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161.
Anastasia M. Alekseeva Ilya V. Tertov Andrey V. Mironov Ivan V. Mikheev Oleg A. Drozhzhin Emiliya V. Zharikova Marina G. Rozova Evgeny V. Antipov 《无机化学与普通化学杂志》2020,646(14):1260-1266
New sodium vanadium(III) hydrogenphosphate hydrate NaV(HPO4)2(H2O)0.5 and sodium vanadium(III) hydrogenphosphate β-NaV(HPO4)2 were prepared in mild hydrothermal conditions. The crystal structures of NaV(HPO4)2(H2O)0.5 [space group Cc, Z = 4, a = 8.46174(19) Å, b = 9.52583(19) Å, c = 8.69376(15) Å, β = 110.9553(11) °, V = 654.41(2) Å3] and β-NaV(HPO4)2 [space group C2/c, Z = 4, a = 7.8681(3) Å, b = 9.8451(3) Å, c = 8.5180(2) Å, β = 107.626(2) °, V = 628.85(3) Å3] were solved and refined from X-ray powder diffraction data. Both compounds were used as precursors in a new route for the preparation of attractive cathode material β-NaVP2O7. The formation of the structure motive providing fast sodium ion diffusion at the first synthesis stage and its further conservation upon stepwise dehydration was revealed. The oversized Na+-embedding channels are stabilized by site-coordinated water in NaV(HPO4)2(H2O)0.5 structure. The topology resemblance and difference in known sodium vanadium(III) complex phosphates are discussed. 相似文献
162.
Karioti A Furlan C Vincieri FF Bilia AR 《Analytical and bioanalytical chemistry》2011,399(4):1715-1723
In the present study, a method based on liquid chromatography with diode array detection (HPLC-DAD) coupled to an electrospray ionisation (ESI) interface was developed for the determination of the constituents in the aqueous preparations of Viola odorata L. flowering tops. The developed assay was fast, simple and effective and permitted the quality control of the preparations. The aim of this work was to assess the qualitative and quantitative profile of the investigated preparations, which find until today wide applications in food and cosmetic industry, and to propose a validated method for their quality control. Characteristic constituents of V. odorata flowers are considered to be the anthocyanins; however, a detailed literature research showed that data concerning their chemical content are scarce. HPLC-DAD-ESI-MS analyses supported by extensive preparative chromatographic investigations and 2D NMR analyses revealed the predominance of complex flavonol glycosides and permitted the complete characterisation of the content of V. odorata preparations. This is the first report of detailed analysis of the chemical composition of V. odorata flowers. 相似文献
163.
Elke Pahl Detlev Figgen Anastasia Borschevsky Kirk A. Peterson Peter Schwerdtfeger 《Theoretical chemistry accounts》2011,129(3-5):651-656
Potential energy curves of the electronic ground states of the group 12 dimers Zn2 and Cd2 were computed at the CCSD(T) level of theory, including full triple corrections $\Updelta$ T in the coupled-cluster procedure, and spin-orbit (SO) contributions from four-component coupled-cluster calculations, extrapolated to the complete basis set (CBS) limit. For Hg2, the potential energy curve published recently (Pahl et al. in J Chem Phys 132:114301, 2010] is complemented in this work by non-relativistic calculations to quantify and discuss relativistic effects. We obtain very accurate fits of our CBS/CCSD(T) and CBS/CCSD(T)+ $\Updelta$ T data points to an analytically simple and computationally efficient extended Lennard Jones form. For the CBS/CCSD(T)+ $\Updelta$ T+SO curves, we obtain dissociation energies of D e?=?226?cm?1 and D e?=?319?cm?1 for Zn2 and Cd2 respectively, in very good agreement with recent theoretical calculations and experimental data. We also present equilibrium distances and rotational and vibrational spectroscopic constants to compare with available theoretical and experimental data. The results obtained for non-relativistically treated Hg2 continue nicely the trends with increasing atom number preset by Zn2 and Cd2, confirming that indeed, relativistic effects account for the known peculiarities for the mercury dimer. 相似文献
164.
Kharlamova A DeMuth JC McLuckey SA 《Journal of the American Society for Mass Spectrometry》2012,23(1):88-101
The exposure of electrospray droplets generated from either highly acidic or highly basic solutions to basic or acidic vapors,
respectively, admitted into the counter-current drying gas, has been shown to lead to significant changes in the observed
charge state distributions of proteins. In both cases, distributions of charge states changed from relatively high charge
states, indicative of largely denatured proteins, to lower charge state distributions that are more consistent with native
protein conformations. Ubiquitin, cytochrome c, myoglobin, and carbonic anhydrase were used as model systems. In some cases, bimodal distributions were observed that are
not noted under any solution pH conditions. The extent to which changes in charge state distributions occur depends upon the
initial solution pH and the pKa or pKb of the acidic or basic reagent, respectively. The evolution of charged droplets in the sampling region of the mass spectrometer
inlet aperture, where the vapor exposure takes place, occurs within roughly 1 ms. The observed changes in the spectra, therefore,
are a function of the magnitude of the pH change as well as the rates at which the proteins can respond to this change. The
exposure of electrospray droplets in this fashion may provide means for accessing transient folding states for further characterization
by mass spectrometry. 相似文献
165.
