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101.
Mimicking the Aromatic‐Ring‐Cleavage Activity of Gentisate‐1,2‐Dioxygenase by a Nonheme Iron Complex
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Rubina Rahaman Dr. Biswarup Chakraborty Prof. Tapan Kanti Paine 《Angewandte Chemie (International ed. in English)》2016,55(44):13838-13842
Gentisate‐1,2‐dioxygenase (GDO), a nonheme iron enzyme in the cupin superfamily, catalyzes the cleavage of the aromatic‐ring of 2,5‐dihydroxybenzoic acid (gentisic acid) to form maleylpyruvic acid in the microbial aerobic degradation of aromatic compounds. To develop a functional model of GDO, we have isolated a nonheme iron(II) complex, [(TpPh2)FeII(DHN‐H)] (TpPh2=hydrotris(3,5‐diphenylpyrazole‐1‐yl)borate, DHN‐H=1,4‐dihydroxy‐2‐naphthoate). In the reaction with O2, the biomimetic complex oxidatively cleaves the aromatic ring of the coordinated substrate with the incorporation of both the oxygen atoms from molecular oxygen into the cleavage product. The presence of para‐hydroxy group on the substrate plays a crucial role in directing the aromatic‐ring cleaving reaction. 相似文献
102.
John B. Paine III Yezdi B. Pithawalla John D. Naworal 《Journal of Analytical and Applied Pyrolysis》2008,82(1):10-41
The flash pyrolysis of d-glucose was investigated by the use of isotopic labeling with 13C, in conjunction with GC/MS. Co-pyrolysis of uniformly labeled and unlabeled d-glucose established the extent of unimolecular formation of each of the pyrolysis products. A complete set of singly labeled d-glucose isotopologs was used to determine the origin of specific carbons within each of the pyrolysis products. The Cyclic Grob 1,3-diol fragmentation and the tandem alkaline pinacol rearrangement/retro-aldol fragmentation (TAPRRAF) discovered from the pyrolysis of glycerin were applied to the analysis of pyrolytic fragmentation pathways for d-glucose. These mechanisms provide means of initial carbon–carbon bond breakage, and are consistent with the high proportion of carbon-unimolecularity observed for many of the volatile low-molecular weight products of the reaction. These and other reactions, including the retro-aldol fragmentation, carbonyl migration, dehydration, ene-reaction, retro-Claisen cleavage, hydrolysis, or alcoholysis were applied conceptually to the initial fragments resulting from either mechanism to ascertain the ultimate fate of the carbons of d-glucose. The “predicted” results were then compared with labeling patterns observed by experiment. The most promising rationalizations provided by this exercise are presented herein, for the formation of five C1 and C2 carbonyl-containing pyrolysis products: formaldehyde, formic acid, acetaldehyde, glycolaldehyde and acetic acid. 相似文献
103.
Mitrali Biswas Sanchaita Dey Abhishek Das Prof. Dr. Tapan Kanti Paine Dr. Sanjib Panda Prof. Dr. Goutam Kumar Lahiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202202088
The unexplored ‘actor’ behavior of redox-active bis(aldimine) congener, p-phenylene-bis(picoline)aldimine (L1), towards dioxygen activation and subsequent functionalization of its backbone was demonstrated on coordination with {Ru(acac)2} (acac= acetylacetonate). Reaction under aerobic condition led to the one-pot generation of dinuclear complexes with unperturbed L1, imino-carboxamido (L2−), and bis(carboxamido) (L32−)-bridged isovalent {RuII(μ-L1)RuII}, 1/ {RuIII(μ-L32−)RuIII}, 3 and mixed-valent {RuII(μ-L2−)RuIII}, 2 . Authentication of the complexes along with the redox non-innocence behavior of their bridge have been validated through structure, spectroelectrochemistry and DFT calculations. Kinetic and isotope labelling experiments together with DFT analyzed transition states justified the consideration of redox shuttling at metal/L1 interface for 3O2 activation despite of the closed shell configuration of 1 (S=0) to give carboxamido derived 2 / 3 . 相似文献
104.
Dr. Martin R. L. Paine Dr. Berwyck L. J. Poad Gert B. Eijkel Dr. David L. Marshall Prof. Stephen J. Blanksby Prof. Dr. Ron M. A. Heeren Dr. Shane R. Ellis 《Angewandte Chemie (International ed. in English)》2018,57(33):10530-10534
Mass spectrometry imaging (MSI) enables the spatial distributions of molecules possessing different mass‐to‐charge ratios to be mapped within complex environments revealing regional changes at the molecular level. Even at high mass resolving power, however, these images often reflect the summed distribution of multiple isomeric molecules, each potentially possessing a unique distribution coinciding with distinct biological function(s) and metabolic origin. Herein, this chemical ambiguity is addressed through an innovative combination of ozone‐induced dissociation reactions with MSI, enabling the differential imaging of isomeric lipid molecules directly from biological tissues. For the first time, we demonstrate both double bond‐ and sn‐positional isomeric lipids exhibit distinct spatial locations within tissue. This MSI approach enables researchers to unravel local lipid molecular complexity based on both exact elemental composition and isomeric structure directly from tissues. 相似文献
105.
R. E. Lothrop S. I. Gertler H. A. Schuette R. J. Pauly und H. S. Paine 《Fresenius' Journal of Analytical Chemistry》1935,102(1-2):56-58
Ohne Zusammenfassung 相似文献
106.
