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131.
Hureau C Eury H Guillot R Bijani C Sayen S Solari PL Guillon E Faller P Dorlet P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(36):10151-10160
The Gly‐His‐Lys (GHK) peptide and the Asp‐Ala‐His‐Lys (DAHK) sequences are naturally occurring high‐affinity copper(II) chelators found in the blood plasma and are hence of biological interest. A structural study of the copper complexes of these peptides was conducted in the solid state and in solution by determining their X‐ray structures, and by using a large range of spectroscopies, including EPR and HYSCORE (hyperfine sub‐level correlation), X‐ray absorption and 1H and 13C NMR spectroscopy. The results indicate that the structures of [CuII(DAHK)] in the solid state and in solution are similar and confirm the equatorial coordination sphere of NH2, two amidyl N and one imidazole N. Additionally, a water molecule is bound apically to CuII as revealed by the X‐ray structure. As reported previously in the literature, [CuII(GHK)], which exhibits a dimeric structure in the solid state, forms a monomeric complex in solution with three nitrogen ligands: NH2, amidyl and imidazole. The fourth equatorial site is occupied by a labile oxygen atom from a carboxylate ligand in the solid state. We probe that fourth position and study ternary complexes of [CuII(GHK)] with glycine or histidine. The CuII exchange reaction between different DAHK peptides is very slow, in contrast to [CuII(GHK)], in which the fast exchange was attributed to the presence of a [CuII(GHK)2] complex. The redox properties of [CuII(GHK)] and [CuII(DAHK)] were investigated by cyclic voltammetry and by measuring the ascorbate oxidation in the presence of molecular oxygen. The measurements indicate that both CuII complexes are inert under moderate redox potentials. In contrast to [CuII(DAHK)], [CuII(GHK)] could be reduced to CuI around ?0.62 V (versus AgCl/Ag) with subsequent release of the Cu ion. These complete analyses of structure and redox activity of those complexes gave new insights with biological impact and can serve as models for other more complicated CuII–peptide interactions. 相似文献
132.
Christelle Freund Author VitaeAuthor Vitae Fritz E. Kühn Author Vitae 《Journal of organometallic chemistry》2006,691(18):3718-3729
Monomeric cyclopentadiene molybdenum oxides were among the first synthesized high oxidation state organometallics. However, their syntheses and applications have long been overshadowed by their rhenium(VII) congeners, in particular by (pentamethylcyclopentadienyl)trioxorhenium(VII) and methyltrioxorhenium(VII). Only during the last decade a renaissance of the cyclopentadienyl molybdenum oxides is starting. Both with respect to synthetic access ways and to applications as oxidation catalysts in homogeneous and heterogeneous phase the interest in cyclopentadienyl molybdenum oxides and their tricarbonyl precursors is increasing. This results from the usually time-easy and straightforward synthetic procedures leading to these compounds and their easy heterogenizability, both on mesoporous materials and in ionic liquids. The catalytic performance, especially in olefin epoxidation with tert-butylhydroperoxide being the oxidant is very good and the derivatization to reach taylor made catalysts seems to be much easier than in the case of the organorhenium oxides. Another advantage in comparison to the latter complexes is the possible presence of two organic functionalities, which can be independently modified, e.g. for heterogenization of the complexes and for the enhancing of their catalytic activity at the same time. 相似文献
133.
