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31.
The understanding of the small-scale termination of the turbulent energy cascade in collisionless plasmas is nowadays one of the outstanding problems in space physics. In the absence of collisional viscosity, the dynamics at small scales is presumably kinetic in nature; the identification of the physical mechanism which replaces energy dissipation and establishes the link between macroscopic and microscopic scales would open a new scenario in the study of turbulent heating in space plasmas. We present a numerical analysis of kinetic effects along the turbulent energy cascade in solar-wind plasmas which provides an effective unified interpretation of a wide set of spacecraft observations and shows that, simultaneously with an increase in the ion perpendicular temperature, strong bursts of electrostatic activity in the form of ion-acoustic turbulence are produced together with accelerated beams in the ion distribution function. 相似文献
32.
E. Cappelli C. Scilletta G. Mattei V. Valentini S. Orlando M. Servidori 《Applied Physics A: Materials Science & Processing》2008,93(3):751-758
The structure of thin films deposited by pulsed laser ablation (PLD) is strongly dependent on experimental conditions, like
laser wavelength and fluence, substrate temperature and pressure. Depending on these parameters we obtained various kinds
of carbon materials varying from dense, mainly tetrahedral amorphous carbon (ta-C), to less compact vertically oriented graphene
nano-particles.
Thin carbon films were grown by PLD on n-Si 〈100〉 substrates, at temperatures ranging from RT to 800°C, from a rotating graphite target operating in vacuum. The laser ablation of the graphite target was performed by a UV pulsed ArF excimer laser (λ=193 nm) and a pulsed Nd:YAG laser, operating in the near IR (λ=1064 nm).
The film structure and texturing, characterised by X-ray diffraction analysis, performed at grazing incidence (GI-XRD), and
the film density, evaluated by X-ray reflectivity measurements, are strongly affected both by laser wavelength and fluence
and by substrate temperature.
Micro-Raman and GI-XRD analysis established the progressive formation of aromatic clusters and cluster condensation into vertically
oriented nano-sized graphene structures as a direct function of increasing laser wavelength and deposition temperature. The
film density, negatively affected by substrate temperature and laser wavelength and fluence, in turn, results in a porous
bulk configuration and a high macroscopic surface roughness as shown by SEM characterisation. These structural property modifications
induce a relevant variation also on the emission properties of carbon nano-structures, as evidenced by field emission measurements.
This work is dedicated to our friend Giorgio who passed away 20th August. 相似文献
33.
Federica Valentini Giulia Brufani Benedetta Di Erasmo Luigi Vaccaro 《Current Opinion in Green and Sustainable Chemistry》2022
The great challenge for modern research is to define the most efficient tools to make more sustainable the industrial production and manufacturing. Among the different aspects that require attention the replacement of toxic and/or non-renewable solvents it is certainly playing a crucial role. Dealing with widely used dipolar aprotic solvents, among the different alternatives proposed in the literature γ-valerolactone (GVL) plays a pivotal role covering different application area. In this contribution, the benefits derived from the use of GVL as a circular, safe, biomass-derived reaction medium are highlighted covering most recent publications (2021). The presentation has been divided into three major sections: (i) biomass valorization, (ii) materials synthesis, manufacturing and recycle and (iii) new synthetic methodologies. 相似文献
34.
Brandaleze Elena Bazán Vanesa Orozco Ivana Valentini Marcelo Gomez Giuliana 《Journal of Thermal Analysis and Calorimetry》2018,133(1):435-441
Journal of Thermal Analysis and Calorimetry - Rhenium production from copper and molybdenum sulphides involves the use of a pyrometallurgical process. In traditional pyrometallurgy processes, gases... 相似文献
35.
