全文获取类型
收费全文 | 219篇 |
免费 | 12篇 |
专业分类
化学 | 126篇 |
力学 | 7篇 |
数学 | 13篇 |
物理学 | 85篇 |
出版年
2023年 | 7篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 15篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 13篇 |
2008年 | 8篇 |
2007年 | 18篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2000年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有231条查询结果,搜索用时 640 毫秒
221.
This paper presents results of an ongoing investigation into modelling fluidized dense-phase pneumatic conveying of powders. For the reliable design of dense-phase pneumatic conveying systems, an accurate estimation of the blockage boundary condition or the minimum transport velocity requirement is of sig- nificant importance. The existing empirical models for fine powder conveying in fluidized dense-phase mode are either based on only a particular pipeline and product or have not been tested for their accuracy under a wide range of scale-up conditions. In this paper, a validated test design procedure has been devel- oped to accurately scale-up the blockage boundary with the help of a modelling format that employs solids loading ratio and Froude number at pipe inlet conditions using conveying data of two different samples of fly ash, electro-static precipitation (ESP) dust and cement (particle densities: 2197-3637 kgJm3; loose poured bulk densities: 634-1070kg/m3; median size: 7-30 l~m). The developed models (in power func- tion format) have been used to predict the blockage boundary for larger diameter and longer pipelines (e.g. models based on 69 mm I.D. ~ 168 m long pipe have been scaled up to 105 mm I.D. and 554 m length). The predicted blockage boundaries for the scale-up conditions were found to provide better accuracy compared to the existing models. 相似文献
222.
K.?Mallick P.?MarcqEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,38(1):99-102
We derive the exact bifurcation diagram of the Duffing oscillator with parametric noise thanks to the analytical study of the associated Lyapunov exponent. When the fixed point is unstable for the underlying deterministic dynamics, we show that the system undergoes a noise-induced reentrant transition in a given range of parameters. The fixed point is stabilised when the amplitude of the noise belongs to a well-defined interval. Noisy oscillations are found outside that range, i.e., for both weaker and stronger noise.Received: 20 February 2004, Published online: 20 April 2004PACS:
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion - 05.10.Gg Stochastic analysis methods (Fokker-Planck, Langevin, etc.) - 05.45.-a Nonlinear dynamics and nonlinear dynamical systems 相似文献
223.
The fluorescence and phosphorescence quantum yields (ΦΓ and ΦΠ) and observed triplet decay time (τP) of phenyl isocyanate and its chloro derivative, parachlorophenyl isocyanate have been measured in the polar solvent ethanol. Kinetic parameters for the energy depletion process have been generated KP the triplet-singlet transition probability is much more sensitive to Cl substitution than KISC the intersystem crossing rate. 相似文献
224.
A.G. Apostolidis S. Mallick D. Rouède J.P. Herriau J.P. Huignard 《Optics Communications》1985,56(2):73-78
Due to the co-existence of optical activity and linear birefringence in a Bi12SiO20 crystal, a phase gratting induced in this medium has many interesting and unusual properties. We study the ellipticity and orientation of the directly transmitted and diffracted beams as a function of the read-beam vector orientation. In image processing experiments the signal to noise ratio can be increased significantly by appropriately choosing the read-beam orientation such that the strong direct beam is linearly polarized and can be eliminated with the help of a polarizer. 相似文献
225.