Cage‐like Copper(II) Silsesquioxanes: Transmetalation Reactions and Structural,Quantum Chemical,and Catalytic Studies 下载免费PDF全文
Dr. Alexey N. Bilyachenko Dr. Marina S. Dronova Alexey I. Yalymov Dr. Frédéric Lamaty Dr. Xavier Bantreil Prof. Jean Martinez Christelle Bizet Lidia S. Shul'pina Prof. Alexander A. Korlyukov Dmitry E. Arkhipov Dr. Mikhail M. Levitsky Prof. Elena S. Shubina Dr. Alexander M. Kirillov Prof. Georgiy B. Shul'pin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(24):8758-8770
The transmetalation of bimetallic copper–sodium silsesquioxane cages, namely, [(PhSiO1.5)10(CuO)2(NaO0.5)2] (“Cooling Tower”; 1 ), [(PhSiO1.5)12(CuO)4(NaO0.5)4] (“Globule”; 2 ), and [(PhSiO1.5)6(CuO)4(NaO0.5)4(PhSiO1.5)6] (“Sandwich”; 3 ), resulted in the generation of three types of hexanuclear cylinder‐like copper silsesqui‐ oxanes, [(PhSiO1.5)12(CuO)6(C4H9OH)2(C2H5OH)6] ( 4 ), [(PhSiO1.5)12(CuO)6(C4H8O2)4(PhCN)2(MeOH)4] ( 5 ), and [(PhSiO1.5)12(CuO)6(NaCl)(C4H8O2)12(H2O)2] ( 6 ). The products show a prominent “solvating system–structure” dependency, as determined by X‐ray diffraction. Topological analysis of cages 1 – 6 was also performed. In addition, DFT theory was used to examine the structures of the Cooling Tower and Cylinder compounds, as well as the spin density distributions. Compounds 1 , 2 , and 5 were applied as catalysts for the direct oxidation of alcohols and amines into the corresponding amides. Compound 6 is an excellent catalyst in the oxidation reactions of benzene and alcohols. 相似文献
134.
135.
A bischloromanganese(II) complex [(LH)MnCl2] (1), where LH is the pentadentate ligand N,N-bis(2-pyridylmethyl)-N'-salicylidene- ethane-1,2-diamine, has been synthesized. Elemental analysis, UV-visible, and cyclic voltammetry experiments showed that the phenol function of the ligand LH remains protonated. Exhaustive electrolysis at 1.0 V vs SCE led to the formation of the Mn(III) derivative [(L)MnCl]+ (3) with the concomitant expulsion of H+ and Cl-. The formation of the Mn(III) species was confirmed by UV-visible spectroscopy and X-ray crystallography. Complex 1 could be regenerated by the reduction of complex 3 in the presence of H+ and Cl-. 相似文献
136.
Biotic and abiotic experimental identification of bacterial influence on calcium isotopic signatures
Cobert F Schmitt AD Calvaruso C Turpault MP Lemarchand D Collignon C Chabaux F Stille P 《Rapid communications in mass spectrometry : RCM》2011,25(19):2760-2768
In this study, we tested experimentally the influence of plant and bacterial activities on the calcium (Ca) isotope distribution between soil solutions and plant organs. Abiotic apatite weathering experiments were performed under two different pH conditions using mineral and organic acids. Biotic experiments were performed using either apatite or Ca-enriched biotite substrates in the presence of Scots pines, inoculated or not with the rhizosphere bacterial strain Bulkholderia glathei PML1(12), or the B. glathei PML1(12) alone. For each experiment, the percolate was collected every week and analyzed for Ca concentrations and Ca isotopic ratios. No Ca isotopic fractionation was observed for the different abiotic experimental settings. This indicates that no Ca isotopic fractionation occurs during apatite dissolution, whatever the nature of the acid (mineral or organic). The main result of the biotic experiments is the 0.22 ‰ (44)Ca enrichment recorded for a solution in contact with Scots pines grown on the bacteria-free apatite substrate. In contrast, the presence of bacteria did not cause Ca isotopic fractionation of the solution collected after 14 weeks of the experiments. These preliminary results suggest that bacteria influence the Ca isotopic signatures by dissolving Ca from apatite more efficiently. Therefore, Ca isotopes might be suitable for detecting bacteria-mediated processes in soils. 相似文献
137.
Moreau C Ashamu GA Bailey VC Galione A Guse AH Potter BV 《Organic & biomolecular chemistry》2011,9(1):278-290
Novel 8-substituted base and sugar-modified analogues of the Ca(2+) mobilizing second messenger cyclic adenosine 5'-diphosphate ribose (cADPR) were synthesized using a chemoenzymatic approach and evaluated for activity in sea urchin egg homogenate (SUH) and in Jurkat T-lymphocytes; conformational analysis investigated by (1)H NMR spectroscopy revealed that a C2'endo/syn conformation of the "southern" ribose is crucial for agonist or antagonist activity at the SUH-, but not at the T cell-cADPR receptor. 相似文献
138.
