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101.
Mapping of platinum group metals in automotive exhaust three-way catalysts using laser-induced breakdown spectrometry 总被引:1,自引:0,他引:1
The use of laser-induced breakdown spectrometry for spatial distribution analysis of platinum, rhodium, and palladium in car catalytic converters is discussed. Fresh converters were extracted from the car exhaust system, cut in pieces of an appropriate size, and analyzed for mapping purposes. Spectral detection, pulse energy, and beam focal conditions were optimized according to the ablation behavior of the material. Difficulties in distribution analysis caused by the complex elemental composition of the sample were overcome by an extensive spectral analysis using appropriate internal standards. Data on the spatial distribution of the active metals in both the axial and radial directions of the catalytic structures are presented. 相似文献
102.
Some published reports have emphasized the similarities between Internet and laboratory research on associative learning processes. However, few of them, if any, studied systematic divergences between both types of research methodologies. In the present experiment, we investigated these divergences using an experimental preparation for the study of associative learning. The results show that discrimination and discrimination-reversal can be obtained both in laboratory and Internet experiments. However, the learning rate was clearly better in the laboratory than in the Internet condition. This result suggests that associative learning experiments performed over the Internet should provide participants with extensive training to assure that asymptotic performance is achieved. 相似文献
103.
Alba María Guadalupe Orellana González Rodrigo Máximo Sánchez-Román Marcos Vinicius Folegatti Cornélio Alberto Zolin 《Water Resources Management》2011,25(13):3371-3386
A dynamic systems simulation model of water resources was developed as a tool to help analyze alternatives to water resources
management for the Piracicaba, Capivari and Jundiaí River Water Basins (RB-PCJ), and used to run six 50-year simulations from
2004 to 2054. The model estimates water supply and demand, as well as contamination load by several consumers. Six runs were
performed using a constant mean precipitation value, changing water supply and demand and different volumes diverted from
RB-PCJ to RB-Alto Tietê. For the Business as Usual scenario, the Sustainability Index went from 0.44 in 2004 to 0.20 by 2054.
The Water Sustainability Index changed from 74% in 2004 to 131% by 2054. The Falkenmark Index changed from 1,403 m3 person − 1 year − 1 in 2004 to 734 m3 person − 1 year − 1 by 2054. We concluded that sanitation is one of the major problems for the PCJ River Basins. 相似文献
104.
Regulation of passive outputs of nonlinear systems can be easily achieved with an integral control (IC). In many applications, however, the signal of interest is not a passive output and ensuring its regulation remains an open problem. Also, IC of passive systems rejects constant input disturbances, but no similar property can be ensured if the disturbance is not matched. In this paper we address the aforementioned problems and propose a procedure to design robust ICs for port-Hamiltonian models, that characterize the behavior of a large class of physical systems. Necessary and sufficient conditions for the solvability of the problem, in terms of some rank and controllability properties of the linearized system, are provided. For a class of fully actuated mechanical systems, a globally asymptotically stabilizing solution is given. Simulations of the classical pendulum system illustrate the good performance of the scheme. 相似文献
105.
Ma. de Guadalupe Garcia-Hernandez Jose Ruiz-Pinales Eva Onaindia J. Gabriel Aviña-Cervantes Sergio Ledesma-Orozco Edgar Alvarado-Mendez Alberto Reyes-Ballesteros 《Artificial Intelligence Review》2012,37(2):157-167
The problem of solving large Markov decision processes accurately and quickly is challenging. Since the computational effort
incurred is considerable, current research focuses on finding superior acceleration techniques. For instance, the convergence
properties of current solution methods depend, to a great extent, on the order of backup operations. On one hand, algorithms
such as topological sorting are able to find good orderings but their overhead is usually high. On the other hand, shortest
path methods, such as Dijkstra’s algorithm which is based on priority queues, have been applied successfully to the solution
of deterministic shortest-path Markov decision processes. Here, we propose an improved value iteration algorithm based on
Dijkstra’s algorithm for solving shortest path Markov decision processes. The experimental results on a stochastic shortest-path
problem show the feasibility of our approach. 相似文献
106.
