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141.
An end pumped Nd:YAP laser at 1341 nm is actively mode locked and passively Q-switched. Pumping was done with a pulsed high power laser diode with maximum power 425 W. V3+:YAG with 61% initial transmission served as saturable absorber, and an acousto-optic modulator is used for active mode locking. The output pulse train with 69 ns duration has a total energy of 3.2 mJ with ±4% shot-to-shot fluctuation. The peak output energy of a single mode locked pulse is 0.25 mJ. The pulse duration of a single mode locked pulse is less than 800 ps. The output laser beam is nearly diffraction limited with 1.6 mm diameter, and beam propagation factor M2 about 1.3. 相似文献
142.
In this paper, a coupled-cavity Er-doped fiber laser is experimentally developed and analyzed. The proposed scheme has the advantage of an all-fiber configuration. Two similar fiber Bragg gratings are employed as reflective components of the main cavity containing the gain medium. The second cavity is generated, in one side, by the reflective flat end of a standard fiber optic pigtail of variable length and, in the other, by one of the Bragg gratings belonging to the main cavity. Depending on the ratio between the lengths of both cavities, trains of stable and short pulses were obtained with a repetition frequency larger than the frequency of the main cavity. The repetition rate of the pulse trains experimentally obtained was as high as 780 MHz (15 times the main cavity frequency) and the pulse width was ∼110 ps. Prediction of the possible repetition rates for each cavities lengths ratio and the upgrading possibilities of this laser system are analyzed. 相似文献
143.
A stable and short pulse train of ∼100 MHz repetition frequency was obtained from an erbium doped fiber laser excited by a “continuous” semiconductor laser and by using a linear cavity defined by a Bragg grating pair. The operation frequency of the fiber laser was greater (∼5-15 times) than the cavity round-trip frequency. Emission properties obtained from the erbium doped fiber laser were correlated with those taken from the pump laser, which presented a particular optical noise (very short pulses) added to the continuous emission. From the temporal and radio-frequency analysis of both systems, we conclude that the pump emission characteristics are the responsible of the fiber laser pulsed behaviour. 相似文献
144.
In this paper, we give an alternative suggestion that both the observed optical and electron paramagnetic resonance (EPR) spectra of Yttrium oxide (Y2O3):V3+ are attributed to V3+ ions at the S6 site of Y2O3. This suggestion is different from the opinion in the previous paper that the optical and EPR spectra are attributed to V3+ ions at the C2 and S6 sites, respectively. From the suggestion, the optical band positions and spin-Hamiltonian parameters are calculated by diagonalizing the complete energy matrix for 3d2 ions in trigonal symmetry. The results are in good agreement with the experimental values, suggesting that both the observed optical and EPR spectra in Y2O3:V3+ may be due to V3+ at S6 site of Y2O3 crystal. 相似文献
145.
A liquid nitrogen cooled dual-wavelength Tm,Ho:GdVO4 microchip laser is reported. The output dual wavelengths axe at 2038.9nm and 2050.1 nm. At each wavelength, the laser has a single longitudinal mode. The threshold power is nearly 20mW and the slope efficiency is 18.7%. The single longitudinal mode output power reaches 98mW, and the ratio of power is about 60% (2038.9nm) and 40% (2050.1 nm). 相似文献
146.
We report a highly efficient and high power self-starting femtosecond Cr:forsterite laser pumped by a 1064-nm Yb doped fibre laser. Five chirped mirrors are used to compensate for the intra-cavity group-delay dispersion, and the mode-locking is initiated by a semiconductor saturable absorber mirror (SESAM). Under pump power of 7.9 W, stable femtosecond laser pulses with average power of 760mW are obtained, yielding a pump power slope efficiency of 12.3%. The measured pulse duration and spectral bandwidth (FWHM) are 46 fs and 45 nm; the repetition rate is 82 MHz. 相似文献
147.
Physical Explanation on Designing Three Axes as Different Resolution Indexes from GRACE Satellite-Borne Accelerometer 总被引:8,自引:0,他引:8
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The GRACE Earth's gravitational field complete up to degree and order 120 is recovered based on the same and different three-axis resolution indexes from satellite-borne accelerometer using the improved energy conservation principle. The results show that designing XA1(2) as low-sensitivity axis (3 × 10^-9 m/s^2) of accelerometer and designing YA1(2) and ZA1(2) as high-sensitivity axes (3 × 10^-10 m/s^2) are reasonable. The physical reason why the resolution of XA1(2) is one order of magnitude lower than YA1(2) and ZA1(2) is that non-conservative forces acting on GRACE satellites are mainly decomposed into YA1(2) and ZA1(2) in the orbital plane. Since XA1(2) is not orthogonal accurately to orbital plane during the development of accelerometer, the measurement of XA1(2) can not be thrown off entirely, but be reduced properly. 相似文献
148.
Ji-Young Kim Vladimir P. Drachev Hsiao-Kuan Yuan Reuben M. Bakker Vladimir M. Shalaev 《Applied physics. B, Lasers and optics》2008,93(1):189-198
Periodic arrays of paired and single gold nanorods were imaged in the near field using reflection and transmission modes of
a near-field scanning optical microscope at various wavelengths and polarizations of light in the visible range. The paired
nanorods act like nanoantenna, and an array of them was initially designed as a negative-index material for the near infrared.
Reverse contrast in reflection and transmission images is observed under illumination from the small aperture of a metal-coated
fiber probe. By changing the relative orientation of the rods to the polarization, the reverse contrast switches to the normal
contrast of near-field imaging. Coupling between the aperture and the nanorod array makes the contrast higher. Transmission
through the aperture is enhanced if the aperture probe is positioned between the nanorods. The average near-field transmission
exhibits an opposite sign of anisotropy relative to the far-field case. Aperture probes with larger diameters always show
normal imaging contrast. The results demonstrate that the broad angular spectra of small-aperture sources play a crucial role
in near-field interactions with nanorod arrays. The results also show that angular redistributions of these spectra after
transmission or reflection from the nanorod array are likely due to excitation of localized and propagating plasmons. 相似文献
149.
Thorsten Ulm Florian Harth Harry Fuchs Johannes A. L’huillier Richard Wallenstein 《Applied physics. B, Lasers and optics》2008,92(4):481-485
This paper reports the generation of fs light pulses by a passively mode-locked InGaAs master oscillator power amplifier (MOPA)
system. The laser system generates chirped pulses with 6.2 ps duration, a center wavelength of 922 nm and 4 GHz repetition
rate. Pulse compression by an external grating compressor reduces the pulse duration to 580 fs. The average power of the compressed
pulses of 851 mW corresponds to a peak power of 366 W. 相似文献
150.
Near-field Scanning Optical Microscopy (NSOM) is a powerful tool for investigating optical field with resolution greater than
the diffraction limit. In this work, we study the spectral response that would be obtained from an aperture NSOM system using
numerical calculations. The sample used in this study is a bowtie nanoaperture that has been shown to produce concentrated
and enhanced field. The near- and far-field distributions from a bowtie aperture are also calculated and compared with what
would be obtainable from a NSOM system. The results demonstrate that it will be very difficult to resolve the true spectral
content of the near-field using aperture NSOM. On the other hand, the far-field response may be used as a guide to the near-field
spectrum. 相似文献