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61.
Cambodia is recovering from three decades of violence. The Tonle Sap region is the poorest part of this deprived country. Its economy now suffers from substantial informal and destructive activities. A socio-economic analysis of the region--a part of the Mekong River Commission's Water Utilization Programme, which serves the lower Mekong's Basin Development Plan (BDP)--is documented. Besides the multifaceted collection and analysis of data and information from participatory fieldwork, various databases, mathematical models, expert interviews and so forth, a crucial part of the work is to build up and reinforce links between the Mekong River Commission, ministries, provincial authorities, non-governmental organizations, universities and ultimately local communities, and thereby root the BDP into the emerging civil society. Otherwise, the BDP is at high risk of sharing the fate of its predecessors on the Mekong as well as in many other parts of the world. This fate has too often been a failure of the plan, however integrated it has attempted to be. 相似文献
62.
Ristimäki J Vaaraslahti K Lappi M Keskinen J 《Environmental science & technology》2007,41(18):6397-6402
The semivolatile mass fraction of diesel exhaust particles was studied using size-resolved on-line techniques (DMA-ELPI; TDMA-ELPI). The average density of the semivolatile liquid on the particles was measured to be approximately 0.8 g/cm3. The measured size resolved values of mass transfer imply that condensation, or diffusion-limited mass transfer, plays a major role in driving the volatile matter to the diesel exhaust particles. The measured mass change values correspond to highly size dependent mass fractions for the semivolatile component, ranging from approximately 20-80%. Integrated over particle size distribution, the volatile mass fractions were 25 and 45% for the two load points studied. Calculation, based on the measured particle properties, indicates that only 10% volatile mass fraction could be explained by monolayer adsorption. The size resolved changes in particle effective density, fractal dimension, volatile mass fractions and mass are all in agreement with theoretical considerations of condensation. 相似文献
63.
Recently, many reviews on pre-combustion CO2 capture (CCS) in an IGCC plant have been focused on the techno-economic performance of palladium-based membrane reactor modules downstream of conventional steam reforming or shift reactors. Although the determination and minimisation of the amount of palladium necessary for a specific power production capacity has been the target of many research studies, surprisingly little attention has been paid in the open literature to the availability of this metal in the large quantities required for large scale applications. To fill this gap, the scope of this work was to compare the amount of palladium needed for pre-combustion CCS with Pd-membranes and the available production capacity of palladium. Two specific techno-economic studies with a different net IGCC power output were selected from the literature. In each case, the amount of palladium that is necessary for the plant to be in operation was compared with the world supply and demand for palladium. The results show that even for a power plant of “only” 1 GWe net electricity production utilizing membranes with the best reported performance, a relatively large (∼0.7%) amount of palladium is required compared to the total world supply. Considering the total worldwide electricity production from fossil fuels (14,455 TWh in 2010) a tremendous increase in the world supply of Palladium would be required to redirect from the traditional IGCC power plants without CO2 capture units to the new membrane technology. We conclude that large scale pre-combustion capture of CO2 using palladium membranes seems to be unfeasible and research on Pd-based membrane reactors should focus on small(er) scale applications. 相似文献
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65.
Vaaraslahti K Ristimäki J Virtanen A Keskinen J Giechaskiel B Solla A 《Environmental science & technology》2006,40(15):4776-4781
The effect of a conventional oxidation catalyst and a novel particle oxidation catalyst (POC) on diesel particles is studied using identical methodology. Regulated particulate matter emission measurement is followed by analyzing soluble organic fraction. In addition, size distributions are measured using a partial flow sampling system with a thermodenuder as an option. A parallel ELPI-SMPS method is used to study the particle effective density and, further, the mass. Tests are conducted using a heavy duty diesel engine with a very low sulfur fuel. A decrease in particle mass was observed when using a catalyst. When using a conventional catalyst the decrease was attributed to the decrease of soluble organic fraction, while using POC the nonsoluble fraction was also found to decrease, by 8-38%. This observation is confirmed by particle number measurement, and POC was found to decrease the dry particle number concentration measured downstream of a thermodenuder by 13-28%. Further particle structure analysis indicated lower density values when using conventional catalyst or POC. The physical size of the particles was not changed noticeably over either catalyst--implying the soluble organic fraction was condensed onto the soot, filling the voids in the porous structure of soot agglomerates, when no catalyst is used. 相似文献
66.
Jun-ichi Nozawa Junko Suda Azizul Helmi Bin Sofian Hiroshi Hagiwara Hiroshi Suda Takahiko Kawai Tadashi Komoto Hiroyuki Kumehara 《Wear》2009,266(7-8):639-645
In order to verify our hypothesis proposed from the previous paper where a polymer sheet-adhered metal hybrid gear has superior properties of antiwear, self-lubrication and noise reduction, studies were first made on a possibility of nylon66/poly(phenylene oxide) (PPO) alloy injection-molding onto shot-blasted aluminum and steel disks. Adhesion of the coated polymer layer to the metal surfaces and no crack formation of the polymer layer were found under certain molding conditions. This molding method was then applied to a stainless steel spline, a sort of gears used in clutches, giving rise to adhesion of the coated polymer alloy without surface crack formation of the resultant hybrid gear. Tribological properties of the hybrid gear were examined by a vibrational test under a severe condition of a predetermined acceleration amplitude of 10 G and a frequency of 100 Hz. A very high antiwear was found in the hybrid gear, while a same type of stainless steel gear without polymer coating showed a severe wear not only on the gear teeth but also on the meshing teeth of the counter stainless steel disk. Taking into consideration excellent tribological properties with antiwear, self-lubrication and noise reduction, it is concluded that the injection-molded hybrid gear is promising for a wide range of industrial applications. 相似文献
67.
