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211.
(Anti)-/ferromagnetic Heisenberg spin models arise from discretization of Landau–Lifshitz models in micromagnetic modelling. In many applications it is essential to study the behavior of the system at a fixed temperature. A formulation for thermostatted spin dynamics was given by Bulgac and Kusnetsov, which incorporates a complicated nonlinear dissipation/driving term while preserving spin length. It is essential to properly model this term in simulation, and simplified schemes give poor numerical performance, e.g., requiring an excessively small timestep for stable integration. In this paper we present an efficient, structure-preserving method for thermostatted spin dynamics. 相似文献
212.
It is shown that hysteresis and susceptibility studies at various temperatures could provide an idea whether a magnetic sample
contains multidomain, single-domain or superparamagnetic particles. Our results on titanomagnetites with those of others on
cobalt substituted magnesium ferrites suggest that domain wall formation is inhibited in some of them whereby only single-domain
or superparamagnetic particles occur irrespective of the physical grain size of such materials. At high concentration of titanium
in titanomagnetites, the magnetic behaviour is similar to a spin glass, which we interpret as a transition of optimum single-domains
going over to superparamagnetic state. 相似文献
213.
Möhrle BP Köhler K Jaehrling J Brock R Gauglitz G 《Analytical and bioanalytical chemistry》2006,384(2):407-413
Reflectometric interference spectroscopy (RIfS) is a label-free, time-resolved technique for detecting interactions of molecules
immobilized on a surface with ligands in solution. Here we show that RIfS also permits the detection of the adhesion of tissue
culture cells to a functionalized surface in a flow system. Interactions of T cells with other leukocytes or epithelial cells
of blood vessels are crucial steps in the regulating immune response and inflammatory reactions. Jurkat T cell leukemia cells
rapidly attached to a transducer functionalized with a monoclonal antibody directed against the T cell receptor (TCR)/CD3
complex, followed by activation-dependent cell spreading. RIfS curves were obtained for the Jurkat derivative JCaM 1.6 (which
lacks the key signaling protein Lck), cells preincubated with cytochalasin D (an inhibitor of actin polymerization), and for
surfaces functionalized with an antibody directed against the coreceptor CD28. These curves differed with respect to the maximum
signal and the initial slope of the increase in optical thickness. The testing of chemical inhibitors, cell surface molecules
and gene products relevant to a key event in T cell immunity illustrates the potential of label-free techniques for the analysis
of activation-dependent cell-surface contacts.
The first two authors contributed equally to this paper 相似文献
214.
This paper presents results computed using a meshless method in a point collocation formulation to investigate the effects of temperature and frequency on the magnetization switching mode in the circular amorphous magneto-impedance sensor (element). Specifically, the solutions characterizing the MI effect are solved from a set of coupled nonlinear equations consisting of the Maxwell’s equations, the Landau-Lifshitz-Gilbert equation, and the thermal diffusion equation. This coupled nonlinear space-time model predicts the formation and propagation of dynamic domain walls in switching and it is shown how they contribute to experimentally observed temperature and frequency effects. Computed results (that agree well with reported experimental data) suggest radial domain walls may play a larger role in the MI effect than originally believed even for the realistic conditions considered here at 1 MHz or more. 相似文献
215.
We propose a new mechanism for leptogenesis, which is naturally realized in models with a flavor symmetry based on the discrete group A4, where the symmetry breaking parameter also controls the Majorana masses for the heavy right-handed (RH) neutrinos. During the early universe, for T?TeV, part of the symmetry is restored, due to finite temperature contributions, and the RH neutrinos remain massless and can be produced in thermal equilibrium even at temperatures well below the most conservative gravitino bounds. Below this temperature the phase transition occurs and they become massive, decaying out of equilibrium and producing the necessary lepton asymmetry. Unless the symmetry is broken explicitly by Planck-suppressed terms, the domain walls generated by the symmetry breaking survive till the quark–hadron phase transition, where they disappear due to a small energy splitting between the A4 vacua caused by the QCD anomaly. 相似文献
216.
217.
Hiroaki Nishikawa 《Journal of computational physics》2010,229(11):3989-4016
In this paper, we unify advection and diffusion into a single hyperbolic system by extending the first-order system approach introduced for the diffusion equation [J. Comput. Phys., 227 (2007) 315–352] to the advection–diffusion equation. Specifically, we construct a unified hyperbolic advection–diffusion system by expressing the diffusion term as a first-order hyperbolic system and simply adding the advection term to it. Naturally then, we develop upwind schemes for this entire system; there is thus no need to develop two different schemes, i.e., advection and diffusion schemes. We show that numerical schemes constructed in this way can be automatically uniformly accurate, allow O(h) time step, and compute the solution gradients (viscous stresses/heat fluxes for the Navier–Stokes equations) simultaneously to the same order of accuracy as the main variable, for all Reynolds numbers. We present numerical results for boundary-layer type problems on non-uniform grids in one dimension and irregular triangular grids in two dimensions to demonstrate various remarkable advantages of the proposed approach. In particular, we show that the schemes solving the first-order advection–diffusion system give a tremendous speed-up in CPU time over traditional scalar schemes despite the additional cost of carrying extra variables and solving equations for them. We conclude the paper with discussions on further developments to come. 相似文献
218.
R. Balakrishnan 《Phase Transitions》2013,86(6):489-493
Electric field effects on FSLC films of p-pentyl cyano biphenyl (5CB) have been optically studied. Due to the initial alignment of the molecules, initially formed transition layers grow with increasing field and merge to form a linear wall at the middle of the sample. This linear wall splits into two disclinations at relatively high fields. But a sudden application of relatively high electric field results in the formation of closed metastable walls. The wall orientation shows interesting behaviour with the field frequency. At high field, the closed walls undergo distortion and division into two or more parts. 相似文献
219.
In this paper, we demonstrated an integrated digital image processing framework that is training‐free for high throughput beads or biological cells detection and enumeration by the bead aggregation splitting algorithm. By making contour extraction processing, the aggregated beads can be clearly split for precise counting. It can be potentially embedded on‐chip in a miniaturized medical equipment to automatically adjust illumination condition and de‐noise. This study demonstrates that the existing hematological analysis can be updated from manual classification and counting by high‐speed and precise machine‐based programs. 相似文献
220.
D. R. K. Reddy P. Govinda Rao R. L. Naidu 《International Journal of Theoretical Physics》2008,47(11):2966-2970
Five dimensional Kaluza-Klein space-time is considered in the presence of thick domain walls in the framework of scalar-tensor
theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, [1986]). Exact cosmological model, which represents a stiff domain wall, is presented. Some physical and kinematical properties
of the model are also discussed. 相似文献