全文获取类型
收费全文 | 301篇 |
免费 | 59篇 |
专业分类
化学 | 1篇 |
晶体学 | 4篇 |
力学 | 1篇 |
物理学 | 354篇 |
出版年
2013年 | 2篇 |
2010年 | 5篇 |
2009年 | 71篇 |
2008年 | 72篇 |
2007年 | 50篇 |
2006年 | 19篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 14篇 |
2002年 | 21篇 |
2001年 | 24篇 |
2000年 | 17篇 |
1999年 | 15篇 |
1998年 | 12篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有360条查询结果,搜索用时 15 毫秒
51.
Jian Zhou 《Physics letters. A》2008,372(48):7183-7186
The radial breathing-like mode (RBLM), an interesting Raman mode, of the carbon nanoribbons (CNRs) with different widths have been calculated by the empirical Brenner potential. It is found that the RBLM frequencies of CNRs whose widths are larger than 25 Å follow a new 1/w rule, which is different from the rule, obtained for the narrow CNRs [J. Zhou, J. Dong, Appl. Phys. Lett. 91 (2007) 173108]. A continuum rod model is proposed to explain the new 1/w rule, which is also different from the previous simple one-dimensional oscillator model, suitable only for the narrow CNRs. Based upon the CNR's RBLMs, we have proposed a practical experimental method to determine the widths of CNRs by their Raman spectra. 相似文献
52.
P. Dietrich F. Michalik R. Schmidt C. Gahl G. Mao M. Breusing M. B. Raschke B. Priewisch T. Elsässer R. Mendelsohn M. Weinelt K. Rück-Braun 《Applied Physics A: Materials Science & Processing》2008,93(2):285-292
A mild and efficient procedure has been developed to obtain covalently attached self-assembled monolayers (SAMs) on Si(111)
with photochromic azobenzene head-groups. Starting from neat or diluted carboxylic acid functionalized monolayers on-chip
coupling reactions were applied to attach hydroxyl-functionalized azobenzene units to the SAMs by ester bond formation. The
modified surfaces were characterized by high-resolution X-ray photoelectron spectroscopy (XPS), transmission Fourier transform
infrared spectroscopy (FT-IR), and contact angle measurements. Reversible cis
↔
trans isomerizations of photoswitchable SAMs were monitored by wettability measurements.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users.
Dedicated with respect and compliments to Professor Helmut Schwarz on the occasion of his 65th birthday. 相似文献
53.
A. Paolone P. Roy A. Pimenov A. Loidl A.A. Mukhin A.M. Balbashov 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):245-250
The optical conductivity of La0.85Sr0.15MnO3 single crystals was studied by means of submillimeter and infrared spectroscopy for frequencies cm-1 and temperatures 10 K <
T
<300 K. The submillimeter conductivity follows the temperature dependence of the dc-data. The phonon spectrum of La0.85Sr0.15MnO3 changes considerably below K revealing a structural phase transition induced by charge or orbital order. At T
=10 K a number of phonon modes can be identified in addition to the room-temperature spectrum. The optical conductivity () in the mid-infrared reveals the characteristics of small polaron absorption. Below the magnetic ordering temperature the
polaron binding energy is highly reduced, but the onset of charge order interrupts the formation of free charge carriers with
a Drude-like behavior. The frequency and temperature dependence of in this regime qualitatively resembles the small polaron predictions by Millis et al. (Phys. Rev. B 54, 5405 (1996)).
Received 5 November 1999 相似文献
54.
B. Ratajska-Gadomska W. Gadomski 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):281-288
Herewith we report on the measurements of the time evolution of the fluorescence yield and the Rayleigh scattering, performed
during the gelation process in the following solutions: gelatin in water, gelatin in a heavy water and agarose in water. Our
results provide the experimental evidence of the universal power law, resulting from the percolation theory, which expresses
the dependence of the fluorescence yield on the number of intermolecular bonds created during the sol-gel transition. The
values of universal critical exponents present in this law are found to have the same values for all investigated materials.
Received 4 May 2000 相似文献
55.
M. Sassetti F. Napoli B. Kramer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):643-654
Using the bosonization technique, a theory for the collective excitations of the interacting electrons in quantum wires with
two subbands occupied is developed. The dispersion relations for the inter-subband charge and spin density excitations are
determined. The results are used to interpret the features observed in recent measurements of the Raman spectra of AlGaAs/GaAs
quantum wires, particularly for photon energies near band gap resonance. It is shown that peaks previously identified as “single
particle excitations” are signatures of higher order collective spin density excitations. Predictions about the observability
of the interband modes are made.
Received 8 February 1999 相似文献
56.
H. Hornburger M. Melzig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(2):173-180
It is shown that predissociation can be perceived as a primary process due to the continuum part of a Morse oscillator potential.
