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71.
Tristan Allard Benjamin Nguyen Philippe Pucheral 《Distributed and Parallel Databases》2014,32(2):191-244
The goal of Privacy-Preserving Data Publishing (PPDP) is to generate a sanitized (i.e. harmless) view of sensitive personal data (e.g. a health survey), to be released to some agencies or simply the public. However, traditional PPDP practices all make the assumption that the process is run on a trusted central server. In this article, we argue that the trust assumption on the central server is far too strong. We propose Met ??P, a generic fully distributed protocol, to execute various forms of PPDP algorithms on an asymmetric architecture composed of low power secure devices and a powerful but untrusted infrastructure. We show that this protocol is both correct and secure against honest-but-curious or malicious adversaries. Finally, we provide an experimental validation showing that this protocol can support PPDP processes scaling up to nation-wide surveys. 相似文献
72.
Tetraalkylammonium cellulosates were prepared by means of an exchange reaction between cellulose and tetraalkylammonium methoxides in anhydrous methanol and dimethylsulfoxide up to a degree of substitution of about 0,7 without chain degradation. The course of this reaction and the structure of the cellulosates in comparison to lithium and sodium cellulosate has been studied. The reaction rate and the equilibrium substitution decreased with increasing size of the cation in the methoxide. The distribution of the alcoholate groups in equilibrium at C-2, C-3 and C-6 of the glucopyranosyl unit in the cellulosates, which was investigated by methylation, hydrolysis of the methylcelluloses, and analysis of the methylglucoses by gas chromatography, was independent of the nature of the cation. Under the given reaction conditions the hydroxyl group at C-2 was more acidic than those at C-3 and C-6, while for the latter practically no difference was found. The tetraalkylammonium cellulosates are highly reactive intermediates for the preparation of cellulose derivatives. The reactivity of the cellulosates increased with increasing size of the cation, Li⊕ < Na⊕ < N(CH3)4⊕ <[(CH3)3N? CH2? C6H5]⊕. 相似文献
73.
Nguyen Van Nguu 《Nutrient Cycling in Agroecosystems》1987,14(2):135-142
The shortening of fallow period in several areas in tropical Africa has reduced soil fertility and exposed soils to erosion and run-off. Fertilizer application and crop conservation practices are needeed to sustain high crop yield and to conserve the natural resource base for upland crop production in the continent. Field trials were carried out to evaluate the effect of fertilizer application and soil and crop residues management practices on yield of maize (Zea mays L.) planted on a Plinthudult soil at Bertoua, Eastern Cameroon. Maize yields increased significantly with nitrogen and phosphorus fertilizer application. Under the rainfall pattern prevailing in the area, the amount of nitrogen required for maximum yield was higher in the second season. On the other hand, the amount of phosphorus required for maximum yield appeared to decrease with time. The burning of crop residues and weeds prior to planting together with no-till practive gave higher yield of maize than other soil and crop residues management practices. 相似文献
74.
The liver microsomal Δ9 and Δ6 desaturase activities have been studied in rats with carbon tetrachloride-induced hepatitis. Immediately after poisoning,
significant decreases were observed for both types of desaturase activity. However, recovery kinetics were slower for the
Δ6 desaturase than for the Δ9 desaturase. The activities of NADH-ferricyanide and NADH-cytochrome C reductases, proteins involved in the electron transfers
associated with microsomal desaturation, were also measured. There was a fall in both activities after poisoning, but this
decrease was less than that of the desaturase activities. 相似文献
75.
A one-dimensional steady-state mathematical model has been developed to simulate the process of calcination of petroleum coke in a rotary kiln. A simulation is made to reproduce the operating conditions prevailing during a normal working day, in order to validate the model, and to study the effects of the main process control variables. It has been found that of the energy provided by combustion, 59.5 % comes from hydrogen, 14.6 % from the carbon of the coke bed, 13.8 % from coke dust, 11.3 % from methane and 0.8 % from tar. A comparison with existing models is made to identify eventual similarities between the various kilns under study. It appears that maximum coke temperature occurs at 45 to 55 % of kiln length, while volatile matters evolution takes place between 5 and 60 % of kiln length, measured from feed end. 相似文献
76.
Kinetics of steam gasification of delayed and fluid cokes derived from Athabasca bitumen have been studied in 6.35 cm diameter stirred and fixed bed reactors. Experiments were carried out at atmospheric pressure and at temperatures between 800°C and 930°C. The coke particle size ranged from 0.1 to 3.5 mm, and the steam partial pressure was varied from 15.2 to 60.6 kPa. Scanning electron microscopy, surface area analysis, and mercury porosimetry were employed to relate physical structure changes in the solids to experimental kinetic data. Several kinetic models for gasification were tested with the experimental gasification data. Rate expressions are presented for carbon conversion and for the release of sulphur. 相似文献
77.
