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通过对省CMNET骨干网、IP城域数据网、IP宽带数据接入网3个主要网络层次的工程建设定位、技术特点、建设原则进行的分析,总结出在目前市场竞争条件下进行移动数据网络建设的相关思路。 相似文献
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An analysis of desorption isotherms for potato shows the following probable qualities in the water-potato system. In the natural state the water is bound rather strongly due to loss of rotational degrees of freedom in the sorbed molecules, which is caused by small molecular voids in the cellulose structure. This structure therefore is formed as a uniformly cross bound state of the OH-groups. This state prevails up to a certain temperature, above which a reaction sets in, where OH bonds are successively broken, giving possibility for a partial rotation of sorbed molecules. In the range of lower moisture content the cellulose structure is changed into a crystalline state as in wood, although the degree of crystallinity is lower, which is the probable reason why the statistical fluctuations in the isotherms are greater for potato than for wood. 相似文献
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It is claimed that any reliability measure defined in connection with a limit state theory of a high reliability technological system is a purely formal comparative measure of safety. It only makes sense to make comparisons within classes of “similar” technological systems which are all accessible to the same theory. Interpretation of calculated formal failure probabilities as predictions of real failure rates are generally not justified. 相似文献
77.
de Caritat P Hall G Gìslason S Belsey W Braun M Goloubeva NI Olsen HK Scheie JO Vaive JE 《The Science of the total environment》2005,336(1-3):183-199
At the end of the northern winter 1996/1997, 21 snow samples were collected from 17 arctic localities in Norway, Sweden, Finland, Svalbard, Russia, Alaska, Canada, Greenland and Iceland. Major element concentrations of the filtered (0.45 mum) melted snow indicate that most samples are consistent with a diluted seawater composition. Deviations from this behaviour indicate additional SO(4)(2-) and Cl(-) relative to seawater, suggesting a minor contribution from (probably local) coal combustion emissions (Alaska, Finland, Sweden, Svalbard). The samples with the highest Na and Cl(-) content (Canada, Russia) also have higher Na/SO(4)(2-) and Cl(-)/SO(4)(2-) ratios than seawater, suggesting a slight contamination from (probably local) deicing activities. Local soil or rock dust inputs in the snow are indicated by 'excess' Ca contents (Alaska, Svalbard, Greenland, Sweden). No overall relationship was found between pH (range: 4.6-6.1) and total or non-seasalt SO(4)(2-) (NSS), suggesting that acidification due to long-range transport of SO(2) pollution is not operating on an arctic-wide scale. In a few samples (Alaska, Finland, Sweden, Svalbard), a significant proportion (>50%) of SO(4)(2-) is non-marine in origin. Sources for this non-marine SO(4)(2-) need not all be found in long-range atmospheric transport and more likely sources are local industry (Finland, Sweden), road traffic (Alaska) or minor snow-scooting traffic (one Svalbard locality). A few samples from northern Europe show a relatively weak trend of decreasing pH with increasing NO(3)(-). 相似文献
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Bustnes JO Borgå K Dempster T Lie E Nygård T Uglem I 《Environmental science & technology》2012,46(14):7836-7843
The latitudinal distribution of persistent organic pollutants (POPs: legacy organochlorines [OCs], polybrominated diphenyl ethers [PBDEs,] and hexabromocyclododecane [HBCD]) was examined in livers of two species of marine fish, the pelagic saithe (Pollachius virens,n = 40) and the demersal cod (Gadus morhua,n = 40), along a south-north gradient (59°-70°N) on the Norwegian Coast. Cod had in general two to three times higher concentrations of POPs than saithe, probably because of higher exposure in the benthic food chain. The concentrations of heavy halogenated compounds were higher in the southernmost region than further north. Moreover, the POP pattern showed a gradual shift in the compositions from south to north, especially for OCs in cod: i.e. the relative importance of low-chlorinated polychlorinated biphenyl (PCB) congeners and some OC-pesticides (e.g., hexachlorobenzen [HCB]) in the contaminant burdens increased with latitude. The latitudinal fractionation signal was weaker in saithe, possibly due to its pelagic and nomadic behavior. Hence, this study shows not only a strong latitudinal fractionation in the compositional patterns of POPs in marine fish but also the effects of habitat use and fish behavior. 相似文献
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We report thermal conductivity (κ) of low-density, high-density and ultra-high density polyethylene (PE) with different crystallinity and microstructures. PE was crystallized under high-pressure and high-temperature conditions which produce extended chain crystals. By applying a two-phase model, we estimate κ of 100% crystallized PE as a function of pressure and temperature. The increased crystallinity and lamellar thickness (fold length) reduce the thermal resistance, which is reflected not only in the absolute value of κ but also in more pronounced pressure and temperature dependencies approaching those of polycrystalline low-molecular weight materials. The results suggest that it is crucial to increase the lamellar thickness to significantly improve κ of PE with randomly oriented lamellae. 相似文献
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