全文获取类型
收费全文 | 263篇 |
免费 | 12篇 |
专业分类
化学 | 159篇 |
晶体学 | 1篇 |
力学 | 11篇 |
数学 | 20篇 |
物理学 | 38篇 |
无线电 | 46篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 1篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 13篇 |
2012年 | 21篇 |
2011年 | 30篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 14篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有275条查询结果,搜索用时 0 毫秒
31.
This study considers evolutionary games with non-uniformly random matching when interaction occurs in groups of \(n\ge 2\) individuals using pure strategies from a finite strategy set. In such models, groups with different compositions of individuals generally co-exist and the reproductive success (fitness) of a specific strategy varies with the frequencies of different group types. These frequencies crucially depend on the matching process. For arbitrary matching processes (called matching rules), we study Nash equilibrium and ESS in the associated population game and show that several results that are known to hold for population games under uniform random matching carry through to our setting. In our most novel contribution, we derive results on the efficiency of the Nash equilibria of population games and show that for any (fixed) payoff structure, there always exists some matching rule leading to average fitness maximization. Finally, we provide a series of applications to commonly studied normal-form games. 相似文献
32.
Self-organization and pattern formation of janus particles in two dimensions by computer simulations
Vanakaras AG 《Langmuir : the ACS journal of surfaces and colloids》2006,22(1):88-93
The phase behavior and associated pattern formation of two-dimensional systems of hard disks decorated with amphiphilic coronae (Janus disks) are studied by means of Monte Carlo computer simulations. A primitive interaction potential that captures the essential interparticle interactions is introduced. Despite its simplicity, the system exhibits a very rich phase polymorphism. Apart from the isotropic phase and depending upon the coronal thickness, the simulated systems self-organize in a number of two-dimensional mesophases of various symmetries exhibiting a variety of novel patterns. The results of these simulations suggest that 2D Janus particles are promising candidates for bottom-up design of precise two-dimensional templates. 相似文献
33.
Roniotis A Sakkalis V Karatzanis I Zervakis ME Marias K 《IEEE transactions on information technology in biomedicine》2012,16(3):299-307
Glioma is one of the most aggressive types of brain tumor. Several mathematical models have been developed during the past two decades, toward simulating the mechanisms that govern the development of glioma. The most common models use the diffusion-reaction equation (DRE) for simulating the spatiotemporal variation of tumor cell concentration. Nevertheless, despite the applications presented, there has been little work on studying the details of the mathematical solution and implementation of the 3-D diffusion model and presenting a qualitative analysis of the algorithmic results. This paper presents a complete mathematical framework on the solution of the DRE using different numerical schemes. This framework takes into account all characteristics of the latest models, such as brain tissue heterogeneity, anisotropic tumor cell migration, chemotherapy, and resection modeling. The different numerical schemes presented have been evaluated based upon the degree to which the DRE exact solution is approximated. Experiments have been conducted both on real datasets and a test case for which there is a known algebraic expression of the solution. Thus, it is possible to calculate the accuracy of the different models. 相似文献
34.
Three-dimensional reconstruction of the digestive wall in capsule endoscopy videos using elastic video interpolation 总被引:1,自引:0,他引:1
Wireless capsule endoscopy is a revolutionary technology that allows physicians to examine the digestive tract of a human body in the minimum invasive way. Physicians can detect diseases such as blood-based abnormalities, polyps, ulcers, and Crohn's disease. Although this technology is really a marvel of our modern times, currently it suffers from two serious drawbacks: 1) frame rate is low (3 frames/s) and 2) no 3-D representation of the objects is captured from the camera of the capsule. In this paper we offer solutions (methodologies) that deal with each of the above issues improving the current technology without forcing hardware upgrades. These methodologies work synergistically to create smooth and visually friendly interpolated images from consecutive frames, while preserving the structure of the observed objects. They also extract and represent the texture of the surface of the digestive tract in 3-D. Thus the purpose of our methodology is not to reduce the time that the gastroenterologists need to spend to examine the video. On the contrary, the purpose is to enhance the video and therefore improve the viewing of the digestive tract leading to a more qualitative and efficient examination. The proposed work introduces 3-D capsule endoscopy textured results that have been welcomed by Digestive Specialists, Inc., Dayton, OH. Finally, illustrative results are given at the end of the paper. 相似文献
35.
