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611.
The dissociation of apoferritin into subunits at pH 2 followed by its re-formation at pH 8.5 in the presence of hexacyanoferrate(III) gave rise to a solution containing hexacyanoferrate(III) trapped within the apoferritin and hexacyanoferrate(III) outside it. The addition of Fe(II) to the dialyzed solution resulted in the appearance of the characteristic Prussian blue color. The UV-vis spectrum of this solution showed a broad band centered at 710 nm, and the IR spectrum contained a broad-medium band at 2083 cm(-1). Both features are consistent with the charge-transfer band and the C[bond]N stretching mode in the Fe(II)[bond]CN[bond]Fe(III) fragment of PB. TEM images of the obtained Prussian blue solution showed discrete spherical electron dense iron particles with an average size of about 5 nm. This represents a new route for preparing metallic nanoparticles that offers control over the size and protection against aggregation. Moreover, the fact that the particles are obtained by reaction of hexacyanoferrate(III) and iron(II) building blocks opens up the possibility of obtaining not only homo- but also heterobimetallic nanoparticles. 相似文献
612.
Rodríguez A Malyshev VA Sierra G Martín-Delgado MA Rodríguez-Laguna J Domínguez-Adame F 《Physical review letters》2003,90(2):027404
The single-parameter scaling hypothesis predicts the absence of delocalized states for noninteracting quasiparticles in low-dimensional disordered systems. We show analytically, using a supersymmetric method combined with a renormalization group analysis, as well as numerically that extended states may occur in the one- and two-dimensional Anderson model with a nonrandom hopping falling off as some power of the distance between sites. The different size scaling of the bare level spacing and the renormalized magnitude of the disorder seen by the quasiparticles finally results in the delocalization of states at one of the band edges of the quasiparticle energy spectrum. 相似文献
613.
5,5-Diphenyl-4-imidazolidinethiones (5) are converted by AlCl3 into 2-amino-3-phenylbenzo[b]thiophene 8 and/or Schiff's bases 7 derived from the latter. 2,2-Diarylglycinethioamides furnish only type 8 products. On the basis of a crossing experiment, a mechanism is suggested for the above rearrangements. 相似文献
614.
The 1-substituted-3-aryltetrahydroisoquinolines I have been converted into the corresponding 3,4-dihydroor isoquinoline derivatives by treatment with several oxidizing agents: iodine in ethanol, palladium on carbon, DDQ and Fremy's salt. The oxidation reactions with iodine always resulted in the formation of the 3,4-dihydroisoquinolines II, whereas the use of palladium on carbon and the DDQ led to the aromatic isoquinolines. Both the 3,4-dihydro- and the isoquinoline derivatives were obtained by means of Fremy's salt. 相似文献
615.
V.H. Cortínez P.N. Domínguez 《Revista Internacional de Métodos Numéricos para Cálculo y Dise?o en Ingeniería》2013,29(1):1-11
In order to design or redesign urban transportation networks, the employment of mathematical models is very useful for predicting the effects of possible modifications of implementing. Such models allow the determination of vehicular flows and travel times for every link of the network from the knowledge of its inherent features and the corresponding traffic demand. They are based on a phenomenological law of the social collective behavior of the drivers called Wardrop principle. It is an optimization problem, in general, very demanding from the computational point of view.In order to accelerate the computation process, in this paper, a continuum model for the urban traffic is proposed. The fundamental assumption behind this theory is that the variation of network properties is small in close regions when compared with the full system. Accordingly, it is possible to use continuous functions for representing travel times or vehicular flows. Essentially, the problem is formulated as a system of non-linear anisotropic diffusion (differential) equations that can be conveniently solved by means of the finite element method. The efficiency of the proposed model is studied by means of a comparison with results obtained with the classical optimization approach. As shown, the results are similar although the computation times are significantly reduced. 相似文献
616.
We show that the three-junction SQUID device designed for the Josephson flux qubit can be used to study the dynamics of quantum chaos when operated at high energies. We determine the parameter region where the system is classically chaotic. We calculate numerically the fidelity or Loschmidt echo (LE) in the quantum dynamics under perturbations in the magnetic field and in the critical currents, and study different regimes of the LE. We discuss how the LE could be observed experimentally considering both the preparation of the initial state and the measurement procedure. 相似文献
617.
In situ recording of the voltammetric response of Aloe vera L. leaves using graphite and platinum microelectrodes inserted in the subcuticular region is described. The plant response against the mechanical stress results in changes of the voltammetric signals associated to signal transduction compounds salicylic and jasmonic acids and hydrogen peroxide, which were separately monitored. A kinetic model is proposed to describe the time variation of the respective voltammetric signatures, denoting the possibility of in vivo electrochemical monitoring of biochemical processes in plants. The obtained results suggest that two defense pathways with different participation of ROS are operative. 相似文献
618.
Kansiz M Domínguez-Vidal A McNaughton D Lendl B 《Analytical and bioanalytical chemistry》2007,388(5-6):1207-1213
FTIR spectroscopy has been used to monitor and determine the degree of crystallisation in a sample of polyhydroxybutyrate-co-14%valerate
(PHB–co-14%HV). Time series spectra of solution-cast films of the polymer revealed spectral changes attributed to the onset
of crystallisation. Curve fitting was used to obtain an absolute measure of crystallinity. Mean centred principal-component
analysis (PCA) revealed that 99.9% of the spectral variance could be attributed to factor 1. The loadings plot for factor
1 contained features attributable to crystalline and amorphous phases. These features were opposite in sign, indicating that
changes in the spectra with the onset of crystallisation are simultaneous and opposite in direction, i.e. as the crystalline
band increases the amorphous band decreases. Cross-peaks in asynchronous 2D correlation maps indicate there are likely to
be very minor components that are changing out of phase. The presence of these minor components is supported by examination
of the loadings of higher factors in the PCA model. PCA has been shown to be suitable for determining the number of dynamic
spectral features and has enabled relative and objective monitoring of crystallisation kinetics. 相似文献
619.
Carabias-Martínez R Rodríguez-Gonzalo E Domínguez-Alvarez J Miranda-Cruz E 《Analytica chimica acta》2007,584(2):410-418
We propose a procedure for estimating acid-base constants in organic solvents or mixture of solvents from the corresponding pKa values in aqueous medium and from certain properties of the organic solvents that characterize them. To accomplish this, we developed and validated a chemometric correlation for the calculation of the acid-base constants of different cationic acids in a broad variety of non-aqueous solvents. The parameters chosen for building the model were as follows: the acid-base constant of the compound in aqueous medium and those corresponding to the polarity-polarizability, basicity and acidity scales of the solvent. The results of the fitting were significant (p < 0.01), with a root mean error in cross-validation of 18%, with no overfitting. The prediction of the acid-base constants for an external set of compounds had a mean absolute prediction error value of less than 0.8 pKa units. 相似文献
620.
Acetone and diazotized anthranilic acid react in alkaline solution, giving a fluorescent intermediate that can be measured at excitation and emission wavelengths of 305 and 395 nm, respectively. Based on this, a fluorimetric flow-injection method is proposed for the determination of acetone in aqueous solution. Under the proposed conditions, acetone can be detected at concentrations higher than 8 × 10−7 M, with a linear application range from 1 × 10−6 to 2 × 10−4 M and an R.S.D. of 2.7% (1.0 × 10−5 M, n = 10). A sampling frequency of 24 h−1 is achieved. Some potentially interfering species are investigated. 相似文献