全文获取类型
收费全文 | 71篇 |
免费 | 0篇 |
国内免费 | 4篇 |
专业分类
化学 | 22篇 |
力学 | 11篇 |
数学 | 25篇 |
物理学 | 17篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有75条查询结果,搜索用时 31 毫秒
31.
Two-photon excitation (2PE) of "caged" biomolecules represents a powerful method to investigate the temporal and spatial relevance of physiological function in real time and on living tissue, because the excitation volume can be restricted to 1 fL. Additionally, low-energy IR light is used, which minimizes tissue destruction and enables deeper penetration into tissue preparations. Exploitation of this technology for studying cell physiology requires the further development of photoremovable protecting groups with sufficient sensitivity to 2PE for use in "caged" compounds. 8-Bromo-7-hydroxyquinoline (BHQ) is efficiently photolyzed by classic 1PE (365 nm) and 2PE (740 nm) under simulated physiological conditions (aqueous buffer of high ionic strength, pH 7.2) to release carboxylates, phosphates, and diols-functional groups commonly found on bioactive molecules such as neurotransmitters, nucleic acids, and drugs. It is stable in the dark, soluble in water, and exhibits low levels of fluorescence, which will enable use in conjunction with fluorescent indicators of biological function. BHQ-protected effectors are synthetically accessible. Stern-Volmer quenching, time-resolved infrared (TRIR), and (18)O-labeling experiments suggest that the photolysis occurs through a solvent-assisted photoheterolysis (S(N)1) reaction mechanism on the sub-microsecond time scale. BHQ has the requisite photochemical and photophysical properties as a photoremovable protecting group to regulate the action of biological effectors in cell and tissue culture with light, especially 2PE. 相似文献
32.
Pavlos Tzermias 《Transactions of the American Mathematical Society》2004,356(3):939-951
We investigate low-degree points on the Fermat curve of degree 13, the Snyder quintic curve and the Klein quartic curve. We compute all quadratic points on these curves and use Coleman's effective Chabauty method to obtain bounds for the number of cubic points on each of the former two curves.
33.
Rindermann JJ Pozina G Monemar B Hultman L Amano H Lagoudakis PG 《Physical review letters》2011,107(23):236805
We investigate the dependence of resonance energy transfer from Wannier-Mott excitons to an organic overlayer on exciton dimensionality. We exploit the excitonic potential disorder in a single quantum well to tune the balance between localized and free excitons by scaling the Boltzmann distribution of excitons through temperature. Theoretical calculations predict the experimentally observed temperature dependence of resonance energy transfer and allow us to quantify the contribution of localized and free excitons. We show that free excitons can undergo resonance energy transfer with an order of magnitude higher rate compared to localized excitons, emphasizing the potential of hybrid optoelectronic devices utilizing resonance energy transfer as a means to overcome charge transfer related limitations. 相似文献
34.
G.P. Pavlos V.G. TsoutsourasD.V. Sarafopoulos D.S. SfirisL.P. Karakatsanis E.G. Pavlos 《Physica A》2011,390(15):2819-2839
In this paper strong evidence is provided for significant far from equilibrium phase transition processes in the Earth’s magnetosphere as revealed by the nonlinear analysis of in situ observations. These results constitute the solid base for the solution of the durable controversy about the chaotic or non-chaotic character of the magnetospheric dynamics. During the last two decades the concept of low dimensional chaos was supported by theoretical and experimental methods by our group in Thrace and others scientists, as an explicative paradigm of the magnetospheric dynamics including substorm processes. In parallel, the concept of self-organized criticality (SOC) and space-time intermittency was introduced as new and opposing to low dimensional chaos concepts for modeling the magnetospheric dynamics. Novel results concerning the nonlinear analysis of in situ space plasma data (magnetic-electric field, energetic particles and bulk plasma flow time series) obtained by the Geotail spacecraft presented in this paper for the first time reveal the following: (a) Coexistence of SOC and chaos states in the magnetospheric system and global phase transition from one state to the other during substorms. (b) Strong intermittent turbulent character of the magnetospheric system at the SOC or the low dimensional chaos states. (c) Clear indications for non-extensivity and q-Gaussian statistics during periods of low dimensional and chaotic dynamics of the magnetosphere. (d) Low dimensional and nonlinear space plasma dynamics in the day side magnetopause and bow shock dynamics. The dual character of the magnetospheric dynamics including low dimensional chaotic (coherent) and high dimensional turbulent states, as supported in this paper, is in agreement and verifies previous theoretical and experimental studies. 相似文献
35.
The field of study of complex systems considers that the dynamics of complex systems are founded on universal principles that may be used to describe a great variety of scientific and technological approaches of different types of natural, artificial, and social systems. Several authors have suggested that earthquake dynamics and the dynamics of economic (financial) systems can be analyzed within similar mathematical frameworks. We apply concepts of the nonextensive statistical physics, on time-series data of observable manifestations of the underlying complex processes ending up with these different extreme events, in order to support the suggestion that a dynamical analogy exists between a financial crisis (in the form of share or index price collapse) and a single earthquake. We also investigate the existence of such an analogy by means of scale-free statistics (the Gutenberg–Richter distribution of event sizes). We show that the populations of: (i) fracto-electromagnetic events rooted in the activation of a single fault, emerging prior to a significant earthquake, (ii) the trade volume events of different shares/economic indices, prior to a collapse, and (iii) the price fluctuation (considered as the difference of maximum minus minimum price within a day) events of different shares/economic indices, prior to a collapse, follow both the traditional Gutenberg–Richter law as well as a nonextensive model for earthquake dynamics, with similar parameter values. The obtained results imply the existence of a dynamic analogy between earthquakes and economic crises, which moreover follow the dynamics of seizures, magnetic storms and solar flares. 相似文献
36.
