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101.
In this paper transmitter antenna diversity for the downlink of a cellular system is proposed in conjunction with optimum anti-fading diversity. In spectrally efficienttransmitter antenna, frequency and time diversity schemes the information bit stream is divided into sub-streams and each sub-stream is transmitted over a different antenna, a different frequency, or a different time slot.The present work provides a fading resistant transmission scheme where a base station uses M1 antennas and M2 time slotsM=M1+M2. These transmissions are coordinated tomitigate the effects of multi-path Rayleigh fading and the mobilereceiver can recover the entire M-dimensional transmitted vector as longas the signal energy of at least one coordinate is large enough. TheSelective Transmitter Antenna Diversity (space diversity) scheme iscoordinated with new Orthonormal Complex Rotation Matrices(time diversity) to get the highest BER performance for low and medium signaltonoise ratio. Orthonormal Complex Rotation Matrices with variable and maximum peak toaverage amplitude ratio (PAR) are presented. The modulations considered in this workareQPSK, 8PSK and 16QAM. 相似文献
102.
Amélie Veillère Jean-François Silvain Joël Douin Michel Lahaye Namas Chandra Jean-Marc Heintz 《Journal of Materials Science》2011,46(7):2105-2111
The aim of this paper is to synthesize a copper/chromium oxide composite material. The use of a chemical processing method
like the Pechini method is the best approach to control the chemistry and the microstructure. Nevertheless, the standard Pechini
method has to be modified to obtain this specific type of composite. In this work, we have adapted two steps. Firstly we have
eliminated the step involving ethylene glycol and secondly a reduction step has been added at the end. The new method is now
capable of obtaining a Cu/Cr2O3 composite with specific stoichiometric ratios and a grain size ranging from 0.1 to 1 μm. We have used chemical and microstructural
analyses to validate this work. 相似文献
103.
Janin A Coudert L Riche P Mercier G Cooper P Blais JF 《Journal of hazardous materials》2011,186(2-3):1880-1887
Chromated copper arsenate (CCA)-treated wood was widely used until 2004 for residential and industrial applications. Since 2004, CCA was replaced by alternative copper preservatives such as alkaline copper quaternary (ACQ), copper azole (CA) and micronized copper quaternary (MCQ), for residential applications due to health concerns. Treated wood waste disposal is becoming an issue. Previous studies identified a chemical process for decontaminating CCA-treated wood waste based on sulfuric acid leaching. The potential application of this process to wood treated with the copper-based preservatives (alkaline copper quaternary (ACQ), copper azole (CA) and micronized copper quaternary (MCQ)) is investigated here. Three consecutive leaching steps with 0.1 M sulfuric acid at 75°C for 2 h were successful for all the types of treated wood and achieved more than 98% copper solubilisation. The different acidic leachates produced were successively treated by coagulation using ferric chloride and precipitation (pH=7) using sodium hydroxide. Between 94 and 99% of copper in leachates could be recovered by electrodeposition after 90 min using 2 A electrical current. Thus, the process previously developed for CCA-treated wood waste decontamination could be efficiently applied for CA-, ACQ- or MCQ-treated wood. 相似文献
104.
José Elias Claudio Arroyo Ana Amélia de Souza Pereira 《The International Journal of Advanced Manufacturing Technology》2011,55(5-8):741-753
This paper presents a multi-objective greedy randomized adaptive search procedure (GRASP)-based heuristic for solving the permutation flowshop scheduling problem in order to minimize two and three objectives simultaneously: (1) makespan and maximum tardiness; (2) makespan, maximum tardiness, and total flowtime. GRASP is a competitive metaheuristic for solving combinatorial optimization problems. We have customized the basic concepts of GRASP algorithm to solve a multi-objective problem and a new algorithm named multi-objective GRASP algorithm is proposed. In order to find a variety of non-dominated solutions, the heuristic blends two typical approaches used in multi-objective optimization: scalarizing functions and Pareto dominance. For instances involving two machines, the heuristic is compared with a bi-objective branch-and-bound algorithm proposed in the literature. For instances involving up to 80 jobs and 20 machines, the non-dominated solutions obtained by the heuristic are compared with solutions obtained by multi-objective genetic algorithms from the literature. Computational results indicate that GRASP is a promising approach for multi-objective optimization. 相似文献
105.
