全文获取类型
收费全文 | 891篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 231篇 |
金属工艺 | 6篇 |
机械仪表 | 29篇 |
建筑科学 | 34篇 |
矿业工程 | 1篇 |
能源动力 | 26篇 |
轻工业 | 90篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 69篇 |
一般工业技术 | 180篇 |
冶金工业 | 98篇 |
原子能技术 | 19篇 |
自动化技术 | 133篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 43篇 |
2021年 | 63篇 |
2020年 | 30篇 |
2019年 | 44篇 |
2018年 | 34篇 |
2017年 | 27篇 |
2016年 | 34篇 |
2015年 | 20篇 |
2014年 | 47篇 |
2013年 | 55篇 |
2012年 | 48篇 |
2011年 | 75篇 |
2010年 | 40篇 |
2009年 | 38篇 |
2008年 | 34篇 |
2007年 | 25篇 |
2006年 | 20篇 |
2005年 | 21篇 |
2004年 | 13篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 24篇 |
1997年 | 25篇 |
1996年 | 18篇 |
1995年 | 5篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1926年 | 1篇 |
排序方式: 共有926条查询结果,搜索用时 15 毫秒
911.
T. Siciliano A. Tepore G. Micocci A. Genga M. Siciliano E. Filippo 《Journal of Materials Science: Materials in Electronics》2011,22(6):649-653
Indium monoselenide (InSe) nanowires were grown by the thermal evaporation method in argon atmosphere without the presence of any catalysts using InSe polycrystalline powder as the source material. No nanostructure growth was observed at deposition temperatures below 580 °C. The nanostructures were discernable at temperatures above 620 °C. Pure InSe nanowires were obtained at the deposition temperature of 660 °C for 50 min. The diameters of the nanowires were from 50 to 240 nm and their lengths were up to several micrometers. X-ray diffraction spectrum reveals that the synthesized products were single-crystalline of the β-phase hexagonal structure of InSe with lattice constants a = 4.006 Å and c = 16.642 Å. The strong peak due to the reflection from the (004) crystal plane reveals that most nanowires grow with a strong preferred orientation. 相似文献
912.
We investigated industrially produced chalcopyrite solar cells based on the absorber modifications Cu(In,Ga)Se2 and Cu(In,Ga)(S,Se)2 in order to study the nature of the experimentally verified efficiency improvement, mainly caused by an increased open circuit voltage. We show that the introduction of sulfur during the absorber formation via rapid thermal processing leads to a substantial lowering of the surface doping concentration and widening of the space charge region (SCR). Temperature dependent diode analysis revealed a reduction of the SCR recombination in (Se,S) devices which would lead to a larger splitting of quasi-Fermi levels and hence to an increased open circuit voltage as compared to neat Cu(In,Ga)Se2 devices. 相似文献
913.
Filippo Maggi 《Propellants, Explosives, Pyrotechnics》2014,39(5):755-760
Aluminum is used as a metal fuel in energetic materials for the improvement of propulsion performance and density. Both nano‐sized and micrometer‐sized activated powders represent valuable options in order to improve metal combustion properties, each possessing advantages and drawbacks. These ingredients bear peculiar properties (namely, higher specific surface, coatings, or surface characteristics) which generate high mixing viscosity once suspended in a polymer as well as altered mechanical properties of the final product. Four different powders dispersed in a polymer binder are taken into consideration and the evolution of viscosity in time during the curing process is investigated. The suspending medium is represented by a mixture of hydroxyl‐terminated polybutadiene (HTPB), isophorone diisocyanate (IPDI) and dioctyl adipate (DOA). Viscosity was measured for 5 h on samples under isothermal curing at 60 °C. Non‐isothermal DSC kinetic analyses were also performed using the Kissinger method. It was found that, for the test conditions, a size reduction of metal particles slowed down the increment rate of curing viscosity while some peculiar coatings, such as fatty acids, introduced opposite trends. 相似文献
914.
