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91.
Ville Saarimaa Jere Manni Esko Kauppinen Antti Markkula Jyrki Juhanoja Bengt‐Johan Skrifvars 《Surface and interface analysis : SIA》2014,46(9):620-624
Hexavalent chromium containing pretreatments and primers for coil coating are soon to be entirely prohibited, which sets new demands for Cr‐free alternatives. Most of the presently used Cr‐free pretreatment layers operate predominantly via barrier formation and adhesion promotion mechanisms and lack the self‐healing effect typical for Cr6+‐pretreatments. This sets new demands also for the formation and monitoring of these layers. The barrier thickness and chemical composition of Cr‐free pretreatment layers on hot dip galvanized steel were studied using cross sections from broad ion beam (BIB) sample preparation and ultramicrotome cutting. BIB milling provided finely polished cross sections of pretreated samples. Film thicknesses of 20–50 nm were accurately determined for Cr‐free pretreatments containing 4–10 mg Ti/m2 using BIB milling and scanning electron microscopy imaging. Scanning transmission electron microscopy, integrated with aberration correctors and X‐ray energy dispersive spectrometry, of an ultramicrotome cut pretreated and painted samples provided detailed chemical information. Metal complexes were detected close to the pretreatment/zinc interface, while the polymeric part of the pretreatment layer prevailed closer to paint. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
92.
Ultrafast Two‐Dimensional NMR Relaxometry for Investigating Molecular Processes in Real Time
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Nuclear spin–lattice (T1) and spin–spin (T2) relaxation times provide versatile information about the dynamics and structure of substances, such as proteins, polymers, porous media, and so forth. Multidimensional experiments increase the information content and resolution of NMR relaxometry, but they also multiply the measurement time. To overcome this issue, we present an efficient strategy for a single‐scan measurement of a 2D T1–T2 correlation map. The method shortens the experimental time by one to three orders of magnitude as compared to the conventional method, offering an unprecedented opportunity to study molecular processes in real‐time. We demonstrate that, despite the tremendous speed‐up, the T1–T2 correlation maps determined by the single‐scan method are in good agreement with the maps measured by the conventional method. The concept of the single‐scan T1–T2 correlation experiment is applicable to a broad range of other multidimensional relaxation and diffusion experiments. 相似文献
93.
Ville Hakulinen 《Communications in Mathematical Physics》2003,235(1):1-45
We prove estimates for the stationary state n-point functions at zero molecular diffusivity in the Kraichnan model [13]. This is done by proving upper bounds for the heat
kernels and Green's functions of the degenerate elliptic operators M
n
that occur in the Hopf equations for the n-point functions.
Received: 25 August 2001 / Accepted: 30 September 2002 Published online: 20 January 2003
Communicated by A. Kupiainen 相似文献
94.
95.
Ville Anton Vuorinen Harri Hillamo Ossi Kaario Mika Nuutinen Martti Larmi Laszlo Fuchs 《Flow, Turbulence and Combustion》2011,86(3-4):533-561
The paper is mainly focused to the vast number of researchers who work within direct injection (DI) engine fuel spray simulations. The most common simulation framework today within the community is the Reynolds Averaged Navier Stokes (RANS) approach together with the Lagrangian Particle Tracking (LPT) method. In fact, this study is one of the first studies where high resolution LES/LPT diesel spray modeling is considered. The potential of LES to deepen the present day multidimensional LPT fuel spray simulations is discussed. Spray evolution is studied far from an injector by modeling a spray as a particle laden jet (PLJ). The effect of d on mixing in non-atomizing and atomizing sprays is thoroughly investigated at jet inlet Reynolds number Re?=?104 and Mach number Ma?=?0.3. Based on and justified by rather recent and also quite old ideas, novel and compact views on droplet breakup in turbulent flows are pointed out from the literature. We use LES/LPT to illustrate that even in a low Weber number flow (We?<?13) the droplet breakup modeling may need considerable attention in contrast to what is typically assumed in the present-day breakup models. LES and LPT techniques are first applied to essentially confirm certain expected droplet size effects on spray shape in non-atomizing monodisperse sprays. In the simulations LES e.g. produces an expected turbulent dispersion pattern that depends on droplet diameter (d) without a droplet dispersion model in contrast to RANS. A new compact droplet breakup model is formulated and tested for droplets that break with a natural resonance time rate according to the Poisson process. As a result of the study: 1) the analysis gives a rigorous and enriching proof of currently existing views on droplet size effects on mixing, and 2) the presented a priori analysis points out the importance of modeling the resonance breakup even at a low We. 相似文献
96.
We present an all-electron method for time-dependent density functional theory which employs hierarchical nonuniform finite-element bases and the time-propagation approach. The method is capable of treating linear and nonlinear response of valence and core electrons to an external field. We also introduce (i) a preconditioner for the propagation equation, (ii) a stable way to implement absorbing boundary conditions, and (iii) a new kind of absorbing boundary condition inspired by perfectly matched layers. 相似文献
97.
James R. Wootton Ville Lahtinen Benoit Doucot Jiannis K. Pachos 《Annals of Physics》2011,(9):2307-2314
In three spatial dimensions, particles are limited to either bosonic or fermionic statistics. Two-dimensional systems, on the other hand, can support anyonic quasiparticles exhibiting richer statistical behaviors. An exciting proposal for quantum computation is to employ anyonic statistics to manipulate information. Since such statistical evolutions depend only on topological characteristics, the resulting computation is intrinsically resilient to errors. The so-called non-Abelian anyons are most promising for quantum computation, but their physical realization may prove to be complex. Abelian anyons, however, are easier to understand theoretically and realize experimentally. Here we show that complex topological memories inspired by non-Abelian anyons can be engineered in Abelian models. We explicitly demonstrate the control procedures for the encoding and manipulation of quantum information in specific lattice models that can be implemented in the laboratory. This bridges the gap between requirements for anyonic quantum computation and the potential of state-of-the-art technology. 相似文献
98.
Kramers-Kronig analysis on the real refractive index of porous media in the terahertz spectral range
We present a terahertz time-domain experimental technique for the detection of scattering from porous media. The method for detection of the scattering enables one to make a decision when Fresnel or Kramers-Kronig (K-K) analysis can be applied for a porous medium. In this study the real refractive index of a tablet is calculated using the conventional K-K dispersion relation and also using a singly subtractive K-K relation, which are applied to the extinction coefficient obtained from the Beer-Lambert law. The advantage of the K-K analysis is that one gets estimates both for absolute refractive index and also dispersion of the porous tablet, whereas Fresnel analysis provides only the absolute value of the index. 相似文献
99.
Controlled lateral spreading and pinning of oil droplets based on topography and chemical patterning
Jokinen V Sainiemi L Franssila S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):7314-7320
Geometric pinning sites can be used to control the lateral spreading and pinning of oils on surfaces. The geometric pinning effect combined with lithographic surface chemistry patterning allows controlling the shapes of oil droplets. We study the confinement effect on test structures of various protruding and intruding geometries, and employ scanning electron microscopy analysis to study the shape of the meniscus at the edges of the chemical patterns. Nanopillar and micropillar topographies are compared, revealing that it is a necessity for accurate oil patterns that the length scale of the roughness is smaller than the resolution of the surface chemistry pattern. We also find that there exists a critical, geometry-dependent threshold contact angle, below which the geometric confinement does not work, as olive oil with a static advancing contact angle of 57° accurately replicated the chemical pattern on top of nanopillar topography, but hexadecane with a static advancing contact angle of 50° penetrated the pinning sites and wetted the whole surface. 相似文献
100.