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991.
Hassan Saadat 《International Journal of Theoretical Physics》2011,50(6):1769-1775
In this article we consider the cosmological model based on the holographic dark energy. We study dark energy density in Universe
with arbitrary spatially curvature described by the Friedmann-Robertson-Walker metric. We use Chevallier-Polarski-Linder parametrization
to specify dark energy density. 相似文献
992.
Based on the geodesic equation in a static spherically symmetric metric we discuss the rotation curve and gravitational lensing.
The rotation curve determines one function in the metric without assuming Einstein’s equations. Then lensing is considered
in the weak field approximation of general relativity. From the null geodesics we derive the lensing equation. The gravitational
potential U(r) which determines the lensing is directly give by the rotation curve U(r) = −v
2(r). This allows to test general relativity on the scale of galaxies where dark matter is relevant. 相似文献
993.
Alexander Gersten 《Foundations of Physics》2011,41(1):88-98
We deal with Lagrangians which are not the standard scalar ones. We present a short review of tensor Lagrangians, which generate
massless free fields and the Dirac field, as well as vector and pseudovector Lagrangians for the electric and magnetic fields
of Maxwell’s equations with sources. We introduce and analyse Lagrangians which are equivalent to the Hamilton-Jacobi equation
and recast them to relativistic equations. 相似文献
994.
Polymer electrolyte membranes, comprising of poly(methyl methacrylate) (PMMA), lithium tetraborate (Li2B4O7) as salt and dibutyl phthalate (DBP) as plasticizer were prepared using a solution casting method. The incorporation of DBP
enhanced the ionic conductivity of the polymer electrolyte. The polymer electrolyte containing 70 wt.% of poly(methyl methacrylate)–lithium
tetraborate and 30 wt.% of DBP presents the highest ionic conductivity of 1.58 × 10−7 S/cm. The temperature dependence of ionic conductivity study showed that these polymer electrolytes obey Vogel–Tamman–Fulcher
(VTF) type behaviour. Thermogravimetric analysis (TGA) was employed to analyse the thermal stability of the polymer electrolytes.
Fourier transform infrared (FTIR) studies confirmed the complexation between poly(methyl methacrylate), lithium tetraborate
and DBP. 相似文献
995.
Vladimir Petukhov John Stoemenos Johan Rothman Andrey Bakin Andreas Waag 《Applied Physics A: Materials Science & Processing》2011,102(1):161-168
In order to interpret results of temperature dependent Hall measurements in heteroepitaxial ZnO-thin films, we adopted a multilayer conductivity model considering carrier-transport through the interfacial layer with degenerate electron gas as well as the upper part of ZnO layers with lower conductivity. This model was applied to the temperature dependence of the carrier concentration and mobility measured by Hall effect in a ZnO-layer grown on c-sapphire with conventional high-temperature MgO and low-temperature ZnO buffer. We also compared our results with the results of maximum entropy mobility-spectrum analysis (MEMSA). The formation of the highly conductive interfacial layer was explained by analysis of transmission electron microscopy (TEM) images taken from similar layers. 相似文献
996.
The crystallization and glass transition kinetics using differential scanning calorimetry (DSC) in 50AgI–33.33Ag2O–16.67[(V2O5)1−x
–(MoO3)
x
] superionic glassy system is discussed. Thermal stability of glass, studied using various criteria, does not vary significantly
with glass former variation. However, the activation energies for structural relaxation (E
s) at glass transition temperature and crystallization (E
c) obtained using Moynihan and Kissinger, Matusita-Sakka formulations found to exhibit interesting trends with MoO3 substitution in the glass matrix. It is noticed that the electrical conductivity (σ)–temperature (T) cycles obtained at a typical heating rate of 1 °C/min do exhibit significant thermal events. The conductivity after first
heating cycle at room temperature is found to be increasing with MoO3 content and maximum for x = 0.3 (~10−3 Ω−1 cm−1 at 30 °C) which is comparable to that of the host 50AgI–33.33Ag2O–16.67V2O5 glassy system. The parameters obtained from σ–T plots and DSC scans do complement each other in a particular range of composition. 相似文献
997.
Yi-Cheng Hsu 《Optical Review》2011,18(1):27-33
The effect of lens inner structure on radiation pattern and light extraction efficiency of light-emitting diode (LED) and
the application to artificial light in compact greenhouse is demonstrated. A commercial software package of Trace Pro and
one-factor at-a-time (OFAT) method are used to simulate the lens with different inner structure. The optimum parameters of
lens inner structure design for the maximum light extraction efficiency and the best uniform luminous are described by the
corner radius of curvature, lens width, and lens height, respectively. For a real single LED module, base on the optimum parameters
of lens inner structure, the corresponding best luminous uniformity is 62% and corresponding output extraction is 14.11 lm.
The maximum uniformity of illumination for LED matrix assembled by LED modules with optimum lens is 88% and corresponding
light extraction 1141 lm. In comparison with a commercial artificial light of LED matrix used in agriculture, the high-power
LED module with proposed lens inner structure exhibit good improvement in uniformity of illumination and light extraction.
This study may provide a practical guideline for design and fabrication of a high-performance lens used in various compact
agricultural applications. 相似文献
998.
Santanu Pyne Priyanka Sarkar Samita Basu Gobinda Prasad Sahoo Dipak Kumar Bhui Harekrishna Bar Ajay Misra 《Journal of nanoparticle research》2011,13(4):1759-1767
Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl
alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis
of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag+ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done
by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study.
The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to
dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles
has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static
theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell
suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles. 相似文献
999.
A numerical investigation has been carried out to examine the electrostatic loss of nanoparticles in a corona needle charger.
Two-dimensional flow field, electric field, particle charge, and particle trajectory were simulated to obtain the electrostatic
deposition loss at different conditions. Simulation of particle trajectories shows that the number of charges per particle
during the charging process depends on the particle diameter, radial position from the symmetry axis, applied voltage, Reynolds
number, and axial distance along the charger. The numerical results of nanoparticle electrostatic loss agreed fairly well
with available experimental data. The results reveal that the electrostatic loss of nanoparticles increases with increasing
applied voltage and electrical mobility of particles; and with decreasing particle diameter and Reynolds number. A regression
equation closely fitted the obtained numerical results for different conditions. The equation is useful for directly calculating
the electrostatic loss of nanoparticles in the corona needle charger during particle-charging process. 相似文献
1000.
Primordial black holes evaporate due to Hawking radiation. We find that the evaporation times of primordial black holes increase
when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial black holes are existing
today, which strengthens the conjecture that the primordial black holes are the proper candidates for dark matter. 相似文献