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排序方式: 共有267条查询结果,搜索用时 0 毫秒
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M Flores-Díaz A Alape-Girón B Persson P Pollesello M Moos C von Eichel-Streiber M Thelestam I Florin 《Canadian Metallurgical Quarterly》1997,272(38):23784-23791
We previously isolated a mutant cell that is the only mammalian cell reported to have a persistently low level of UDP-glucose. In this work we obtained a spontaneous revertant whose UDP-glucose level lies between those found in the wild type and the mutant cell. The activity of UDP-glucose pyrophosphorylase (UDPG:PP), the enzyme that catalyzes the formation of UDP-glucose, was in the mutant 4% and in the revertant 56% of the activity found in the wild type cell. Sequence analysis of UDPG: PP cDNAs from the mutant cell showed one missense mutation, which changes amino acid residue 115 from glycine to aspartic acid. The substituted glycine is located within the largest stretch of strictly conserved residues among eukaryotic UDPG:PPs. The analysis of the cDNAs from the revertant cell indicated the presence of an equimolar mixture of the wild type and the mutated mRNAs, suggesting that the mutation has reverted in only one of the alleles. In summary, we demonstrate that the G115D substitution in the Chinese hamster UDPG:PP dramatically impairs its enzymatic activity, thereby causing cellular UDP-glucose deficiency. 相似文献
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Pei Lian Ma Basil D. Favis Michel F. Champagne Michel A. Huneault Florin Tofan 《Polymer Engineering and Science》2002,42(10):1976-1989
Blends of polyethylene terephthalate (PET) and ethylene‐ethyl acrylate‐maleic anhydride terpolymer (E‐EA‐MAH) were dynamically crosslinked in a one‐step extrusion process. An amine‐terminated glycol reacting with MAH moieties was used as the crosslinking agent. The effect of blend composition and dynamic crosslinking on the microstructure and mechanical properties were investigated. Blend ratios ranging from 80:20 to 20:80 PET/E‐EA‐MAH were studied. The region of phase inversion was located for uncrosslinked and dynamically crosslinked blends. The rheological characterization was also carried out for these blends in comparison with the neat materials. After dynamic crosslinking, the phase inversion is shifted from the 30–40% range to the 70–80% range of elastomer content. This shift is induced by the increase of viscosity and elasticity of the network formed. Dynamically crosslinked blends show significant improvements in impact strength but also exhibit a decrease in elongation at break. 相似文献
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Constantin Florin Caruntu 《国际通用系统杂志》2015,44(2):182-197
State feedback control is very attractive due to the precise computation of the gain matrix, but the implementation of a state feedback controller is possible only when all state variables are directly measurable. This condition is almost impossible to accomplish due to the excess number of required sensors or unavailability of states for measurement in most of the practical situations. Hence, the need for an estimator or observer is obvious to estimate all the state variables by observing the input and the output of the controlled system. As such, the goal of this paper is to provide a control design methodology based on a Luenberger observer design that can assure the closed-loop performances of a vehicle drivetrain with backlash, while compensating the network-enhanced time-varying delays. This goal is achieved in a sequential manner: firstly, a piecewise linear model of two inertias drivetrain, which takes into consideration the backlash nonlinearity and the network-enhanced time-varying delay effects is derived; then, a Luenberger observer which estimates the state variables is synthesized and the robust full state-feedback predictive controller based on flexible control Lyapunov functions is designed to explicitly take into account the bounds of the disturbances caused by time-varying delays and to guarantee also the input-to-state stability of the system in a non-conservative way. The full state-feedback predictive control strategy based on the Luenberger observer design was experimentally tested on a vehicle drivetrain emulator controlled through controller area network, with the aim of minimizing the backlash effects while compensating the network-enhanced delays. 相似文献
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Soledad Escolar Díaz Florin Isaila Alejandro Calderón Mateos Luis Miguel Sanchez García David E. Singh 《The Journal of supercomputing》2010,51(1):76-93
In the last years the Wireless Sensor Networks’ (WSN) technology has been increasingly employed in various application domains.
The extensive use of WSN posed new challenges in terms of both scalability and reliability. This paper proposes Sensor Node
File System (SENFIS), a novel file system for sensor nodes, which addresses both scalability and reliability concerns. SENFIS
can be mainly used in two broad scenarios. First, it can transparently be employed as a permanent storage for distributed
TinyDB queries, in order to increase the reliability and scalability. Second, it can be directly used by a WSN application
for permanent storage of data on the WSN nodes. The experimental section shows that SENFIS implementation makes an efficient
use of resources in terms of energy consumption, memory footprint, flash wear levelling, while achieving execution times similarly
with existing WSN file systems. 相似文献
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Renata FurtunaSilvia Curteanu Florin Leon 《Engineering Applications of Artificial Intelligence》2011,24(5):772-785
This paper presents an original software implementation of the elitist non-dominated sorting genetic algorithm (NSGA-II) applied and adapted to the multi-objective optimization of a polysiloxane synthesis process. An optimized feed-forward neural network, modeling the variation in time of the main parameters of the process, was used to calculate the vectorial objective function of NSGA-II, as an enhancement to the multi-objective optimization procedure. An original technique was utilized in order to find the most appropriate parameters for maximizing the performance of NSGA-II. The algorithm provided the optimum reaction conditions (reaction temperature, reaction time, amount of catalyst, and amount of co-catalyst), which maximize the reaction conversion and minimize the difference between the obtained viscometric molecular weight and the desired molecular weight. The algorithm has proven to be able to find the entire non-dominated Pareto front and to quickly evolve optimal solutions as an acceptable compromise between objectives competing with each other. The use of the neural network makes it also suitable to the multi-objective optimization of processes for which the amount of knowledge is limited. 相似文献
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We consider two complementary operations: Hairpin completion introduced in [D. Cheptea, C. Martin-Vide, V. Mitrana, A new operation on words suggested by DNA biochemistry: Hairpin completion, in: Proc. Transgressive Computing, 2006, pp. 216–228] with motivations coming from DNA biochemistry and hairpin reduction as the inverse operation of the hairpin completion. Both operations are viewed here as formal operations on words and languages. We settle the closure properties of the classes of regular and linear context-free languages under hairpin completion in comparison with hairpin reduction. While the class of linear context-free languages is exactly the weak-code image of the class of the hairpin completion of regular languages, rather surprisingly, the weak-code image of the class of the hairpin completion of linear context-free languages is a class of mildly context-sensitive languages. The closure properties with respect to the hairpin reduction of some time and space complexity classes are also studied. We show that the factors found in the general cases are not necessary for regular and context-free languages. This part of the paper completes the results given in the earlier paper, where a similar investigation was made for hairpin completion. Finally, we briefly discuss the iterated variants of these operations. 相似文献