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991.
Rafael Taboryski Jonatan Kutchinsky Jrn Bindslev HansenMorten Wildt Claus B. Srensen Poul Erik Lindelof 《Superlattices and Microstructures》1999,25(5-6)
We report new measurements on subgap energy structures originating from multiple Andreev reflections in mesoscopic SNS junctions. The junctions were fabricated in a planar geometry with high-transparency superconducting contacts of Al deposited on highly diffusive and surface δ -dopedn + + -GaAs. For samples with a normal GaAs region of active length 0.3μ m, the Josephson effect with a maximal supercurrent Ic = 3μ A at T = 237 mK was observed. The subgap structure was observed as a series of local minima in the differential resistance at dc bias voltages V = ± 2Δ / (ne) with n = 1, 2, 4, i.e. only the even subgap positions. While at V = ± 2Δ / e(n = 1) only one dip is observed, then = 2 and the n = 4 subgap structures each consists of two separate dips in the differential resistance. The mutual spacing of these two dips is independent of temperature, and the mutual spacing of the n = 4 dips is half the spacing of the n = 2 dips. The voltage bias positions of the subgap differential resistance minima coincide with the maxima in the oscillation amplitude when a magnetic field is applied in an interferometer configuration, where one of the superconducting electrodes has been replaced by a flux-sensitive open loop. 相似文献
992.
Nastaran Alinezhadbalalami Temple A. Douglas Nikita Balani Scott S. Verbridge Rafael V. Davalos 《Electrophoresis》2019,40(18-19):2592-2600
Cancer stem cells (CSCs) are aggressive subpopulations with increased stem‐like properties. CSCs are usually resistant to most standard therapies and are responsible for tumor repropagation. Similar to normal stem cells, isolation of CSCs is challenging due to the lack of reliable markers. Antigen‐based sorting of CSCs usually requires staining with multiple markers, making the experiments complicated, expensive, and sometimes unreliable. Here, we study the feasibility of using dielectrophoresis (DEP) for isolation of glioblastoma cells with increased stemness. We culture a glioblastoma cell line in the form of neurospheres as an in vitro model for glioblastoma stem cells. We demonstrate that spheroid forming cells have higher expression of stem cell marker, nestin. Next, we show that dielectric properties of neurospheres change as a result of changing culture conditions. Our results indicate that spheroid forming cells need higher voltages to experience the same DEP force magnitude compared to normal monolayer cultures of glioblastoma cell line. This study confirms the possibility of using DEP to isolate glioblastoma stem cells. 相似文献
993.
Lorena S.R. Martelli Lucas C.C. Vieira Márcio W. Paixão Julio Zukerman-Schpector Juliana O. de Souza Anna Caroline C. Aguiar Glaucius Oliva Rafael V.C. Guido Arlene G. Corrêa 《Tetrahedron》2019,75(25):3530-3542
The organocatalysed asymmetric vinylogous Michael addition of α,α-dicyanoolefins to α,β-unsaturated aldehydes and ketones have been reported in the last decade, however, chalcones have been poorly explored. Moreover, a considerable part of the publications in this theme still employs undesirable solvents, such as toluene and THF, with concerns related to health and environmental safety. We report herein the use of a bifunctional catalyst derived from a Cinchona alkaloid to perform the enantio- and diastereoselective Michael addition of α,α-dicyanoolefins to chalcones using 2-MeTHF as solvent. The Michael adducts were obtained in moderate to good yields and were evaluated for their antiplasmodial and cytotoxic activity. 相似文献
994.
Clayane Carvalho dos Santos Marcelo de Assis Thales Rafael Machado Paula Fabiana dos Santos Pereira Gladys Minguez‐Vega Eloisa Cordoncillo Hector Beltran‐Mir Carlos Doate‐Buendía Juan Andrs Elson Longo 《Particle & Particle Systems Characterization》2019,36(6)
In this work, for the first time, the instantaneous nucleation and growth processes of Ag nanoparticles on Ag3PO4 mediated by femtosecond laser pulses are reported and analyzed. The investigated samples are pure Ag3PO4 sample, electron‐irradiated Ag3PO4 sample, and laser‐irradiated sample. Complete characterization of the samples is performed using X‐ray diffraction (XRD), Rietveld refinements, field emission scanning electron microscopy, and energy dispersive spectroscopy (EDS). XRD confirms that the irradiated surface layer remains crystalline, and according to EDS analysis, the surface particles are composed primarily of Ag nanoparticles. This method not only offers a one‐step route to synthesize Ag nanoparticles using laser‐assisted irradiation with particle size control, but also reports a complex process involving the formation and subsequent growth of Ag nanoparticles through an unexpected additive‐free in situ fabrication process. 相似文献
995.
