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91.
A multiphase model based on unsaturated flow in a hygroscopic porous medium, which accounts for the important physical phenomena that take place during thermal treatment of meat, is developed. Frozen meat is considered as a porous solid comprising of water, fat and protein with gas trapped in its pores. As it is heated, water and fat melt, and, are gradually released from the solid protein matrix to the pore space. With further rise in temperature, liquid water evaporates. Since four fluid components (liquid water phase, liquid fat phase, water vapor and air) are present in the pore space, a mass balance equation is written for each component. Local thermal equilibrium assumption leads to one energy balance equation for the whole system. The model is validated for double-sided contact heating of hamburger patties by comparing temperature and moisture profiles with experimental studies. Dominant modes of transport are identified. 相似文献
92.
Depolarization current characteristics of solution grown pure ethyl cellulose (EC) films of about 20μm thickness have been studied as a function of electrode materials at constant poling field (5 × 104 V/cm) and poling temperature 40°C. Thermally stimulated current (TSC) thermograms of EC consists of two well resolved peaks
(located at 60°C and 140°C) for Al-Al system, which are attributed to the deorientation of strongly attached ethoxy groups
of glycosidal units and diffusion of space charges either at electrodes or due to their thermal release at higher temperatures
from the defect levels. For dissimilar electrode combinations (Al-Ag/Cu/Au/Sn/Pb), an indication of peak of lower magnitude
at around (50–70°C) alongwith a higher temperature peak (140–155°C), have been observed. TSC parameters are found to change
with the choice of electrode material. The dependence of dark current at 40°C in metal-ethyl cellulose-metal systems on applied
voltage in the range (2·0–5·0) × 104V/cm has also been studied. The results of current-voltage measurement on EC have been interpreted to show that the Schottky-Richardson
mechanism is the controlling transport mechanism. Zero field current density extrapolated fromI-E
1/2 plots are found to vary with metal work function. 相似文献
93.
In this paper, we present a collision free MAC protocol for wireless networks with smart antennas that provides proportional
service differentiation to various classes of traffic based on their respective bandwidth demand. The proposed protocol works
for diverse physical parameters such as number of interfaces at each node, number of communication frequencies, and antenna
beamwidth. To the best of our knowledge, this is the first work that provides link layer differentiated services for wireless
networks with smart antennas and explores the influence of the physical parameters and network topology on the performance
of the MAC layer.
Ashish Deopura received his B.Tech degree in Electrical Engineering from the Indian Institute of Technology Delhi, India, in 2003, and he
received his M.S. degree in Computer Systems Engineering from the University of Massachusetts Amherst, in 2005. He currently
works as a Modeling Engineer for OPNET Technologies located in Bethesda, MD
Professor Aura Ganz is the director of the Multimedia Networking Laboratory at the University of Massachusetts at Amherst. She has authored more
than 170 journal and conference papers in the areas of multimedia wireless networks, ubiquitous computing, telemedicine, and
security. She is a co-author of the book: “Multimedia Wireless Networks”, Prentice Hall, 2003. Some of her recent assignments
include: general co-chair of the IEEE UWBNETS workshop, general co-chair of the IEEE BROADMED workshop, general co-chair of
the Massachusetts 3rd Annual R&D Conference, keynote speaker at the NSF sponsored workshop in Mobile Computing, and invited
speaker at Personal and Local Wireless Network Solutions conference, and Motorola’s Wireless Communications Futures Forum,
Wireless Local Area Networks Conference. She has a PhD, MSc and BSc in Computer Science from the Technion in Israel. More
details can be found at: dvd1.ecs.umass.edu/wireless. 相似文献
94.
