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排序方式: 共有167条查询结果,搜索用时 15 毫秒
1.
2.
Mohammed Sadeq Eyad Masad Hussain Al-Khalid Okan Sirin Loujaine Mehrez 《International Journal of Pavement Engineering》2018,19(10):857-864
Warm-Mix Asphalt (WMA) is a widely used product, which proved a contribution to the reduction in asphalt mixing and compaction temperatures. This reduction leads to lower fuel consumption and smoke emission in asphalt plants. Most of the characterisation of binders used in WMA has focused in the past on measuring linear viscoelastic properties and associated Superpave parameters. Several studies have shown that the average stresses and strains of the asphalt mixture remain mostly within the linear viscoelastic response. However, localised strains in the binder phase of the mixture could reach values high enough to induce nonlinear viscoelastic and viscoplastic deformations. Therefore, this study focuses on an experimental and analytical evaluation of linear, nonlinear viscoelastic and viscoplastic responses of selected binders modified for use in WMA. The first part of the paper analyses the linear viscoelastic material properties and their ability to evaluate permanent deformation resistance. Then, the non-recoverable creep compliance parameter obtained from the Multiple Stress Creep Recovery (MSCR) test is analysed to assess the nonlinear response and permanent deformation of asphalt binders. The paper utilises a nonlinear plasto-viscoelastic (NPVE) approach to assess and quantify the nonlinear plasto-viscoelastic response of binders by separating the recoverable and irrecoverable strains measured in the MSCR test. Two WMA additives were included in this study by mixing them with polymer-modified and unmodified asphalt binders. Analysis of results showed that the NPVE approach captured a higher percentage of recovery than the NLVE approach. However, binder’s performance evaluation and ranking did not change by adopting the NPVE approach. The nonlinear viscoelastic parameters provided insight on the behaviour of asphalt binders mixed with WMA additives during loading cycles. Sasobit showed higher influence than Advera on binders in resisting permanent deformation by increasing the recoverable strain during the unloading phase. 相似文献
3.
Amina L. Mohamed Mehrez E. El-Naggar Tharwat I. Shaheen Ahmed G. Hassabo 《Microsystem Technologies》2016,22(5):979-992
An innovative strategy for functional finishing of cellulosic based materials is based on the incorporation of a thin layer of surface modifying systems (SMS) in the form of stimuli-sensitive nanogels containing combining metal nanoparticles and silica. The silver–silica core–shell nanoparticles (NPs) were synthesized by simple one pot chemical method. Silica/silver nanoparticles have been synthesized using low concentration of dextran as reducing and stabilizing agent and using ascorbic acid as antioxidant agent. The core–shell NPs were characterized for their structural, morphological, compositional and optical behaviour using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Stimuli-responsive nanogel was prepared by copolymerization of poly(N-isopropylacrylamide) with pullulan, results in a nanogel that is responsive to both temperature and pH, the nano-particulate hydrogel of poly-NiPAAm-pullulan copolymer was synthesized using surfactant-free emulsion method. The prepared nano-particles were used during the preparation steps of the pullulan nanogel to obtain nanogel/combining metal/silica NPs to produce a composite materials. The nanoparticle size in dry (collapsed) state is estimated at 250 nm by SEM and TEM, and effect of temperature and pH on gel-nanoparticles was investigated by DLS and UV–vis spectrophotometry. The incorporation of the nanoparticles to cellulosic material was done by a simple pad dry-cure procedure from aqueous nanoparticle dispersion that contained a cross-linking agent. This application method provided sufficient integrity to coating by maintaining the responsiveness of surface modifying system. The stimuli responsiveness of modified cellulosic materials has been confirmed in terms of regulating its water uptake in dependence of pH and temperature. 相似文献
4.
Amos Zemel Israel David & Abraham Mehrez 《International Transactions in Operational Research》2001,8(5):585-601
We consider development projects in which the activities can be classified in two types: uncertainty resolving R&D efforts that accumulate in the form of knowledge to eventually give rise to a discovery; and routine technical investments which aim at improving the profitability of the project once the discovery has been made. The advantage of initiating routine preparatory activities prior to the achievement of a technological breakthrough in such projects, sometimes termed as 'concurrent engineering', is analyzed within a suitable dynamic optimization framework. The optimal double expenditure policy is compared with the conservative delayed investment policy, under which all the routine engineering activities are delayed until the risky R&D efforts culminate in a breakthrough. A criterion for the optimality of the latter policy is developed on the basis of the probability distribution of the discovery date. The application of the criterion is illustrated for a variety of specifications regarding the uncertainty associated with the R&D process. We find that simultaneous investment is the optimal policy for a large class of probability distributions. However, if the conditional probability of immediate discovery is always below some critical value, it is optimal to delay the preparatory activities until the discovery. 相似文献
5.
Mourad Elhadef Lotfi Ben Romdhane 《International Journal of Parallel, Emergent and Distributed Systems》2014,29(2):119-146
This paper presents a modified Hopfield neural network (HNN) for solving the system-level fault diagnosis problem which aims at identifying the set of faulty nodes. This problem has been extensively studied in the last three decades. Nevertheless, identifying the set of all faulty nodes using only partial syndromes, i.e. when some of the testing or comparison outcomes are missing prior to initiating the diagnosis phase, remains an outstanding research issue. The new HNN-based diagnosis algorithm does not require any prior learning or knowledge about the system, nor about any faulty situation, hence providing a better generalisation performance. Results from a thorough simulation study demonstrate the effectiveness of the HNN-based fault diagnosis algorithm in terms of diagnosis correctness, diagnosis latency and diagnosis scalability, for randomly generated diagnosable systems of different sizes and under various fault scenarios. We have also conducted extensive simulations using partial syndromes. Simulations showed that the HNN-based diagnosis performed efficiently, i.e. diagnosis correctness was around 99% when at most half of the test or comparison outcomes are missing, making it a viable alternative to existing diagnosis algorithms. 相似文献
6.
