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91.
本文首先回顾了反斯托克斯荧光制冷的历史发展,简单讨论了激光制冷的循环过程及其制冷条件;其次,概述了反斯托克斯Raman散射、反斯托克斯荧光制冷的热力学理论和热力学限制,重点介绍了适用于各种制冷材料(如稀土离子掺杂玻璃、半导体和晶体等)反斯托克斯荧光制冷研究的理论模型,并简单讨论了激光制冷实验中各种测量温度变化的实验方法及其基本原理。最后,就反斯托克斯荧光制冷的一种最新应用及其前景进行了简单介绍与展望。 相似文献
92.
J. C. Li J. Zhu Z. J. Peng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):325-330
We study analytically and numerically the properties of one-dimensional
chain of cold ions placed in a periodic potential of optical lattice
and global harmonic potential of a trap.
In close similarity with the Frenkel-Kontorova model, a transition from
sliding to pinned phase takes place with the increase of
the optical lattice potential for the density of ions
incommensurate with the lattice period. We show that at zero temperature the quantum
fluctuations lead to a quantum phase transition
and melting of pinned instanton glass phase at large values of dimensional Planck constant.
After melting the ion chain can slide in an optical lattice.
The obtained results are also relevant for a Wigner crystal placed
in a periodic potential. 相似文献
93.
We proposed for the first time the concept of the nano liquid-metal fluid, aiming to establish an engineering route to make the highest conductive coolant. Using several widely accepted theoretical models for characterizing the nano fluid, the thermal conductivity enhancement of the liquid-metal fluid due to addition of more conductive nano particles was predicted. Further, the effects of particle size, cluster of nano particle, solid-like layer due to adsorption, volume fraction and particle types were evaluated. Having the highest conductivity, being electromagnetically drivable, the liquid metal with low melting point is expected to be an idealistic base fluid for making super conductive solution which may lead to the ultimate coolant in a wide variety of heat transfer enhancement area. 相似文献
94.
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96.
Toshinobu Kanai Hiroki Ishibashi. Yoshikazu Hayashi Kunio Oka Takaaki Dohmaru Tatsuo Ogawa Shoji Furukawa Robert West 《Journal of Polymer Science.Polymer Physics》2001,39(11):1085-1092
The thermochromic behavior of poly(di‐n‐octylsilane) {[Si(C8H17)2]n; PDOS} was studied by ultraviolet (UV) absorption, differential scanning calorimetry, and X‐ray diffraction measurements. The structure of PDOS in the low‐temperature phase strongly depended on not only the temperature but also the rate of cooling, that is, the thermal history. Temperature‐dependent UV absorption spectra were highly dependent on thermal hysteresis. Cooled rapidly (10 K/min), PDOS showed two absorption peaks at 3.32 and 3.51 eV in low‐temperature‐ordered phases, whereas a single absorption peak at 3.32 eV became predominant with slow cooling (0.3 K/min). The appearance of the two peaks at low temperatures suggested that a mixture of different conformations was introduced by rapid cooling. A fiber diffraction pattern measured at 240 K after rapid cooling also showed evidence of the existence of novel conformation. A temperature‐dependent powder X‐ray diffraction pattern changed significantly between 270 and 280 K. Rapid cooling reduced the intensity of the X‐ray diffraction peak in this temperature region. This intensity change was explained by the conformational mixture in the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1085–1092, 2001 相似文献
97.
98.
Y. Hashimoto L. Matsuoka D. NagamotoS. Hasegawa 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
We developed an ion trap — laser cooling system for observing the laser induced fluorescence (LIF) of a single ion, in the view of utilizing it for the trace isotope analysis of Ca. We observed stepwise LIF signals, which correspond to the numbers of trapped 40Ca+ ions (40Ca/Ca = 96.9%). The detection efficiency was evaluated and the observation of single ions demonstrated the experimental feasibility of trace isotope analysis. Furthermore, as the next step towards trace isotope analysis, we report observation of the even calcium isotopes, 44Ca (44Ca/Ca = 2.09%) and 48Ca (48Ca/Ca = 0.187%), without the use of a selective loading method. 相似文献
99.
Improving the specularity of magnetic mirrors for atoms 总被引:1,自引:0,他引:1
G. Zabow M. Drndić J.H. Thywissen K.S. Johnson R.M. Westervelt M. Prentiss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):351-359
An array of anti-parallel current-carrying wires creates an inhomogeneous magnetic field capable of reflecting neutral atoms.
We present analytical and numerical analyses of the magnetic field produced by such an array, and describe methods for reducing
the resulting rms angular deviation from specular reflection to less than 0.1 mrad. Careful choice of cross-sectional wire
profiles is shown to dramatically improve specularity of reflection close to the surface. Additionally, we find that the specularity
depends on whether the number of wires in the mirror is even or odd, and that there exists an optimal turning height above
the surface that maximizes the specularity of reflection from the mirror.
Received 16 November 1998 相似文献
100.
Hakvoort G. Hol C. M. van Ekeren P. J. 《Journal of Thermal Analysis and Calorimetry》2001,64(1):367-375
A number of compounds is investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions
and can be applied both for temperature and for heat calibrations. A third compound, namely 4,4’-azoxyanisole, has a liquid
crystal to isotropic liquid transition at 409K. This compound can be used for temperature calibration. Heat calibration with
this compound is more problematic because of the small heat effect and the construction of the baseline. Other compounds like
NaNO3, In, Hg and Pb, show a slight supercooling. Nevertheless they can be used for heat calibration. The use of large samples
of NaNO3 and In gives the possibility to construct the equilibrium onset temperatures of the cooling peaks, so these two compounds
are also appropriate for temperature calibration on cooling.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献