Viel A Genuardi M Lucci-Cordisco E Capozzi E Rovella V Fornasarig M Ponz de Leòn M Anti M Pedroni M Bellacosa A Percesepe A Covino M Benatti P Del Tin L Roncucci L Valentini M Boiocchi M Neri G 《Community genetics》1998,1(4):229-236
OBJECTIVE: Identification of clinical and molecular characteristics associated with constitutional MLH1 and MSH2 mutations and definition of a stepwise strategy for the selection of colorectal cancer (CRC) patients amenable to MLH1 and MSH2 genetic testing. METHODS: 90 unrelated CRC patients were initially selected on the basis of either familial or early onset occurrence of CRC. They were screened for the presence of constitutional MLH1 and MSH2 mutations and for microsatellite instability (MSI). RESULTS: 16 pathogenetic mutations (9 MLH1 and 7 MSH2) were identified in 41% of Amsterdam hereditary nonpolyposis colorectal cancer (HNPCC) families, 5% of suspected HNPCC families, and 14% of sporadic early-onset CRC patients. The presence of the mutations correlated with MSI, with early age of onset and proximal location of the tumor, and with the presence of some extracolonic tumors of the HNPCC spectrum and/or multiple tumors in the family. CONCLUSIONS: Evaluation of clinical and molecular characteristics is useful for the identification of candidates to MLH1 and MSH2 mutational analysis and allows the application of a rational approach to genetic testing. 相似文献
36.
Diffusion data from pulsed‐field gradient spin‐echo (PGSE) methods are shown to be qualitatively useful in the investigation of problems involving unknown molecular aggregation and/or the nature of inter‐ionic interactions in metal complexes. For charged species possessing anions such as PF, BF, CF3SO or BArF−, both 19F‐ and 1H‐PGSE methods offer a valid alternative and, sometimes, unique view of gross and subtle solution molecular structure and dynamics. Problems associated with solvents, concentration, and reproducibility are discussed. 相似文献
37.
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39.
Austin Nevin Daniela Comelli Iacopo Osticioli Lucia Toniolo Gianluca Valentini Rinaldo Cubeddu 《Analytical and bioanalytical chemistry》2009,395(7):2139-2149
The assessment of the influence of natural and artificial ageing on the spectrofluorescence of triterpenoid varnishes dammar
and mastic is the focus of this work. Both Fourier transform infrared (FTIR) microscopy using attenuated total reflectance
and Raman spectroscopy have been employed for complementary molecular analysis of samples. Synchronous fluorescence spectroscopy,
excitation emission spectroscopy, and statistical analysis of data have been used to monitor changes in the optical properties
of varnish samples. Assessment of naturally and artificially aged samples using excitation emission spectroscopy suggests
that extensive exposure to visible light does not lead to easily appreciable differences in the fluorescence of mastic and
dammar; cluster analysis has been used to assess changes, which occur with artificial ageing under visible light, indicating
that differences in the fluorescence spectra of aged triterpenoids may be insufficient for their discrimination. The results
highlight significant differences between the initial fluorescence of films of dammar and mastic and the fluorescence, which
develops with ageing and oxidation, and specific markers, which change with ageing in FTIR and Raman spectra, have been identified. 相似文献
40.
Wang J Scampicchio M Laocharoensuk R Valentini F Gonzalez-García O Burdick J 《Journal of the American Chemical Society》2006,128(14):4562-4563
Nanowires have received considerable attention owing to their broad potential applications. We report here on the application of nanowires for magnetic control of the electrochemical reactivity and demonstrate how one can modulate the electrocatalytic activity by orienting catalytic nanowires at different angles. Unlike early "on/off" magnetic switching studies based on functionalized magnetic spheres, the present magnetoswitchable protocol relies on modulating the electrochemical reactivity without removing the magnetic material from the surface. Such behavior is attributed to the reversible blocking of the redox processes and to changes in the tortuosity-dependent flux rate. The nanowire-based magnetoswitchable protocol may be extremely useful for adjusting the electrochemical reactivity, such as for tuning the power output of fuel cells (rather than switching the power on/off). 相似文献