Xiaofei Xue Khalil Hanna Christelle Despas Feng Wu Nansheng Deng 《Journal of molecular catalysis. A, Chemical》2009,311(1-2):29-35
The complex [Rh(CO)2Cl]2 reacts with two molar equivalent of pyridine carboxylic acids ligands Py-2-COOH(a), Py-3-COOH(b) and Py-4-COOH(c) to yield rhodium(I) dicarbonyl chelate complex [Rh(CO)2(L/)](1a) {L/ = η2-(N,O) coordinated Py-2-COO−(a/)} and non-chelate complexes [Rh(CO)2ClL//](1b,c) {L// = η1-(N) coordinated Py-3-COOH(b), Py-4-COOH(c)}. The complexes 1 undergo oxidative addition (OA) reactions with different electrophiles such as CH3I, C2H5I, C6H5CH2Cl and I2 to give penta coordinated Rh(III) complexes of the types [Rh(CO)(CORn)XL/], {n = 1,2,3; R1 = CH3(2a); R2 = C2H5(3a); X = I and R3 = CH2C6H5 (4a); X = Cl}, [Rh(CO)I2L/](5a), [Rh(CO)(CORn)ClXL//] {R1 = CH3(6b,c); R2 = C2H5(7b,c); X = I and R3 = CH2C6H5 (8b,c); X = Cl} and [Rh(CO)ClI2L//](9b,c). The complexes have been characterized by elemental analysis, IR and 1H NMR spectroscopy. Kinetic data for the reaction of 1a–b with CH3I indicate a first order reaction. The catalytic activity of 1a–c for the carbonylation of methanol to acetic acid and its ester is evaluated and a higher turn over number (TON = 810–1094) is obtained compared with that of the well-known commercial species [Rh(CO)2I2]− (TON = 653) at mild reaction conditions (temperature 130 ± 5 °C, pressure 35 ± 5 bar). 相似文献
139.
Olivier Alvêque Pierre-Yves Blanchard Tony Breton Marylne Dias Christelle Gautier Eric Levillain Fawzia Seladji 《Electrochemistry communications》2009,11(9):1776-1780
Mixed SAMs of nitroxyl radical derivative and alkanethiol have been studied by cyclic voltammetry in both aqueous and non-aqueous solvents. Cyclic voltammograms exhibit shapes as a function of surface coverage deviating from an “ideal system”. Confronted to Laviron’s interaction model, the agreement observed between theory and experiments provides evidence of a random distribution of electroactive centers on surface and indicates that the local ionic environment of charged redox centers plays a major role in the electrochemical behaviour of SAMs. 相似文献
140.
Grégory Nocton Aline Nonat Christelle Gateau Marinella Mazzanti 《Helvetica chimica acta》2009,92(11):2257-2273
A series of europium(III) and terbium(III) complexes of three 1,4,7‐triazacyclononane‐based pyridine containing ligands were synthesized. The three ligands differ from each other in the substitution of the pyridine pendant arm, namely they have a carboxylic acid, an ethylamide, or an ethyl ester substituent, i.e., these ligands are 6,6′,6″‐[1,4,7‐triazacyclononane‐1,4,7‐triyltris(methylene)]tris[pyridine‐2‐carboxylic acid] (H3tpatcn), ‐tris[pyridine‐2‐carboxamide] (tpatcnam), and ‐tris[pyridine‐2‐carboxylic acid] triethyl ester (tpatcnes) respectively. The quantum yields of both the europium(III) and terbium(III) emission, upon ligand excitation, were highly dependent upon ligand substitution, with a ca. 50‐fold decrease for the carboxamide derivative in comparison to the picolinic acid (=pyridine‐2‐carboxylic acid) based ligand. Detailed analysis of the radiative rate constants and the energy of the triplet states for the three ligand systems revealed a less efficient energy transfer for the carboxamide‐based systems. The stability of the three ligand systems in H2O was investigated. Although hydrolysis of the ethyl ester occurred in H2O for the [Ln(tpatcnes)](OTf)3 complexes, the tripositive [Ln(tpatcnam)](OTf)3 complexes and the neutral [Ln(tpatcn)] complexes showed high stability in H2O which makes them suitable for application in biological media. The [Tb(tpatcn)] complex formed easily in H2O and was thermodynamically stable at physiological pH (pTb 14.9), whereas the [Ln(tpatcnam)](OTf)3 complexes showed a very high kinetic stability in H2O, and once prepared in organic solvents, remained undissociated in H2O. 相似文献