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1.
Uptake of trace elements into fish otoliths is governed by several factors such as life histories and environment in addition to stock and species differences. In an attempt to elucidate the elemental signatures of rare earth elements (REEs) in otoliths, a solid phase extraction (SPE) protocol was used in combination with electrothermal vaporization (ETV) as a sample introduction procedure for the determinations by inductively coupled plasma quadrupole mass spectrometry (ICP-MS). Effects of various parameters, such as carrier gas flow rate, atomization temperature and chemical modification, were examined for optimization of the conditions by ETV-ICP-MS. Atomization was achieved at 2800 °C. Lower temperatures (i.e. 2600 °C) resulted in severe memory problems due to incomplete atomization. Palladium was used as a chemical modifier. It was found that an increase in Pd concentration up to 0.5 μg in the injection volume (70 μl) led up to four-fold enhancement in the integrated signals. This phenomenon is attributed to the carrier effect of Pd rather than the stabilization since no significant losses were observed for high temperature drying around 700 °C even in the absence of Pd. Preconcentration was performed on-line at pH 5 by using a mini-column of Toyopearl AF-Chelate 650M chelating resin, which also eliminated the calcium matrix of otolith solutions. After preconcentration of 6.4 ml of solution, the concentrate was collected in 0.65 ml of 0.5% (v/v) HNO3 in autosampler cups, and then analyzed by ETV-ICP-MS. The method was validated with the analysis of a fish otolith certified reference material (CRM) of emperor snapper, and then applied to samples. Results obtained from otoliths of fish captured in the same habitat indicated that otolith rare earth element concentrations are more dependent on environmental conditions of the habitat than on species differences. 相似文献
2.
Vaporizing solid samples of metals and semiconductors with a YAG Laser is a method well suited for producing molecules and
clusters of those materials. The clusters are examined by either laser-induced fluorescence (LIF) or mass spectroscopic methods.
The technique is valuable for both gas phase and matrix studies. The method is described and some applications, studying either
the structure of small metal molecules or their reactions, are reviewed, with emphasis on our recent results from the LIF
studies of LiBe, Al2 and the reaction of Al with oxygen, yielding A12O. For larger clusters, Ion Cyclotron Resonance is an extremely valuable method, as we demonstrate by its application to the
reactions of small charged silicon clusters with strong oxidising agents. 相似文献
3.
本文考察了以微波等离子体炬(MPT)为光源,电热钽丝环进样时,溶液中共存元素对发射信号的影响。 相似文献
4.
5.
The standard enthalpies of formation ΔfHo (liq. or cr.) at the temperature T = 298.15 K were measured using combustion calorimetry for benzophenone (A), 1-indanone (B), -tetralone (C), 9-fluorenone (D), anthrone (E) and dibenzosuberone (F). The standard enthalpies of vaporization ΔvHo or sublimation ΔsHo of A-F and 5,7-dihydro-6H-dibenzo[a,c]cyclohepten-6-one (G) were obtained from the temperature function of the vapor pressure measured in a flow system. Enthalpies of fusion ΔmH of solid compounds were measured by DSC. From the enthalpies of formation of the gaseous compounds of A-G the values of their strain enthalpies were derived and structural effects discussed.
6.
Reginald B. Little 《Journal of Cluster Science》2003,14(2):135-185
The discovery, synthesis, characterization, and applicability of carbon nanotubes have produced tremendous excitement and interest among scientists and engineers. In particular, the use of these unique tubular nanostructures for new strong lightweight materials, nanoelectronics, fuel storage and cells, electron emitters and bio, scanning probe microscopy, and chemical sensing devices has created an intense effort to advance the synthesis so as to mass produce carbon nanotubes with control over diameter and helicity. The massive and controlled synthesis of this heralded nanostructure has been a great challenge. Although significant progress has advanced the preparation, more synthetic development is required. The syntheses have so far involved three main approaches: arc discharge vaporization, laser vaporization, and catalytic chemical vapor deposition. The synthetic trend has progressed to a point where further advancement with these techniques will require a better understanding of the mechanism of nucleation and growth. The mechanics of carbon nanotube nucleation and growth involve very complex and diverse phenomena occurring under extreme conditions and on the mesoscopic scale. As yet the detail mechanism is unknown. Difficulties with experimental probing and computational simulation have increased the mystery of this mechanism. This review presents an account of research on the synthesis of carbon nanotubes and the mechanism of formation. This overview includes all three mentioned synthetic approaches and hybrids thereof. On the basis of this broad account a comprehensive mechanism for carbon nanotube nucleation and growth naturally arises. This mechanism is qualitative and it hopes to inspire more quantitative exploration and synthetic advancement. 相似文献
7.
