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11.
Riccardo d'Agostino Vincenzo Colaprico Francesco Cramarossa 《Plasma Chemistry and Plasma Processing》1981,1(4):365-375
The spectroscopic emission intensities from excited F atoms in SF6-O2 discharges at 1 torr have been correlated to the densities of atoms in their ground electronic state by measuring the excitation efficiencies of the electrons in the energy range 11 to 17 eV with a method which essentially consists in the analysis of the emission of Ar or N2, added as actinometer gases to the discharge mixtures. The general applicability of the method has been tested by a direct titration of F atoms with chlorine. The spectroscopic analysis has allowed the determination of useful information on the trends of both the electron densities and their energies as a function of the oxygen percent in the feed. 相似文献
12.
A. Labate N. R. Heckenberg R. Meucci M. Ciofini 《Applied physics. B, Lasers and optics》1993,56(5):307-311
Measurements of the pressure dependence of the relaxation rate of vibrationally excited molecules in the 119 m CH3OH laser have been correlated with the pressure and pump power dependence of the output power in the framework of a rate-equation model for which numerical and approximate analytical solutions have been obtained. Both diffusion and collisional de-excitation are important, and substantial deviations from thermal equilibrium populations are deduced, consistent with an operating pressure range which increases with pump power. 相似文献
13.
We compare two different theoretical models for a CO(2) laser, namely, the two- and four-level model, and show that the second one traces with much better accuracy the experimentally observed chaotic dynamics when the cavity losses are sinusoidally modulated. Even though the two-level model provides a qualitative explanation of the chaotic dynamics, only the four-level one assures a quantitative fitting. We also show that, at the onset of chaos, the chaotic dynamics is low dimensional and can be described in terms of a noninvertible one-dimensional map. 相似文献
14.
Pietro Favia Gerardo Caporiccio Riccardo D'Agostino 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):121-130
Thin films have been deposited from radio-frequency glow discharges fed with vapors of a silicon- and fluorine-containing organic compound, namely 2,4,6-tris[(3,3,3-trifluoropropyl) (methyl)] cyclotrisiloxane, in mixture with argon. 2,4,6-tris[(3,3,3-trifluoropropyl)(methyl)]cyclotrisiloxane A triode reactor has been utilized to deposit films by independently changing substrate temperature and bias-induced ion-bombardment. Laser interferometry, electron spectroscopy for chemical analysis and Fourier-transform infrared spectroscopy have been used to monitor film growth rate and composition. Results unambiguously show an activating effect of the ion-bombardment, which confirm the validity of the ion-assisted deposition model utilized for the plasma deposition of both teflon- and silicone-like films. In our experiments, low substrate temperature and bias conditions results in films with a “monomer-like” stoichiometry, while drastic conditions give origin to materials with a completely different composition and a markedly increased hardness. © 1994 John Wiley & Sons, Inc. 相似文献
15.
Luisa Citerio Donato Pocar Maria Luisa Saccarello Riccardo Stradi 《Tetrahedron》1979,35(20):2453-2461
The reaction between N-chloro-N'-aroyl-amidines and β,β-disubstituted enamines affords 1 - aroyl - 4 -amino - 4,5 - dihydro - imidazoles in low yields, the main reaction product being N - (2 - morpholino - 2,2 -disubstituted) - ethylidene - N' - aroyl - amidines. A similar reaction course was not observed with enamines bearing a hydrogen atom in the β-position. In this case only products derived from electrophilic chlorination on enamines were isolated. 相似文献
16.
A method is described whereby molecular symmetry is employed to reduce the number of two-electron integrals in perturbed Hartree–Fock calculations of second-order properties. The method is a generalization of the Dacre–Elder procedure. First- and second-rank perturbing tensor operators are examined in the coupled HF approach to electric dipole polarizabilities, magnetic susceptibilities, quadrupole polarizabilities, and spin-dopolar contributions to spin–spin coupling constants. The procedure sketched here permits a large saving of computer efforts, which is shown by some illustrative examples. 相似文献
17.
