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61.
Mark Paton Karri Muinonen Lauri J. Pesonen Tomas Kohout Martti Lehtinen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(11):1803-1814
Meteorites have advanced our knowledge of processes in the Solar System with the application of high precision instruments here on Earth. The study of asteroids, the source of most meteorites, has in turn given us knowledge regarding the large scale evolution of the Solar System. Using the complementary information that asteroids and meteorites give us the story of our cosmic backyard can be more easily read. One efficient way to link meteorites to asteroids is by matching their respective reflectance spectra. There have been few convincing matches because of observational and scale differences as well as an incomplete knowledge of the light scattering physics involved. To better interpret the reflectance data we need to know the dependencies of the reflectance on physical properties and develop techniques for better comparisons of data sets. For these purposes we utilise our own measurements of 26 different meteorites together with spectra available on the NASA PDS.We find that normalisation of reflectance at a wavelength between 1.1 and 1.3 μm gives the closest match of spectra from meteorites common to both data sets. The depth of the spectra bands deepens by similar amounts for different types of surface texture alterations i.e. rock to sawn surface, rock to polished surface and rock to powdered surface. Principal Component Analysis (PCA) is able to easily place carbonaceous chondrites, ordinary chondrites and achondrites into distinct groups using their reflectance spectra. We track the variation of spectral features in principal component space by using a set of meteorite spectra synthesised from mineral and elemental spectra. A spectral agent that reduces the reflectance at all wavelengths is required, in addition to olivine, pyroxene and carbon, to generate a set of synthesised spectra to match the distribution of measured spectra, in principal component space. 相似文献
62.
Stable operation of a cw optical parametric oscillator near the signal-idler degeneracy 总被引:1,自引:0,他引:1
The frequency stability of a cw optical parametric oscillator (cw OPO) near the signal-idler degeneracy has been studied. The strong tendency of a near-degenerate OPO to mode hop has been suppressed by using a bulk Bragg grating as a spectral filter in the OPO cavity. An experimental demonstration of stable parametric oscillation in a single longitudinal mode of the OPO cavity is reported, together with the capability of tuning the signal-idler difference frequency from 1 to 4 THz. The OPO has potential use in cw terahertz generation. 相似文献
63.
Anu Teearu Signe Vahur Uku Haljasorg Ivo Leito Tõiv Haljasorg Lauri Toom 《Journal of mass spectrometry : JMS》2014,49(10):970-979
2,5‐Dihydroxybenzoic acid (DHB) is one of the most widely used and studied matrix compounds in matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. However, the influence of ageing of the DHB solution on the MALDI mass spectra has not been yet systematically studied. In this work, the possible changes occurring in the acidified acetonitrile/water solution of the MALDI matrix compound DHB during 1‐year usage period have been monitored with MALDI‐Fourier transform ion cyclotron resonance mass spectrometer (MALDI‐FT‐ICR‐MS) and attenuated total reflectance Fourier transform infrared (ATR‐FT‐IR) spectroscopy. No significant ageing products have been detected. The ability of the aged DHB solution to act as a MALDI matrix was tested with two materials widely used in art and conservation – bone glue (a proteinaceous material) and shellac resin (a resinous material) – and good results were obtained. A number of peaks in the mass spectra measured from the DHB solution were identified, which can be used for internal calibration of the mass axis. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
64.
