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41.
J. W. Goodman 《Applied Physics A: Materials Science & Processing》1973,2(2):95-101
The accuracy with which the amplitude and phase of an interference fringe can be measured in quasi-thermal light is limited
by the finite integration time used. The statistical errors expected in such a measurement are derived analytically, and their
dependence on measurement time, the coherence time of the light, and the complex coherence factor are explored. An example
illustrating the utility of the results is presented.
Work supported by the Office of Naval Research 相似文献
42.
Hitoshi Fujii Toshimitsu Asakura 《Applied Physics A: Materials Science & Processing》1974,3(2):121-129
The general formula for multiple-beam interference due to regular slit arrays illuminated with partially coherent quasi-monochromatic
light is derived. The correlation functions chosen for partially coherent light assume Gaussian, sinc and besinc forms of
correlation. The intensity distribution in the interference patterns is presented and discussed as a function of the spatial
coherence condition. It is shown that spatial coherence of the illumination largely affects the features of multiple-beam
interference patterns. 相似文献
43.
The generalized Stokes parameters, which are two-point extensions of conventional Stokes parameters, are determined for a pair of points in the cross-section of a partially coherent broadband light beam. For this purpose, using a two-mirror and two-beam-splitter assembly, unpolarized, linearly polarized and partially polarized electromagnetic beams are generated. This simple experimental method for determining generalized Stokes parameters establishes an analogy with the experimental scheme of determining conventional Stokes parameters, which in succession contributes to appreciable reduction in uncertainty in the measurements. 相似文献
44.
45.
Emil Wolf 《Optics Communications》2011,284(22):5240-5241
Two-beam interference law for the superposition of stochastic, spatially coherent, electromagnetic beams is derived. Only a single phase is found to enter the interference law, in spite of the vector nature of the problem. The meaning of the phase is elucidated. 相似文献
46.
A. Harfouche 《Optics Communications》2011,284(22):5348-5352
It has been demonstrated in a previous work (Opt. Commun. 233 (2004) 39-43), for a monochromatic laser beam, that imperfect collimation leads to systematic errors in the determination of the spectral bandwidth of a Gaussian beam. In this work, we demonstrate that such transverse effects could also make wrong the measurement of the coherence length of a non-monochromatic Gaussian beam. In addition, we have demonstrated that this systematic error is increased when the laser beam under study is made up of a mixing of spatial modes. 相似文献
47.
Lin J Griffin RG Khaneja N 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,212(2):402-411
The paper describes two-dimensional solid state NMR experiments that use powdered dephased antiphase coherence (γ preparation) to encode chemical shifts in the indirect dimension. Both components of this chemical shift encoded gamma-prepared states can be refocused into inphase coherence by a recoupling element. This helps to achieve sensitivity enhancement in 2D NMR experiments by quadrature detection. The powder dependence of the gamma-prepared states allows for manipulating them by suitable insertion of delays in the recoupling periods. This helps to design experiments that suppress diagonal peaks in 2D spectra, leading to improved resolution. We describe some new phase modulated heteronuclear and homonuclear recoupling pulse sequences that simplify the implementation of the described experiments based on γ prepared states. Recoupling in the heteronuclear spin system is achieved by matching the difference in the amplitude of the sine/cosine modulated phase on the two rf-channels to the spinning frequency while maintaining the same power on the two rf-channels. 相似文献
48.
We develop a notion of an n-fold monoidal category and show that it corresponds in a precise way to the notion of an n-fold loop space. Specifically, the group completion of the nerve of such a category is an n-fold loop space, and free n-fold monoidal categories give rise to a finite simplicial operad of the same homotopy type as the classical little cubes operad used to parametrize the higher H-space structure of an n-fold loop space. We also show directly that this operad has the same homotopy type as the n-th Smith filtration of the Barratt-Eccles operad and the n-th filtration of Berger's complete graph operad. Moreover, this operad contains an equivalent preoperad which gives rise to Milgram's small model for when n=2 and is very closely related to Milgram's model of for n>2. 相似文献
49.
Using pulsed-field-gradient (PFG) experiments, the sizes of the pores in ordered porous media can be estimated from the "diffraction" pattern that the signal attenuation curves exhibit. A different diffraction pattern is observed when the experiment is extended to a larger number (N) of diffusion gradient pulse pairs. Simulations to calculate signal values from arbitrary gradient waveforms are performed for diffusion in restricted geometries using a matrix operator formalism. The simulations suggest that the differences in the characteristics of the attenuation curves are expected to make it possible to measure smaller pore sizes, to improve the accuracy of pore size measurements and potentially to distinguish different pore shapes using the N-PFG technique. Moreover, when an even number of PFG pairs is used, it is possible to observe the diffraction pattern at shorter diffusion times and measure an approximation to the average pore size even when the sample contains pores with a broad distribution of sizes. 相似文献
50.
Sh.B. Abdulvagidov I.K. Kamilov 《Physica C: Superconductivity and its Applications》2008,468(6):453-457
To study a behavior of the thermal conductivity near Tc specific heat and thermal diffusivity of the YBa2Cu3O7−δ high-Tc ceramics were simultaneously measured. Close to Tc = 92.30 K the thermal diffusivity and the thermal conductivity discovered minima and the specific heat – maximum. Quantitative analysis of the influence of thermodynamical fluctuations showed the same power laws with Gaussian exponent equal to 0.5 and existing of crossover from the 3D Gaussian to 3D XY critical behavior in the specific heat and thermal conductivity at the approach to Tc. To explain the minimum in thermal conductivity at Tc we propose a mechanism of scattering of phonons on the superconducting fluctuations. 相似文献