Rota P Allevi P Agnolin IS Mattina R Papini N Anastasia M 《Organic & biomolecular chemistry》2012,10(14):2885-2894
A simple protocol for the synthesis of N-perfluoroacylated and N-acylated glycals of neuraminic acid, with a secondary cyclic amine (morpholine or piperidine) at the 4α position, has been set-up, starting from peracetylated N-acetylneuraminic acid methyl ester that undergoes, sequentially to its direct N-transacylation followed by a C-4 amination, a β-elimination, and a selective hydrolysis of the ester functions, without affecting the sensitive perfluorinated amide. 相似文献
166.
A general approach to 6-phenylthio-substituted 2,3,4,5-tetrahydro-1H-1,3-diazepin-2-ones based on the ring expansion reaction of 1,2,3,4-tetrahydropyrimidin-2-ones under the action of nucleophiles has been developed. The first step of the synthesis was preparation of N-[(2-benzoyloxy-1-tosyl)ethyl]urea by three-component condensation of 2-benzoyloxyethanal, urea and p-toluenesulfinic acid. Nucleophilic substitution of the tosyl group in the obtained sulfone with sodium enolates of α-phenylthioketones followed by cyclization-dehydration, and debenzoylation gave 4-hydroxymethyl-5-phenylthio-1,2,3,4-tetrahydropyrimidin-2-ones which were transformed into the 4-mesyloxymethyl-derivatives. Treatment of the latter with nucleophilic reagents, such as NaCN, sodium diethyl malonate, PhSNa, MeONa, NaBH(4), sodium succinimide, or potassium phthalimide, afforded the target multi-functionalized diazepinones. The obtained 6-phenylthio-diazepinones and their 6-tosyl-substituted analogues were converted into 3-substituted 1-carbamoyl-1H-pyrroles under acidic conditions as a result of ring contraction. Effective one-pot synthesis of the latter from 4-mesyloxymethyl-pyrimidines was realized using a ring expansion/ring contraction sequence. 相似文献
167.
This critical review discusses the applicability of vibrational spectroscopic techniques, specifically Raman and mid-infrared, to the study of molecule-based electronics through a series of examples. We focus on a number of devices currently of interest, such as solar cells, organic light emitting diodes, molecular junctions, switches and transistors. Infrared and Raman spectroscopic techniques and their variations, the main focus of this article, can be used to investigate properties such as crystallinity, multiphasic distributions in three dimensions, as well as lifetimes, structures and energetics of excited-states on ultrashort to very long timescales (210 references). 相似文献
168.
The stability of gaseous vanadium molybdate and vanadium tungstates was confirmed by high-temperature mass spectrometry. A number of gas-phase reactions involving vanadium-containing salts were studied. On the basis of equilibrium constants, the standard formation enthalpies of gaseous VMoO(4) (-676 ± 27 kJ/mol), VWO(3) (-331 ± 29 kJ/mol), and VWO(4) (-706 ± 23 kJ/mol) at 298 K were determined. A theoretical study of these salts revealed the structure with bidentate binding of the vanadium cation to the anion part to be the lowest-lying isomer, with a quartet spin state for VMoO(4) and VWO(4) molecules as well as a sextet spin state for the VWO(3) molecule. On the basis of critical analysis of the literature data concerning standard formation enthalpies of gaseous VO and VO(2), we adopted new values of Δ(f)H°(298) = 135 ± 10 kJ/mol for VO(g) and -185 ± 15.0 kJ/mol for VO(2)(g). Overall, the results obtained allowed us to estimate the standard formation enthalpy of VMoO(3) to be -318 kJ/mol with an accuracy near 40 kJ/mol. 相似文献
169.
The field theory renormalization group is used for analyzing the fractional Langevin equation with the order of the temporal derivative 0<α<1, fractional Laplacian of the order σ, and Gaussian noise correlator. The case of non-linearity φm with odd m≥3 is considered. It is proved that the model is multiplicatively renormalizable. Propagators were found in the momentum and coordinate representation, expressed in terms of Fox’s H functions. 相似文献
170.
Using a method of stochastic perturbation of a Langevin system associated with the non-viscous Burgers equation we introduce a system of PDE that can be considered as a regularization of the pressureless gas dynamics describing sticky particles. By means of this regularization we describe how starting from smooth data a δ-singularity arises in the component of density. Namely, we find the asymptotics of solution at the point of the singularity formation as the parameter of stochastic perturbation tends to zero. Then we introduce a generalized solution in the sense of free particles (FP-solution) as a special limit of the solution to the regularized system. This solution corresponds to a medium consisting of non-interacting particles. The FP-solution is a bridging step to constructing solutions to the Riemann problem for the pressureless gas dynamics describing sticky particles. We analyze the difference in the behavior of discontinuous solutions for these two models and the relations between them. In our framework we obtain a unique entropy solution to the Riemann problem in 1D case. 相似文献