Nora Abigail Wilson García Jorge Luis Almaral Sánchez Ramón Álvaro Vargas Ortiz Abel Hurtado Macías Nelly Flores Ramírez Ernesto Aguilar Palazuelos Joaquín Flores Valenzuela Andrés Castro Beltrán Clemente Guadalupe Alvarado Beltrán 《应用聚合物科学杂志》2021,138(44):51305
In this study, composites of unsaturated polyester resin (UPR), synthesized from recycled polyethylene terephthalate (PET), with 10 to 40% in volume of corn straw fiber (CSF), were elaborated and studied the effect of fiber content on their physical and mechanical properties. The content of cellulose (48.97%), hemicellulose (24.06%), and lignin (6.59%) were determined by chemical characterization of CSF. The characteristic bonds of the UPR were identified as a cross-linking network between the styrene monomer (ST) and the unsaturated polyester (UP) through FTIR. Two decomposition stages were observed by TGA–DTG. The results of physical and mechanical properties showed that as the fiber content increased in the UPR, the water absorption increased (0.6% to 2.56%), on the other hand, the density (1218.23 to 1150.28 kg/m3), flexural strength (50.58 to 26.98 MPa), flexural modulus (2.66 to 2.29 GPa), tensile strength (8.62 to 3.65 MPa), tensile modulus (1.18 to 0.43 GPa), and hardness (81.67 to 65.67 Shore D), they decreased. SEM analysis showed some defects in the fiber distribution in the UPR, which affected the mechanical properties of the composites. This research contributes to the development of new material from use of two waste materials for the benefit of the environment. 相似文献
107.
108.
Ana Niurka Hernndez‐Lauzardo Guadalupe Mndez‐Montealvo Miguel Gerardo Velzquez del Valle Javier Solorza‐Feria Luis Arturo Bello‐Prez 《Starch - St?rke》2004,56(8):357-363
The chemical, physicochemical and rheological characteristics of Oxalis tuberosa starch were investigated. Oxalis starch presented an apparent amylose content of 33%, similar to maize starch used as control, with a granule size between 25–50 μm with oval and elliptical shapes and A‐type X‐ray diffraction pattern. The gelatinization temperature of oxalis starch was 64.0°C, that was lower than the one determined in maize starch (73.0°C), with an enthalpy value of 12.2 J/g, which was similar to that of maize starch. Both oxalis and maize starch pastes behaved as weak viscoelastic systems with the elastic character (G′) predominating over the viscous character (G′′). An increase in the level of solids in the pastes increased the values of the moduli. The results suggest that heating the systems (gelatinization), causes a more pronounced enhancement in the structure of the maize starch pastes than in that of oxalis starch pastes. Overall, it was concluded that due to its physicochemical, functional and rheological properties, Oxalis starch could be suitable for testing its use in the cosmetic and in the food industry. 相似文献
109.
Laura Snchez‐Hernndez Javier Solorza‐Feria Guadalupe Mndez‐Montealvo Octavio Paredes‐Lpez Luis Arturo Bello‐Prez 《Starch - St?rke》2002,54(5):193-197
Okenia hypogaea (Schlech. & Cham.) belongs to the family of the Nyctaginacea, which produces a seed that is composed mainly of starch, the probable origin of Okenia hypogaea is Mexico. The aim of this work was to isolate the starch from Okenia hypogaea and to evaluate its chemical composition, along with some physicochemical and functional properties. Okenia gave a starch yield of 36 %; this starch had an amylose content of 26.1 %, with a fat content similar to corn starch, but with a higher ash fraction. Okenia starch possessed a small granule size (1—3 μm), the same as amaranth starch, with similar characteristics of stability and clarity of pastes as corn starch. At 60 °C the water retention capacity of okenia starch was higher than that of corn starch, but at higher temperatures an inverse pattern was found. When the temperature in the experiments increased, solubility and swelling values increased; okenia starch had higher swelling values than corn starch over the range of temperatures assayed. Okenia starch also presented a lower freeze‐thaw stability than corn starch on the first two cycles. Overall, it was concluded that due to its physicochemical and functional properties, it is worthwhile to test the use of okenia starch in the cosmetic and food industry. 相似文献
110.