D Awasthi DF Church D Torbati ME Carey WA Pryor 《Canadian Metallurgical Quarterly》1997,47(6):575-81; discussion 581-2
BACKGROUND: Free radicals may be involved in the pathophysiology of traumatic brain injury (TBI) through oxidative damage of neurovascular structures. Endogenous antioxidants, such as ascorbate and alpha-tocopherol, may play a critical role in combating these oxidative reactions and their oxidized products can serve as an important index of oxidative stress. METHODS: We used electron spin resonance (ESR) spectroscopy and in vivo spin trapping (reaction of an organic compound with free radical species) to detect the possible generation of free radicals after TBI. Injury was inflicted by a weight drop technique over the head (5.7 kg-cm). Rats were intravenously infused with either 1 mL, 0.1 M of the spin trap, alpha-phenyl-N-tert-butyl nitrone (PBN), or an equivalent volume of saline immediately before TBI or sham-injury. Animals were divided into four groups: (1) Group I: PBN-infused sham-injured, (2) Group II: PBN-infused injured, (3) Group III: saline-infused sham-injured, and (4) Group IV: saline-infused injured. Additional groups of saline-infused uninjured, saline-infused, and PBN-infused injured animals were used for histopathology. Sixty minutes after TBI or sham-injury, rats were again anesthetized and decapitated. The brains were removed within 1 minute, homogenized, and extracted for lipids. The extracts were analyzed by ESR spectroscopy. Brain ascorbic acid (AA) concentration was determined spectrophotometrically, using the ascorbate oxidase assay. RESULTS: No PBN spin adduct signals (indicating trapped free radical species) were visible 60 minutes after TBI. All groups of rats showed an ascorbyl free radical signal. The ascorbyl signal intensity (AI) was, however, significantly higher in the injured rats, while the brain (AA) was significantly reduced. In addition, the ratio of AI/AA, which eliminates the effect of variable ascorbate concentrations in the brain, was also significantly higher in the injured animals. CONCLUSIONS: We conclude that 60 minutes following TBI there was a significantly increased level of oxidative stress in the brain. This may reflect formation of free radical species with subsequent interaction with ascorbate (antioxidant) during the 60 minute period. The lack of PBN spin adduct signals 1 hour after TBI may indicate that free radical generation is time dependent and might be detectable earlier or later than the 60 minute period. 相似文献
95.
Vishnu Awasthi Sushil K. Pandey Saurabh K. Pandey Shruti Verma Mukul Gupta Shaibal Mukherjee 《Journal of Materials Science: Materials in Electronics》2014,25(7):3069-3076
The growth of CIGS thin films on soda-lime glass substrates at different substrate temperatures by dual ion beam sputtering system in a single-step route from a single quaternary sputtering target with the composition of Cu (In0.70 Ga0.30) Se2 was reported. The effects of the substrate temperature on structural, optical, morphological and electrical properties of CIGS films were investigated. Stoichiometry of one such film was investigated by X-ray photoelectron spectroscopy. All CIGS films had demonstrated a strong (112) orientation located at 2θ ~26.70o, which indicated the chalcopyrite structure of films. The value of full-width at half-maximum of (112) peak was reduced from 0.58° to 0.19° and crystallite size was enlarged from 14.98 to 43.05 nm as growth temperature was increased from 100 to 400 °C. However, atomic force microscope results showed a smooth and uniform surface at lower growth temperature and the surface roughness was observed to increase with increasing growth temperature. Hall measurements exhibited the minimum film resistivity of 0.09 Ω cm with a hole concentration of 2.42 × 1018 cm?3 and mobility of 28.60 cm2 V?1 s?1 for CIGS film grown at 100 °C. Film absorption coefficient was found to enhance nominally from 1 × 105 to 2.3 × 105 cm?1 with increasing growth temperature from 100 to 400 °C. 相似文献
96.