In the model proposed here internal conversion to the ground state is thus not necessarily the primary process of a consecutive
dissociation but may be a simultaneous decay. As a consequence, dissociation rates should show strong variations from specific
(ro-) vibrational states of the first excited electronic states that are similar to those known from “pure” internal conversion
rates. This behaviour is demonstrated by calculating predissociation rates for the process. Especially the out-of-plane modes seem to play an extraordinary role in the excess energy behaviour of the predissociation
rate. At lower excess energies, rates from single vibronic levels with out-of-plane mode characteristics may show an increase
by several orders of magnitude.
Received: 13 November 1998 相似文献
57.
Young-Dae Jung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):291-294
The classical electron-ion Coulomb Bremsstrahlung process is investigated in nonideal plasmas. An effective pseudopotential
model taking into account the plasma screening and collective effects is applied to describe the electron-ion interaction
potential in a classical nonideal plasma. The classical straight-line trajectory method is applied to the motion of the projectile
electron in order to visualize the variation of the differential Bremsstrahlung radiation cross-section (DBRCS) as a function
of the scaled impact parameter, nonideal plasma parameter, projectile energy, photon energy, and Debye length. The results
show that the DBRCS in ideal plasmas described by the Debye-Hückel potential is always greater than that in nonideal plasmas,
i.e., the collective effects reduce the DBRCS for both the soft and hard photon cases. For large impact parameters, the DBRCS
for the soft photon case is found to be always greater than that for the hard photon case.
Received 1st December 1999 相似文献
58.
K. Bescherer J. A. Barnes S. Dias G. Gagliardi H.-P. Loock N. R. Trefiak H. Waechter S. Yam 《Applied physics. B, Lasers and optics》2009,96(1):193-200
Multi-exponential decay waveforms are common occurrences in cavity ring-down spectroscopy and the respective ring-down times
are typically obtained by fitting the ring-down waveform to the sum of exponential decay functions. In phase-shift cavity
ring-down (CRD) spectroscopy the measurement of a single phase angle will not provide sufficient information and needs to
be complemented by either intensity measurements or phase angle measurements at different modulation frequencies. Here, a
formalism analogous to that developed for fluorescence lifetime spectroscopy is adapted to the phase-shift CRD technique and
is tested for two types of waveguide CRD systems: (1) a single-mode fiber cavity in which light is confined by two identical
Fiber Bragg Gratings and (2) a multimode fiber loop. By measuring the phase angle at different modulation frequencies, lifetimes
for up to three different decay processes were obtained. 相似文献
59.
D. S. L. Pontes E. Longo F. M. Pontes M. S. Galhiane L. S. Santos Marcelo A. Pereira-da-Silva J. H. D. da Silva A. J. Chiquito P. S. Pizani 《Applied Physics A: Materials Science & Processing》2009,96(3):731-740
Ferroelectric Pb1−x−y
Ca
x
Sr
y
TiO3 thin films (denoted by PCST90, PCST70, and PCST30) were deposited on the Pt/Ti/SiO2/Si substrates by a chemical solution deposition method. Their properties were investigated from the viewpoint of crystal
structure, microstructure, dielectric, and ferroelectric properties. X-ray diffraction patterns revealed the formation of
PCST90, PCST70, and PCST30 thin films without any secondary phases. Infrared and Raman spectroscopy results show that a gradual
phase transition from tetragonal to pseudocubic or cubic perovskite structure may occur in PCST thin films with the simultaneous
increase of Ca2+ and Sr2+ contents. Both substitution of isovalent Ca2+ and Sr2+ at Pb2+-site enhanced the dielectric constant and reduced the remnant polarization. In addition, ferroelectric test analyses show
that the PCST thin films undergo a ferroelectric-to-paraelectric phase transformation with an amount of Pb2+, Ca2+, and Sr2+ at 30%, 35%, and 35% mol, respectively. Hence, the absence of ferroelectric property may be attributed to a decreasing of
the octahedron distortion in the perovskite structure accompanied by a weakening of long-range ferroelectric order. 相似文献
60.
Lead-free (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics have been prepared by an ordinary sintering technique and their structure, ferroelectric and piezoelectric properties
have been studied. The results of X-ray diffraction show that La2+ and Ba2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a new solid solution with a pure perovskite structure, and a morphotropic phase boundary (MPB) exists at
0.04<x<0.10. Compared with pure Bi0.5Na0.5TiO3 ceramics, the (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics possess much smaller coercive field E
c and larger remanent polarization P
r. Because of the low E
c (3.38 kV/mm), large P
r (46.2 μC/cm2) and the formation of the MPB of rhombohedral and tetragonal phases, the piezoelectric properties of the ceramics are significantly
enhanced at x=0.06: d
33=181 pC/N and k
p=36.3%. The depolarization temperature T
d reaches a minimum value near the MPB. The ceramics exhibit relaxor characteristic, which is probably a result from the cation
disordering in the 12-fold coordination sites. The temperature dependences of the ferroelectric and dielectric properties
suggest that the ceramics may contain both polar and non-polar regions at the temperatures above T
d. 相似文献