Helmi Abdelkefi Hamadi Khemakhem Annie Simon Jacques Darriet 《Journal of Alloys and Compounds》2008,463(1-2):423-427
The Ba0.985Na0.015Ti0.985Nb0.015O3, Ba0.6Na0.4Ti0.6Nb0.4O3 and Ba0.3Na0.7Ti0.3Nb0.7O3 compositions of the (1 − x) BaTiO3–xNaNbO3 (BTNNx) system have been studied by X-ray diffraction and by measurements of dielectric properties. The specimens with composition BTNN (x = 0.015, 0.40 and 0.70) have been refined by the JANA program from X-ray powder diffraction data. Ceramic samples with composition (1 − x) BaTiO3 + xNaNbO3 (where x = 0.015, 0.40 and 0.70) were prepared by calcinations from appropriate mixture of BaCO3, TiO2, Na2CO3 and Nb2O5. The calcined powder was sintered at temperature range 1200–1400 °C. As the composition x increased from 0.015 (and 0.70), the ferroelectric ceramics (x = 0.015, FE) with tetragonal phase changed to the ferroelectric relaxors (RFE, x = 0.40). RFE ceramics showed a peculiar diffuse phase transition and dielectric relaxation at the low temperature (down to 180 K) due to a frustration between RFE and FE state. These ceramics present the classical ferroelectric character when 0 ≤ x < 0.075 and 0.55 < x ≤ 1 and relaxor character when 0.075 ≤ x ≤ 0.55. 相似文献
68.
Protein Arginine N‐Methyltransferase Substrate Preferences for Different Nη‐Substituted Arginyl Peptides 下载免费PDF全文
Dylan Thomas Timo Koopmans Dr. Ted M. Lakowski Helmi Kreinin Mynol I. Vhuiyan Shona A. Sedlock Dr. Jennifer M. Bui Dr. Nathaniel I. Martin Dr. Adam Frankel 《Chembiochem : a European journal of chemical biology》2014,15(11):1607-1613
Protein arginine N‐methyltransferases (PRMTs) catalyze methyl‐group transfer from S‐adenosyl‐L ‐methionine onto arginine residues in proteins. In this study, modifications were introduced at the guanidine moiety of a peptidyl arginine residue to investigate how changes to the PRMT substrate can modulate enzyme activity. We found that peptides bearing Nη‐hydroxy or Nη‐amino substituted arginine showed higher apparent kcat values than for the monomethylated substrate when using PRMT1, whereas this catalytic preference was not observed for PRMT4 and PRMT6. Methylation by compromised PRMT1 variants E153Q and D51N further supports the finding that the N‐hydroxy substitution facilitates methyl transfer by tuning the reactivity of the guanidine moiety. In contrast, Nη‐nitro and Nη‐canavanine substituted substrates inhibit PRMT activity. These findings demonstrate that methylation of these PRMT substrates is dependent on the nature of the modification at the guanidine moiety. 相似文献
69.
Samara Carbone Hilkka J. Timonen Antti Rostedt Matti Happonen Topi Rönkkö Jorma Keskinen 《Aerosol science and technology》2019,53(5):594-607
The main sources of particulate emissions from engines are fuel and lubricating oil. In this study, particles emitted by a medium speed diesel engine for locomotive use were characterized chemically by using a soot particle aerosol mass spectrometer (SP-AMS). Additionally, positive matrix factorization (PMF) was applied to the SP-AMS data for the separation of fuel from lubricating oil and/or oil additives in diesel engine emissions. The mass spectra of refractory species, i.e., metals and rBC, were included in the PMF input matrix in addition to organics in order to utilize the benefit of the SP-AMS to measure non-refractory and refractory species. In general, particulate matter emitted by the diesel engine was dominated by organics (51%) followed by refractory black carbon (rBC; 48%), trace metals and inorganic species (1%). Regarding the sources of particles, PMF indicated four factors for particle mass of which two were related to lubricating oil-like aerosol (LOA1, 29% and LOA2, 24%) and two others to diesel-like fuel aerosol (DFA1, 35% and DFA2, 12%). The main difference between LOA1 and LOA2 was the presence of soot in LOA1 and metals in LOA2 factors. DFA factors represented burned (DFA1) and unburned fuel (DFA2). The results from the PMF analysis were completed with particle size distributions, volatility measurements and particle morphology analyses.
Copyright © 2019 American Association for Aerosol Research 相似文献
70.