全文获取类型
收费全文 | 1203篇 |
免费 | 79篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 292篇 |
金属工艺 | 9篇 |
机械仪表 | 15篇 |
建筑科学 | 60篇 |
矿业工程 | 2篇 |
能源动力 | 22篇 |
轻工业 | 219篇 |
水利工程 | 13篇 |
石油天然气 | 10篇 |
无线电 | 55篇 |
一般工业技术 | 156篇 |
冶金工业 | 290篇 |
原子能技术 | 16篇 |
自动化技术 | 111篇 |
出版年
2023年 | 8篇 |
2022年 | 26篇 |
2021年 | 50篇 |
2020年 | 26篇 |
2019年 | 37篇 |
2018年 | 33篇 |
2017年 | 36篇 |
2016年 | 35篇 |
2015年 | 30篇 |
2014年 | 37篇 |
2013年 | 76篇 |
2012年 | 67篇 |
2011年 | 74篇 |
2010年 | 61篇 |
2009年 | 65篇 |
2008年 | 50篇 |
2007年 | 63篇 |
2006年 | 52篇 |
2005年 | 28篇 |
2004年 | 43篇 |
2003年 | 24篇 |
2002年 | 31篇 |
2001年 | 26篇 |
2000年 | 13篇 |
1999年 | 30篇 |
1998年 | 33篇 |
1997年 | 33篇 |
1996年 | 30篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1976年 | 7篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1962年 | 1篇 |
排序方式: 共有1283条查询结果,搜索用时 46 毫秒
111.
112.
Rafael Bernardo Carmona Benítez Rafael Bernardo Carmona Paredes Gabriel Lodewijks Joao Lemos Nabais 《Expert systems with applications》2013,40(12):4915-4921
This paper presents a modification of the Grey Model (GM) to forecast routes passenger demand growth in the air transportation industry. Forecast methods like Holt-Winters, autoregressive models, exponential smoothing, neural network, fuzzy logic, GM model calculate very high airlines routes pax growth. For this reason, a modification has been done to the GM model to damp trend calculations as time grows. The simulation results show that the modified GM model reduces the model exponential estimations grow. It allows the GM model to forecast reasonable routes passenger demand for long lead-times forecasts. It makes this model an option to calculate airlines routes pax flow when few data points are available.The United States domestic air transport market data are used to compare the performance of the GM model with the proposed model. 相似文献
113.
Juliana Q. Mollica Denise C. Cara Mirna D’Auriol Verena B. Oliveira Isabela C. Cesar Maria G.L. Brandão 《Journal of Functional Foods》2013,5(4):1975-1984
Tropical ecosystems are particularly rich in edible plant species with different bioactive substances. Among the plants with promising benefits for health are species from the genus Dioscorea (Dioscoreaceae), especially those named yam. Recent studies have shown the beneficial effects of different species of Dioscorea, and its main constituent, diosgenine, in the treatment of food allergy. In this study we evaluated the potential of D. trifida, the only yam native from South America, in the treatment of ovalbumin (OVA) induced food allergy in Balb/c mice. HPLC/DAD analysis showed the presence of three very distinctive groups of natural products in extracts and fractions: (I) very polar substances, including allantoin, (II) phenolic substances as flavonoids and phenolic acids and (III) diosgenin and derivatives. Sensitive mice received casein feed with supplementation of crude extract (CE) and fractions. The supplementation with all products from D. trifida reduced IGE, intestinal oedema and mucus production, parameters observed in OVA allergic mice. The results showed the potential of this food to prevent or treat this disease and the necessity to be better explored. 相似文献
114.
V.M.F. Alexandre A.M. Valente Magali C. Cammarota Denise M.G. Freire 《Renewable Energy》2011,36(12):3439-3444
The effect of a lipase-rich enzyme preparation produced by the fungus Penicillium simplicissimum on solid-state fermentation was evaluated in a 4.9 L up-flow anaerobic sludge blanket bioreactor (UASB) treating fish-processing plant wastewater containing 1500 mg oil and grease (O&G)/L. The oil and grease hydrolysis step was carried out with 0.5% or 0.2% (w/v) of the solid enzyme preparation (SEP) at 30 °C for 8 h. The bioreactor operated at 30 °C with a hydraulic retention time of 10 h for a period of over 100 days, showed high total COD removal efficiencies (85.3% for 0.5% SEP and 90.9% for 0.2% SEP), when fed with pre-hydrolyzed wastewater, compared to a Control bioreactor fed with raw wastewater (79.9%). The Control bioreactor also showed high oil and grease accumulation in the biomass throughout the operational period (the O&G content reached 1.7 times that found in the inoculum of the UASB bioreactor), intensive scum formation, and several episodes of cessation of treatment to clean the three-phase separator. Thus it can be concluded that the enzyme pre-hydrolysis step together with anaerobic treatment of the fish-processing plant wastewater improved the quality of the treated effluent and reduced operational problems. 相似文献
115.
