首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   81篇
  免费   1篇
化学   33篇
力学   1篇
数学   24篇
物理学   24篇
  2022年   2篇
  2021年   4篇
  2020年   1篇
  2017年   5篇
  2016年   3篇
  2015年   1篇
  2014年   5篇
  2013年   11篇
  2012年   7篇
  2011年   6篇
  2010年   5篇
  2009年   5篇
  2008年   7篇
  2007年   4篇
  2006年   6篇
  2005年   4篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
排序方式: 共有82条查询结果,搜索用时 15 毫秒
1.
Zhao  Yi  Liang  Kaitai  Zhao  Yanqi  Yang  Bo  Ming  Yang  Panaousis  Emmanouil 《Designs, Codes and Cryptography》2022,90(4):921-937
Designs, Codes and Cryptography - An algorithm substitution attack (ASA) can undermine the security of cryptographic primitives by subverting the original implementation. An ASA succeeds when it...  相似文献   
2.
Choline-based electrolytes have been proposed as environmentally friendly and low-cost alternatives for secondary zinc air batteries. Choline acetate [Ch]+[OAc] in protic (D2O) and aprotic (DMSO-d6) solvents has been studied by means of concentration-dependent 1H NMR, viscosity, and density measurements. The viscosities have been calculated on the basis of the Jones-Dole equation and showed that the dominant contribution originates from short-range ion-solvent interactions. Site-specific association affinities were assigned from NMR chemical shift titrations. In DMSO-d6, the hydroxyl group of choline was found to have the smallest dissociation constant followed by the methyl group of acetate. The corresponding Gibbs energies at low concentration were found to be in agreement with a solvent-separated ion pair (2SIP) configuration, whereas at concentrations above 300 mM, a solvent-shared ion pair (SIP) configuration was assigned. For [Ch]+[OAc] in D2O, association effects were found to be weaker, attributed to the high dielectric constant of the solvent. On time scales on the order of 100 ms, NMR linewidth perturbations indicated a change in the local rotational dynamics of the ions, attributed to short-range cation-solvent interactions and not to solvent viscosity. At 184 mM, 40 % of the cations in DMSO-d6 and 10 % in D2O were found to exhibit short-range interactions, as indicated by the linewidth perturbations. It was found that at about 300 mM, the ions in DMSO-d6 exhibit a transition from free to collective translational dynamics on time scales on the order of 400 ms. In DMSO-d6, both ions were found to be almost equally solvated, whereas in D2O solvation of acetate was stronger, as indicated by the obtained effective hydrodynamic radii. For [Ch]+[OAc] in DMSO-d6, the results suggest a solvent-shared ion association with weak H-bonding interactions for concentrations between 0.3–1 M. Overall, the extent of ion association in solvents such as DMSO is not expected to significantly limit charge transport and hinder the performance of choline-based electrolytes.  相似文献   
3.
4.
This study uses atomic force microscopy (AFM) force-deformation (F-Δ) curves to investigate for the first time the Young's modulus of a phospholipid microbubble (MB) ultrasound contrast agent. The stiffness of the MBs was calculated from the gradient of the F-Δ curves, and the Young's modulus of the MB shell was calculated by employing two different mechanical models based on the Reissner and elastic membrane theories. We found that the relatively soft phospholipid-based MBs behave inherently differently to stiffer, polymer-based MBs [Glynos, E.; Koutsos, V.; McDicken, W. N.; Moran, C. M.; Pye, S. D.; Ross, J. A.; Sboros, V. Langmuir2009, 25 (13), 7514-7522] and that elastic membrane theory is the most appropriate of the models tested for evaluating the Young's modulus of the phospholipid shell, agreeing with values available for living cell membranes, supported lipid bilayers, and synthetic phospholipid vesicles. Furthermore, we show that AFM F-Δ curves in combination with a suitable mechanical model can assess the shell properties of phospholipid MBs. The "effective" Young's modulus of the whole bubble was also calculated by analysis using Hertz theory. This analysis yielded values which are in agreement with results from studies which used Hertz theory to analyze similar systems such as cells.  相似文献   
5.
