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   587篇
  免费   8篇
  国内免费   53篇
化学   627篇
晶体学   4篇
物理学   17篇
  2023年   8篇
  2022年   1篇
  2021年   5篇
  2020年   7篇
  2019年   5篇
  2018年   10篇
  2017年   9篇
  2016年   9篇
  2015年   11篇
  2014年   10篇
  2013年   21篇
  2012年   23篇
  2011年   49篇
  2010年   45篇
  2009年   57篇
  2008年   51篇
  2007年   65篇
  2006年   53篇
  2005年   52篇
  2004年   45篇
  2003年   16篇
  2002年   9篇
  2001年   4篇
  2000年   9篇
  1999年   15篇
  1998年   7篇
  1997年   4篇
  1996年   6篇
  1995年   6篇
  1994年   9篇
  1993年   5篇
  1992年   8篇
  1991年   4篇
  1990年   3篇
  1989年   2篇
  1988年   2篇
  1985年   1篇
  1982年   1篇
  1976年   1篇
排序方式: 共有648条查询结果,搜索用时 343 毫秒
101.
用2-二茂铁基-1,3-二噻烷的锂代物与芳基羰基化合物的反应,合成了16种2-二茂铁基-2-(芳基羟甲基)-1,3-二噻烷.简要讨论了产物的1HNMR谱以及羰基化合物结构对反应的影响.  相似文献   
102.
We investigated Langmuir-Blodgett(LB) films built from the mixture of an amphiphilic push-pull ferrocene derivative(P) and behenic acid. Langmuir films of P diluted by behenic acid exhibit a very good cohesion, and the mixed films can easily be transferred onto solid substrates. Linear dichroism UV-visible and IR spectroscopy measurements of the mixed LB multilayers confirm that the molecules(P) are oriented to the substrate. The nonlinear optical experiments on the mixed monolayer deposited on the CaF2 slide showed that P displays efficient optical second harmonic generation(SHG) with a molecular hyperpolarizability (β)h, high as 6.0×10-29e. s. u..  相似文献   
103.
FT-RamanSpectraStudiesonOpenFerroceneWANGYue;JIANGShi-mei;FANYu-guoandSUNChun-ting(TheKeyLaboratoryforMolecularSpectrumandStr...  相似文献   
104.
Reaction of phenyl magnesium bromide with the ,β-unsaturated ketone 3-methyl-2,3,4,5,6,7-hexahydroind-8(9)-en-1-one, followed by an aqueous work-up, generates the pro-chiral tetra-substituted cyclopentadiene, 1-phenyl-3-methyl-4,5,6,7-tetrahydroindene, CpH, a precursor to the η5-cyclopentadienyl ligand in (Cp)2Fe and [(Cp)Fe(CO)]2(μ-CO)2. Both complexes were generated as mixtures of rac-(RR and SS)- and meso-(RS)-isomers, and in either case pure meso-isomer was isolated by crystallisation and characterised by single crystal X-ray structure, both molecules having crystallographic Ci symmetry. Reduction with Na/Hg cleaves meso-(RS)-[(Cp)Fe(CO)]2(μ-CO)2 and the resulting mixture of (R)- and (S)-[(Cp)Fe(CO)2] anions reacts with MeI to give racemic (Cp)Fe(CO)2Me, which was characterised by the X-ray crystal structure. The Cp ligand is more electron donating than (η-C5H5) as revealed by the reduction potential of the (Cp)2Fe+/(Cp)2Fe couple, E°=−0.127 V (vs. Ag  AgCl). Reaction of LiCp with ZrCl4 yields the zirconocene dichloride [Zr(Cp)2Cl2] as mixture of rac- and meso-isomers, from which pure rac-isomer is obtained as a mixture of RR and SS crystals by recrystallisation. The reaction of rac-[Zr(Cp)2Cl2] with LiMe gives rac-[Zr(Cp)2Me2]. The structures of RR-[Zr(Cp)2Cl2] and rac-[Zr(Cp)2Me2] have been determined by X-ray diffraction. The structural studies reveal the influence of the bulky substituted cyclopentadienyl ligand on the metal---Cp distances and other metric parameters.  相似文献   
105.
Octamethyl‐1, 1′‐di(2‐pyridyl)ferrocene ( 1 ) acts as molecular electrochemical sensor for magnesium, calcium, zinc, and cadmium ions in acetonitrile solution. The new redox peak, anodically shifted by ca. 0.40 V, which appears in the cyclic voltammogram of 1 in the presence of even small amounts (10 mol %) of these ions, is unaffected by an excess of alkali metal ions. Metal complexation is accompanied by a batho‐ and hyper‐chromic shift of the band in the visible region of the UV‐Vis spectrum of 1 . A detailed study of the behaviour of 1 towards zinc chloride in acetonitrile solution has revealed that 1 is able to accommodate a maximum of two zinc ions. Oxidation of zinc‐coordinated 1 leads to partial decomplexation. The N‐methyl and N‐benzyl species 1 Me+, 1 Me22+, 1 Bzl+ and 1 Bzl22+ have been synthesized and the former two structurally investigated by X‐ray diffraction. Alkylation causes an anodic shift of the redox potential of the ferrocene nucleus, which is linearly dependent on the number of alkyl groups introduced. Octamethyl‐1, 1′‐di(2‐thiophenyl)ferrocene ( 2 ) has also been synthesized and structurally characterized by X‐ray diffraction. Cyclic voltammetry has revealed that, in contrast to 1 , 2 does not respond to the divalent metal ions studied.  相似文献   
106.
