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751.
Rahim Hekmatshoar Ghodsieh Nanva Kenary Sodeh Sadjadi Yahya S. Beheshtiha 《合成通讯》2013,43(13):2007-2013
An efficient method for the synthesis of 4-amino-5-pyrimidinecarbonitriles by three-component reaction of malononitrile, aldehydes, and N-unsubstituted amidines, under aqueous conditions, using ZnO nanoparticles as catalyst is reported. The catalyst exhibited remarkable activity and is recyclable. 相似文献
752.
Yiu-chung YipAuthor Vitae Siu-kay WongAuthor Vitae 《Trends in analytical chemistry : TRAC》2011,30(4):628-640
This review evaluates commonly used methodologies for assessing the chemical purity of organic reference materials. Direct assay of the principal component can be established by methodologies such as gas chromatography, liquid chromatography (LC), quantitative nuclear magnetic resonance (NMR), elemental analysis and titrimetry. Measurements of detectable impurity components mainly include determination of water or moisture content, and analysis of residual solvents, and organic and inorganic impurities. To complete assessment of chemical purity, it is necessary to determine the enantiomeric purity of chiral organic reference materials. Promising methodologies for analysis include LC with chiral stationary phases, capillary electrophoresis using chiral selectors, and NMR with chemical-shift reagents. 相似文献
753.
754.
Roberto Luiz Andrade HaidukeAuthor Vitae Ubirajara Pereira Rodrigues-FilhoAuthor Vitae 《Polyhedron》2011,30(8):1396-1403
We employed the Density Functional Theory along with small basis sets, B3LYP/LANL2DZ, for the study of FeTIM complexes with different pairs of axial ligands (CO, H2O, NH3, imidazole and CH3CN). These calculations did not result in relevant changes of molecular quantities as bond lengths, vibrational frequencies and electronic populations supporting any significant back-donation to the carbonyl or acetonitrile axial ligands. Moreover, a back-donation mechanism to the macrocycle cannot be used to explain the observed changes in molecular properties along these complexes with CO or CH3CN. This work also indicates that complexes with CO show smaller binding energies and are less stable than complexes with CH3CN. Further, the electronic band with the largest intensity in the visible region (or close to this region) is associated to the transition from an occupied 3d orbital on iron to an empty π∗ orbital located at the macrocycle. The energy of this Metal-to-Ligand Charge Transfer (MLCT) transition shows a linear relation to the total charge of the macrocycle in these complexes as given by Mulliken or Natural Population Analysis (NPA) formalisms. Finally, the macrocycle total charge seems to be influenced by the field induced by the axial ligands. 相似文献
755.
Seyed Javad Ahmadi Sodeh Sadjadi Morteza Hosseinpour 《Monatshefte für Chemie / Chemical Monthly》2011,44(24):1163-1168
Abstract
An efficient method for the synthesis of 4-amino-5-pyrimidinecarbonitriles by the three-component reaction of malononitrile, aldehydes, and N-unsubstituted amidines under aqueous conditions using CuO microspheres as catalyst is reported. The catalyst exhibited remarkable reusable activity. 相似文献756.
Jhillu S. Yadav Author Vitae Aneesh Antony Author VitaeAuthor Vitae Basi V. Subba Reddy Author Vitae 《Journal of organometallic chemistry》2011,696(1):16-36
The electrophilic activation(C-H activation) of alkenes by transition metal catalysts is a fundamental step in a rapidly growing number of catalytic processes since it would provide simple, clean, and economic methods for making controlled and selectively functionalized organic moieties directly from simple olefins. Also catalytic activation of C-H bonds leading to useful organic reactions such as new C-C, C-N and C-O bond formation is of considerable interest for the chemical and pharmaceutical industries and remained a long-term challenge to chemists. A substantial progress has made in the last decade in this area. Contrary to traditional belief, it is nowadays possible to control the regiochemistry of various additions of nucleophiles to alkenes by the choice of transition metal catalysts. Atom economy, an inevitable factor of current research also can be accomplished in these reactions. Developments in this area of selective hydrofunctionalisation of alkenes by taking into consideration of the mechanistic aspects and the role of organometallic catalyst or active species formed during the reaction on the outcome of the reactions are reviewed. 相似文献
757.