Henning Helmers Andreas W. Bett Jürgen Parisi Carsten Agert 《Progress in Photovoltaics: Research and Applications》2014,22(4):427-439
An energy balance model for concentrating photovoltaic and thermal (CPVT) systems is presented. In the model, the CPVT system and its environment are represented using a set of input parameters. The main outputs of the model are the system's electrical and thermal efficiencies. The model accounts for optical losses. Thermal losses are derived from a thermal network model of the hybrid receiver. The solar cell performance is modeled as a function of the temperature and the irradiance. The robustness of the model is demonstrated by a sensitivity analysis of all input parameters. The influence of the operating temperature on the electrical and thermal performances and the overall efficiency of the CPVT system are discussed. The limiting cases of maximum electrical and thermal power outputs are presented. Further, the influence of the concentration ratio on the electrical and thermal performance and on the partitioning of these two power outputs is analyzed in detail. It is shown that high concentration reduces the thermal losses considerably and increases the electrical efficiency. At concentration ratios above 300, the system operates with an overall efficiency of 75% at temperatures up to 160 °C. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
915.
We present a theoretical study of the lineup of the LUMO of Ru(II)-polypyridyl (N3 and N719) molecular dyes with the conduction band edge of a TiO(2) anatase nanoparticle. We use density functional theory (DFT) and the Car-Parrinello scheme for efficient optimization of the dye-nanoparticle systems, followed by hybrid B3LYP functional calculations of the electronic structure and time-dependent DFT (TDDFT) determination of the lowest vertical excitation energies. The electronic structure and TDDFT calculations are performed in water solution, using a continuum model. Various approximate procedures to compute the excited state oxidation potential of dye sensitizers are discussed. Our calculations show that the level alignment for the interacting nanoparticle-sensitizer system is very similar, within about 0.1?eV, to that for the separated TiO(2) and dye. The excellent agreement of our results with available experimental data indicates that the approach of this work could be used as an efficient predictive tool to help the optimization of dye-sensitized solar cells. 相似文献
916.
Terrorist threats have precipitated the need for information on the ultraviolet (UV) resistance of potential biothreat agents in food processing, such as Yersinia pestis. The objective of this study was to characterize the resistance of the Yersinia species to UV treatment using a single-lamp annular UV reactor. A novel method is proposed to measure the inactivation kinetics of Yersinia pseudotuberculosis, a surrogate of Y. pestis. This proposed method can overcome the disadvantages of the traditional collimated beam approach for liquids with high absorptive properties, such as liquid foods. As a reference, an inactivation rate of Escherichia coli K12 in caramel model solutions was measured first. Both first-order and series-event inactivation models were used to fit UV inactivation data. For the series-event model, an inactivation constant of k(SE)= 0.675 cm(2)/mJ and threshold n= 4 were obtained for E. coli K12 with the coefficient of determination R(2)= 0.987 and the standard deviation of log(10) reductions sigma(y)= 0.133. For Y. pseudotuberculosis, k(SE)= 0.984 cm(2)/mJ and n= 3 were obtained with R(2)= 0.972 and sigma(y)= 0.212. In contrast, for the first-order inactivation model, the first-order inactivation constant k(1)= 0.325 cm(2)/mJ with R(2)= 0.907 and sigma(y)= 0.354 was found for E. coli; and k(1)= 0.557 cm(2)/mJ with R(2)= 0.916 and sigma(y)= 0.402 was obtained for Y. pseudotuberculosis. Based on R(2), sigma(y), and the maximum absolute and relative errors, the series-event inactivation model describes the UV inactivation kinetics of Y. pseudotuberculosis and E. coli better than the first-order model. It is apparent that Y. pseudotuberculosis is less resistant to UV light than E. coli K12. 相似文献
917.