Alexandros Avdis Sylvain Lardeau Michael Leschziner 《Flow, Turbulence and Combustion》2009,83(3):343-370
Large Eddy Simulations for two flows separating from a two-dimensional hump in a duct are reported and discussed. The flows
differ through the presence or absence of a synthetic slot-jet injected in a sinusoidal manner, i.e. at zero net mass-flow
rate, close to the location of separation and intended to reduce (“control”) the extent of the separated region. Results reported
include instantaneous visualisations, pre-multiplied spectra, wall-pressure distributions, streamfunction fields and profiles
of velocity and second moments. For both flows, agreement between the simulations and the experimental results is generally
good, especially in respect of the overall control effectiveness of the synthetic jet, despite the use of an approximate wall
treatment bridging the viscous sublayer. Proper Orthogonal Decomposition of the velocity field is used to study structural
features, and this shows that the most energetic mode in the base flow is representative of large streamwise vortices in the
separated region, while in the controlled flow, most of the energetically dominant modes are associated with large spanwise
vortices. 相似文献
36.
37.
Arik M Aune S Barth K Belov A Borghi S Bräuninger H Cantatore G Carmona JM Cetin SA Collar JI Dafni T Davenport M Eleftheriadis C Elias N Ezer C Fanourakis G Ferrer-Ribas E Friedrich P Galán J García JA Gardikiotis A Gazis EN Geralis T Giomataris I Gninenko S Gómez H Gruber E Guthörl T Hartmann R Haug F Hasinoff MD Hoffmann DH Iguaz FJ Irastorza IG Jacoby J Jakovčić K Karuza M Königsmann K Kotthaus R Krčmar M Kuster M Lakić B Laurent JM Liolios A Ljubičić A Lozza V Lutz G Luzón G Morales J 《Physical review letters》2011,107(26):261302
The CERN Axion Solar Telescope (CAST) has extended its search for solar axions by using (3)He as a buffer gas. At T=1.8 K this allows for larger pressure settings and hence sensitivity to higher axion masses than our previous measurements with (4)He. With about 1 h of data taking at each of 252 different pressure settings we have scanned the axion mass range 0.39 eV?m(a)?0.64 eV. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g(aγ)?2.3×10(-10) GeV(-1) at 95% C.L., the exact value depending on the pressure setting. Kim-Shifman-Vainshtein-Zakharov axions are excluded at the upper end of our mass range, the first time ever for any solar axion search. In the future we will extend our search to m(a)?1.15 eV, comfortably overlapping with cosmological hot dark matter bounds. 相似文献
38.
Alexandros Dimitriadis Nikolaos Kantartzis Theodoros Tsiboukis 《Applied Physics A: Materials Science & Processing》2012,109(4):1065-1070
An enhanced metamaterial absorber based on the circumscribed-cross resonator is introduced in this paper. The new structure is polarization-independent, due to the symmetry of its unit cell, and is proven efficient for the attenuation of obliquely incident waves. The absorption mechanism is thoroughly investigated and is found to be mainly related to the losses of the dielectric substrate. Furthermore, by exploiting the scalability property of metamaterials, the operational bandwidth of our design can be drastically improved by placing unit cells with properly scaled resonators adjacent to each other. In this context, various combinations of three, four, and nine unit cells that can increase the full width at half maximum up to as much as 11.18?%, are developed. The overall performance of the proposed configurations is deemed promising for the realization of microwave metamaterial absorbers for several practical applications. 相似文献
39.
Chousainov Iskanter-Alexandros Moscholios Ioannis Kaloxylos Alexandros Logothetis Michael 《Wireless Networks》2020,26(6):3953-3965
Wireless Networks - In this paper we consider a cloud radio access network (C-RAN) where the remote radio heads (RRHs) are separated from the baseband signal processing servers, named baseband... 相似文献
40.
Kostas Tsagkaris Gerard Nguengang Aristi Galani Imen Grida Ben Yahia Majid Ghader Alexandros Kaloxylos Markus Gruber Apostolis Kousaridas Mathieu Bouet Stylianos Georgoulas Aimilia Bantouna Nancy Alonistioti Panagiotis Demestichas 《International Journal of Network Management》2013,23(6):402-423
Academic and industrial research initiatives have sought to make fully autonomic networks a reality. Some of these initiatives pursued a holistic approach, while others focused on setting up functionalities for specific networking domains. These efforts did not succeed in being extensively deployed, because the goals of network operators were not satisfactorily met. These goals include unification of management operations, enablement of end‐to‐end management and enhancement of the overall system performance in a trusted way, while reducing management cost. In this paper, we analyse a set of existing autonomic management architectures and frameworks with respect to a selected set of criteria. We then identify missing parts and challenges and propose a framework to unify the most promising attributes towards a novel approach of realization of autonomic networking management. We call this proposal Unified Management Framework (UMF). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献