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221.
The electronic structures of several highly electron-rich 2,7-dimethoxynaphthalene peri-dichalcogenides were evaluated using optical and electrochemical methods, as well as by DFT calculations. Charge transfer complexes were formed with tetracyanoquinodimethane and resulted in absorption features that span from 300 nm to 1600 nm and HOMO–LUMO energy gaps as low as 0.8 eV. 相似文献
222.
F. Camera A. Bracco V. Nanal M. P. Carpenter F. Della Vedova S. Leoni B. Million S. Mantovani M. Pignanelli O. Wieland B. B. Back A. M. Heinz R. V. F. Janssens D. Jenkins T. L. Khoo F. G. Kondev T. Lauritsen C. J. Lister B. McClintock S. Mitsuoka E. F. Moore D. Seweryniak R. H. Siemssen R. J. Van Swol D. Hofman M. Thoennessen K. Eisenman P. Heckman J. Seitz R. Varner M. Halbert I. Dioszegi A. Lopez-Martens 《Physics letters. [Part B]》2003,560(3-4):155-160
The spectra of high-energy γ rays emitted by the Giant Dipole Resonance (GDR) built on moderately excited states associated with the evaporation of 0, 1 and 2 nucleons were measured in the 90Zr + 89Y symmetric fusion reaction. The radiative fusion data suggest statistical emission from the compound nucleus. In addition, the analysis of the high-energy γ-ray spectra associated with the different evaporation channels at the present temperature of 0.7 MeV and spin range 15–20 show a fairly narrow width of 5.0±0.35 MeV. This value is smaller than what would be expected in a nucleus where shell effects do not play a role. 相似文献
223.
Synthesis and Structural Features of New Schiff Base Complexes of Mononuclear MnIV,Dinuclear CoIICoIII,and Tetranuclear CuII
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Davi F. Back Gelson Manzoni de Oliveira Cibele Mensch Canabarro Bernardo Almeida Iglesias 《无机化学与普通化学杂志》2015,641(5):941-947
2‐(((2‐Hydroxy‐3‐methoxyphenyl)methylene)amino)‐2(hydroxymethyl)‐1,3‐propanediol (LH4, as abbreviation) reacts with MnCl2 · 4H2O, CoCl2 · 6H2O, and Cu(ClO4)2 · 6H2O to give the new complexes [Mn(LH2)2] ( 1 ), [Co2Cl(H2O)(LH2)2] · 4H2O ( 2 ), and [Cu4(LH2)4(H2O)4] ( 3 ). Complex 1 is formed by the assembly of two molecules of the ligand with one manganese(IV) ion. In the mixed‐valence cobalt complex 2 there is an asymmetry between the coordination spheres of cobalt(II) and cobalt(III). In the tetramer 3 four copper(II) ions attain a distorted tetrahedral configuration surrounded by four molecules of the ligand. 相似文献
224.
Evaluation of the Antioxidant Activity of Copper(II) Complexes containing Tris‐(hydroxymethyl)aminomethane (TRIS) Units
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Cibele M. Canabarro Joice Ceolin Josiéli D. Siqueira Bernardo A. Iglesias Gelson Manzoni de Oliveira Davi F. Back Patrick T. Campos 《无机化学与普通化学杂志》2016,642(21):1192-1197
The structural analysis and the SOD‐like activity of CuII complexes [(Cu)(C16H18N3O5)]ClO4 ( 1 ) and [(Cu)4(C36H52N8O12)] ( 2 ) are described with ligands obtained from the condensation of picolinaldehyde and 2‐formylpyrrole with tris(hydroxymethyl)aminomethane (TRIS). Finally, complex 1 catalyzes the dismutation of superoxide efficiently with IC50 values in the range of 0.43 micromolar solution, evaluated through the inhibition of the photoreduction of nitro blue tetrazolium (NBT) (superoxide dismutase assay). 相似文献
225.
226.
The palladium-catalyzed heteroannulation of o-iodoanilines with dienyl sulfones provides a convenient route to vinylogous 2-sulfonylindolines 3. The reaction proceeds in DMF/water in the presence of potassium carbonate and catalytic palladium(II) acetate and is compatible with both electron-donating and -withdrawing substituents in the para position of the aniline, and with an alkyl substituent at C-2 of the dienyl sulfone. The indolines underwent oxidation with DDQ to afford the corresponding indoles 4. The latter were then employed as dienes in Diels-Alder reactions with dimethyl acetylenedicarboxylate (DMAD), methyl propiolate, or methyl acrylate. In the case of the latter two dienophiles, the cycloadditions were highly regioselective, affording the corresponding 1,3-products (with respect to the relative positions of the sulfone and ester groups), exclusively. The cycloadducts from acetylenic dienophiles were converted to the corresponding carbazoles by elimination of the sulfone moiety with DBU, and that from methyl acrylate was subjected to reductive desulfonylation and oxidation to the corresponding carbazole with DDQ. The method thus provides access to carbazoles with various substituents at the 3-, 4-, and 6-positions. 相似文献
227.
