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971.
A generic Fourier-space approach to solve the self-consistent field theory of block copolymers is developed. This approach is based on the fact that, for any computational box with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the box. The method reproduces all known diblock copolymer phases. The application of this method to a model "frustrated" triblock copolymer leads to a phase diagram with a number of new phases. Furthermore, the capability of the method to reproduce experimentally observed structures is demonstrated using the knitting pattern of triblock copolymers. 相似文献
972.
We demonstrate that we realize large-delay slow light based on stimulated Brillouin scattering in a short length of our fabricated small-core photonic crystal fiber (PCF). The cavity effect from the partially reflective splices in the end of the PCF enhances slow-light delay significantly. Our experiments show that large slow-light delay can be easily realized in a very short length of the PCF with a moderate pump power. Up to a one-half pulse-width delay is achieved in only 50 m of PCF in a single pump segment. 相似文献
973.
Indoor barriers are now widely used for sound insulation. This paper examines the performance of indoor barriers in the low-medium frequency range and analyses the interaction between different natural modes of a room-barrier-room system. Morse proposed a theoretical model to calculate the sound field in a coupled-room, but this model neglects the surface integral of the boundary values of sound pressure. To estimate the performance of a barrier in an indoor environment, an analytical model is proposed that modifies the Green’s function for a non-rigid boundary enclosure and approximates the surface integral by a pre-estimated sound pressure based on Morse’s model. An additional approximation has been made in the proposed model to neglect the coupling area in the calculation of the surface integral. The proposed model used to predict the insertion loss of the barrier is verified by the experimental results using a 1:5 scale model. The predicted results agree well with the measured results at lower frequencies. 相似文献
974.
Jun Zhu Jianxian Qiu Chi-Wang Shu Michael Dumbser 《Journal of computational physics》2008,227(9):4330-4353
In [J. Qiu, C.-W. Shu, Runge–Kutta discontinuous Galerkin method using WENO limiters, SIAM Journal on Scientific Computing 26 (2005) 907–929], Qiu and Shu investigated using weighted essentially non-oscillatory (WENO) finite volume methodology as limiters for the Runge–Kutta discontinuous Galerkin (RKDG) methods for solving nonlinear hyperbolic conservation law systems on structured meshes. In this continuation paper, we extend the method to solve two-dimensional problems on unstructured meshes, with the goal of obtaining a robust and high order limiting procedure to simultaneously obtain uniform high order accuracy and sharp, nonoscillatory shock transition for RKDG methods. Numerical results are provided to illustrate the behavior of this procedure. 相似文献
975.
Considering the mixture after muon‐catalyzed fusion (μ CF) reaction as overdense plasma, we study muon motion in the plasma produced by a superintense linearly polarized femtosecond laser pulse. Muon drift along the propagation of laser radiation remains after the end of the laser pulse. At the peak laser intensity of 1021W/cm2, muon goes from the skin layer into field‐free matter at short time which is much less than the pulse duration, before the laser pulse reaches its maximum. Besides, the influence of the laser on other particles in the plasma is less. Hence, this work can avoid muon sticking to alpha (α) effectively and reduce muon‐loss probability in μ CF. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
976.
977.
978.
Jing‐Jun Ma Chun Wang Qiu‐Hua Wu Ran‐Xiao Tang Hai‐Yan Liu Qing Li 《Heteroatom Chemistry》2008,19(6):609-611
Xanthenedione derivatives were prepared through the condensation reaction of aromatic aldehydes with 5,5‐dimethyl‐1,3‐cyclohexanedione promoted by acidic ionic liquid. The reaction time was 20–40 min with the yields between 82.3% and 95.3%. It was shown that the proposed method was fast, high efficient, and environmentally benign. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:609–611, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20486 相似文献
979.
Jianrong Qiu Mingying Peng Jinjun Ren Xiangeng Meng Xiongwei Jiang Congshan Zhu 《Journal of Non》2008,354(12-13):1235-1239
Broadband infrared luminescence is observed in various Bi-doped oxide glasses prepared by conventional melting-quenching technique. The absorption spectrum of the Bi-doped germanium oxide glass consists of five broad peaks at below 370, 500, 700, 800 and 1000 nm. The fluorescence spectrum exhibits a broad peak at about 1300 nm with full width at half maximum (FWHM) of more than 300 nm when excited by an 808 nm laser diode. The fluorescence lifetime at room temperature decreases with increasing Bi2O3 concentration. Influence of the glass composition and melting atmosphere on the fluorescence lifetime and luminescent intensity is investigated. The mechanism of the broadband infrared luminescence is suggested. The product of stimulated emission cross-section and lifetime of the Bi-doped aluminophosphate glass is about 5.0 × 10?24 cm2 s. The glasses might be promising for applications in broadband optical fiber amplifiers and tunable lasers. 相似文献
980.
Fanqing Zeng Guozhong Ren Xiannian Qiu Qibin Yang Jingwu Chen 《Journal of Non》2008,354(29):3428-3432
The Er3+ doped transparent oxyfluoride glass ceramics were obtained by appropriate heat treatment of the precursor glasses with composition (mol%) 50SiO2-xPbF2-(50 − x)PbO-0.5ErF3. The microstructure and optical properties of the glasses and glass ceramics were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), absorption spectra and luminescence spectra. The intensity of upconversion luminescence significantly increased in glass ceramics compared to that in precursor glass. The emission bands centered around 660 nm (4F9/2 → 4I15/2) and 410 nm (2H9/2 → 4I15/2) were simultaneously observed in glass ceramics but cannot be seen in the corresponding precursor glass. The influence of different PbF2 content on the microstructure and upconversion luminescence of the samples was analyzed in detail. The results indicated that with the increase of PbF2 content, the Ω2 was almost the same and the ratios of red to green upconversion luminescence decreased in glass ceramics. 相似文献