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101.
Sudden changes in wind speed, so‐called wind speed ramps, are a major concern for wind power system operators. The present study applies the mesoscale ensemble forecast method for the prediction of wind speed ramps at wind farms in Japan and evaluates the ability and utility of this method. The mesoscale ensemble forecast in this study (ENS21) consists of 21 members with a horizontal resolution of 10 km for a 5‐year period. The simulated results show that ENS21 produces better accuracy than the deterministic forecast with a horizontal resolution of 10 km (DET_L). On the other hand, the deterministic forecast with a horizontal resolution of 5 km (DET_H) also produces better accuracy than DET_L. From a practical perspective, however, the ENS21 is computationally expensive. Thus, the eight‐member mesoscale ensemble forecast (ENS8) with as same computational cost as a deterministic forecast with a horizontal resolution of 5 km (DET_H) is also evaluated. The simulated results show that ENS8 has almost same accuracy as ENS21 and DET_H in wind speed ramp forecasts. ENS8 has advantages over ENS21 and DET_H because ENS8 is computationally efficient and is able to benefit wind power operators with flexibility in the selection of probability thresholds for decision processes compared with a single. It can be concluded that the mesoscale ensemble forecast method is more useful for prediction of the wind speed ramp than the single deterministic forecast method with the same computational cost if the ensemble members are successfully selected. 相似文献
102.
103.
Screening of marine microalgae for biodiesel feedstock 总被引:1,自引:0,他引:1
Thi Thai Yen Doan Balasubramanian SivaloganathanJeffrey Philip Obbard 《Biomass & bioenergy》2011,35(7):2534-2544
Biodiesel production from microalgae lipids is increasingly regarded as a more sustainable and feasible alternative to conventional biodiesel feedstocks derived from terrestrial bioenergy crops. A total of ninety-six strains of marine microalgae, with an elevated biomass productivity and intracellular lipid content, were isolated from the coastal waters of Singapore using an automated flow cytometric cell-sorting technique. Cell sorting was based on the two-dimensional distribution of algal cells for red fluorescence (representing chlorophyll auto-fluorescence) against forward-light scatter (representing cell size) and red vs. green fluorescence. Twenty-one of the strains were further characterized with respect to cell growth rate, biomass concentration, lipid content (total and neutral lipid) and fatty acid profile. The growth rates of Skeletonema costatum, Chaetoceros and Thalassiosira species were greatest among the entire strains, but in terms of absolute lipid yield Nannochloropsis strains predominated. Nannochloropsis strains had a lipid content ranging from 39.4% to 44.9% of dry weight biomass. Transesterification of the lipids yielded 25-51% of fatty acid methyl ester (FAME) i.e. biodiesel, where total FAME content ranged between 11 and 21% of dry weight biomass. This study describes the microalgae screening process and demonstrates that Nannochloropsis is a promising species for biodiesel feedstock. 相似文献
104.
Shiyang Liu Damon Kent Hongyi Zhan Nghiem Doan Chang Wang Sen Yu Matthew Dargusch Gui Wang 《材料科学技术学报》2021,86(27):237-250
This work investigates the strain rate dependence of dynamic recrystallization behaviour of high-purity zinc in room temperature compression under strain rates of 10-4 s-1,10-2 s-1 and 0.5 s-1.Results from electron backscatter diffraction provide insight into the deformation and dynamic recrystallization mech-anisms operative.Continuous dynamic recrystallization,twin-induced dynamic recrystallization,and discontinuous dynamic recrystallization are all active under compressive deformation at room temper-ature.Due to the high stacking fault energy of Zn,continuous dynamic recrystallization is the dominant mechanism while discontinuous dynamic recrystallization only operates in the early stages of compres-sion at 10-4 S-1.Dynamic recrystallization kinetics are enhanced at higher strain rates(10-2 s-1 and 0.5 s-1)due to an increased contribution from twin-induced dynamic recrystallization.The present study reveals that the controlling mechanisms for continuous dynamic recrystallization are basalslip and 2nd order pyramidalslip activity.Because the activation of slip systems is mainly deter-mined by crystallographic orientation,continuous dynamic recrystallization behaviour varies with grain orientation according to their propensity for basal and 2nd order pyramidal slip. 相似文献
105.
