全文获取类型
收费全文 | 2072篇 |
免费 | 145篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 24篇 |
化学工业 | 449篇 |
金属工艺 | 49篇 |
机械仪表 | 38篇 |
建筑科学 | 62篇 |
矿业工程 | 3篇 |
能源动力 | 73篇 |
轻工业 | 364篇 |
水利工程 | 15篇 |
石油天然气 | 10篇 |
无线电 | 155篇 |
一般工业技术 | 307篇 |
冶金工业 | 348篇 |
原子能技术 | 26篇 |
自动化技术 | 297篇 |
出版年
2024年 | 6篇 |
2023年 | 12篇 |
2022年 | 32篇 |
2021年 | 55篇 |
2020年 | 37篇 |
2019年 | 51篇 |
2018年 | 53篇 |
2017年 | 69篇 |
2016年 | 67篇 |
2015年 | 53篇 |
2014年 | 86篇 |
2013年 | 140篇 |
2012年 | 117篇 |
2011年 | 124篇 |
2010年 | 110篇 |
2009年 | 114篇 |
2008年 | 94篇 |
2007年 | 100篇 |
2006年 | 63篇 |
2005年 | 63篇 |
2004年 | 66篇 |
2003年 | 58篇 |
2002年 | 45篇 |
2001年 | 41篇 |
2000年 | 38篇 |
1999年 | 31篇 |
1998年 | 130篇 |
1997年 | 84篇 |
1996年 | 56篇 |
1995年 | 39篇 |
1994年 | 28篇 |
1993年 | 42篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1974年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有2220条查询结果,搜索用时 31 毫秒
141.
Juana Bernabé Juana Mulero Begoña Cerdá Cristina García-Viguera Diego A. Moreno Soledad Parra Francisco Avilés Angel Gil-Izquierdo José Abellán Pilar Zafrilla 《Journal of Functional Foods》2013,5(3):1031-1038
Bioactive substances found in numerous foods can be successfully and safely used to modify various cellular functions and affect the oxidative stress. The aim of this study was to analyze the effect of a citrus-based juice (juice citrus (95%) with 5% of aronia extract (Aronia melanocarpa)) on biomarkers of oxidative stress in patients with metabolic syndrome compared with healthy individuals. The study comprised 20 healthy subjects and 33 patients with metabolic syndrome. Eighteen patients consumed daily 300 mL of a citrus-based juice during 6 months and 15 patients consumed 300 mL of a placebo beverage. The control group consumed a citrus-based juice (CJ). Before, and at sixth months after consuming of a citrus-based juice the following parameters were determined: 15-isoprostane F2, 8-hydroxydeoxyguanosine (8-OHdG), reduced and oxidized glutathione (GSH/GSSH), carbonyl groups and oxidized LDL (ox-LDL). After consuming CJ during 6 months the values of 8-OHdG, carbonyl groups and LDL-ox decreased in both analyzed groups and the values of GSH/GSSH increased. Significant differences were observed in both groups. Thus consumption of citrus-based juice improved the biomarkers of oxidative stress in metabolic syndrome patients. 相似文献
142.
Javier Sanchis Miguel A. Martínez Xavier Blasco Gilberto Reynoso-Meza 《Engineering Applications of Artificial Intelligence》2010,23(8):1255-1264
The multi-objective optimization strategy called physical programming (PP) provides engineers with a flexible tool to express design preferences with a ‘physical’ meaning. For each objective or specification design, preferences are established through linguistic categories to which numerical values are assigned. In PP, this mapping is made using preference functions as piecewise splines whose curvatures are calculated with an expensive and iterative algorithm. However, mapping between design parameter space and objective space may be largely non-convex and is uninfluenced by the use of gradient-based methods for solving the optimization problem. In this paper, the philosophy of the PP method has been used, but two components have been totally redesigned: a simpler algorithm is used for the construction of preference functions; and the optimizer is replaced by a genetic algorithm that avoids possible local minima problems. Three engineering applications are shown to illustrate the value of this new method. 相似文献
143.
Angela M. Moreno 《Journal of power sources》2010,195(7):1964-8475
In this paper, the authors present the first demonstration of a new class of integrated ceramic microchannel reactors for all-in-one reforming of hydrocarbon fuels. The reactor concept employs precision-machined metal distributors capable of realizing complex flow distribution patterns with extruded ceramic microchannel networks for cost-effective thermal integration of multiple chemical processes. The presently reported reactor is comprised of five methanol steam reforming channels packed with CuO/γ-Al2O3, interspersed with four methanol combustion channels washcoated with Pt/γ-Al2O3, for autothermal hydrogen production (i.e., without external heating). Results demonstrate the capability of this new device for integrating combustion and steam reforming of methanol for autothermal production of hydrogen, owing to the axially self-insulating nature of distributor-packaged ceramic microchannels. In the absence of any external insulation, stable reforming of methanol to hydrogen at conversions >90% and hydrogen yields >70% was achieved at a maximum reactor temperature of 400 °C, while simultaneously maintaining a packaging temperature <50 °C. 相似文献
144.
