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101.
The choir singer has two acoustic signals to attend to: the sound of his or her own voice (feedback), and the sound of the rest of the choir (reference). The balance in loudness between feedback and reference is governed mainly by the room acoustics. Although earlier experiments have shown that singers have a fairly large tolerance for imbalance, with references ranging from −23 to +5 dB, experience suggests that, when singers are given control over this parameter, their preferences are much narrower. A quantification of the optimum balance would be useful in the design of concert stages and rehearsal halls. A method is described for measuring the feedback and reference levels as experienced by singers under live performance conditions. Recordings were made using binaural microphones worn by choir singer subjects. With the given combination of choir and room, it was possible to achieve adequate separation of the feedback and reference signals with simple signal processing. The feedback-to-reference ratio averaged over the 12 singers was found to be +3.9 dB, with extremes of +1.5 and +7.3 dB. 相似文献
102.
I.IntroductionAnti-soundisalsocal1edactivenoisecontro1(ANC).Itsbasicidea,presentedintheLueg'spatentinl936l'l,isthatthenoisereductionisobtainedbyuseofthesignalpro-cessingofthepreliminarysoundsource(i.e.noisesource)toformcoherenceinfluencebe-twccnthepreliminarysoundsourceandthesecondarysoundsourcc(i.c.anti-soundsource).Therearesomeadvantagesofanti-soundsuchasactivecontro1,lcsseffectonthecharacteristicsofnoisesourccandmorereductionoflowfrequcncynoisc.Inrecentyears,therewerealotoftheoreticalande… 相似文献
103.
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105.
It has been shown experimentally that the channel wall material has a substantial effect on the behaviour of Hall discharges. For this reason, the radial profile inside the Hall thruster SPT‐100 is investigated in detail. This is done by a one‐dimensional fully kinetic self‐consistent Particle‐in‐Cell model between the two walls in the acceleration region of the channel. A detailed Monte Carlo probabilistic model for secondary electron emission is implemented as boundary module. Using the local field approximation, two different operative conditions (axial electric field Ez =100 V/cm and 300 V/cm) have been simulated. For high discharge voltage case, a strong radial asymmetry and a stream instability propagating all along the radial domain are detected, while in the low voltage case a stable classical situation is recovered. The critical parameters for triggering this unstable regime are the electron azimuthal drift energy and the induced secondary electron emission, while the saturation mechanism is the increasing of the temperature of the initially cold secondary‐electrons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
106.
107.
The purpose of this study was to determine whether individuals show differences in speech and voice during reading of the same news before and after attending a radio announcing course. Twenty-five students of a Radio Announcing Course in Sao Paulo city, 17 men and 8 women, aged 19 to 55 years, participated in this study. The readings were recorded in a professional audio studio, and the speech samples were submitted to perceptual and acoustic analysis. For the perceptual analysis, the samples were randomly presented in pairs and five trained speech pathologists identified each recording as pre- and posttraining, and also justified their choices by indicating what parameters better based their judgment: type of voice, articulation and pronunciation, loudness, pitch, resonance, speech rate, respiratory coordination, and use of emphasis. The acoustic parameters analyzed were mean, minimum, and maximum fundamental frequency, frequency range, text duration, and pause duration. The perceptual analysis showed that the posttraining speech samples were considered the best productions in 80% of the evaluations. Emphasis characterized the readings (70.4%), followed by type of voice (44.8%) and pitch (40.8%). Acoustic analysis showed higher mean fundamental frequency and increase of frequency range posttraining. These results indicated richer modulation in the posttraining readings. There are differences in the readings of the same news pre- and posttraining in a radio announcing course, and the posttraining reading was considered the best production, indicating the positive effect of the training. 相似文献
108.
Y. W. Yao F. G. Wu Z. L. Hou Y. Y. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):353-360
The transmission and reflection coefficients of two-dimensional semi-infinite solid-solid phononic crystal systems and fluid-fluid
phononic waveguide structures have been investigated. The numerical results show that the transmission spectra for longitudinally
and transversally polarized incident waves are different, and the spectra of the transmission and reflection coefficients
of the semi-infinite system agree well with the band structure. The numerical results show that when a guided wave incident,
localized modes are excited, and different polarities have different coupling efficiencies with the incident guided wave.
At the same time, far from the cutoff frequency, the guided wave couples out of semi-infinite waveguide highly efficiently. 相似文献
109.
T. Hamida T. Babadagli 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):447-462
This paper aims at identifying and analyzing the influence of
high-frequency, high-intensity ultrasonic radiation at the interface between
immiscible (different types of oils and aqueous solutions) and miscible
(different types of oil and solvent) fluids. An extensive set of Hele-Shaw
type experiments were performed for several viscosity ratios, and
interfacial tension. Fractal analysis techniques were applied to quantify
the degree of fingering and branching. This provided a rough assessment of
the degree of perturbation generated at the interface when the capillary
forces along with the viscous forces are effective. Miscible Hele-Shaw
experiments were also presented to isolate the effect of viscous forces. We
found that ultrasound acts to stabilize the interfacial front, and that such
effect is most pronounced at low viscosity ratios.
An erratum to this article is available at . 相似文献
110.
N. Mujica R. Wunenburger S. Fauve 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):209-213
We report an experimental study of the scattering of a sound wave of frequency f by a surface vibrating at frequency F. Both the Doppler shift at the vibrating surface and acoustic nonlinearities in the bulk of the fluid, generate the frequencies
f±nF (n integer) in the spectrum of the scattered wave. We show that these two contributions can be separated because they scale
differently with respect to the vibration frequency and to the distance between the vibrating scatterer and the detector.
We determine the parameter ranges in which one or the other mechanism dominates and present quantitative studies of these
two regimes.
Received 2 December 2002 / Received in final form 27 March 2003 Published online 4 June 2003
RID="a"
ID="a"e-mail: fauve@physique.ens.fr
RID="b"
ID="b"UMR 8550 相似文献