A simple procedure for the determination of manganese in different sections of human brain samples by graphite furnace atomic absorption spectrometry has been developed. Brain sections included cerebellum, hypothalamus, frontal cortex, vermix and encephalic trunk. Two sample preparation procedures were evaluated, namely, slurry sampling and microwave-assisted acid digestion. Brain slurries (2% w/v) could be prepared in distilled, de-ionized water, with good stability for up to 30 min. Brain samples were also digested in a domestic microwave oven using 5 ml of concentrated HNO3. A mixed palladium+magnesium nitrate chemical modifier was used for thermal stabilization of the analyte in the electrothermal atomizer up to pyrolysis temperatures of 1300 °C, irrespective of the matrix. Quantitation of manganese was conducted in both cases by means of aqueous standards calibration. The detection limits were 0.3 and 0.4 ng ml−1 for the slurry and the digested samples, respectively. The accuracy of the procedure was checked by comparing the results obtained in the analysis of slurries and digested brain samples, and by analysis of the NIST Bovine Liver standard reference material (SRM 1577a). The ease of slurry preparation, together with the conventional set of analytical and instrumental conditions selected for the determination of manganese make such methodology suitable for routine clinical applications. 相似文献
8.
Determination of trace elements in biological materials using tetramethylammonium hydroxide for sample preparation 总被引:1,自引:0,他引:1
Patrícia Martins Dirce Pozebon Valderi L. Dressler Gisele A. Kemieciki 《Analytica chimica acta》2002,470(2):62-204
A method to prepare milk powder, bovine liver and bovine muscle samples for analysis by electrothermal atomic absorption spectrometry (ETAAS) is proposed. Samples are mixed with a small amount of tetramethylammonium hydroxide (TMAH) and a stable and homogeneous slurry is produced in ca. 2 h with heating at 60–70 °C. After such sample preparation and dilution with water, trace elements are determined in certified reference materials. Pyrolysis and atomisation temperatures are optimised for each element, and several modifiers are investigated. External calibration is used for every analyte. Limits of detection (LODs), precision and accuracy are reported for Cd, Pb, Ni, Cr, Cu and Ag and compared with those obtained after conventional acid digestion. The main advantages of the proposed method are the simplicity of sample preparation and the longer lifetime of the graphite tube. 相似文献
9.
T. Kimura Y. Takahashi T. Kamiyama M. Fujisawa 《Journal of Thermal Analysis and Calorimetry》2007,88(2):587-595
Excess enthalpies (H
E)
of 17 binary mixtures of o- and m-isomers of dichlorobenzene, difluorobenzene, methoxymethylbenzene,
dimethylbenzene, dimethoxybenzene, aminofluorobenzene, fluoronitrobenzene,
diethylbenzene, chlorofluorobenzene, fluoroiodobenzene, bromofluorobenzene,
chloromethylbenzene, fluoromethylbenzene, bromomethylbenzene, iodomethylbenzene,
fluoromethoxybenzene, dibromobenzene at 298.15 K were measured. All excess
enthalpies measured were very small, and those of o-+m-isomers of aminofluorobenzene, dibromobenzene and
iodomethylbenzene were negative but 14 other binary mixtures of isomers were
positive over the whole range of mole fractions. H
E
of o-+m-isomers
of dimethoxybenzene showed the largest enthalpic instability and those of
aminofluorobenzene showed the largest enthalpic stability. There was a correlation
between dipole–dipole interaction, dipole–induced dipole interaction
or entropies of vaporization and excess partial molar enthalpies at infinite
dilution. 相似文献
10.
In this work, the phenomenon of double retrograde vaporization (DRV) is simulated using the Peng–Robinson equation of state with the classical mixing rules and several combining rules for the cross-energy and cross-co-volume parameters. The binary interaction parameters are set equal to zero in all cases, i.e., the calculations are entirely predictive. An interesting conclusion is that the predictions using the classical combining rules (geometric mean rule for aij and arithmetic mean rule for bij) provide the best agreement with the experimental data for all the systems tested: methane + n-butane, methane + n-pentane, ethane + limonene, and ethane + linalool. Another interesting observation is that several combining rules for bij, other than the arithmetic mean rule, predict the existence of three phases in equilibrium in a very narrow temperature range close to the critical temperature of methane in the methane + n-pentane system, even though, literature data indicates that n-hexane is the first n-alkane to present partial liquid phase immiscibility with methane. 相似文献