Cacciapaglia R Casnati A Mandolini L Reinhoudt DN Salvio R Sartori A Ungaro R 《The Journal of organic chemistry》2005,70(2):624-630
The calix[4]arene scaffold, blocked in the cone conformation by proper alkylation of the lower rim hydroxyls, was used as a convenient molecular platform for the design of bi- and trimetallic Zn2+ catalysts. The catalytic activity of the Zn2+ complexes of calix[4]arenes decorated at the 1,2-, 1,3-, and 1,2,3-positions of the upper rim with 2,6-bis[(dimethylamino)methyl]pyridine units were investigated in the cleavage of ester 6 and of the RNA model compound HPNP. High rate enhancements, up to 4 orders of magnitude, were observed in a number of catalyst-substrate combinations. Interestingly the order of catalytic efficiency among regioisomeric dinuclear complexes in the cleavage of ester 6 is 1,2-vicinal > 1,3-distal, but it is reversed in the reaction of HPNP. The higher efficiency of trinuclear compared to dinuclear complexes provides an indication of the cooperation of three Zn2+ ions in the catalytic mechanism. 相似文献
18.
The structure of compound C12H15N3, obtained by Perkin and Riley in 1923, through the reduction of cyclohexanone 2-nitrophenylhydrazone, was reexamined. This compound, considered originally as 3,4-cyclotetramethylene-4,5-dihydro-1,2,5-benzotriazepine (I) and later as 2-aminophenylazocyclohexene (II), is now defined through the nmr spectrum and chemical behaviour as cyclohexane-3-spiro-3,4-dihydro-1,2,4-benzotriazine (V). It is formed by spontaneous oxidation of the cyclic form of cyclohexanone 2-aminophenylhydrazone (namely, cyclohexane-3-spiro-1,2,3,4-tetrahydro-1,2,4-benzotriazine) obtained through amino group addition on the hydrazone double bond. 相似文献
19.
Castagnola M Zuppi C Rossetti DV Vincenzoni F Lupi A Vitali A Meucci E Messana I 《Electrophoresis》2002,23(12):1769-1778
The general properties of dendrimers and in particular their electrolytic characteristics that are relevant in electrokinetic separations, are described. In order to confirm theoretical considerations on commercial dendrimer charge and hydrodynamic radius, several capillary zone electrophoresis (CZE) experiments were performed. Electrophoretic mobilities measured at different pH values indicated a sensible increase of dendrimer hydrodynamic radius at pH values lower than 2.5. This was probably due to the Coulombic repulsion of charged amine groups of the inner dendrimer shells. The principal reasons that should address the use of dendrimers as pseudostationary phases in micellar electrokinetic chromatography (MEKC) are discussed. Moreover, a survey of different separations performed utilizing dendrimers in MEKC as well as of several future plausible uses of various classes of dendrimers is presented. 相似文献
20.
Pettinari C Pettinari R Fianchini M Marchetti F Skelton BW White AH 《Inorganic chemistry》2005,44(22):7933-7942
New [CpM(Q)Cl] complexes (M = Rh or Ir, Cp = pentamethylcyclopentadienyl, HQ = 1-phenyl-3-methyl-4R(C=O)-pyrazol-5-one in general, in detail HQ(Me), R = CH(3); HQ(Et), R = CH(2)CH(3); HQ(Piv), R = CH(2)-C(CH(3))(3); HQ(Bn), R = CH(2)-(C(6)H(5)); HQ(S), R = CH-(C(6)H(5))(2)) have been synthesized from the reaction of [CpMCl(2)](2) with the sodium salt, NaQ, of the appropriate HQ proligand. Crystal structure determinations for a representative selection of these [CpM(Q)Cl] compounds show a pseudo-octahedral metal environment with the Q ligand bonded in the O,O'-chelating form. In each case, two enantiomers (S(M)) and (R(M)) arise, differing only in the metal chirality. The reaction of [CpRh(Q(Bn))Cl] with MgCH(3)Br produces only halide exchange with the formation of [CpRh(Q(Bn))Br]. The [CpRh(Q)Cl] complexes react with PPh(3) in dichloromethane yielding the adducts CpRh(Q)Cl/PPh(3) (1:1) which exist in solution in two different isomeric forms. The interaction of [CpRh(Q(Me))Cl] with AgNO(3) in MeCN allows generation of [CpRh(Q(Me))(MeCN)]NO(3).3H(2)O, whereas the reaction of [CpRh(Q(Me))Cl] with AgClO(4) in the same solvent yields both [CpRh(Q(Me))(H(2)O)]ClO(4) and [CpRh(Cl)(H(2)O)(2)]ClO(4); the H(2)O molecules derive from the not-rigorously anhydrous solvents or silver salts. 相似文献