Aziz Rezig Tinh Nguyen David Martin Lipiin Sung Xiaohong Gu Joan Jasmin Jonathan W. Martin 《Journal of Coatings Technology and Research》2006,3(3):173-184
The relationship between chemical degradation and thickness loss of an unpigmented, non UV-stabilized, crosslinked amine-cured
epoxy coating exposed to three UV conditions was investigated. Spin-coated samples having a thickness of approximately 7 μm
on an Si substrate were prepared from a stochiometric mixture of a bisphenol A epoxy resin and a tetra-functional amine curing
agent. Samples were exposed outdoors and to two accelerated laboratory UV environments. Chemical degradation and thickness
loss were measured by transmission Fourier transform infrared spectroscopy (FTIRS) and laser scanning confocal microscopy
(LSCM), respectively. In addition, surface roughness and morphological changes were measured by atomic forcemicrosocopy (AFM)
and LSCM. Substantial chemical degradation, thickness loss, and morpholocal changes occurred in the exposed films, and the
rate of chemical degradation was greater than that due to the thickness loss. This additional chemical loss was attributed
to an inhomogeneous degradation process in which nanoscale localized depressions initiate at certain sites on the surface,
which then enlarge and deepen with exposure time. The results of this study provide a better understanding of the degradation
mechanism and should lead to the development of scientific-based models for predicting the service life of crosslinked amine-cured
epoxy coatings.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago,
IL 相似文献
78.
This paper proposes a new approach for color transfer between two images. Our method is unique in its consideration of the scene illumination and the constraint that the mapped image must be within the color gamut of the target image. Specifically, our approach first performs a white‐balance step on both images to remove color casts caused by different illuminations in the source and target image. We then align each image to share the same ‘white axis’ and perform a gradient preserving histogram matching technique along this axis to match the tone distribution between the two images. We show that this illuminant‐aware strategy gives a better result than directly working with the original source and target image's luminance channel as done by many previous methods. Afterwards, our method performs a full gamut‐based mapping technique rather than processing each channel separately. This guarantees that the colors of our transferred image lie within the target gamut. Our experimental results show that this combined illuminant‐aware and gamut‐based strategy produces more compelling results than previous methods. We detail our approach and demonstrate its effectiveness on a number of examples. 相似文献
79.
Ba Nghiep Nguyen Brian J Koeppel Said Ahzi Mohammad A Khaleel Prabhakar Singh 《Journal of the American Ceramic Society》2006,89(4):1358-1368
This paper addresses the damage and fracture issues of glass and ceramic materials used in solid oxide fuel cells. Analyses of an internal crack and of an interface crack between dissimilar materials were conducted using a modified boundary layer modeling approach. In this approach, fracture is allowed to occur in a small process window situated at an initial crack tip. Elastic displacement crack-tip fields are prescribed as remote boundary conditions. Crack propagation was first modeled discretely. Next, a continuum damage mechanics (CDM) model for brittle materials was developed to capture damage and crack growth in the process window. In particular, the damage model was applied to a glass-ceramic material that had been developed in-house for sealing purposes. Discrete and continuum damage solutions were then compared. Finally, the CDM model was used to determine the crack propagation direction as a function of a mode mixity measure. 相似文献
80.
Tinh Nguyen W. Eric Byrd David Alshed Joannie Chin Cyril Clerici Jon Martin 《The Journal of Adhesion》2007,83(6):587-610
Water at the polymer/substrate interface is often the major cause of adhesion loss in coatings, adhesives, and fiber-reinforced polymer composites. This study critically assesses the relationship between the interfacial water layer and the adhesion loss in epoxy/siliceous substrate systems. Both untreated and silane-treated Si substrates and untreated and silane-treated E-glass fibers were used. Thickness of the interfacial water layer was measured on epoxy/Si systems by Fourier transform infrared-multiple total internal reflection (FTIR-MTIR) spectroscopy. Adhesion loss of epoxy/Si systems and epoxy/E-glass fiber composites was measured by peel adhesion and short-beam shear tests, respectively. Little water accumulation at the epoxy/Si substrate interface was observed for silane-treated Si substrates, but about 10 monolayers of water accumulated at the interface between the epoxy and the untreated Si substrate following 100 h of exposure at 24 °C. More than 70% of the initial epoxy/untreated Si system peel strength was lost within 75 h of exposure, compared with 20% loss after 600 h for the silane-treated Si samples. Shear strength loss in composites made with untreated E-glass fiber was nearly twice that of composites fabricated with silane-treated fiber after 6 months of immersion in 60 °C water. Further, the silane-treated composites remained transparent, but the untreated fiber composites became opaque after water exposure. Evidence from FTIR-MTIR spectroscopy, adhesion loss, and visual observation strongly indicated that a water layer at the polymer/substrate interface is mostly responsible for the adhesion loss of epoxy/untreated siliceous substrate systems and epoxy/untreated glass fiber composites and that FTIR-MTIR is a viable technique to reliably and conveniently assess the adhesion loss attributable to water sorption at the interface. 相似文献