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991.
Hamada Elsayed Luca Grigolato Gianpaolo Savio Paolo Colombo Enrico Bernardo 《International Journal of Applied Ceramic Technology》2023,20(1):131-140
Pastes based on preceramic polymers have a great potential for direct ink writing of bioceramic scaffolds. In this paper, we discuss the fabrication of phase pure sphene (CaTiSiO5) bioceramics, developed by firing, at 1300°C, of silicone-based printed scaffolds containing CaCO3 and TiO2 as active fillers. As a proof of the flexibility of the combination of preceramic polymers and additive manufacturing technologies, several lattice geometries of increasing complexity were successfully explored. In particular, the approach allowed the fabrication of sphene scaffolds with gyroid-like structure exhibiting an impressive compressive strength, given the high porosity. Moreover, different lattice topologies of sphene scaffolds were compared also in terms of permeability. 相似文献
992.
Motelay-Massei A Harner T Shoeib M Diamond M Stern G Rosenberg B 《Environmental science & technology》2005,39(15):5763-5773
This is the second of two papers demonstrating the feasibility of using passive air samplers to investigate persistent organic pollutants along an urban-rural transect in Toronto. The first paper investigated spatial trends for polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). This second paper investigates the seasonality of air concentrations for polycyclic aromatic hydrocarbons (PAHs), PCBs, and OCPs along this transect. Air samplers, consisting of polyurethane foam (PUF) disks housed in stainless steel domed chambers, were deployed for three 4-month integration periods from June 2000 to July 2001. The seasonal variations of derived air concentrations for PAHs, PCBs, and OCPs reflected the different source characteristics for these compounds. PAHs showed a strong urban-rural gradient with maximum concentrations at urban sites during the summer period (July-October). These high summer values in Toronto were attributed to increases in evaporative emissions from petroleum products such as asphalt. PCBs also exhibited a strong urban-rural gradient with maximum air concentrations (approximately 2-3 times higher) during the spring period (April-June). This was attributed to increased surface-air exchange of PCBs that had accumulated in the surface layer over the winter. alpha-HCH was fairly uniformly distributed, spatially and temporally, as expected. This pattern and the derived air concentration of approximately 35 to approximately 100 pg m(-3) agreed well with high volume air data from this region, adding confidence to the operation of the passive samplers and showing that site-to-site differences in sampling rates was not an issue. For other OCPs, highest concentrations were observed during the spring period. This was associated with either (i) their local and/or regional application (gamma-HCH, endosulfan) and (ii) their revolatilization (chlordanes, DDT isomers, dieldrin, and toxaphene). Principal component analysis resulted in clusters for the different target chemicals according to their chemical class/source type. The results of this study demonstrate how such a simple sampling technique can provide both spatial and seasonal information. These data, integrated over seasons, can be used to evaluate contaminant trends and the potential role of large urban centers as sources of some semivolatile compounds to the regional environment, including the Great Lakes ecosystem. 相似文献
993.
Although the nutrition situation in most Latin American countries is improving and malnutrition is easing, worrisome factors are emerging. Huge rural-to-urban migrations have been accompanied by a worsening nutrition situation in rural populations, especially in Mexico, Colombia, and Brazil, a phenomenon not readily apparent from average food availability and malnutrition data. Average figures can also mask the severe nutrition problems that persist in four densely populated areas: the Caribbean Islands, Central America, the Andean region, and parts of Brazil. Although globalization is improving the nutritional status of many population groups in Latin America, it is also creating new pressures. Latin American countries dependent on agriculture are especially vulnerable. 相似文献
994.
Aguirre RC Colombo EM Barraza JF 《Journal of the Optical Society of America. A, Optics, image science, and vision》2011,28(10):2187-2191
When a bright light is present in the field of view, visibility is dramatically reduced. Many studies have investigated the effect of glare on visibility considering foveal vision. However, the effects on peripheral vision have received little attention. In a previous work [J. Opt. Soc. Am. A 25, 1790 (2008)], we showed that the effect of glare on reaction time (RT) for foveal vision at mesopic adaptation depends on the stimulus spatial frequency. In this work, we extend this study to peripheral vision. We measured the RT of achromatic sinusoidal gratings as a function of contrast for a range of spatial frequency, and eccentricity, and for two glare levels, in addition to the no-glare condition. Data were fitted with Piéron's law, following a linear relationship. We found that glare increases the slope of these lines for all conditions. These slopes seem to depend critically on eccentricity for 4 cycles/degree (c/deg), but not for 1 and 2 c/deg. We explain our results in terms of the contrast sensitivity (gain) of the underlying detection mechanisms. 相似文献
995.
