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241.
Potential dependences of the angle of contact between perfluorodecaline C10F18 and copper, copper(I) sulfide, and copper telluride Cu4Te3 in 0.1 M CH3COONa are measured. The data are in good agreement with the metal hardness measured in 1 M KOH. The uncharged-surface potentials (USP) for copper, copper(I) sulfide, and copper telluride equal 0.05–0.07, –0.02 to –0.04, and 0.05–0.07 V (NHE) in 0.1 M CH3COONa. Studying the effect of Br– ions shows that USP for copper and Cu2S shift in, respectively, the negative and positive directions with an increase in [Br–]. For copper telluride, USP shifts in the positive direction at low Br– concentrations, and at NaBr concentrations in excess of 0.04 M, in the negative direction. 相似文献
242.
Vashchenko V. V. Kutulya L. A. Pivnenko M. N. Shkolnikova N. I. 《Russian Chemical Bulletin》2003,52(11):2406-2418
(1R,4R)-2-(4-Hydroxybenzylidene)- and (1R,4R)-2-(4"-hydroxybiphenyl-4-yl)methylene-p-menthan-3-ones were synthesized by condensation of (–)-menthone with O-tetrahydropyran-2-yl derivatives of 4-hydroxybenzaldehyde and 4"-hydroxy-4-formylbiphenyl, respectively, in a DMSO—base medium followed by the removal of the protective group. The reactions of these hydroxy derivatives with 4-alkylbenzoic, 4-alkyloxybenzoic, trans-4-alkylcyclohexane-4-carboxylic, and 4"-alkylbiphenyl-4-carboxylic acids afforded three series of new chiral esters. Compounds containing the arylidene moiety with three benzene rings were found to exhibit liquid-crystalline properties. The characteristic features of these compounds are discussed based on the results of studies by polarizing microscopy, differential scanning calorimetry, and small-angle X-ray scattering. It was found that the mesomorphic compounds under study can form a smectic A mesophase, twist grain boundary mesophases (TGBA), and blue phases in a wide temperature range. Upon dissolution of certain of chiral compounds in 4"-cyano-4-pentylbiphenyl, a rather high twisting power and the thermal stabilizing effect on mesophases were observed. 相似文献
243.
Electrochemical impedance spectroscopy is used to characterize thin p-doped polypyrrole (PPy) films in propylene carbonate (PC) solutions and poly(trifluorophenyl)thiophene (PTFPT), in solutions based on sulfolane (SF). It appears that the latter film is much less swelled compared to the former one. One consequence of this difference is that the PTFPT film shows a much higher bulk resistance compared to that for the PPy film. Another important consequence is that the swelling of the PTFPT film is essentially physically non-homogeneous. Two parallel, uncoupled paths, with different chemical diffusion coefficients, model the experimental results adequately. In order to quantify the impedance spectra for both polymer films, we use a model proposed by Rubinstein et al. explaining the difference in the diffusion coefficients of Ru(bpy)3+/2+
3 within a thin Nafion film. The model can also predict the impedance spectra for composite powdery electrodes containing different particle sizes, such as composite cathodes and graphite anodes used in lithium batteries. 相似文献
244.
靛红掺杂聚吡咯膜修饰电极的电荷传输 总被引:5,自引:1,他引:5
利用交流阻抗法研究了靛红掺杂聚吡咯膜内的电荷传输,通过非线性最小二乘法拟合,得出了体系的等效电路,并计算出其电荷扩散系数和异相电子传递反应速率常数。实验结果表明,随着膜厚的增加,活性点增多,异相电子传递反应速率常数增大,同时表观扩散系数也增大。 相似文献
245.
Thermogalvanic cells(also known as thermo-electrochemical cells) that convert waste heat energy to electricity are a new type of energy conversion device. However, the electron transfer kinetics and mass transfer of redox couples have not been thoroughly studied. Here, the ion reaction and charge transport in thermogalvanic cells are investigated by electrochemical impedance analysis. We first propose the detailed impedance model followed experimental verification on three types of electrode materials. Parameters including kinetic rate constants and ion diffusion coefficients for the electrodes are obtained by fitting the impedance data. Our study shows explicitly that impedance analysis can provide useful information on selecting suitable electrode materials for thermogalvanic cells. 相似文献
246.
David W. Schwenke Steven L. Mielke Donald G. Truhlar 《Theoretical chemistry accounts》1991,79(3-4):241-269
Summary We have developed efficient and accurate techniques for the calculation of quantum mechanical reaction probabilities of atom-diatom exchange reactions in the gas phase, and we have optimized a computer code employing these techniques and applied it sucessfully to several systems. In this paper we consider further strategies for improving the algorithm to allow even more demanding applications. In this context, improvement means that equivalent results can be obtained using fewer computational resources (computer time or storage) or that an equivalent expenditure of resources can yield higher accuracy. The new strategies discussed here lead to improvement in both of these areas. Two areas of special focus in the present paper are (i) the finite difference boundary value method used for calculating distorted wave Green's functions and regular solutions for scattering by the distortion potential and (ii) the choice of the distortion potential itself. Among other results included here is the first application of the outgoing wave or scattered wave variational principle to reactive scattering. 相似文献
247.
The viscosity deviation (Δη), the excess molar volume (V
E) and the ultrasonic speed (u) have been investigated from viscosity (η) and density (ρ ) measurements of binary liquid mixtures of 1,2-dimethyoxyethane with methanol, ethanol, propan-1-ol, butan-1-ol,
pentan-1-ol, hexan-1-ol or octan-1-ol over the entire range of composition at 298.15 K. The excess volumes are negative over
the entire range of composition for all of the mixtures with the exception of hexan-1-ol and octan-1-ol. The excess isentropic
compressibilities (K
S
E) and viscosity deviations are negative for all of the mixtures. The magnitudes of the negative values of V
E decrease with the number of carbon atoms of the alkan-1-ol. The trend of increasing K
S
E values with the chain length of the alkanol is similar to that observed in the case of V
E. Graphs of V
E, Δ η, K
S
E, Δ u, L
f
E and Z
E against composition are presented as a basis for a qualitative discussion of the results. 相似文献
248.
Long chain alkanethiols self-assembled monolayers (SAMs) formed on Au microelectrodes showed higher sensitivity towards defects than the same monolayers on macroelectrodes. The analysis of cyclic voltammetry and electrochemical impedance spectroscopy (EIS) experiments performed on covered microelectrodes were consistent with the formation of pinholes of about 10 nm in diameter. Moreover, the EIS data exhibited a specific behavior that was interpreted invoking the short circuiting of the pinholes impedance by the surrounding surface of the microelectrode in the high frequency domain, whereas in the low frequencies, the surface covered by the SAM was assume to act as an insulator. 相似文献
249.
Electrochemistry and in situ electrochemical scanning tunneling microscopy (STM) were used to study the blocking and structural properties of Shiff base V-ape-V self-assembled monolayers (SAMs) on the surface of Au(111) in perchloric acid solution. The complex-plane impedance plots for the SAM covered Au(111) electrodes, with the redox couple of Fe(CN)64–/3– present in solution, exhibit arc shapes, revealing that the electrochemical kinetics were controlled by the electron-transfer step. For bare Au(111), the electrode process was mass transport limited. The molecules adsorb on Au(111) with a flat-lying orientation and form a long-range well-defined adlayer. A new structure of
was observed in the double-layer potential region. A structural model is proposed to interpret the molecular registry with Au(111) substrate. 相似文献
250.