Nikolay Radychev Dorothea ScheunemannMarta Kruszynska Katja FrevertRany Miranti Joanna Kolny-OlesiakHolger Borchert Jürgen Parisi 《Organic Electronics》2012,13(12):3154-3164
Colloidally synthesized CuInS2 nanocrystals are a promising candidate for hybrid solar cell applications due to suitable optical and transport properties of copper indium disulfide and being it an eco-friendly material. However, as opposite to solar cells where CuInS2 is synthesized in situ in a conductive polymer matrix, advances in the field of hybrid solar cells containing colloidal CuInS2 nanocrystals that are blended after synthesis with a polymer are still negligible. Here, we report about the influence of pyridine, alkylamine, and hexanethiol stabilizing ligands on the morphology of the active layer and the electrical characteristics of solar cells based on elongated and pyramidal CuInS2 nanocrystals blended with poly(3-hexylthiophene) (P3HT). All CuInS2 nanocrystals used within this study had a wurtzite crystal structure as revealed by X-ray diffraction. With pyridine as ligand, the morphology was found to depend strongly on the shape of the nanocrystals. Strong agglomeration was observed in the case of elongated nanocrystals and explains the low performance of corresponding solar cells. Employment of hexanethiol as ligand resulted in an improvement of the morphology of the CuInS2/P3HT layers and enhancement of the rectification ratio of the laboratory solar cells. Nevertheless, it was found that morphology of the active layer is not the main limiting factor in the CuInS2/P3HT system. According to cyclic voltammetry measurements, unsuitable alignment of the energy levels for CuInS2 nanocrystals and P3HT was observed. Taking this fact into account, appropriate donor materials for CuInS2 based bulk heterojunctions are discussed. 相似文献
918.
Normanno G Parisi A Addante N Quaglia NC Dambrosio A Montagna C Chiocco D 《International journal of food microbiology》2006,106(2):219-222
Mytilus galloprovincialis is one of the most commonly consumed of all bivalve molluscs. The consumption of raw bivalve molluscs has caused outbreaks of food poisoning due to Vibrio parahaemolyticus and Vibrio vulnificus. This paper reports the results of a survey on the presence of V. parahaemolyticus, V. vulnificus fecal coliform bacteria, Escherichia coli and Salmonella spp. in 600 M. galloprovincialis samples collected from retail outlets in the Puglia region. V. parahaemolyticus and V. vulnificus were found in 47 (7.83%) and 17 (2.83%) of the samples, respectively. One sample (0.16%) was contaminated with Salmonella spp. but no relationship was observed between vibrios and fecal coliforms and E. coli. There were no significant differences among vibrios present in bivalve molluscs during the 3-year survey. 相似文献
919.
Godone A Micalizio S Calosso CE Levi F 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(3):525-529
In this paper, we describe a laboratory prototype of pulsed optically pumped clock based on a rubidium vapor cell with buffer gas. The measured frequency stability (overlapping Allan deviation) is sigma(y)(tau) = 3 x 10(-12)tau(-1/2) and the level of 4 x 10(-14) is reached for averaging time of r = 3 x 10(14) s. For the same set of data, the statistical tool Theol predicts a frequency stability of 2 x 10(-14) for tau = 10(5) s. This result confirms the theoretical predictions regarding this kind of frequency standard and makes it very attractive for satellite navigation and space applications in which a simple and reliable implementation is required, and the short and medium term stability (till one day) is the main concern. 相似文献
920.
Roya Malekkhouyan Rasoul Esmaeely Neisiany Saied Nouri Khorasani Oisik Das Filippo Berto Seeram Ramakrishna 《应用聚合物科学杂志》2021,138(10):49964
Among the several approaches for the protection of metallic structures from corrosion, covering with a polymeric coating has attracted more attention due to their convenient application, cost-effective price, and the relatively benign environmental impact. However, the polymeric coatings are sensitive to mechanical/thermal shocks and aggressive environments, leading to damages in the coatings that affect their barrier performance. Self-healing polymeric coatings have introduced remarkable development by extending the service life and reducing maintenance costs, leading to a significant boost in the reliability and durability of the conventional polymeric coatings. Among the different strategies to develop self-polymeric coatings, encapsulating healing agent within micro/nanocapsules, micro/nanofibers, and microvascular systems and incorporating them within the conventional coatings have been widely acknowledged as the most applicable approach. However, several factors, such as the effect of the healing system's size and content, have a significant influence on healing performance. Therefore, this review aims to reveal the effects of healing system size and healing content on the self-healing performance in polymeric coatings through the analysis of recently published articles. 相似文献