Ramesh Neppalli Valerio Causin Carla Marega Roberta Saini Miriam Mba Antonio Marigo 《Polymer Engineering and Science》2011,51(8):1489-1496
Biodegradable polycaprolactone/organoclay nanocomposites were prepared by solvent casting, using different amounts of filler and matrices differing by average molecular weight. Intercalated nanocomposites were obtained. The nanocomposites were characterized by wide‐angle X‐ray diffraction (WAXD) and small‐angle X‐ray scattering (SAXS) methods. Negligible variations in the degree of crystallinity were detected by WAXD. The thickness of crystalline lamellae, measured by SAXS, increased in low molecular weight polymer nanocomposites with increasing clay amount; this effect was weakened in matrices with high molecular weight. Differential scanning calorimetry showed an inhibiting effect of clay on crystallization. The composites' ductility was largely increased, whereas stiffness was retained. After biodegradation in compost, in all samples, the degree of crystallinity was increased, meaning that the less ordered portion of the sample was preferentially degraded. Clay slowed down the biodegradation rate, coherently with the observed increase in the lamellar thickness due to the filler. This may offer a strategy for tuning the biodegradability by calibrating their semicrystalline framework. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers. 相似文献
996.
Negar Babaei Omali Lakshman N. Subbaraman Miriam Heynen Alan Ng Chantal Coles-Brennan Zohra Fadli Lyndon Jones 《Contact lens & anterior eye》2018,41(4):329-334
Purpose
To determine and compare the levels of surface versus bulk active lysozyme deposited on several commercially available hydrogel contact lens materials.Methods
Hydrogel contact lens materials [polymacon, omafilcon A, nelfilcon A, nesofilcon A, ocufilcon and etafilcon A with polyvinylpyrrolidone (PVP)] were incubated in an artificial tear solution for 16?h. Total activity was determined using a standard turbidity assay. The surface activity of the deposited lysozyme was determined using a modified turbidity assay. The amount of active lysozyme present within the bulk of the lens material was calculated by determining the difference between the total and surface active lysozyme.Results
The etafilcon A materials showed the highest amount of total lysozyme activity (519?±?8?μg/lens, average of Moist and Define), followed by the ocufilcon material (200?±?5?μg/lens) and these two were significantly different from each other (p?<?0.05). The amount of surface active lysozyme on etafilcon and ocufilcon lens materials was significantly higher than that found on all other lenses (p?<?0.05). There was no active lysozyme quantified in the bulk of the nelfilcon material, as all of the active lysozyme was found on the surface (1.7?±?0.3?μg/lens). In contrast, no active lysozyme was quantified on the surface of polymacon, with all of the active lysozyme found in the bulk of the lens material (0.6?±?0.6?μg/lens).Conclusions
The surface and bulk activity of lysozyme deposited on contact lenses is material dependent. Lysozyme deposited on ionic, high water content lens materials such as etafilcon A show significantly higher surface and bulk activity than many other hydrogel lens materials. 相似文献997.
Simcha Finkelman Shlomo Navarro Miriam Rindner Refael Dias Avi Azrieli 《Journal of Stored Products Research》2004,40(5):499-506
This study forms part of an effort to eliminate the need for methyl bromide fumigation to control insects in stored commodities, through development of a novel “vacuum-hermetic” technology. The effects of low pressures and exposure times on the mortality of insects in stored cocoa beans were studied at a temperature of 30°C in order to simulate cocoa bean storage conditions in tropical climates. Insects were exposed within test chambers containing the cocoa beans at a moisture content in equilibrium with 55% r.h. and at a constant temperature of 30°C. Three species of insects were used, all being major pests of cocoa beans in producer countries: Ephestia cautella (Walker), Plodia interpunctella (Hübner) and Tribolium castaneum (Herbst). At 50±5 mmHg, the egg stage was the most resistant in all three species, times needed to obtain 99% mortality being 45, 49 and 22 h, respectively. Results show that low-pressure treatment can provide an additional and more effective option to the 5 days fumigation with phosphine used today in the replacement of methyl bromide. The use of low pressures allows the control of insect pests at shorter exposure times without the need for toxic chemicals with their environmental impact. 相似文献
998.
999.
Shanmugavelayutham Sundaram Paolo Colombo Yutai Katoh 《International Journal of Applied Ceramic Technology》2013,10(5):731-739
Novel ceramic materials and advanced techniques for processing them and controlling their microstructure are breaking new ground in the areas of energy, environment, and transportation. For example, terahertz (THz) properties of ceramic materials and advanced structures reveal their potential for sensing in energy and environmental applications as well as local communication networks in transportation. Emerging opportunities for the development of improved porous ceramics for engine emissions control are discussed in particular, in consideration of the key role that this technology has with respect to global environmental and transportation concerns. Moreover, it is anticipated that advanced ceramics and composites of certain classes will enable innovation in nuclear energy by providing breakthrough accident‐tolerant features. In this article, we highlight these three areas of ceramics that are critical to the future and also show promise for growth. 相似文献
1000.