Nguyen Doan Quoc Anh 《中国工程学刊》2016,39(7):871-875
In this paper, we propose and discuss how to enhance the color uniformity and the lumen output of multi-chip white LED lamps (MCW-LEDs). This can be done by combining the green Ce0.67Tb0.33MgAl11O19:Ce,Tb phosphor (CeTb) and phosphor compounding. We find that the proposed method can have a significant effect on MCW-LEDs performance. Through simulation results, it is confirmed that the color uniformity and the lumen output of MCW-LEDs with average correlated color temperatures of 7000 and 8500 K grow with the concentration of CeTb, while the color rendering ability decreases. With proper choice of CeTb concentration, good performance of MCW-LEDs can be obtained. 相似文献
106.
PREPARE: a tool for knowledge base verification 总被引:4,自引:0,他引:4
The knowledge base is the most important component in a knowledge-based system. Because a knowledge base is often built in an incremental, piecemeal fashion, potential errors may be inadvertently brought into it. One of the critical issues in developing reliable knowledge-based systems is how to verify the correctness of a knowledge base. The paper describes an automated tool called PREPARE for detecting potential errors in a knowledge base. PREPARE is based on modeling a knowledge base by using a predicate/transition net representation. Inconsistent, redundant, subsumed, circular, and incomplete rules in a knowledge base are then defined as patterns of the predicate/transition net model, and are detected through a syntactic pattern recognition method. The research results to date have indicated that: the methodology ran be adopted in knowledge-based systems where logic is used as knowledge representation formalism; the tool can be invoked at any stage of the system's development, even without a fully functioning inference engine; the predicate/transition net model of knowledge bases is easy to implement and provides a clear and understandable display of the knowledge to be used by the system 相似文献
107.
We study packet combining techniques for retransmission schemes over intersymbol interference (ISI) channels. Two types of combining schemes are investigated, namely, maximum-likelihood combining (MLC) and iterative combining (IC). By first employing a precoding technique and then by interpreting the ISI channel as a trellis code, the transmissions of the same data packet at different times through the channel can be treated as the parallel concatenation of recursive trellis codes. If interleavers are used in between retransmissions, "turbo" coding gains can be achieved by iterative equalization. It is shown that IC provides excellent performance and outperforms other forms of combining in terms of frame error rate performance both analytically and through simulations 相似文献
108.
J. Rawers G. Slavens D. Govier C. Doğan R. Doan 《Metallurgical and Materials Transactions A》1996,27(10):3126-3134
Data on mechanical properties of nanocrystalline materials have been limited, due in part to the difficulty in producing consolidated
nanocrystalline materials of sufficient quantity for characterization and evaluation. A second problem is consolidation and
retention of the nanostructure. A vacuum hot-pressing consolidation program has been developed to produce full-dense compacts
from attrition milled, mechanically alloyed, nanograin micron-size particles of Fe-2 wt pet Al powder. The resulting compacts
were of sufficient size to allow evaluation of microstructure, density, hardness, and tensile properties. The compacted microstructure
was a composite of pure iron submicrograins and Fe-A1 nanograin clusters. Tensile strength was found to be proportional to
the sample’s density squared. For full-dense compacts, tensile strength of nanocrystalline compacts approaching 1 GPa was
obtained. 相似文献
109.
This article summarizes the results of a study whose purpose was to identify and analyze events at U.S. pressurized water reactors (PWRs) which either resulted in or could be considered as precursors to pressure vessel thermal shock (PVTS). The data base includes 16,000 Licensee Event Reports on 49 PWRs, covering 329 reactor-years from 1963 through 1981. The 99 identified events were assigned to one of five categories of severity. On this basis, 34 of the events were considered significant to PVTS. The events are categorized by cause and by vendor of the plant at which the event occurred. Some probabilistic risk assessment data are also developed. 相似文献
110.
The gas content and microstructural characteristics of rapidly solidified powders manufactured by different techniques were studied by Bureau of Mines researchers. Powders were screened and classified into size fractions. Powder characteristics including gas content and porosity were measured and related to powder particle size. Three different atomizing gases, argon, helium, and nitrogen were used in manufacturing the powders. In one series of experiments one gas was used to atomize the melt while a different gas was used in the melting and powder collection chambers. The gas content of the powders was shown to consist of three separate components: (1) solid solution, (2) physical entrapment associated with macroporosity, and (3) surface reaction such as surface oxide. The various components of gas content could be identified by the shape of the curve plotting gas content versus particle size. The identification of the presence of entrained gas as porosity from these curves is important because after consolidation, high-pressure bubbles of inert gas can result. This porosity can cause problems during subsequent heating or joining operations, seriously degrading mechanical properties. Analysis of gas content versus particle size represents a sensitive, technique to detect the presence of porosity. 相似文献