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排序方式: 共有463条查询结果,搜索用时 15 毫秒
1.
2.
Robert Groth Luke T. Cravigan Sadegh Niazi Zoran Ristovski Graham R. Johnson 《Journal of the Royal Society Interface》2021,18(178)
The airborne dynamics of respiratory droplets, and the transmission routes of pathogens embedded within them, are governed primarily by the diameter of the particles. These particles are composed of the fluid which lines the respiratory tract, and is primarily mucins and salts, which will interact with the atmosphere and evaporate to reach an equilibrium diameter. Measuring organic volume fraction (OVF) of cough aerosol has proved challenging due to large variability and low material volume produced after coughing. Here, the diametric hygroscopic growth factors (GF) of the cough aerosol produced by healthy participants were measured in situ using a rotating aerosol suspension chamber and a humidification tandem differential mobility analyser. Using hygroscopicity models, it was estimated that the average OVF in the evaporated cough aerosol was 0.88 ± 0.07 and the average GF at 90% relative humidity (RH) was 1.31 ± 0.03. To reach equilibrium in dry air the droplets will reduce in diameter by a factor of approximately 2.8 with an evaporation factor of 0.36 ± 0.05. Hysteresis was observed in cough aerosol at RH = ∼35% and RH = ∼65% for efflorescence and deliquescence, respectively, and may depend on the OVF. The same behaviour and GF were observed in nebulized bovine bronchoalveolar lavage fluid. 相似文献
3.
Pressurized fabric tubes, pressure-stabilized beams (known as air beams) and air-inflated structures are considered to be valuable technologies for lightweight, rapidly deployable structures. Design optimization of an inflated structure depends on a thorough understanding of woven fabric mechanics. In this paper the bending response of woven pressure-stabilized beams have been experimentally tested and analytically investigated. Additionally, the micromechanical effects of interacting tows have been studied through finite element models containing contact surfaces and nonlinear slip/stick conditions. Local unit cell models consisting of pairs of woven tows were created to characterize the effective constitutive relations. The material properties from the unit cell models were then used for the global continuum model subjected to 4-point flexure. An experimental set-up was designed and manufactured for testing of Vectran and PEN air beams. The air beam mid-span deflections were measured as functions of inflation pressure and bending load. Plots of the elastic and shear moduli with respect to the pressure and coefficient of friction have been generated. It was determined that the effective elastic and shear moduli were functions of inflation pressure, the material used and the geometry of the weave. It was shown that pneumatic or pressurized tube structures differ fundamentally from conventional metal structures. 相似文献
4.
5.
S Jamali D Archer P Ravussin M Bonnafous P David C Ecoffey 《Canadian Metallurgical Quarterly》1997,84(6):1292-1296
Directed delivery and distribution of anaesthetics (novocaine, lidocaine, trimecaine) immobilized on finely dispersed iron powders under the influence of an external magnetic field in body tissues of test animals have been studied. The data of emission spectral analysis relating to concentration of iron in soft and bone tissues of animals influenced by constant and alternating magnetic field on front and reverse sides over a period from 0 to 180 min are given. 相似文献
6.
Mohammadi Hossein Mohammadi Mohammad Amiri Iraj Sadegh Hosseinghadiry Mahdiar 《SILICON》2021,13(3):747-755
Silicon - In this paper, a new structure: triple work function metal gate SOI MESFET, intended for integration into the deep-submicron CMOS technology, is proposed. The gate of the device consists... 相似文献
7.
M. R. Jamali M. Dehyadegari A. Arami C. Lucas Z. Navabi 《Neural computing & applications》2010,19(1):13-19
Recent studies show that emotion is a mechanism for fast decision-making in human and other animals. Mathematical models have
been developed for describing emotion in mammals. These models, similar to other bioinspired models, must be implemented in
embedded platforms for industrial and real applications. In this paper, brain emotional learning based intelligent controller,
which is based on mammalian middle brain, is designed and implemented on field-programmable gate arrays, and this emotional
controller is applied for controlling of laboratorial overhead traveling crane in model-free and embedded manner. The main
features of this controller are leaning capability, providing a model-free control algorithm, robustness and the ability to
respond swiftly. By designing appropriate stress signals, a designer can implement a proper trade among control objectives. 相似文献
8.
In this paper, fuzzy threshold values, instead of crisp threshold values, have been used for optimal reliability-based multi-objective Pareto design of robust state feedback controllers for a single inverted pendulum having parameters with probabilistic uncertainties. The objective functions that have been considered are, namely, the normalized summation of rising time and overshoot of cart (SRO–C) and the normalized summation of rising time and overshoot of pendulum (SRO–P) in the deterministic approach. Accordingly, the probabilities of failure of those objective functions are also considered in the reliability-based design optimization (RBDO) approach. A new multi-objective uniform-diversity genetic algorithm (MUGA) is presented and used for Pareto optimum design of linear state feedback controllers for single inverted pendulum problem. In this way, Pareto front of optimum controllers is first obtained for the nominal deterministic single inverted pendulum using the conflicting objective functions in time domain. Such Pareto front is then obtained for single inverted pendulum having probabilistic uncertainties in its parameters using the statistical moments of those objective functions through a Monte Carlo simulation (MCS) approach. It is shown that multi-objective reliability-based Pareto optimization of the robust state feedback controllers using MUGA with fuzzy threshold values includes those that may be obtained by various crisp threshold values of probability of failures and, thus, remove the difficulty of selecting suitable crisp values. Besides, the multi-objective Pareto optimization of such robust feedback controllers using MUGA unveils some very important and informative trade-offs among those objective functions. Consequently, some optimum robust state feedback controllers can be compromisingly chosen from the Pareto frontiers. 相似文献
9.
Jalil Layegh Fariborz Jolai Mohsen Sadegh Amalnik 《Advances in Engineering Software》2009,40(10):1074-1077
In this paper, we consider minimizing total weighted completion time criteria on a single machine. Jobs processing times are step function of its starting time and all jobs have a common due date. First, we present some new lemmas and dominance properties for this NP-hard problem, and then a memetic algorithm using these properties is developed. We compare the solutions of the memetic algorithm with optimal solutions obtained from complete enumeration. The results show that the average percentage error of the proposed algorithm from optimal solutions is about 2% and as the variance of processing time increase, the percentage errors decrease. 相似文献
10.
Interaction between refractory crucible materials and the melted NiTi shape-memory alloy 总被引:2,自引:0,他引:2
S. K. Sadrnezhad Sadegh Badakhshan Raz 《Metallurgical and Materials Transactions B》2005,36(3):395-403
Attempts have been made to quantify the amount of contaminants absorbed by liquid metal from commercial ZrO2-, Al2O3-, and SiC-base crucibles used for vacuum melting of Ni-45 wt pct Ti alloy. The molten alloy was held under vacuum for 90
minutes at 1450 °C to become homogenized. Reactions between the liquid metal and the crucible were investigated by visual
observation, chemical analysis, scanning electron microscopy (SEM) image processing, and X-ray mapping. The relative degree
of contamination declined in the following sequence: commercially pure SiC>SiC-5 wt pct Al2O3-5 wt pct SiO2>slurry cast alumina>recrystallized alumina>zircon type A>oxygen deficient high-purity zirconia. Thermodynamic calculations
showed a difference between the equilibrium and the experimental data, indicating that except for commercially pure SiC crucible,
the amount of the crucible elements entering the melt is greater than the calculated equilibrium values. This discrepancy
seems to be due to the immersion into the melt of the undissolved chemical compounds formed due to the reactions between the
crucible and the liquid phase. 相似文献