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71.
A surface-enhanced Raman scattering sensor is developed by etching polymer optical fiber and coating with gold nanorods. The SERS sensing experiments are demonstrated with the analyte molecules of rhodamine 6G (R6G) at 514.5 nm laser excitation. The results show that a strong fiber Raman background scattering overwhelm the R6G molecule Raman signal in common optrod configuration, but a distinct R6G SERS spectrum with 9 order magnitude enhancement can be observed while directly focusing light on the probe. Further modeling indicates the enhancement is attributed to both nanorods local field and their coupling. 相似文献
72.
Shifeng Du Dongxiang Zhang Baohua Feng Jing-Yuan Zhang Jing-Cun Zang 《Optics Communications》2009,282(14):2960-12186
We report the generation of high-peak power multi-wavelength picosecond laser pulses using optical parametric amplification (OPA) in BBO seeded with pulses generated in a 5-mm length BaWO4 crystal by stimulated Raman scattering of 18-ps laser pulses at 532 nm. The maximum output energy of the amplified first-Stokes component at 559.7 nm was about 1.76 mJ. The corresponding maximum peak power, pulse duration and spectral line width were measured to be 117.3 MW, 15 ps and 18.0 cm−1, respectively. The multi-wavelength picosecond laser pulses were in the visible and near infrared ranges. Using this Raman-seeded OPA technique, the beam quality of the stimulated Raman scattering pulses can be improved. 相似文献
73.
Formation and evolution details of a blocky microstructure in AISI 304 stainless steel are studied by quenching method during directional solidification. Results show that a coupled growth microstructure, consisting of lathy ferrite and austenite, forms first from the melt. At solid-state transformation stage, most lathy ferrite disappears due to the phase transformation from ferrite to austenite. With further decreasing of the temperature, plenty of fine ferrite colonies occur in the original austenite region. The formation of the blocky ferrite indicates that reverse solid-state transformation from austenite to ferrite takes place. This transformation is due to the segregation and the instability of austenite during the growth of austenite under low cooling rate. The fine ferrite colonies transform into blocky ferrite at room temperature. TEM and EDS analyses were carried out to identify the phases and determine the phase composition, respectively. 相似文献
74.
Defect configurations of Ge-S binary glasses have been studied systemically by Raman scattering technique and positron annihilation lifetime spectra (PALS). The correlations between the positron lifetime data, structural features, and chemical compositions of Ge-S binary glasses have been established, and also the identification of open volume originated from coordination defects has been carried out. The cognizance of defect configuration will be very helpful to further understand the unique photosensitivity of chalcogenide glasses. 相似文献
75.
Cells of Voronoi diagrams in two dimensions are usually considered as having edges of zero width. However, this is not the case in several experimental situations in which the thickness of the edges of the cells is relatively large. In this paper, the concept of a thick Voronoi tessellation, that is with edges of non-zero width, is introduced and the statistics of cell areas, as thickness changes, are analyzed. 相似文献
76.
L. Natarajan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):287-292
In this work, the multiplet splitting in terms of a spin-dependent model is analyzed. The spin-polarized and unpolarized single
configuration Dirac-Fock-Slater wavefunctions have been used in the evaluation of the total energies of highly ionized argon
with different L shell population The transition energies of hollow argon atom with initial configurations 1s
0
1/22s
m
1/22p
n
1/22p
l
3/2 with m = 0 to 2 and n + l varying from 6 to 1 are reported in this work. The calculations have been carried out by taking into account a relativistic
exchange potential in the Dirac-Slater potential. To account for the correlation effects, a correction term has also been
considered perturbatively. The present calculations show that the spin-polarized technique which is mainly applied to the
ground states of atoms may also be applied to atoms ionized in the inner shells with a good degree of accuracy.
Received 5 December 2000 and Received in final form 9 April 2001 相似文献
77.
M.E. Garcia H.O. Jeschke I. Grigorenko K.H. Bennemann 《Applied physics. B, Lasers and optics》2000,71(3):361-371
We present a theoretical study of the short-time relaxation of clusters in response to ultrafast excitations using femtosecond
laser pulses. We analyze the excitation of different types of clusters (Hgn, Agn, Sin, C60 and Xen) and classify the relaxation dynamics in three different regimes, depending on the intensity of the exciting laser pulse.
For low-intensity pulses (I<1012 W/cm2) we determine the time-dependent structural changes of clusters upon ultrashort ionization and photodetachment. We also study
the laser-induced non-equilibrium fragmentation and melting of Sin and C60 clusters, which occurs for moderate laser intensities, as a function of the pulse duration and energy.
As an example for the case of high intensities (I>1015 W/cm2), the explosion of clusters under the action of very intense ultrashort laser fields is described.
Received: 26 November 1999 / Published online: 2 August 2000 相似文献
78.
S. Krishnamurthy A. Tanguy S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):149-153
The depinning transition of a front moving in a time-independent random potential is studied. The temporal development of
the overall roughness w(L,t) of an initially flat front, , is the classical means to have access to the dynamic exponent. However, in the case of front propagation in quenched disorder
via extremal dynamics, we show that the initial increase in front roughness implies an extra dependence over the system size
which comes from the fact that the activity is essentially localized in a narrow region of space. We propose an analytic expression
for the exponent and confirm this for different models (crack front propagation, Edwards-Wilkinson model in a quenched noise etc.).
Received 27 August 1999 相似文献
79.
S.V. Golovkin A.P. Kozhevnikov V.P. Kubarovsky V.F. Kurshetsov L.G. Landsberg V.V. Molchanov V.A. Mukhin S.V. Petrenko V.A. Senko D.V. Vavilov V.A. Victorov V.Z. Kolganov G.S. Lomkatsi A.F. Nilov V.T. Smolyankin 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):409-416
New data for the diffractive reaction p+N→ [Σ0
K
+] +N at E
p= 70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous
study of this reaction. In the mass spectrum M(Σ0
K
+) a structure at the threshold region with a mass ∼1810 MeV and a distinct X(2000) peak with M= 1989 ± 6 MeV and γ= 91 ± 20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously
large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark
baryon with hidden strangeness |qqqsˉs>. We also present new results on the narrow threshold structure X(1810) with M= 1807 ± 7 MeV and γ= 62 ± 19 MeV which is produced in the region of very small P
2
T < 0.01 GeV2. The possibility of the Coulomb production mechanism for X(1810) is discussed.
Received: 28 April 1999 相似文献
80.
S. A. Aseyev Yu. A. Kudryavtsev V. V. Petrunin 《Applied physics. B, Lasers and optics》1993,56(6):391-398
The main properties of longitudinal and transverse electric field ionizers for fast Rydberg atoms n=21–40 have been investigated. The dispersion and the background due to collisional processes between fast atoms and residual gas molecules have been measured and calculated. The kinetic energy spread of ions formed by field ionization of Rydberg atoms and their trajectories have been calculated. The potassium beam energy was 3.9 keV. 相似文献