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31.
We consider the problem of optimal worksharing between two adjacent workers each of whom processes a fixed task in addition to their shared task(s). We use a Markov Decision Process (MDP) model to compute optimal policies and provide a benchmark for evaluating threshold policy heuristics. Our approach differs from previous studies of dynamic line balancing in that we focus on system architecture factors that affect the performance improvement opportunity possible through worksharing relative to a traditional static worker allocations, as well as practical heuristics for worksharing. We find that three such factors are significant whether we use an optimal or a heuristic control policy: ability to preempt the shared task, granularity of the shared task and overall variability of the task times. Understanding the role of these factors in a given production environment provides a means for determining where and how worksharing can have significant logistical benefits. 相似文献
32.
33.
Osteosclerosis due to endemic fluorosis 总被引:2,自引:0,他引:2
Tamer MN Kale Köroğlu B Arslan C Akdoğan M Köroğlu M Cam H Yildiz M 《The Science of the total environment》2007,373(1):43-48
Endemic water borne fluorosis is a public health problem in Isparta, a city located in southern Turkey. In order to investigate the association between osteosclerosis and fluorosis, we retrospectively screened the results of lumbar spine and femur neck bone mineral density (BMD) of 1500 patients who were examined before, for any reason in between 2001-2003. Sixty nine patients (67 females and 2 males, mean age 52.6+/-10.2) with vertebra T-scores>or=+2 were found only except a patient with osteoid osteoma in the femur neck (femur T-score+6.64). Thirty-four of the patients could be reexamined with lateral vertebra BMD and investigated for fluorosis and the other etiologic causes of osteosclerosis. Of 34 patients, 14 had either mottled tooth enamel or urine fluoride level greater than 1.5 mg/l. Other etiologic causes were hypothyroidism (2), hypoparathyroidism (1), history of lumbar fracture (1), use of retinoids (1), vitamin D (7), oral calcium preparations (9), and bisphosphanates (3). Lateral lumbar vertebral T-score was greater than+2 in 12 patients (35.3%). Femur T-score was greater than+2 in 7 patients (20.6%). Fourteen patients (41.2%) had lateral vertebral or femur T-score>or=+2. Five (35.7%) of these patients had signs of fluorosis, as discussed before. Mean body mass index of individuals with fluorosis was 36.4+/-7.9 and this result was significantly higher than other osteosclerotic subjects (31.6+/-4.4). In conclusion we believe that approximately one third of the osteosclerosis in our region was due to endemic skeletal fluorosis and obesity may enhance this osteosclerotic type bone changes in endemic fluorosis. 相似文献
34.
A UV-curable acrylated urethane prepolymer was synthesized from tolylene-2,4-diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2-hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent. The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films. The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules. 相似文献
35.
Localized Neuron Stimulation with Organic Electrochemical Transistors on Delaminating Depth Probes 下载免费PDF全文
36.
A review of cryogenic cooling in machining processes 总被引:1,自引:0,他引:1
Yakup Yildiz Muammer Nalbant 《International Journal of Machine Tools and Manufacture》2008,48(9):947-964
The cooling applications in machining operations play a very important role and many operations cannot be carried out efficiently without cooling. Application of a coolant in a cutting process can increase tool life and dimensional accuracy, decrease cutting temperatures, surface roughness and the amount of power consumed in a metal cutting process and thus improve the productivity. In this review, liquid nitrogen, as a cryogenic coolant, was investigated in detail in terms of application methods in material removal operations and its effects on cutting tool and workpiece material properties, cutting temperature, tool wear/life, surface roughness and dimensional deviation, friction and cutting forces. As a result, cryogenic cooling has been determined as one of the most favourable method for material cutting operations due to being capable of considerable improvement in tool life and surface finish through reduction in tool wear through control of machining temperature desirably at the cutting zone. 相似文献
37.