Cara Cocking Stephan Helling Marcus Oswald Peter Rammelsberg Gerhard Reinelt Alexander J. Hassel 《Color research and application》2010,35(3):233-239
A key criterion in the design of dental shade guides used for matching tooth color is that the shade tabs cover the natural tooth color space as completely as possible with a manageable number of tabs. Earlier studies have designed hypothetical shade guides from a given population of tooth colors described in the CIELAB system using the goal of minimizing the mean coverage error. In this study, we investigate this topic using the goal of maximizing coverage, meaning that as many measured colors as possible were within a given color difference from the nearest shade tab of the guide. We use techniques of linear discrete optimization to determine the positions of the shade tabs and consider both color difference formulas, CIELAB and CIEDE2000, in an exemplary tooth color population. We obtain coverage error and coverage figures for hypothetical shade guides of various numbers of tabs designed with the goal of either minimizing coverage error or maximizing coverage. Results show that discrete optimization and the goal of maximizing coverage could be used to improve shade guide development. The described technique could be used not only for dental shade guides development, but also for any purpose requiring coverage of as many colors as possible while keeping the number of reference colors manageable. © 2009 Wiley Periodicals, Inc. Col Res Appl, 2010 相似文献
116.
Comments on the article by N. F. Kozlowski et al (see record 1998-10341-011) about HIV infected clients and whether or not there ought to be notification. Kozlowski et al cite the California case of Tarasoff v. Regents of University of California (1976) 9 times, however, they never officially cite it, nor do they put it in their reference section. Without going into a refresher course about the meaning of Tarasoff, when employing this case law in a study it is important to (1) carefully read the case, (2) become familiar with the case law in your state or states, (3) shepardize all relevant cases to make sure that they are still good law (there has been a lot of movement with Tarasoff over the years), and (4) have at least a consultation with an attorney who is familiar with this area of law. Legal accuracy is extremely important and without it, our studies cannot withstand interdisciplinary scrutiny. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
117.
Head Denise; Raz Naftali; Gunning-Dixon Faith; Williamson Adrienne; Acker James D. 《Canadian Metallurgical Quarterly》2002,17(1):72
This study examined the impact of age-related differences in regional cerebral volumes and cognitive resources on acquisition of a cognitive skill. Volumes of brain regions were measured on magnetic resonance images of healthy adults (aged 22-80). At the early stage of learning to solve the Tower of Hanoi puzzle, speed and efficiency were associated with age, prefrontal cortex volume, and working memory. A similar pattern of brain-behavior associations was observed with perseveration measured on the Wisconsin Card Sorting Test. None of the examined structural brain variables were important at the later stages of skill acquisition. When hypertensive participants were excluded, the effect of prefrontal shrinkage on executive aspects of performance was no longer significant, but the effect of working memory remained. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
118.
Manuel Carmona Ana M Sánchez Federico Ferreres Amaya Zalacain Francisco Tomás-Barberán Gonzalo Luis Alonso 《Food chemistry》2007,100(2):445-450
The flavonoid fraction in saffron spice has been analysed, for the first time, by LC-DAD-MS/MS ESI and five kaempferol derivatives have been found. Compounds such as kaempferol-3-sophoroside, kaempferol-3-sophoroside-7-glucoside and kaempferol-3,7,4′-triglucoside were tentatively identified, whereas other compounds, such as kaempferol tetrahexoside and kaempferol-3-dihexoside were detected. Saffron samples from different geographical origins were clearly separated by their kaempferol 3-sophoroside contents that were able to explain 100% of the variance when a discriminant test was carried out. 相似文献
119.
Giuseppe Curr Marco Camalleri Denise Calì Francesca Monforte Fortunato Neri 《Microelectronics Reliability》2007,47(4-5):819
A detailed study of the interface state properties shown by the silicon/oxynitride/oxide gate layers used in Vertically Diffused PowerMOSFET (PowerVDMOS) technologies is reported. A quantitative analysis of interface states versus the specific N2O based nitridation process, extracted from current–voltage characteristics in depletion regime, provided a clear trend and turns to be of great importance for reliability performances of the final device. 相似文献
120.
Walker Denise D.; Roffman Roger A.; Stephens Robert S.; Wakana Kim; Berghuis James 《Canadian Metallurgical Quarterly》2006,74(3):628
This study's aims were (a) to investigate the feasibility of a school-based motivational enhancement therapy (MET) intervention in voluntarily attracting adolescents who smoke marijuana regularly but who are not seeking formal treatment and (b) to evaluate the efficacy of the intervention in reducing marijuana use. Ninety-seven adolescents who had used marijuana at least 9 times in the past month were randomly assigned to either an immediate 2-session MET intervention or to a 3-month delay condition. Two thirds of the sample characterized themselves as in the precontemplation or contemplation stages of change regarding marijuana use. Participants' marijuana use and associated negative consequences were assessed at baseline and at a 3-month follow-up. Analyses revealed that both groups significantly reduced marijuana use at the 3-month follow-up ( p = .001); however, no between-group differences were observed. Despite the absence of a clear effect of MET, this study demonstrated that adolescents could be attracted to participate in a voluntary marijuana intervention that holds promise for reducing problematic levels of marijuana use. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献