Treatment of a sanitary landfill leachate using combined solar photo-Fenton and biological immobilized biomass reactor at a pilot scale 总被引:1,自引:0,他引:1
A solar photo-Fenton process combined with a biological nitrification and denitrification system is proposed for the decontamination of a landfill leachate in a pilot plant using photocatalytic (4.16 m2 of Compound Parabolic Collectors - CPCs) and biological systems (immobilized biomass reactor). The optimum iron concentration for the photo-Fenton reaction of the leachate is 60 mg Fe2+ L−1. The organic carbon degradation follows a first-order reaction kinetics (k = 0.020 L kJUV−1, r0 = 12.5 mg kJUV−1) with a H2O2 consumption rate of 3.0 mmol H2O2 kJUV−1. Complete removal of ammonium, nitrates and nitrites of the photo-pre-treated leachate was achieved by biological denitrification and nitrification, after previous neutralization/sedimentation of iron sludge (40 mL of iron sludge per liter of photo-treated leachate after 3 h of sedimentation). The optimum C/N ratio obtained for the denitrification reaction was 2.8 mg CH3OH per mg N-NO3−, consuming 7.9 g/8.2 mL of commercial methanol per liter of leachate. The maximum nitrification rate obtained was 68 mg N-NH4+ per day, consuming 33 mmol (1.3 g) of NaOH per liter during nitrification and 27.5 mmol of H2SO4 per liter during denitrification. The optimal phototreatment energy estimated to reach a biodegradable effluent, considering Zahn-Wellens, respirometry and biological oxidation tests, at pilot plant scale, is 29.2 kJUV L−1 (3.3 h of photo-Fenton at a constant solar UV power of 30 W m−2), consuming 90 mM of H2O2 when used in excess, which means almost 57% mineralization of the leachate, 57% reduction of polyphenols concentration and 86% reduction of aromatic content. 相似文献
106.
Amélia Guimarães Carvalho Fábio Akira Mori Rafael Farinassi Mendes Antônio José Vinha Zanuncio Marcela Gomes da Silva Lourival Marin Mendes Cláudia Lopes Selvati de Oliveira Mori 《Holz als Roh- und Werkstoff》2014,72(4):425-432
Stryphnodendron adstringens (Mart.) Coville is a species from the Cerrado (Brazilian tropical savanna) popularly known as barbatimão. Its main use of economic value lies in the extraction of the tannins found in its bark and leaves. The purpose of this study was to assess the technical viability of using a tannin-based adhesive coming from the bark of Stryphnodendron adstringens (Mart.) Coville for the production of Oriented Strand Board (OSB) panels. Tannin-based adhesives were produced from tannins extracted from the bark of barbatimão, and these adhesives were used in proportions of 0, 25, 50, 75 and 100 % with commercial urea–formaldehyde adhesive. The properties of the pure adhesives and the mixtures were determined. Subsequently, OSB panels were produced with urea–formaldehyde adhesives, tannin–formaldehyde adhesives and their mixtures. The panels were produced with wood from Pinus oocarpa, with 8 % adhesive, a press cycle of 40 kgf cm?2, and temperature of 160 °C for a period of 8 min. Only the OSB panels produced with 100 % urea–formaldehyde adhesive, 100 % barbatimão tannin adhesive and 25 % barbatimão adhesive combined with 75 % urea–formaldehyde fulfilled all the pre-requisites stipulated in the standard EN 300 (2006) for type 1 panels, thus proving to be technically viable for application in OSB panels. 相似文献
107.
T. L. Pitt J. McClure M. D. Parker A. Amézquita P. J. McClure 《International journal of cosmetic science》2015,37(2):165-174
Bacillus cereus is ubiquitous in nature and thus occurs naturally in a wide range of raw materials and foodstuffs. B. cereus spores are resistant to desiccation and heat and able to survive dry storage and cooking. Vegetative cells produce several toxins which on ingestion in sufficient numbers can cause vomiting and/or diarrhoea depending on the toxins produced. Gastrointestinal disease is commonly associated with reheated or inadequately cooked foods. In addition to being a rare cause of several acute infections (e.g. pneumonia and septicaemia), B. cereus can also cause localized infection of post‐surgical or trauma wounds and is a rare but significant pathogen of the eye where it may result in severe endophthalmitis often leading to loss of vision. Key risk factors in such cases are trauma to the eye and retained contaminated intraocular foreign bodies. In addition, rare cases of B. cereus‐associated keratitis (inflammation of the cornea) have been linked to contact lens use. Bacillus cereus is therefore a microbial contaminant that could adversely affect product safety of cosmetic and facial toiletries and pose a threat to the user if other key risk factors are also present. The infective dose in the human eye is unknown, but as few as 100 cfu has been reported to initiate infection in a susceptible animal model. However, we are not aware of any reports in the literature of B. cereus infections in any body site linked with use of personal care products. Low levels of B. cereus spores may on occasion be present in near‐eye cosmetics, and these products have been used by consumers for many years. In addition, exposure to B. cereus is more likely to occur through other routes (e.g. dustborne contamination) due to its ubiquity and resistance properties of spores. The organism has been recovered from the eyes of healthy individuals. Therefore, although there may be a perceived hazard, the risk of severe eye infections as a consequence of exposure through contaminated near‐eye cosmetics is judged to be vanishingly small. It is unlikely that more stringent microbiological standards for near‐eye cosmetics will have any impact on the risk of severe eye infections caused by B. cereus, as these are not linked to use of personal care products. 相似文献
108.
