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971.
972.
Z. Kozhoukharova C. Rozé 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):125-135
The primary stationary and oscillatory Bénard-Marangoni instability is investigated in a fluid layer of infinite horizontal
extent, bounded below by a rigid plane and above by a deformable upper surface, subjected to a vertical temperature gradient.
Since the viscosity is temperature-dependent the consequences of relaxing Oberbeck-Boussinesq approximation and free surface
deformability are theoretically examined by means of small disturbance analysis. The problem has been solved numerically by
the Taylor series expansion method. The results obtained confirm that when the free surface is undeformable, stationary convection
develops in the form of polygonal cells, and oscillatory motion cannot be detected. When the surface deformability is considered,
stationary convection sets in, either as a short-wavelength hexagonal instability or as a long-wavelengh mode or as both,
and oscillatory convection is also possible. The stability threshold for the short-wavelength mode depends mainly on the viscosity
variation while the long-wavelength mode is determined by the surface deformation. Numerically, it is found that the neutral
oscillatory Marangoni numbers are only negative. When a variable-viscosity model is used the theoretical and experimental
results are in better agreement.
Received 15 May 1997 相似文献
973.
H. Feldmann R. Oppermann 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):429-445
We analyse the competition between spin glass (SG) order and local pairing superconductivity (SC) in the fermionic Ising spin
glass with frustrated fermionic spin interaction and nonrandom attractive interaction. The phase diagram is presented for
all temperatures T and chemical potentials μ. SC-SG transitions are derived for the relevant ratios between attractive and frustrated-magnetic
interaction. Characteristic features of pairbreaking caused by random magnetic interaction and/or by spin glass proximity
are found. The existence of low-energy excitations, arising from replica permutation symmetry breaking (RPSB) in the Quantum
Parisi Phase, is shown to be relevant for the SC-SG phase boundary. Complete 1-step RPSB-calculations for the SG-phase are
presented together with a few results for -step breaking. Suppression of reentrant SG-SC-SG transitions due to RPSB is found and discussed in context of ferromagnet-SG
boundaries. The relative positioning of the SC and SG phases presents a theoretical landmark for comparison with experiments
in heavy fermion systems and high superconductors. We find a crossover line traversing the SG-phase with as its quantum critical (end)point in complete RPSB, and scaling is proposed for its vicinity. We argue that this line indicates
a random field instability and suggest Dotsenko-Mézard vector replica symmetry breaking to occur at low temperatures beyond.
Received 26 November 1998 and Received in final form 25
January 1999 相似文献
974.
It is shown that for Gaussian diffusions, the transformation back to Brownian motion, usually accomplished via the Girsanov (or Feynman–Kac) formula and time-shift, can be obtained by a classical canonical, i.e. symplectic, transformation in phase space. The method is based on constants of motion, in this case the Wronskian. Similar transformations for general diffusions are briefly discussed. 相似文献
975.
976.
977.
The new capabilities of AC calorimetry, when working at frequencies above the classical limit were demonstrated. The appropriate frequency range of classical AC calorimetry was substantially enlarged. It was shown that the advanced AC calorimetry can be applied for studying dynamic heat capacity of polymers in the frequency range 0.1–1 Hz. Thus, the processes with characteristic time as short as ca. 5 s was registered. The advanced AC technique was applied for investigation of the melting kinetics in polycaprolactone. It was found that melting in polycaprolactone is related to an activated process. The activation of the melting process after a step heating is described by a stretched exponent and the decay of the melting by only one exponent at short times. The dependencies of the exponent on temperature and thermal treatment were investigated at frequencies in the range 0.1–1Hz and modulation amplitudes 0.005–0.2 K. 相似文献
978.
Water vapor sorption on morphine sulphate was studied in a twin double sorption microcalorimeter at 25°C. The vapor sorption isotherm and the differential heats of sorption were determined simultaneously from dry condition to a water activity of 0.99. Two well resolved hydration steps were obtained on the sorption isotherm at water activities of 0.01 and 0.22 corresponding to the formation of dihydrate and pentahydrate of morphine sulphate. They were accompanied by constant values of the differential heats of sorption: –24 kJ mol–1(H2O) for the dihydrate formation and –10 kJ mol–1(H2O) for the pentahydrate formation.The calorimetrically obtained sorption isotherms were compared with the results of Karl Fisher titrations of morphine sulphate samples equilibrated at different water activities. The appearance of a liquid phase in the morphine sulphate at high water activities is discussed on the basis of the obtained differential heats of sorption and measured heat capacities of morphine sulphate at different water activities.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
979.
J. Ma. Rincon J. Cáceres C. J. González-Oliver D. O. Russo A. Petkova H. Hristov 《Journal of Thermal Analysis and Calorimetry》1999,56(2):931-938
A study of three Spanish and one Bulgarian basaltic rock demonstrated that, after thermal treatment at temperatures higher
than 800°C, crystallization of pyroxenes, anorthite and magnetic occurred. Following sintering of the original basalts and
powdered original glasses, the same crystalline phases were nucleated and grown in the resulting glass-ceramics. Chemical
and DTA/TG analyses suggested similar behaviour for the synthesized Canarian basalt glasses, which are located in the tephrite-basanite
field, and different behaviour for the trachy-andesite Canarian and the basaltic-andesite Bulgarian basalt glass. In consequence
of the high sensitivity of the specific heat to phase transformations, Cp(T) and TMA experiments allowed a distinction between the tephrite-basanite and trachy-andesite Canarian glasses on the basis
of their different thermal behaviour.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
980.
The steady state of temperature modulated power compensation DSC has been theoretically investigated for measurements of complex
heat capacity, taking accounts of heat capacities of heat paths, heat loss to the environment, and mutual heat exchange between
the sample and the reference material. Thermal contact between the sample cell and the cell holder is also taken into accounts.
Rigorous and general solutions are obtained. From these solutions application of the technique to heat capacity measurements
is discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献