Benjamin H. Timmins Brandon W. Wilson Barton L. Smith Pavlos P. Vlachos 《Experiments in fluids》2012,53(4):1133-1147
The uncertainty of any measurement is the interval in which one believes the actual error lies. Particle image velocimetry (PIV) measurement error depends on the PIV algorithm used, a wide range of user inputs, flow characteristics, and the experimental setup. Since these factors vary in time and space, they lead to nonuniform error throughout the flow field. As such, a universal PIV uncertainty estimate is not adequate and can be misleading. This is of particular interest when PIV data are used for comparison with computational or experimental data. A method to estimate the uncertainty from sources detectable in the raw images and due to the PIV calculation of each individual velocity measurement is presented. The relationship between four error sources and their contribution to PIV error is first determined. The sources, or parameters, considered are particle image diameter, particle density, particle displacement, and velocity gradient, although this choice in parameters is arbitrary and may not be complete. This information provides a four-dimensional “uncertainty surface” specific to the PIV algorithm used. After PIV processing, our code “measures" the value of each of these parameters and estimates the velocity uncertainty due to the PIV algorithm for each vector in the flow field. The reliability of our methodology is validated using known flow fields so the actual error can be determined. Our analysis shows that, for most flows, the uncertainty distribution obtained using this method fits the confidence interval. An experiment is used to show that systematic uncertainties are accurately computed for a jet flow. The method is general and can be adapted to any PIV analysis, provided that the relevant error sources can be identified for a given experiment and the appropriate parameters can be quantified from the images obtained. 相似文献
37.
Ming H. Zheng K. Hinterkeuser K. Solomon V. Kunert N. J. Pavlos J. Xu 《Macromolecular Symposia》2007,253(1):179-185
Summary: We have analyzed a number of collagen-derived biomaterials for the matrix- induced and assisted bone and cartilage tissue regeneration. These include the Small intestine submuosa (SIS) Restor ™, ACI-Maix collagen membrane, Chondro- Gide collagen membrane, Permacol collagen Ossix and lycoll collagen membrane and five types of collagen-based marine sponge skeletons. Certain characteristics of different scaffold materials with comparable chemical composition may vary significantly. This variation may have a relevant impact on the suitability of the scaffolds for bone and cartilage regeneration. It suggests that the ACI-Maix® membrane is the best available collagen-derived material for an MACI®/MACT® application. In addition, the study of marine sponge indicates that the collagenous fibre skeleton of marine sponges provides a suitable bioscaffold for bone regeneration, as it supports the adhesion, migration and proliferation of osteoblasts in vitro. 相似文献
38.
Moshe Ben-Akiva Andr de Palma Pavlos Kanaroglou 《European Journal of Operational Research》1987,30(3)
This note presents a brief summary of the emerging stream of research on dynamic network equilibrium. Here we study the implications of the variability of the travel time as a function of the time of day. 相似文献
39.
Violeta Kourbeli Eleni Chontzopoulou Kalliopi Moschovou Dimitrios Pavlos Thomas Mavromoustakos Ioannis P. Papanastasiou 《Molecules (Basel, Switzerland)》2021,26(15)
The protozoan diseases Human African Trypanosomiasis (HAT), Chagas disease (CD), and leishmaniases span worldwide and therefore their impact is a universal concern. The present regimen against kinetoplastid protozoan infections is poor and insufficient. Target-based design expands the horizon of drug design and development and offers novel chemical entities and potential drug candidates to the therapeutic arsenal against the aforementioned neglected diseases. In this review, we report the most promising targets of the main kinetoplastid parasites, as well as their corresponding inhibitors. This overview is part of the Special Issue, entitled “Advances of Medicinal Chemistry against Kinetoplastid Protozoa (Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp.) Infections: Drug Design, Synthesis and Pharmacology”. 相似文献
40.
Wall-mounted roughness features, such as ribs, are often placed along the walls of a channel to increase the convective surface
area and to augment heat transfer and mixing by increasing turbulence. Depending on the relative roughness size and orientation,
the ribs also have varying degrees of increased pressure losses. Designs that use ribs to promote heat transfer encompass
the full range of having only a few streamwise ribs, which do not allow fully developed flow conditions, to multiple streamwise
ribs, which do allow the flow to become fully developed. The majority of previous studies have focused on perturbing the geometry
of the rib with little attention to the spatially and temporally varying flow characteristics and their dependence on the
Reynolds number. A staggered rib-roughened channel study was performed using time-resolved digital particle image velocimetry
(TRDPIV). Both the developing (entry region) and a fully developed region were interrogated for three Reynolds numbers of
2,500, 10,000, and 20,000. The results indicate that the flow was more sensitive to Reynolds number at the inlet than within
the fully developed region. Despite having a similar mean-averaged flowfield structure over the full Reynolds number range
investigated, the population and distribution of coherent structures and turbulent dissipation within the fully developed
region were also found to be Reynolds number dependent. Exploring the time-accurate flow characteristics revealed that in
addition to vortices shed from the rib shear layer, the region of the rib wake was governed by a periodic process of bursting
of the wake vortices resulting in the intermittent ejection of the inter-rib recirculation region into the core flow. This
periodic process was the driving mechanism resulting in mixing and heat transfer augmentation. A quadrant-splitting burst
analysis was also performed to determine the characteristic frequency and duration of inter-rib bursting as well as the wake
shedding frequency, both of which were determined to be Reynolds number dependent. 相似文献