Hasnia Benmoussa Asma Farhat Rafik Bachoual Zina Nasfi Mehrez Romdhane 《分离科学与技术》2016,51(13):2145-2152
The present study aims to compare two innovative extraction techniques: microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME) through traditional extraction techniques: hydrodistillation (HD) and steam distillation (SD) for their efficiency in the extraction of the volatile compounds from Tunisian Thymus vulgaris leaves; the kinetic, yield, composition and antibacterial activities of the essential oil were assessed in vitro. Results show that the essential oils extracted by microwaves were quantitatively (yield) similar to those obtained through the conventional methods, but qualitatively, essential oils analysed by gas chromatography–mass spectrometry (GC–MS) presented 17, 11, 11 and 8 compounds obtained through SFME, MAHD, SD and HD, respectively, mostly consisting of carvacrol (89.24–41.17%), followed by γ-terpinene (11.37–1.37%) and para-cymene (27.95–2.05%). The essential oils were screened for antibacterial activity against 5 microorganisms. All essential oils obtained by studied extraction methods showed the same resistance against Gram (?) and Gram (+) bacteria. The SFME method gave the best results: rapid kinetic of extraction (30 min vs. 35 min for MAHD, 120 min for SD, and 180 min for HD), less energy saving and cleanest process. 相似文献
7.
Amir Mowla Mehrez Agnaou Tanyakarn Treeratanaphitak Hector M. Budman Nasser M. Abukhdeir Marios A. Ioannidis 《American Institute of Chemical Engineers》2020,66(6):e16959
We quantify the ability of the two-fluid Euler–Euler model to predict the overall gas hold-up during two-phase flow in vertical columns using a combination of experiments and simulations. Gas hold-up in a bubble column and gas hold-up in the less-frequently studied co-current flow are investigated. For homogeneous flow characterized by nearly uniform bubble size, Euler–Euler model predictions are within 10% of the experimental values for both modes of operation, if the bubble diameter supplied as input to the model is the average bubble diameter in the physical system. This also holds true for heterogeneous flow in bubble columns despite the presence of a broad distribution of bubble sizes, if turbulence and bubble swarm effects on momentum exchange between phases are properly accounted for. Swarm corrections adequate for bubble columns, are less successful for co-current heterogeneous flow, for which gas hold-up predictions are least accurate (average error of 22%). 相似文献
8.
9.
Brahim Bchir Souhail Besbes Romdhane Karoui Michel Paquot Hamadi Attia Christophe Blecker 《Food and Bioprocess Technology》2012,5(3):999-1009
Pomegranate seeds were osmodehydrated using date juice added with sucrose (final °Brix, 55) as immersion solution. The kinetics
of osmotic dehydration showed that the most significant changes of mass transfer took place during the first 20 min of the
process, regardless of date juice varieties. During this time, seed water loss and solid gain were estimated to be ∼39% and
∼6%, respectively. After 20 min of the process, the percentage of water loss and solid gain varied slightly and ranged on
average close to ∼40% and ∼9%, respectively. During osmotic dehydration, there was a leaching of natural solutes from seeds
into the solution, which is quantitatively not negligible, and might have an important impact on the sensorial and nutritional
value of seeds and date juices. Both scanning electron microscopy and texture (compression) analysis revealed that osmotic
dehydration process induced modifications of seed texture and cell structure. Sucrose was found to be the essential element
which influences the texture of seed and the viscosity of date juice. Additionally, natural sugar present in date juice permits
substituting 35% of the total quantity of sucrose added to the osmotic solution. 相似文献
10.
Tahar Boubellouta Romdhane Karoui Annick Lebecque Éric Dufour 《European Food Research and Technology》2010,231(6):873-882
Twelve samples of cheeses (three types of Saint-Nectaire PDO cheeses and Savaron cheeses) differing by manufacturing and ripening
conditions, from 12 different producers, were characterised by attenuated total reflectance mid-infrared (MIR) and front-face
fluorescence spectroscopies, dynamic testing rheology and physico-chemical analysis. Fluorescence spectra (tryptophan residues,
vitamin A and riboflavin) and MIR (3,000–2,800 (fat region), 1,700–1,500 (protein region) and 1,500–900 cm−1 (fingerprint region)) spectra were recorded on cheese samples. The potential of the data tables was investigated for discriminating
the four different groups of cheeses. The results of factorial discriminant analysis (FDA) performed on the fluorescence and
mid-infrared spectra showed a good discrimination of the four cheese groups. Considering cross-validation results, the best
classifications (100%) were achieved from mid-infrared and fluorescence spectra, while only 91.7 and 72.2% of correct classification
were obtained by applying FDA to rheology and physico-chemical data, respectively. Spectroscopic techniques could provide
useful fingerprints and allow the identification of investigated cheeses according to manufacturing conditions. Simple and
rapid spectroscopic methods offer a promising approach to the authentication of cheeses. 相似文献