The adulteration of extra virgin olive oil with low-quality and inexpensive seed oil is a serious problem in the industry. In recent years, the characterization of extra virgin olive oil adulteration with various techniques has been successfully implemented. In this work, a comparative study of Raman and visible spectroscopy is presented. These methods are rapid, noninvasive, and no sample pretreatment is required. We used both methods to study Cretan extra virgin olive oil adulterated with sunflower oil. Statistical analysis based on partial least square regression was used to determine the detection limits of the methods. Raman spectroscopy was superior in comparison to visible spectroscopy with adulteration detection limits of 3.5 and 5.5%, respectively, for the same samples. These results indicate that both techniques are suitable for olive oil quality control.  相似文献   
6.
We study groups whose cohomology functors commute with filtered colimits in high dimensions. We relate this condition to the existence of projective resolutions which exhibit some finiteness properties in high dimensions, and to the existence of Eilenberg–Mac Lane spaces with finitely many n-cells for all sufficiently large n. To that end, we determine the structure of completely finitary Gorenstein projective modules over group rings. The methods are inspired by representation theory and make use of the stable module category, in which morphisms are defined through complete cohomology. In order to carry out these methods, we need to restrict ourselves to certain classes of hierarchically decomposable groups.  相似文献   
7.
8.
We present a metaheuristic methodology for the Capacitated Vehicle Routing Problem with two-dimensional loading constraints (2L-CVRP). 2L-CVRP is a generalisation of the Capacitated Vehicle Routing Problem, in which customer demand is formed by a set of two-dimensional, rectangular, weighted items. The purpose of this problem is to produce the minimum cost routes, starting and terminating at a central depot, to satisfy the customer demand. Furthermore, the transported items must be feasibly packed into the loading surfaces of the vehicles. We propose a metaheuristic algorithm which incorporates the rationale of Tabu Search and Guided Local Search. The loading aspects of the problem are tackled using a collection of packing heuristics. To accelerate the search process, we reduce the neighbourhoods explored, and employ a memory structure to record the loading feasibility information. Extensive experiments were conducted to calibrate the algorithmic parameters. The effectiveness of the proposed metaheuristic algorithm was tested on benchmark instances and led to several new best solutions.  相似文献   
9.
An analytical method using inductively coupled plasma atomic emission spectrometry (ICP-AES) for rapid simultaneous determination of seven heavy metals (Cd, Co, Cr, Cu, Mn, Ni and Pb) in human blood fractions, like plasma, cells fraction and whole blood, is performed. The optimum wavelength was selected using as criterions the sensitivity, the linearity and recovery of aqueous standard solutions. The pretreatment of the sample, the centrifugal conditions, the necessity of digestion and the dilution of the digests were also studied. For plasma it was possible to avoid digestion of the sample, but for cells fractions and whole blood the digestion is necessary. The samples were acid-digested by HNO3 in closed Teflon tubes under high temperature and pressure conditions and were diluted before injection into ICP-AES. Also, optimization of the inductively coupled plasma conditions like nebulizer argon flow rate, sample flow rate and power of radio frequency was performed for each analyte. Finally, the effect of the type of the employed calibration technique on the total variation of the method was examined. Calibration using the standard addition technique was proved more accurate for the determination in terms of analyte recovery. The sensitivity and recovery (Cd 99%, Co 101%, Cr 100%, Cu 99%, Mn 101%, Ni 100% and Pb 97%) of the developed method are presented for all examined blood fractions. Correspondence: George A. Zachariadis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University, Thessaloniki 54124, Greece  相似文献   
10.
In this letter, we have studied transient photoinduced absorption in as‐grown nanocrystalline silicon films with thickness varied from 5 to 30 nm. Effects of quantum confinement (QC) in z ‐direction and grain boundary distortions alter the carrier dynamics of these films considerably. Based on the determination of critical points in the first Brillouin zone of the band structure of materials, we have time‐resolved the relaxation times of surface‐related states and indirect valleys. When decreasing the film thickness down to the QC limit (∼10 nm) new ultrafast relaxation mechanisms start to play a dominant role in carrier dynamics due to the topological disordering of these ultrathin films. These relaxation mechanisms seem to be related with the traping/de‐traping of the excited carriers prior to recombination. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号