Mário Marques da Silva Américo Correia Nuno Souto José Seguro Paulo Gomes Rui Dinis 《Wireless Personal Communications》2012,66(4):833-853
A coordinated multi-resolution and multi-point MIMO transmission method for the LTE-Advanced is presented considering the Evolved-Multimedia Broadcast/Multicast Service (E-MBMS). Fixed relays with MIMO and different adaptive frequency reuse schemes are considered in the proposed scheme to improve the E-MBMS spectral efficiency at the cell borders and/or to save transmission power from the base stations and relays. In order to provide additional diversity over Rayleigh multi-path fading channels, a signal space diversity based on Complex Rotation Matrices (CRM) is used, associated to MIMO, as a multi-resolution technique. The decoding of these signals are facilitated with the use of Maximum Likelihood Soft Output (MLSO) criterion, included in the proposed receiver. The link performance of the MIMO system turbo-coded with hierarchical constellations and CRM is analyzed in terms of bit and block error rate (BER/BLER). The corresponding system level coverage and throughput gains are also evaluated associated to the presence or not of fixed relays and measuring the maximum spectral efficiencies at cell borders of single cell point-to-multipoint or single frequency network. The influence of the cell radius in the performance of the previous cellular topologies with coordinated MIMO transmissions is also evaluated. 相似文献
109.
Franciele Pereira Camargo Isabel Kimiko Sakamoto Ariane Bize Iolanda Cristina Silveira Duarte Edson Luiz Silva Maria Bernadete Amâncio Varesche 《International Journal of Hydrogen Energy》2021,46(11):7794-7809
Different nutritional and physicochemical conditions to obtain H2 from Citrus Peel Waste (CPW) were evaluated. For this, a screening design was carried out using Plackett and Burman design, in order to verify the main significant conditions of this process. The variables studied were pH (5.5–8.5), temperature (30–44 °C), autochthonous inoculum (0.75–2.25 gTVS.L?1), allochthonous inoculum (1–3 gTVS.L?1) and substrate (5–15 g.L?1), headspace (40–60%) and nutritional medium components, such as yeast extract (0–1 g.L?1), CaCO3, NaCl and peptone (0–5 g.L?1). The most significant operational variables were pH (8.5), allochthonous inoculum (3 gTVS.L?1) and substrate concentration (15 g CPW.L?1), conditions that favored the highest H2 (13.29 mmol.L?1) and acetic acid productions (1340 mg.L?1). Escherichia (34.5%) and Clostridium (29.93%) were the main genera identified under these conditions. 相似文献
110.
Maxime Colpaert Marta Zatoń Gérald Lopez Deborah J. Jones Bruno Améduri 《International Journal of Hydrogen Energy》2018,43(35):16986-16997
The radical copolymerizations of vinylidene fluoride (VDF) with perfluoro-3,6-dioxa-4-methyl-7-octene sulfonyl fluoride (PFSVE) and hPFSVE (hydrolyzed form of PFSVE) are presented. The resulting poly(VDF-co-PFSVE) random copolymers were hydrolyzed then cast into proton conducting membranes. Another strategy was first to hydrolyze PFSVE under basic conditions, then to copolymerize it with VDF. The radical copolymerization of VDF with PFSVE led to homogeneous copolymers in contrast to that of VDF with hPFSVE, as assessed by 19F NMR spectroscopy. The thermal and electrochemical properties of all copolymers were determined. As expected, the thermal stability of the poly(VDF-co-PFSVE) copolymers bearing -SO2F groups were higher than that of the hydrolyzed copolymers containing -SO3H moieties. Membranes processed by casting displayed water uptake of ca. 40%, ion exchange capacity of 1.25 meq.g?1 and conductivities up to 28 mS cm?1 at 80 °C and 100% relative humidity. 相似文献