Zi-Ling Xue Author Vitae Laurel A. Morton Author Vitae 《Journal of organometallic chemistry》2011,696(25):3924-3934
Studies from authors’ group (at the University of Tennessee) on alkylidene complexes and α-H migration in alkyl alkylidyne complexes, leading to unusual tautomerization equilibria between bis-alkylidenes and alkyl alkylidynes, are reviewed. Preparation of silyl alkylidene complexes (Me3ECH2)2Ta(CHEMe3)(SiR3) [R3 = (SiMe3)3, E = C, 3a, Si, 3b; R3 = ButPh2, E = C, 4a, Si, 4b] and the pathway in the formation of 3b are discussed first. Pathways in the formation of archetypical Schrock-type alkyl alkylidenes (Me3ECH2)3TaCHEMe3 (E = C, 5a; Si, 5b), including the work using Ta(CD2CMe3)5 (21-d10) to confirm that it is the precursor to (Me3CCD2)3TaCDCMe3 (5a-d7), are then considered. Tautomerization of silyl alkylidyne (Me3CCH2)2W(CCMe3)(SiButPh2) (6a) with bis-alkylidene (Me3CCH2)W(CHCMe3)2(SiButPh2) (6b) as well as (Me3SiCH2)3W(CSiMe3)(PR3) [R3 = Me3, 7a; Me2Ph, 8a; Me2(CH2)2PMe2 (DMPE-P), 9a] with (Me3SiCH2)2W(CHSiMe3)2(PR3) (R3 = Me3, 7b; Me2Ph, 8b; DMPE-P, 9b) [P refers to a dangling P atom in Me2P(CH2)2PMe2] is covered next. Finally the conversion of the tungsten phosphine tautomerization mixtures to alkyl alkylidene alkylidyne (Me3SiCH2)W(CHSiMe3)(CSiMe3)(PR3)2 [(PR3)2 = (PMe3)2, 10; (PMe2Ph)2, 11; DMPE, 12], including its pathway, is presented. 相似文献
758.
Annette E. Buba Author VitaeAuthor Vitae Lukas J. Gooßen Author Vitae 《Journal of organometallic chemistry》2011,696(1):170-7449
A catalyst system formed in situ from bis(2-methallyl)cycloocta-1,5-diene-ruthenium(II) [(cod)Ru(met)2], 1,4-bis(dicyclohexylphosphino)butane (dcypb) and ytterbium(III) triflate hydrate (Yb(OTf)3) was found to catalyze the addition of nitrogen nucleophiles to terminal alkynes under mild conditions to stereoselectively form the Z-enamide or Z-enimide products. Various secondary amides and imides could be added across the triple bond of a range of aliphatic and aromatic alkynes. The new bimetallic catalyst system sets new standards with regard to scope and selectivity for the synthesis of Z-configured anti-Markovnikov enamides. 相似文献
759.
Ruiren Tang Author Vitae Chunhua Tang Author VitaeAuthor Vitae 《Journal of organometallic chemistry》2011,696(10):2040-306
A novel polyamino polycarboxylic pyridine derivative ligand, N,N,N1,N1-(2,6-bis((3-(aminoethyl)-5-methyl-1H-pyrazol-1-yl)methyl)pyridine)hexakis(acetic acid) (L), was designed and synthesized with the motive that it is able to sensitize the emission of lanthanides. Its corresponding Eu(III) and Tb(III) complexes Na4EuLCl3·3H2O and Na4TbLCl3·5H2O were successfully prepared. The ligand and the complexes were characterized by elemental analysis, IR, MS, NMR and TG-DTA. The luminescence properties of the compounds in solid state were investigated; each complex had very narrow emission bands and strong luminescence intensity up to about 10,000. The TG-DTA studies showed that the initial decomposition temperature of both complexes was over 250 °C, elucidating the complexes had a high thermal stability. Meanwhile, the comparison with similar complexes suggested that the ligand with more coordination sites possessed more efficient antenna effect. To explore the potential medicinal value of L, the binding interaction of L and bovine serum albumin (BSA) was carried out by fluorescence spectrum. The studies indicated that the reaction between L and BSA was a static quenching procedure. The binding site number n and binding constant Ka were calculated according to the double logarithm regression equation. The thermodynamic parameters showed the Van der Waals and hydrogen bond interactions were the mainly impulse to the reaction. 相似文献