Acid-catalyzed etherification of bio-glycerol and isobutylene over sulfonic mesostructured silicas 总被引:1,自引:0,他引:1
J.A. Melero G. Vicente G. Morales M. Paniagua J.M. Moreno R. Roldn A. Ezquerro C. Prez 《Applied Catalysis A: General》2008,346(1-2):44-51
Sulfonic-acid-functionalized mesostructured silicas have demonstrated an excellent catalytic behavior in the etherification of glycerol with isobutylene to yield tert-butylated derivates. Di-tert-butylglycerols (DTBG) and tri-tert-butylglycerol (TTBG) have shown to be valuable fuel additives leading to decreases in the emission of particulate matter, hydrocarbons, carbon monoxide and unregulated aldehydes. Likewise, said ethers can also act as cold flow improvers for use in biodiesel, reducing also its viscosity. The activities and selectivities achieved over sulfonic acid-functionalized mesostructured silicas are comparable or even superior to those displayed by widely used macroporous commercial acid resins. Under optimized reaction conditions, these mesostructured catalysts yield a complete glycerol conversion with a combined selectivity towards DTBG and TTBG up to ca. 90%. Furthermore, no formation of undesirable isobutylene oligomers is observed. The acid strength of the sulfonic acid sites has also been found to be an important factor affecting the catalytic performance of these materials. 相似文献
145.
R Capita C Alonso-Calleja M D García-Fernández B Moreno 《Journal of food protection》2001,64(12):1961-1966
A total of 40 eviscerated and refrigerated chicken carcasses were collected from five retail outlets (three supermarkets and two poulterers' shops) in León (Spain). The level of microorganisms on chicken carcasses was assessed using the excised breast-skin technique. Mean counts (log10 CFU/g) of psychrotrophs, pseudomonads, fluorescent pseudomonads, enterococci, Micrococcaceae, Staphylococcus aureus, and yeasts and molds were 4.84, 4.11, 3.32, 2.72, 3.80, 3.67, and 2.99, respectively. A significant correlation coefficient was found between pseudomonads and fluorescent pseudomonad counts (r = 0.827; P < 0.001) and between Micrococcaceae and S. aureus counts (r = 0.915; P < 0.001). Levels of psychrotrophs, pseudomonads, fluorescent pseudomonads, and yeasts and molds were significantly (P < 0.05) higher in supermarkets than in poulterers' shops, possibly due to the longer period of time the carcasses spent in the supermarkets (between 1 and 2 days, as opposed to only 4 to 16 h in the case of poulterers' shops). Carcasses from poulterers' shops showed higher (P < 0.05) counts of enterococci. Micrococcaceae, and S. aureus, which suggests higher storage temperatures in these outlets. Only S. aureus counts (especially those from poulterers' shops) exceeded the established values in the microbiological criteria for poultry meat consulted. 相似文献
146.
Arantxa Rodriguez-Casado Pedro Carmona Pilar Moreno Ignacio Sánchez-González Antonella Macagnano Corado Di Natale Mercedes Careche 《Food chemistry》2007,103(3):1024-1030
Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has been used for the first time to evaluate the postmortem changes in structure of components from sardine muscle in relation to quality loss. Sardines (Sardina pilchardus) were stored in ice for up to thirteen days. The spectroscopic study was focussed on the structural changes produced on the lipids and proteins. 相似文献
147.
148.
149.
Canto E. Moreno J.M. Cabestany J. Lacadena I. Insenser J.M. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2001,9(1):210-218
This paper will describe a systematic method to map synchronous digital systems into dynamically reconfigurable programmable logic (i.e., programmable logic able to swap in real time the configuration defining the functionality of the system). The method is based on a temporal bipartitioning technique that is able to separate the static implementation of a circuit in two temporal independence hardware contexts. As the experimental results show, the method is capable of improving the functional density of the dynamic implementation with respect to the static one 相似文献
150.
Satisfactory sum or shaped antenna radiation patterns can often be synthesized by modifying just the phase distribution of an initial excitation by an arbitrary amplitude distribution. As examples, we calculate linear and circular apertures with uniform, Taylor, or cosine-section amplitude distributions, affording symmetric sum patterns with low sidelobe levels or symmetric shaped patterns with low ripple and sidelobe levels; linear aperture distributions, affording patterns with low sidelobe levels on one side of the beam; and planar arrays, with uniform or cosine-section amplitude distributions affording φ-symmetric or elongated-oval footprints 相似文献