The coordination geometry and supramolecular structures of three copper(II) complexes of two α-hydroxycarboxylates and one α-methoxycarboxylate with nitrogen donor co-ligands are discussed. The complexes have been characterized by elemental analysis, ESI-MS, IR and electronic spectroscopy, thermogravimetric analysis and magnetic measurements. The X-ray structure analysis of all the complexes, namely [(BPCA)CuII(MA)] (1), [(BPCA)CuII(MPA)(H2O)] (2) and [(BPCA)CuII(BA)]n (3), where BPCA = bis(2-pyridylcarbonyl)amidate, MA = racemic mandelate, MPA = racemic α-methoxy phenylacetate and BA = benzilate anion, shows the copper(II) ion in a distorted square-pyramidal geometry. In 1 the mandelate anion is coordinated to the copper(II) center in a bidentate fashion while in 2 the α-methoxycarboxylate is monodentate. In both cases a one-dimensional supramolecular array is formed through hydrogen bonds: the mononuclear units are directly connected in 1 by the MA hydroxyl group, whereas in 2 is the coordinated water that operates as H donor towards the MPA carboxylate group and the BPCA carbonyl oxygens of nearby complexes. In 3 the benzilate anion, acting as bridging ligand between copper ions, gives rise to a one-dimensional coordination polymer. In the latter, intra- and inter-chain π?π stacking interactions between pyridines and one phenyl ring of benzilate anions are observed in the packing. 相似文献
107.
Iron(II) tris(2-pyridylthio)methanido (1) containing an Fe-C bond, obtained from the reaction of tris(2-pyridylthio)methane (HL(1)) and iron(II) triflate, reacts with protic acid to generate iron(II) bis(2-pyridylthio)carbene (1a). The carbene complex is converted to an iron(II) complex (2) of the 1-[bis(2-pyridylthio)methyl]pyridine-2-thione ligand (L(3)) upon treatment with a base. Complex 2 reversibly transforms to 1a in the presence of an acid. During the transformation of 1 to 2, a novel rearrangement of L(1) to L(3) takes place. The iron(II) complexes are reactive toward dioxygen to form the corresponding iron(III) complexes. 相似文献
108.
Partha Halder Sayantan Paria Dr. Tapan Kanti Paine 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(37):11778-11787
An iron(III)–catecholate complex [L1FeIII(DBC)] ( 2 ) and an iron(II)–o‐aminophenolate complex [L1FeII(HAP)] ( 3 ; where L1=tris(2‐pyridylthio)methanido anion, DBC=dianionic 3,5‐di‐tert‐butylcatecholate, and HAP=monoanionic 4,6‐di‐tert‐butyl‐2‐aminophenolate) have been synthesised from an iron(II)–acetonitrile complex [L1FeII(CH3CN)2](ClO4) ( 1 ). Complex 2 reacts with dioxygen to oxidatively cleave the aromatic C? C bond of DBC giving rise to selective extradiol cleavage products. Controlled chemical or electrochemical oxidation of 2 , on the other hand, forms an iron(III)–semiquinone radical complex [L1FeIII(SQ)](PF6) ( 2ox‐PF6 ; SQ=3,5‐di‐tert‐butylsemiquinonate). The iron(II)–o‐aminophenolate complex ( 3 ) reacts with dioxygen to afford an iron(III)–o‐iminosemiquinonato radical complex [L1FeIII(ISQ)](ClO4) ( 3ox‐ClO4 ; ISQ=4,6‐di‐tert‐butyl‐o‐iminobenzosemiquinonato radical) via an iron(III)–o‐amidophenolate intermediate species. Structural characterisations of 1 , 2 , 2ox and 3ox reveal the presence of a strong iron? carbon bonding interaction in all the complexes. The bond parameters of 2ox and 3ox clearly establish the radical nature of catecholate‐ and o‐aminophenolate‐derived ligand, respectively. The effect of iron? carbon bonding interaction on the dioxygen reactivity of biomimetic iron–catecholate and iron–o‐aminophenolate complexes is discussed. 相似文献
109.
110.
An iron(III)-catecholate complex [L(1) Fe(III) (DBC)] (2) and an iron(II)-o-aminophenolate complex [L(1) Fe(II) (HAP)] (3; where L(1) =tris(2-pyridylthio)methanido anion, DBC=dianionic 3,5-di-tert-butylcatecholate, and HAP=monoanionic 4,6-di-tert-butyl-2-aminophenolate) have been synthesised from an iron(II)-acetonitrile complex [L(1) Fe(II) (CH(3) CN)(2) ](ClO(4) ) (1). Complex 2 reacts with dioxygen to oxidatively cleave the aromatic C?C bond of DBC giving rise to selective extradiol cleavage products. Controlled chemical or electrochemical oxidation of 2, on the other hand, forms an iron(III)-semiquinone radical complex [L(1) Fe(III) (SQ)](PF(6) ) (2(ox) -PF(6) ; SQ=3,5-di-tert-butylsemiquinonate). The iron(II)-o-aminophenolate complex (3) reacts with dioxygen to afford an iron(III)-o-iminosemiquinonato radical complex [L(1) Fe(III) (ISQ)](ClO(4) ) (3(ox) -ClO(4) ; ISQ=4,6-di-tert-butyl-o-iminobenzosemiquinonato radical) via an iron(III)-o-amidophenolate intermediate species. Structural characterisations of 1, 2, 2(ox) and 3(ox) reveal the presence of a strong iron?carbon bonding interaction in all the complexes. The bond parameters of 2(ox) and 3(ox) clearly establish the radical nature of catecholate- and o-aminophenolate-derived ligand, respectively. The effect of iron?carbon bonding interaction on the dioxygen reactivity of biomimetic iron-catecholate and iron-o-aminophenolate complexes is discussed. 相似文献