Sarat K. Swain Gyanaranjan Prusty Ashish S. Ray Lingaraj Behera 《Journal of Experimental Nanoscience》2014,9(3):240-248
Poly(methyl methacrylate)/expanded graphite (PMMA/EG) composites were prepared by the incorporation of EG in various proportions (1%, 2%, 3%, 4% and 5%) with PMMA by in situ polymerisation technique. The polymer composites were characterised by ultraviolet–visible (UV–vis) and Fourier transform infra-red spectroscopies. The structural property of PMMA/EG nanocomposites was studied by X-ray diffraction. The scanning electron microscopy and transmission electron microscopy of synthesised composites were taken in order to study their morphological properties. The conductivity of composites was measured as function of EG concentration. It was found that conductivity of composites gradually increased with the increase in EG loading. Oxygen permeability of PMMA/EG nanocomposites was calculated and it was found that the property was reduced substantially with rise of EG proportion. The thermal stability of PMMA/EG nanocomposites was improved by dispersion of EG with PMMA matrix. 相似文献
97.
Bi1-xNdxFeO3 (BNFOx, x = 0-0.15) nano-crystallites were successfully synthesised by solution combustion technique. Neodymium substitution has changed the rhombohedral symmetry of BiFeO3 to the triclinic and reduced the impurity phase. The average particle size found to vary from 74 to 26 nm when Nd concentration was increased from x = 0 to 0.15. The change in the symmetry is also confirmed by Raman spectra of nanocrystallite samples. The value of remnant magnetization has improved due to the continuing collapse of the space-modulated spin structure of BNFOx. Long-range ferromagnetic ordering in BNFOx at room temperature was also confirmed from Mössbauer spectra. 相似文献
98.
Absorption of CW Yb-fiber laser light of 1.07 μm wavelength in water has been measured at different water temperatures and laser intensities. The absorption coefficient was estimated to be 0.135 cm(-1) at 25 °C water temperature, and this was found to decrease with temperature at a rate of 5.7 × 10(-4) cm(-1) °C(-1). The absorption coefficient increased significantly when the laser beam was focused in water, and the increase depended on the distance of the focal point from the water surface. This has been attributed to the absorption and scattering losses of laser radiation in a cavity formed in water by the focused beam at laser intensities in the megawatts per square centimeter and higher range. 相似文献
99.
Smoothness assumptions in traditional image expansion cause blurring of edges and other high-frequency content that can be perceptually disturbing. Previous edge-preserving approaches are either ad hoc, statistically untenable, or computationally unattractive. We propose a new edge-driven stochastic prior image model and obtain the maximum a posteriori (MAP) estimate under this model. The MAP estimate is computationally challenging since it involves the inversion of very large matrices. An efficient algorithm is presented for expansion by dyadic factors. The technique exploits diagonalization of convolutional operators under the Fourier transform, and the sparsity of our edge prior, to speed up processing. Visual and quantitative comparison of our technique with other popular methods demonstrates its potential and promise. 相似文献
100.
Ashish Mehta James Geller Yehoshua Perl Peter Fankhauser 《Journal of Intelligent Information Systems》1996,7(1):75-100
A path-method (PM) is a mechanism to retrieve or to update information relevant to one class, in an object-oriented database (OODB), that is not stored with that class but with some other class. The PM traverses a chain of classes and connections that ends at the class where the required information is stored. However, it is a difficult task for a user to write PMs. This is because it might require comprehensive knowledge of many classes of the conceptual schema. But a typical user has often incomplete or even inconsistent knowledge of the schema. Currently we are developing a system, called Path-Method Generator (PMG), which generates PMs automatically according to a naive user's requests. One algorithm of PMG uses numerical access relevance between pairs of classes as a guide for the traversal of an OODB schema. In this paper we define the notion of access relevance to measure the significance of the (indirect) connection between any two classes in an OODB and present efficient algorithms to compute access relevance. The manual PM generation in an interoperable multi object-oriented database (IM-OODB) is even more difficult than for one OODB since a user has to be familiar with several OODBs. We use a hierarchical approach for developing efficient online algorithms for the computation of access relevances in an IM-OODB, based on precomputed access relevances for each autonomous OODB. In an IM-OODB the access relevances are used as a guide in generating PMs between the classes of different OODBs. 相似文献