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721.
The heats of dilution and heat capacities of the Li2B4O7-Li2SO4-LiCl-H2O quaternary system and the Li2B4O7-Li2SO4-H2O and
Li2B4O7-LiCl-H2O ternary systems were measured in the range of ionic strengths from 19 to 0.1 at 298.15 K. The data of the
heat of dilution were extrapolated to infinite dilution by use of Debye-Hückel limiting law to obtain relative apparent molal
enthalpies over the range of ionic strengths I from 19 to 0.0001.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
722.
Ernest E. Bernarducci Lester R. Morss Andrew R. Miksztal 《Journal of solution chemistry》1979,8(10):717-727
Heats of dilution of concentrated aqueous solutions (4.43 moles-kg–1) of FeCl2 were measured at 15, 25, and 35°C. The heat capacities of these concentrated solutions were also measured at the same temperatures. From these data the partial molal heat capacity, C
p2
0
(FeCl2, aq, 298.15°K)=–2.56±30 J–°K–1–mole–1, was calculated. The partial molal heat capacity of Fe2+(aq), –2±30 J-°K–1-mole–1, was correlated with the correspondence principle equations of Criss and Cobble. 相似文献
723.
724.
Densities and heat capacities at 25°C were measured for N-octyl-, N-decyl- and N-dodecyl-N-methylpiperidinium chlorides and for N-octyl- and N-dodecylpiperidine hydrochlorides in water as functions of concentration. Enthalpies of dilution at 25°C and osmotic coefficients at 37°C of the N-methyl-N-alkylpiperidinium chlorides were also measured as functions of concentration. The partial molar volumes, heat capacities, relative enthalpies, nonideal Gibbs energies and entropies at 25°C were derived as functions of the surfactant concentration. By increasing the alkyl chain length of the surfactant, both the apparent molar volume vs. concentration curves are shifted toward greater values while the corresponding ones for the heat capacity are moved toward more negative values. These results are consistent with the higher hydrophobicity the longer the alkyl chain of the surfactant is. In the micellar region, the entropy and enthalpy vs. log m/m
cmc
curves increase in a parallel manner by decreasing the alkyl chain length of the surfactant. Consequently, the negligible effect of the hydrophobicity of the surfactant on the Gibbs energy vs. log m/m
cmc
trends is due to the enthalpy-entropy compensative effect. The thermodynamic functions of micellization were graphically evaluated on the basis of the pseudo-phase transition model. The absolute values of both the volume and heat capacity of micellization increase with an increasing number of carbon atoms in the alkyl chain (n
c
). The enthalpy and entropy of micellization vs. n
c
are convex curves. Comparisons are also made between the present data and those of some alkylpyridinium chlorides reported elsewhere. 相似文献
725.
Paola A. Mello Juliana S.F. Pereira Marcia F. Mesko Juliano S. Barin Erico M.M. Flores 《Analytica chimica acta》2012
In this review sample preparation strategies used for crude oil digestion in last ten years are discussed focusing on further metals and non-metals determination. One of the main challenges of proposed methods has been to overcome the difficulty to bring crude oil samples into solution, which should be compatible with analytical techniques used for element determination. On this aspect, this review summarizes the sample preparation methods for metals and non metals determination in crude oil including those based on wet digestion, combustion, emulsification, extraction, sample dilution with organic solvents, among others. Conventional methods related to wet digestion with concentrated acids or combustion are also covered, with special emphasis to closed systems. Trends in sample digestion, such as microwave-assisted digestion using diluted acids combined with high-efficiency decomposition systems are discussed. On the other hand, strategies based on sample dilution in organic solvents and procedures recommended for speciation analysis are reported as well as the use of direct analysis in view of the recent importance for crude oil field. A compilation concerning sample preparation for crude oil provided by official methods as well as certified reference materials available for accuracy evaluation is also presented and discussed. 相似文献
726.
The apparent molar heat capacities, Cp,, of alkaline aqueous solutions of aluminum ion in excess NaOH have been measured at temperatures between 50 and 250°C in the overall molality range 0.3–1.7 mol-kg–1. Enthalpies of dilution, L, have also been determined at 99°C and apparent molar relative enthalpies, L, were calculated starting from 2.16 mol-kg–1 as the maximum concentration. Measurements of the above quantities have been performed by means of a differential flow calorimeter built in our laboratory and already described. The thermodynamic data obtained and the corresponding quantities for aqueous NaOH previously determined have been fitted to the equations of the Pitzer ionic interaction model to obtain parameters relative to aqueous NaAl(OH)4. These parameters permit the calculation of Cp,, and L for this species over the examined range of temperatures and concentrations. 相似文献
727.
728.
在电容耦合式PECVD系统中,以CH4和H2为气源,通过控制H2的流量制备了一系列氢化非晶碳膜(a-C:H)样品。利用傅里叶变换红外光谱(FTIR)、光致发光谱(PL)和吸收谱对a-C:H膜的结构及光学性质进行了研究。结果表明:氢稀释可以在一定程度上减少碳的sp^2团簇的形成,增大它的光学带隙,并改变薄的微结构。与此同时,光致发光峰随郑 光学带隙的增大而蓝移;当光学带隙增大2.72eV时,出现了2.4eV(绿光)和2.97eV(蓝光)组成的发光峰。 相似文献
729.
Guillaume Labarraque Caroline Oster Paola Fisicaro Christian Meyer Jochen Vogl Janine Noordmann 《International journal of environmental analytical chemistry》2015,95(9):777-789
The major source of the anthropogenic platinum group element (PGE) emission is attributed to the use of catalytic converters in automobiles. This paper describes the work performed by three National Metrology Institutes (Laboratoire national de métrologie et d’essais, by the Physikalisch-technische bundesanstalt, Bundesanatalt für materialforschung und prûfung), in the framework of the Joint Research Project ‘PartEmission’ under the European Metrology Research Program. An analytical procedure based on a cationic exchange protocol and the isotope dilution or standard addition using an Inductived Coupled Plasma Mass Spectrometer, ICP-MS, for the quantification of the elements Pt, Pd and Rh from automotive exhaust emissions is described. Results obtained on a road dust certified reference (BCR 723) material showed a good agreement with the certified values, at ng/g levels, and relative expanded uncertainties within the range of 7–10%. Analysis of filters impacted with automotive exhaust particle emissions (from a diesel engine) showed the amount of collected PGE at levels of 10–1000 pg/filter. Their quantifications followed the developed analytical protocol that had been carried out with relative expanded uncertainties in the range of a few per cent up to 20% per filter. Nevertheless, a lack of homogeneity between the filters was observed, making the comparison between the project partners difficult in the sake of the validation of their analytical procedures on real samples. 相似文献