We derive the relativistic Vlasov equation from quantum Hartree dynamics for fermions with relativistic dispersion in the mean-field scaling, which is naturally linked with an effective semiclassic limit. Similar results in the non-relativistic setting have been recently obtained in Benedikter et al. (Arch Rat Mech Anal 221(1): 273–334, 2016). The new challenge that we have to face here, in the relativistic setting, consists in controlling the difference between the quantum kinetic energy and the relativistic transport term appearing in the Vlasov equation. 相似文献
996.
Harald Fritzsch Joan Solà Rafael C. Nunes 《The European Physical Journal C - Particles and Fields》2017,77(3):193
We compute the time variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine-structure constant and Newton’s constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance \(\Lambda \)CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level \({\gtrsim } 3\sigma \). Here we use such remarkable status of the RVMs to make definite predictions on the cosmic time variation of the fundamental constants. It turns out that the predicted variations are close to the present observational limits. Furthermore, we find that the time evolution of the dark matter particle masses should be crucially involved in the total mass variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the “micro–macro connection” (viz. the dynamical feedback between the evolution of the cosmological parameters and the time variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS). 相似文献
997.
Russell Johnson Sylvia Novo Carmen Núñez Rafael Obaya 《Journal of Dynamics and Differential Equations》2017,29(2):355-383
In this paper the dissipativity of a family of linear-quadratic control processes is studied. The application of the Pontryagin Maximum Principle to this problem gives rise to a family of linear Hamiltonian systems for which the existence of an exponential dichotomy is assumed, but no condition of controllability is imposed. As a consequence, some of the systems of this family could be abnormal. Sufficient conditions for the dissipativity of the processes are provided assuming the existence of global positive solutions of the Riccati equation induced by the family of linear Hamiltonian systems or by a convenient disconjugate perturbation of it. 相似文献
998.
Rangel Baldasso Otávio Menezes Adriana Neumann Rafael R. Souza 《Journal of statistical physics》2017,167(5):1112-1142
We study the hydrodynamic and the hydrostatic behavior of the simple symmetric exclusion process with slow boundary. The term slow boundary means that particles can be born or die at the boundary sites, at a rate proportional to \(N^{-\theta }\), where \(\theta > 0\) and N is the scaling parameter. In the bulk, the particles exchange rate is equal to 1. In the hydrostatic scenario, we obtain three different linear profiles, depending on the value of the parameter \(\theta \); in the hydrodynamic scenario, we obtain that the time evolution of the spatial density of particles, in the diffusive scaling, is given by the weak solution of the heat equation, with boundary conditions that depend on \( \theta \). If \(\theta \in (0,1)\), we get Dirichlet boundary conditions, (which is the same behavior if \(\theta =0\), see Farfán in Hydrostatics, statical and dynamical large deviations of boundary driven gradient symmetric exclusion processes, 2008); if \(\theta =1\), we get Robin boundary conditions; and, if \(\theta \in (1,\infty )\), we get Neumann boundary conditions. 相似文献
999.
Rafael Tadmor 《Surface science》2008,602(14):L108-L111
The relation between drop radius, r, the force to move the three phase contact line and the advancing and receding contact angles θA and θR is studied. To keep the line energy (energy per 2πr, also named line tension) independent of r, the modified Young equation predicts that the advancing and receding contact angles, θA and θR, change considerably with r. As shown by many investigators, θA and θR change negligibly, if at all, with r. We quantify recent evidences showing that the line energy is a function of the Laplace pressure and show that this way the modified Young equation is correct and still θA and θR should hardly change with r. According to our model, the small surface deformation associated with the unsatisfied normal component of the Young equation results in higher intermolecular interactions at the three phase contact line which corresponds to a higher retention force. This time increasing effect is supported by recent experiments. 相似文献
1000.
Density functional theory is used to study oxygen adsorption and its effect on surface segregation in (2 1 1) surfaces of Pt(shell)/M(core) and Pt3M (M = Co, Ir) alloys. It is found that the most energetically favorable oxygen adsorption site is the bridge site over and parallel to the (1 0 0) step. Surface segregation phenomena is observed in Pt3Co, Pt3Ir and Pt/Co(core) systems. The Pt/Ir(core) structure was the only one, among the studied systems, that showed antisegregation behavior even in presence of oxygen adsorbed. 相似文献