Raili Pönni Lauri Rautkari Callum A. S. Hill Tapani Vuorinen 《Cellulose (London, England)》2014,21(3):1217-1226
Deuterium exchange in a deuterium oxide (D2O) atmosphere (95 % relative humidity), quantified by a dynamic vapor sorption (DVS) apparatus, was applied for assessing the accessibility of hydroxyl groups in birch kraft pulps. Achieving the maximum deuteration level exhibited slower kinetics than was earlier reported for experiments with ground wood and bacterial cellulose. The deuterium exchange process followed two parallel phenomena. Applying multiple drying and rewetting cycles gave kinetic information also on the hornification phenomenon occurring during these cycles. Dry birch pulps treated with sodium hydroxide solution of varying alkalinities at elevated temperatures were assessed for their accessible hydroxyl groups by DVS with deuterium exchange. This method was evaluated against deuteration combined with Fourier transform infra-red spectroscopy and water retention value (WRV). DVS measurements were in correlation with WRV and both the methods indicated that an alkaline treatment of dry birch pulp improves cellulose accessibility. The level of irreversible deuteration also decreased as the alkalinity was increased. DVS was shown to provide quantitative information on the accessibility but to be a time-consuming method for the pulp samples. A potential means to decrease the duration of the measurement is increased D2O exposure by excluding the drying phases. 相似文献
65.
The object of this paper is to show that 4-connected planar graphs are uniquely determined from their collection of edge-deleted subgraphs. 相似文献
66.
Josef Lauri 《Journal of Graph Theory》1979,3(3):269-286
The object of this paper is to show tht every planar graph of minimum valency 5 is reconstructible from its family of edge-deleted subgraphs. 相似文献
67.
The object of this paper is to show that every maximal planar graph is recognizable from its family of vertex-deleted subgraphs. 相似文献
68.
We have calculated the band profiles of the OH-stretching fundamental and overtone transitions in the proton donor unit of the water dimer complex. We have used a local mode Hamiltonian that includes both OH-stretching and OO-stretching motion but separates these adiabatically. The variation of OH-stretching frequency and anharmonicity with OO displacement from equilibrium contributes to the effective OO-stretching potentials for each OH-stretching state. The resulting OO-stretching energy levels and wave functions are used to simulate the vibrational profile of each OH-stretching transition. The coupled cluster with singles, doubles, and perturbative triples ab initio method with an augmented triple-zeta correlation consistent basis set has been used to obtain the necessary parameters, potentials, and dipole moment functions. We find that the OO-stretching transitions associated with a given hydrogen bonded OH-stretching transition are spread significantly and this spread increases with overtone. The spread is minor for the free OH-stretching transition. The inclusion of the OO-stretching mode has a limited effect on the overall OH-stretching band intensity. 相似文献
69.
Walter M Häkkinen H Lehtovaara L Puska M Enkovaara J Rostgaard C Mortensen JJ 《The Journal of chemical physics》2008,128(24):244101
We present the implementation of the time-dependent density-functional theory both in linear-response and in time-propagation formalisms using the projector augmented-wave method in real-space grids. The two technically very different methods are compared in the linear-response regime where we found perfect agreement in the calculated photoabsorption spectra. We discuss the strengths and weaknesses of the two methods as well as their convergence properties. We demonstrate different applications of the methods by calculating excitation energies and excited state Born-Oppenheimer potential surfaces for a set of atoms and molecules with the linear-response method and by calculating nonlinear emission spectra using the time-propagation method. 相似文献
70.
Vehkamäki H Määttänen A Lauri A Kulmala M Winkler P Vrtala A Wagner PE 《The Journal of chemical physics》2007,126(17):174707
In this paper we present a new form of the nucleation theorems applicable to heterogeneous nucleation. These heterogeneous nucleation theorems allow, for the first time, direct determination of properties of nanoclusters formed on pre-existing particles from measured heterogeneous nucleation probabilities. The theorems can be used to analyze the size (first theorem) and the energetics (second theorem) of heterogeneous clusters independent of any specific nucleation model. We apply the first theorem to the study of small water and n-propanol clusters formed at the surface of 8 nm silver particles. According to the experiments the size of the two-component critical clusters is found to be below 90 molecules, and only less than 20 molecules for pure water, less than 300 molecules for pure n-propanol. These values are drastically smaller than the ones predicted by the classical nucleation theory, which clearly indicates that the nucleating clusters are too small to be quantitatively described using a macroscopic theory. 相似文献