylmethyl chlorides are described. These oxidation/oxygenation and hydroaroylation processes were carried out by tert-butyl hydroperoxide as terminal oxidant/oxygen source, and were catalyzed by tetrabutylammonium bromide and tricaprylmethylammonium chloride as the driving force. During this investigation, all these hydroaroylating sources were found to be highly efficient reagents without the need of any transition-metal.  相似文献   
218.
Immobilized triazine bis[mercapto amine] complexes of Pd(0) (NiFe2O4@TABMA-Pd(0)) was easily synthesized and applied as highly efficient and versatile nanocatalyst for the synthesis of various trans stilbenes with high performance for the Heck coupling reaction of several types of aryl halides under thermal conditions. In short reaction time, excellent yields of trans stilbene derivatives have been achieved using NiFe2O4@TABMA-Pd(0) catalyst.  相似文献   
219.
Methylglycine, also known sarcosine, is dramatically used in drug molecules and its metal complexes can interact to DNA and also do cleavage. Hence, to study the influence of methylglycine ligand on biological behavior of metal complexes, two water-soluble platinum (II) complexes with the formula cis-[Pt(NH3)2(CH3-gly)]NO3 and cis-[Pt(NH2-CH3)2(CH3-gly)]NO3 (where CH3-gly is methylglycine) have been synthesized and characterized by spectroscopic methods, molar conductivity measurements, and elemental analyzes. The anticancer activity of synthesized complexes was tested against human breast adenocarcinoma cell line of MCF7 using MTT assay and results showed excellent anticancer activity with Cc50 values of 126 and 292 μM after 24 h incubation time, for both complexes of cis-[Pt(NH3)2(CH3gly)]NO3 and cis-[Pt(NH2-CH3)2(CH3gly)]NO3, respectively. Also, the interaction between Pt(II) complexes with calf thymus DNA was extensively studied by means of absorption spectroscopy, fluorescence titration spectra displacement with ethidium bromide (EtBr), and circular dichroism studied in Tris-buffer. The obtained spectroscopic results revealed that two complexes can bind to highly polymerized calf thymus DNA cooperatively and denature at micromolar concentrations. The fluorescence data indicate that quenching effect for cis-[Pt(NH3)2(CH3gly)]NO3 (Ksv?=?9.48 mM?1) was higher than that of cis-[Pt(NH2-CH3)2(CH3gly)]NO3 (Ksv?= 1.98 mM?1). These results were also confirmed by circular dichrosim spectra. Consequently, docking data showed that cis-[Pt(NH3)2(CH3gly)]NO3 with more interaction energy binds on DNA via groove binding which is more compatible with experimental results.
Graphical Abstract ? Two anticancer Pt(II) complexes, cis-[Pt(NH3)2(CH3gly)]NO3 and cis-[Pt(NH2?CH3)2(CH3gly)]NO3, have been synthesized and interacted with calf thymus DNA. Improving solubility of these compounds reduce side effects and increase anticancer activity against human breast cell line. Modes of binding have been studied by electronic absorption, fluorescence, and CD measurements. Results show that both Pt(II) complexes can interact to DNA via groove binding.
  相似文献   
220.
The electrochemical oxidation of nortriptyline at a carbon ionic liquid electrode (CILE) was investigated. Nortriptyline is electrochemically inactive on conventional electrodes but CILE exhibited excellent electrocatalytic activity toward oxidation of nortriptyline with the well-defined anodic peak at 860 mV. This characteristic was attributed to the outstanding conductivity and electrocatalytic effect of the ionic liquid, 1-octylpyridinum hexaflourophosphate, used as a binder in the construction of the electrode. The influence of experimental parameters such as pH and sweep rate was also studied. The quantitative determination of nortriptyline was performed using differential pulse voltammetry technique. Under selected conditions the anodic peak current was linear to nortriptyline concentration in the ranges of 4.8 × 10–6 to 2.4 × 10–5 M and 2.4 × 10–5 to 6.4 × 10–5 M, with correlation coefficients of 0.9992 and 09949, respectively. The detection limit was 3 × 10–7 M.  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