Dr. Chandrajeet Mohapatra Heidar Darmandeh Henning Steinert Dr. Bert Mallick Dr. Kai-Stephan Feichtner Prof. Viktoria H. Gessner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(66):15145-15149
Dinuclear low-valent compounds of the heavy main group elements are rare species owing to their intrinsic reactivity. However, they represent desirable target molecules due to their unusual bonding situations as well as applications in bond activations and materials synthesis. The isolation of such compounds usually requires the use of substituents that provide sufficient stability and synthetic access. Herein, we report on the use of strongly donating ylide-substituents to access low-valent dinuclear group 14 compounds. The ylides not only impart steric and electronic stabilization, but also allow facile synthesis via transfer of an ylide from tetrylene precursors of type RY2E to ECl2 (E=Ge, Sn; RY=TolSO2(PR3)C with R=Ph, Cy). This method allowed the isolation of dinuclear complexes amongst a germanium analogue of a vinyl cation, [(PhY)2GeGe(PhY)]+ with an electronic structure best described as a germylene-stabilized GeII cation and a ylide(chloro)digermene [CyY(Cl)GeGe(Cl)CyY] with an unusually unsymmetrical structure. 相似文献
226.
We study the structure of nilpotent completely positive maps in terms of Choi-Kraus coefficients. We prove several inequalities, including certain majorization type inequalities for dimensions of kernels of powers of nilpotent completely positive maps. 相似文献
227.
We present a detailed comparison of the motion of a classical and of a quantum particle in the presence of trapping sites, within the framework of continuous-time classical and quantum random walk. The main emphasis is on the qualitative differences in the temporal behavior of the survival probabilities of both kinds of particles. As a general rule, static traps are far less efficient to absorb quantum particles than classical ones. Several lattice geometries are successively considered: an infinite chain with a single trap, a finite ring with a single trap, a finite ring with several traps, and an infinite chain and a higher-dimensional lattice with a random distribution of traps with a given density. For the latter disordered systems, the classical and the quantum survival probabilities obey a stretched exponential asymptotic decay, albeit with different exponents. These results confirm earlier predictions, and the corresponding amplitudes are evaluated. In the one-dimensional geometry of the infinite chain, we obtain a full analytical prediction for the amplitude of the quantum problem, including its dependence on the trap density and strength. 相似文献
228.
Bhattacharya A Vandali A Zeng FG 《The Journal of the Acoustical Society of America》2011,130(5):2951-2960
The present study examined the effect of combined spectral and temporal enhancement on speech recognition by cochlear-implant (CI) users in quiet and in noise. The spectral enhancement was achieved by expanding the short-term Fourier amplitudes in the input signal. Additionally, a variation of the Transient Emphasis Spectral Maxima (TESM) strategy was applied to enhance the short-duration consonant cues that are otherwise suppressed when processed with spectral expansion. Nine CI users were tested on phoneme recognition tasks and ten CI users were tested on sentence recognition tasks both in quiet and in steady, speech-spectrum-shaped noise. Vowel and consonant recognition in noise were significantly improved with spectral expansion combined with TESM. Sentence recognition improved with both spectral expansion and spectral expansion combined with TESM. The amount of improvement varied with individual CI users. Overall the present results suggest that customized processing is needed to optimize performance according to not only individual users but also listening conditions. 相似文献
229.
John Pal AP Kadigachalam P Mallick A Doddi VR Vankar YD 《Organic & biomolecular chemistry》2011,9(3):809-819
A series of sugar-derived spiroaminals has been synthesized by utilizing cross metathesis, ring closing metathesis and lactamization reactions as key steps from 1-C-alkylated glycosyl azides and important correlations in the spectral data between spiroaminals and their respective anomers are reported. 相似文献
230.
R.P. Drake F.W. Doss R.G. McClarren M.L. Adams N. Amato D. Bingham C.C. Chou C. DiStefano K. Fidkowski B. Fryxell T.I. Gombosi M.J. Grosskopf J.P. Holloway B. van der Holst C.M. Huntington S. Karni C.M. Krauland C.C. Kuranz E. Larsen B. van Leer B. Mallick D. Marion W. Martin J.E. Morel E.S. Myra V. Nair K.G. Powell L. Rauchwerger P. Roe E. Rutter I.V. Sokolov Q. Stout B.R. Torralva G. Toth K. Thornton A.J. Visco 《High Energy Density Physics》2011,7(3):130-140