全文获取类型
收费全文 | 142篇 |
免费 | 3篇 |
专业分类
化学 | 92篇 |
力学 | 6篇 |
数学 | 8篇 |
物理学 | 39篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 8篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 11篇 |
2012年 | 13篇 |
2011年 | 6篇 |
2010年 | 10篇 |
2009年 | 1篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
排序方式: 共有145条查询结果,搜索用时 15 毫秒
141.
The distributed permutation flowshop problem has been recently proposed as a generalization of the regular flowshop setting where more than one factory is available to process jobs. Distributed manufacturing is a common situation for large enterprises that compete in a globalized market. The problem has two dimensions: assigning jobs to factories and scheduling the jobs assigned to each factory. Despite being recently introduced, this interesting scheduling problem has attracted attention and several heuristic and metaheuristic methods have been proposed in the literature. In this paper we present a scatter search (SS) method for this problem to optimize makespan. SS has seldom been explored for flowshop settings. In the proposed algorithm we employ some advanced techniques like a reference set made up of complete and partial solutions along with other features like restarts and local search. A comprehensive computational campaign including 10 existing algorithms, together with statistical analyses, shows that the proposed scatter search algorithm produces better results than existing algorithms by a significant margin. Moreover all 720 known best solutions for this problem are improved. 相似文献
142.
Adsorption and deposition from turbid solutions are common in many industrial processes but notoriously difficult to investigate using standard optical techniques such as ellipsometry and reflectometry. In this report, we have addressed this problem by employing a quartz crystal microbalance with dissipation monitoring ability, QCM-D. The system under investigation consisted of a cationic polyelectrolyte, poly(vinylamine), PVAm, and an anionic surfactant, sodium dodecyl sulfate, SDS, which were mixed together in 10 mM NaCl solution. The polyelectrolyte and the surfactant readily associate in bulk solution, resulting in increased solution turbidity once large aggregates are formed. The solutions were placed in contact with a polystyrene surface, and the adsorption process was monitored by following the changes in the resonance frequency and dissipation factor. The results obtained can in most cases be evaluated using the Sauerbrey relation, but in some cases a more elaborate analysis is necessary. It is found that PVAm adsorbs to polystyrene in the absence of SDS. In the turbid region, deposition is observed, and the sensed mass exceeds the sum of that obtained for each of the components alone. On the other hand, at high SDS concentrations, the surfactant dominates in the adsorbed layer. Adsorption equilibrium is in most cases established within 1-2 h, the exception being found around the solution composition that results in the formation of charge-neutralized aggregates. In this case, a slow deposition of aggregates persists over prolonged times. 相似文献
143.
In the current communication, porous silicon samples were prepared by pulsed photoelectrochemical etching using a hydrofluoric acid-based solution. The structural and gas-sensing properties of the samples were studied. Apart from the cycle time T and pause time Toff of the pulsed current, a novel parameter, in the shape of the current named ‘delay time Td’ was introduced. Our results showed that by optimization of delay time, the porosity of samples can be controlled due to the chemical preparation of silicon surface prior to electrochemical anodization. The fourier-transform infrared measurements of porous silicon (PS) layers on Si substrate showed that the typical PS surface was characterized by chemical species like Si–H and Si–O–Si terminations. The two-minute delay before applying electrical current was considered sufficient for the fabrication of higher porosity (83%), more uniform, and more stable structures. The photoluminescence (PL) peak of the optimized sample showed higher intensity than the other samples. An obvious PL blue shift also revealed a change in the crystallographic characteristics of silicon due to quantum confinement effects. Metal–semiconductor–metal diodes with Schottky contacts of nickel were fabricated on PS samples and the potential application of optimized substrates for the improved sensitivity, stability, response time and recovery time of hydrogen gas sensors was subsequently studied. 相似文献
144.
A multi-fiber architecture is proposed to mitigate the nonlinear impairments in fiber-optic systems. The power launched to each fiber is reduced in multi-fiber architecture as compared to the case of single fiber leading to reduction in nonlinear impairments. The optical pulses propagating in the fibers undergo different amount of phase shifts and timing delays. Optical and electrical equalization techniques to compensate for these channel effects are discussed. Our numerical simulation results show that for unrepeatered systems, the performance (Q factor) is improved by 6.2 dB using 8-fiber configuration as compared to single-fiber system. In addition, for multi-span system, the transmission reach at a bit error rate (BER) of 2.1 × 10? 3 is quadrupled in 8-fiber configuration. 相似文献
145.
Tayyeb Ghadimi Soheila Naderi Gharahgheshlagh Noorahmad Latifi Ahmad Hivechi Vahid Hosseinpour Sarmadi Siamak Farokh Forghani Naser Amini Peiman B. Milan Fatemeh Latifi Masoud Hamidi Ghazaleh Larijani Seyed Mohammad Amin Haramshahi Motahareh Abdollahi Fatemeh Ghadimi Saeed Nezari 《Macromolecular bioscience》2023,23(9):2300033
Burn is one of the physically debilitating injuries that can be potentially fatal; therefore, providing appropriate coverage in order to reduce possible mortality risk and accelerate wound healing is mandatory. In this study, collagen/exo-polysaccharide (Col/EPS 1–3%) scaffolds are synthesized from rainbow trout (Oncorhynchus mykiss) skins incorporated with Rhodotorula mucilaginosa sp. GUMS16, respectively, for promoting Grade 3 burn wound healing. Physicochemical characterizations and, consequently, biological properties of the Col/EPS scaffolds are tested. The results show that the presence of EPS does not affect the minimum porosity dimensions, while raising the EPS amount significantly reduces the maximum porosity dimensions. Thermogravimetric analysis (TGA), FTIR, and tensile property results confirm the successful incorporation of the EPS into Col scaffolds. Furthermore,the biological results show that the increasing EPS does not affect Col biodegradability and cell viability, and the use of Col/EPS 1% on rat models displays a faster healing rate. Finally, histopathological examination reveals that the Col/EPS 1% treatment accelerates wound healing, through greater re-epithelialization and dermal remodeling, more abundant fibroblast cells and Col accumulation. These findings suggest that Col/EPS 1% promotes dermal wound healing via antioxidant and anti-inflammatory activities, which can be a potential medical process in the treatment of burn wounds. 相似文献