Stephan Back Martin Lutz Anthony L. Spek Heinrich Lang Gerard van Koten 《Journal of organometallic chemistry》2001,620(1-2)
A series of homodinuclear Pt compounds containing the anionic, potentially terdentate NCN ligand (NCN=[C6H3(Me2NCH2)2-2,6]−) or its 4-ethynyl derivative were prepared. The two platinum centres are linked together in two different fashions: (i) directly linked by an ethynyl or diethynylphenyl group (head-to-head) and (ii) indirectly bonded by a ethynyl- or butadiynyl-linked bis-NCN ligand (tail-to-tail). The reaction of the head-to-head σ,σ′-ethynylide complex {Pt}CC{Pt} ({Pt}=[Pt(C6H3{CH2NMe2}2-2,6)]+) with [CuCl]n yields {Pt}Cl and [Cu2C2]n, while with [Cu(NCMe)4][BF4] a Cu(I) bridged complex was formed: [(η2-{Pt}CC{Pt})2Cu][BF4]. The results of cyclic voltammetry experiments reveal that both connection modes of the two platinum centres lead to electrochemically independent Pt–NCN units. The X-ray crystal structure analysis of the neutral, tail-to-tail bridging butadiyne bis-NCNH ligand [C6H3(CH2NMe2)-1,3-(CC)-5]2 is reported. 相似文献
228.
J. Tōke R. Bock G.X. Dai A. Gobbi S. Gralla K.D. Hildenbrand J. Kuzminski W.F.J. Müller A. Olmi H. Stelzer B.B. Back S. Bjørnholm 《Nuclear Physics A》1985,440(2):327-365
The binary and ternary products from reactions of 238U beams with targets of 16O, 27Al, 48Ca, 45Sc, 48Ti, 58Fe, 64Ni and 89Y have been recorded at 6.0 MeV/u bombarding energy with four position-sensitive avalanche detectors, operated in coincidence. A few runs at 5.4 MeV/u have also been performed. Accurate triple-differential cross sections, , are obtained for the binary events within the full range of mass A and total kinetic energy TKE, and within almost the full range of center-of-mass angle θc.m.. Similar cross sections are obtained with somewhat less accuracy for triple events stemming from the sequential fission of uranium-like products. The distributions are discussed in terms of quasielastic and strongly damped scattering, where the products have partially relaxed energies and negligible average drift in mass, as opposed to capture where the products emerge with fully relaxed energies after a more or less pronounced mass drift towards symmetry. Apart from the reaction with 16O, all the capture product distributions are dominated by the non-equilibrium quasi-fission (or fast fission) process. The central feature of this reaction mechanism is the evolution of the reaction complex towards mass symmetry. With the 27Al target the evolution towards symmetry is almost complete, whereas the heavier targets show very broad mass distributions with clear evidence of dissociation taking place before symmetry is reached. At the same time, the cross section for quasi-fission diminishes as the target Z-value increases. With the 89Y target the strongly damped scattering component dominates completely. The capture cross sections are discussed in terms of the extra-push concept, and the mass and angular distributions in quasi-fission are analyzed in terms of interaction time and mass rearrangement as functions of target Z-value and excess kinetic energy in the entrance channel. 相似文献
229.
The thermal reactions of ethylene at 500°C in the presence and absence of small quantities of oxygen
Initial rates of formation of primary products have been measured in the pyrolysis of ethylene at 500°C, and a mechanism for the reaction is proposed based on the isomerization of the n?hexyl radical. Additions of oxygen in amounts less than 0.1% markedly increased the rate of formation of all products, but oxygen was not completely consumed in the reaction. It is shown that secondary initiation processes are important at very low conversions, and butene-1 is the most reactive product. Bimolecular reactions between olefins and with oxygen are important steps in the mechanism. 相似文献
230.
The rate of the thermal cycloaddition of ethylene to cis-and trans-butene-2 has been measured at 663, 678, 693, and 703°K, and the energy relations between the reactants, intermediates, and products have been determined. The intermediate biradicals formed from the cis reactants and from the trans reactants were shown to be separated by a small but measurable enthalpy difference. This result further supports the conclusion of Part I that the intermediates are distinct species which retain some of the original configuration of the reactant. The significance of the results in relation to the mechanism of “forbidden” reactions is discussed. 相似文献