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991.
We found that the interaction of paramagnetic centers that have different relaxation times differs fundamentally from the
interaction of centers having close relaxation times. Simulation showed that in this case there is an anomalous redistribution
of the spectral-line intensity from the center to the wings with a virtually preserved distance between extremal points (super-Lorentzian
shape of the line), which leads to underestimation of the total intensity recorded. The results obtained make it possible
to explain a number of aspects of the radiospectroscopy of carbon materials of practical importance such as the nature of
the generally accepted maximum on the curve for the dependence of the total intensity of an EPR signal on the temperature
of the heat treatment of organic compounds and the degree of metamorphism of natural coals, the specific features of the effect
of oxygen molecules and paramagnetic ions of metals on the EPR spectra of carbon materials, etc.
Belarusian State University, 4, F. Skorina Ave., Minsk, 220080 Belarus. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 65, No. 2, pp. 224–229, March–April, 1998. 相似文献
992.
Hasok Chang 《Physics in Perspective (PIP)》2002,4(2):127-169
In this paper I examine the debate regarding the positive reality of cold: whether it is merely an absence of heat, or a quality or entity in its own right. Marc-Auguste Pictet stimulated this debate
by showing that radiation from a cold object apparently could be focused by concave mirrors to cool another object some distance
away from it. Pictet and other believers in material theories of heat, most notably Pierre Prevost, sought to understand this
phenomenon as a result of the radiation of caloric in a peculiar arrangement. By contrast, Count Rumford saw in Pictet's experiment
a genuine action of “frigorific rays,” and performed striking new experiments to support his view. For Rumford heat and cold
radiation consisted in sound-like undulations in the ether, a mechanism compatible with his own vibration theory of heat,
and discordant with the caloric theory. Rumford's strong arguments were overruled only because of the general dominance of
the caloric theory of heat. However, Rumford did push the caloric theory to develop in a direction that eventually led to
its downfall. I revisit this debate without preconceived notions of the metaphysical nature of cold and heat. 相似文献
993.
A. I. Karol 《Mathematical Notes》1998,63(1):25-32
We construct the asymptotics ast→0 of the trace of the operator exp(−tP) for an elliptic operatorP on a manifold with conical points.
Translated fromMatematicheskie Zametki, Vol. 63, No. 1, pp. 28–36, January, 1998.
This research was supported by the Belarus Foundation for Basic Research under grant No. 96-01 00790. 相似文献
994.
We consider the boundary value problems in a quarter-plane for a loaded heat conduction operator (one-dimensional in the space variable). A peculiarity of the operator in question is as follows: first, the spectral parameter is the coefficient of the loaded summand; second, the order of the derivative in the loaded summand is equal to that of the differential part of the operator, and third, the load point moves with a variable velocity. We demonstrate that the boundary value problem under study is Noetherian. 相似文献
995.
Ultrafine MgAl2O4 powder has been synthesized by a polymerized complex method. Heating of a precursor solution containing citric acid (CA), ethylene glycol (EG) and Mg and Al salts with a molar ratio of Mg/Al/CA/EG=1/2/8/32 at 180°C produced a transparent polymeric gel, which have been characterized by FT-IR spectroscopy and TG/DTA. The organic fraction was removed by controlled thermal treatments (350–1200°C) whereby the bimetallic oxide was formed. XRD analysis showed the presence of MgAl2O4 at 600°C. TEM observation showed that the spherical nanosized powders with good uniformity was obtained. Furthermore, these powders showed excellent sinterability, relative density up to 99.8% was achieved when sintered at 1550°C for 3 h in air without any sintering additive. 相似文献
996.
A novel technological concept of sorption-enhanced steam reforming of hydrocarbons is suggested. The peculiarity of the concept
is the autothermal regeneration of the carbon dioxide scavenger in the moving super-adiabatic heat wave of an exothermic catalytic
combustion reaction performed directly inside the adsorption-catalytic bed. The capability and high efficiency of the proposed
technological approach are confirmed by process simulation. The approach proposed is shown to open a way for the creation
of an inexpensive, reliable and energy-saving adiabatic packed bed methane processors of unlimited processing capacity. 相似文献
997.
In this paper we study the homogeneous relativistic heat equation (HRHE) obtained as asymptotic limit of the so-called relativistic
heat equation (RHE) when the kinematic viscosity ν → ∞. These equations were introduced in the theory of radiation hydrodynamics
to guarantee a bounded speed of propagation of radiating energy. We shall prove that this is indeed true, and we shall construct
some explicit solutions of the HRHE exhibiting fronts propagating at light speed. 相似文献
998.
Erosion is one of the major problems in many industrial processes, and in particular, in heat exchangers. The effects of flow velocity and sand particle size on the rate of erosion in a typical shell‐and‐tube heat exchanger were investigated numerically using the Lagrangian particle‐tracking method. Erosion and penetration rates were obtained for sand particles of diameters ranging from 10 to 500 µm and for inlet flow velocities ranging from 0.197 to 2.95 m/s. A flow visualization experiment was conducted with the objective of verifying the accuracy of the continuous phase calculation procedure. Comparison with available experimental data of penetration rates was also conducted. These comparisons resulted in a good agreement. The results show that the location and number of eroded tubes depend mainly on the particle size and velocity magnitude at the header inlet. The rate of erosion depends exponentially on the velocity. The particle size shows negligible effect on the erosion rate at high velocity values and the large‐size particles show less erosion rates compared to the small‐size particles at low values of inlet flow velocities. The results indicated that the erosion and penetration rates are insignificant at the lower end of the velocity range. However, these rates were found to increase continuously with the increase of the inlet flow velocity for all particle sizes. The particle size creating the highest erosion rate was found to depend on the flow velocity range. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
999.
车用潜热贮热器的流动与换热实验研究 总被引:5,自引:0,他引:5
本文通过对车用潜热贮热器流动与换热实验研究,获得了该相变过程的流动、传热特性,为修正该装置的设计提供了可靠的数据. 相似文献
1000.