In this study, apples inoculated with pure cultures of Rhizopus stolonifer, Penicillium expansum and Lactobacillus plantarum were utilised as the raw material to produce apple juice concentrate. The effects of microorganisms and various processing
treatments on the fumaric acid, lactic acid and patulin contents of apple juice were investigated. R. stolonifer was found to be the most responsible causative agent of fumaric acid and lactic acid. L. plantarum also produced certain amounts of lactic acid, but not as much as R. stolonifer. L. plantarum caused a significant decrease in L-malic acid content indicating the occurrence of malolactic fermentation. During this complicated
biochemical pathway, a small amount of fumaric acid was also formed by L. plantarum. P. expansum produced only patulin, but did not affect the fumaric acid and lactic acid contents. Fumaric acid contents of the samples
decreased throughout the processing steps excepting evaporation. The fumaric acid contents of the samples increased just after
evaporation depending on the heat applied. The patulin and lactic acid contents of the samples also showed a decreasing trend
throughout processing. However, L. plantarum caused a significant increase in lactic acid content just after depectinization depending on whether the appropriate time-temperature
conditions for incubation were available during depectinization.
Received: 3 November 1998 / Revised version: 4 January 1999 相似文献
38.
Ufuk Yildiz Ignác Capek Dušan Berek Yanko Sarov Ivo W Rangelow 《Polymer International》2007,56(3):364-370
The inverse microemulsion copolymerization of acrylamide and butyl acrylate initiated by ammonium peroxodisulphate, a water‐soluble initiator, and stabilized by anionic emulsifiers sodium bis‐2‐ethylhexylsulfosuccinate and sodium dodecylsulphate (SDS) has been studied. An increase of SDS concentration was observed to increase both the rate of polymerization and the particle size. The average number of radicals per particle (n?) is much below 0.5, which indicates desorption of monomeric radicals from polymer particles. The exit (desorption) rate constants k′des (cm2 s?1) and kdes (s?1) were evaluated as a function of SDS concentration (or the particle size) according to the Ugelstad/O'Toole (I), Nomura (II) and Gilbert (III) models. The value of kdes (s?1) decreases with increasing particle size (or SDS concentration) for all three (I, II and III) models. A complex trend appears for k′des (cm2 s?1): the Ugelstad/O'Toole model estimates a decrease, the Nomura model finds no variation and the Gilbert model estimates even a slight increase in k′des with increasing SDS concentration. Copyright © 2006 Society of Chemical Industry 相似文献
39.
Esra Maltas Mustafa Ozmen Hasibe Cingilli Vural Salih Yildiz Mustafa Ersoz 《Materials Letters》2011,65(23-24):3499-3501
The magnetite (Fe3O4) nanoparticles were prepared by the co-precipitation of ferrous and ferric salts with NH4OH, and then modified with 3-aminopropyltriethoxysilane (APTES) by silanization reaction and subsequent reaction with glutaraldehyde (GA) to obtain functional groups on their surface. The influence of different terminated groups on protein binding was studied with bare and modified magnetite nanoparticles. Amine terminated magnetite nanoparticles were shown the highest binding ability for immobilization process compared to Fe3O4 NPs and GA bonded NPs. This binding ability was shown by using sodium dodecyl polyacrylamide gel electrophoresis technique (SDS-PAGE). Albumin attached magnetite nanoparticles were also examined by Scanning Electron Microscopy (SEM). 相似文献
40.
Eylem Dizman Tomak Mark Hughes Umit C. Yildiz Hannu Viitanen 《Journal of Materials Science》2011,46(3):598-607
The aim of the study was to screen any possible synergistic effect available with combination of plant oils and boron compounds
to decrease boron leaching and improve thermal degradation of wood by means of dual treatment. In order to reduce the leachability
of boron compounds, sapwood of beech and Scots pine samples were treated with oils to create a hydrophobic layer on the wood
cells that may prevent water uptake. Increase (%) of boron retained in double-treated samples after leaching was approximately
20% compared to boron-treated samples without oil. The most promising results on boron leaching obtained in the case of using
waste and sunflower oil. Thermogravimetric residues were increased by the higher loading of boron compounds in double-treated
samples. Spectra of FTIR-Photoacoustic spectrometer showed some deformation of lignin and cellulose followed by degradation
of hemicelluloses of treated wood samples due to heat effect at 160 °C. 相似文献