1-Ethoxycarbonyl-3-ferrocenyl-propane-1,3-dion and Ferrocene-1,1′bis(2,4-dioxobutanoic acid ethylester) as Ligands for Transition Metal Ions. Crystal Structure of Bis(1-ethoxycarbonyl-3-ferrocenyl-propane-1,3dionato)copper(II) The ligands 1-ethoxycarbonyl-3-ferrocenyl-propane-1,3-dion and ferrocene-1,1′-bis(2,4-dioxo-butanoic acid ethylester) have been prepared by reaction of acetylferrocene or 1,1′-diacetylferrocene and diethyl oxalate. They yield neutral chelates with CuII, NiII, ZnII, CoII, and MnII. The acid dissociation constants of the ligands and the stability constants of their metal complexes including FeII complexes are reported. The structure of bis(1-ethoxycarbonyl-3-ferrocenyl-propane-1,3-dionato)copper(II) was determined by X-ray structure analysis. A cis arrangement with a nearly square planar coordination sphere at the Cu atom is found.  相似文献   
107.
One-pot synthesis of novel ferrocene grafted N-methyl-spiropyrrolidines has been accomplished in good yields through a facile 1,3-dipolar cycloaddition reaction of various azomethine ylide derived from ninhydrin and sarcosine with various ferrocene derivatives as dipolarophile. The regiochemical and stereochemical outcome of the cycloaddition reaction is ascertained by X-ray crystallographic studies of one of the cycloadducts.  相似文献   
108.
在Karstedt催化剂的催化作用下,通过把合成的笼型八聚(二甲基硅氧基)倍半硅氧烷与乙烯基二茂铁进行氧化硅烷化反应,合成了二茂铁取代的笼型八聚(二甲基硅氧基)倍半硅氧烷,产物经红外光谱、核磁共振氢谱与硅谱等进行了表征.  相似文献   
109.
P-mSA/mCS双极膜的制备及其在一价、二价离子分离中的应用   总被引:1,自引:1,他引:0  
以五氧化二磷、磷酸三乙酯和磷酸为反应剂, 制备了磷酸化海藻酸钠(P-SA), 经二茂铁离子改性后作为阳膜层(P-mSA); 用乙酰基二茂铁改性壳聚糖制备了阴膜溶胶(mCS). 将阴膜溶胶流延于阳膜层上, 制备了P-二茂铁-SA/乙酰基二茂铁-CS双极膜(P-mSA/mCS BPM). 测定了双极膜的红外光谱、接触角、电荷密度、离子交换容量与交流阻抗. IR与接触角的分析结果表明, SA经磷酸化后, 亲水性能得到了显著提高. 将P-mSA/mCS BPM应用于一价、二价离子的分离, 当压力差为0.3 MPa时, 二价离子的截留率(双极膜截留的离子百分数)为95%, 一价离子的截留率为22%左右.  相似文献   
110.
N-(3-ferrocenyl-2-naphthoyl) dipeptide esters (5-7) and N-(6-ferrocenyl-2-naphthoyl) dipeptide esters (8-10) were prepared by coupling either 3-ferrocenylnaphthalene-2-carboxylic acid 2 or 6-ferrocenylnaphthalene-2-carboxylic acid 4 to the dipeptide ethyl esters GlyAla(OEt) (5, 8), AlaGly(OEt) (6, 9), and AlaAla(OEt) (7, 10) using the standard N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), 1-hydroxybenzotriazole (HOBt) protocol. All the compounds were fully characterized using a combination of 1H NMR, 13C NMR, DEPT-135 and 1H-13C COSY (HMQC) spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and cyclic voltammetry (CV). In vitro, the cytotoxic effects of compounds 5-10 show improvements over the corresponding N-(ferrocenyl)benzoyl derivatives, with IC50 values against the H1299 lung cancer cells ranging from 1.2 μM to 8.0 μM. N-(6-ferrocenyl-2-naphthoyl)-glycine-l-alanine ethyl ester 8 was found to be the most active derivative of the naphthoyl series so far, displaying an IC50 value of 1.3 ± 0.1 μM. This value is slightly lower than that found for the clinically employed anti-cancer drug cisplatin (IC50 = 1.5 ± 0.1 μM against H1299).  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