全文获取类型
收费全文 | 4011篇 |
免费 | 265篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 64篇 |
综合类 | 3篇 |
化学工业 | 1303篇 |
金属工艺 | 80篇 |
机械仪表 | 117篇 |
建筑科学 | 128篇 |
矿业工程 | 4篇 |
能源动力 | 137篇 |
轻工业 | 751篇 |
水利工程 | 29篇 |
石油天然气 | 20篇 |
无线电 | 209篇 |
一般工业技术 | 666篇 |
冶金工业 | 413篇 |
原子能技术 | 21篇 |
自动化技术 | 337篇 |
出版年
2024年 | 14篇 |
2023年 | 45篇 |
2022年 | 201篇 |
2021年 | 216篇 |
2020年 | 131篇 |
2019年 | 142篇 |
2018年 | 144篇 |
2017年 | 159篇 |
2016年 | 153篇 |
2015年 | 116篇 |
2014年 | 190篇 |
2013年 | 274篇 |
2012年 | 253篇 |
2011年 | 273篇 |
2010年 | 205篇 |
2009年 | 213篇 |
2008年 | 189篇 |
2007年 | 191篇 |
2006年 | 144篇 |
2005年 | 108篇 |
2004年 | 84篇 |
2003年 | 87篇 |
2002年 | 66篇 |
2001年 | 56篇 |
2000年 | 40篇 |
1999年 | 45篇 |
1998年 | 99篇 |
1997年 | 74篇 |
1996年 | 55篇 |
1995年 | 40篇 |
1994年 | 32篇 |
1993年 | 37篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 25篇 |
1989年 | 18篇 |
1988年 | 28篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有4282条查询结果,搜索用时 0 毫秒
81.
Identification of potential technologies for 1,4-Butanediol production using prospecting methodology
Ramon Geraldo Campos Silva Tatiana Felix Ferreira Élcio Ribeiro Borges 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(12):3057-3070
1,4-Butanediol (1,4-BDO) is a four-carbon diol used for industrial applications such as organic solvents, and the production of adhesives, fibers and polyurethanes. 1,4-BDO currently is produced through several petrochemical routes: hydrogenation of maleic anhydride, isomerization of propylene oxide, acetoxylation of butadiene, and the reaction between formaldehyde and acetylene. The current trends in 1,4-BDO production involve the utilization of renewable sources such as biomass. In this context, the present study aimed to identify promising technologies of 1,4-BDO production through prospecting methodology based on the analyses of patents and scientific article, describing the most relevant aspects of those emerging technologies. An increasing amount of 1,4-BDO production focused on biotechnological routes has been reported, with the US heavily involved in the development of new technologies. This study tracked three promising technologies which have potential for application in a biorefinery context because those processes involve (i) production of 1,4-BDO from sugars, classified herein as the biotechnological route; (ii) production of intermediates from sugar fermentation followed by catalytic conversion into 1,4-BDO, classified herein as the hybrid route, and (iii) furan/furfural conversion into 1,4-BDO. © 2020 Society of Chemical Industry 相似文献
82.
Gaspar João Ferreira Renato Sebastião Pedro Souto Nuno 《Wireless Personal Communications》2020,115(4):2729-2754
Wireless Personal Communications - The increased use of unmanned aerial vehicles (UAVs), better known as drones, by civilians has grown exponentially and their autonomous flight control systems... 相似文献
83.
A. Ferreira C. Cassier S. Hirai 《Mechatronics, IEEE/ASME Transactions on》2004,9(2):321-333
We proposed an automated micromanipulation workcell for visually servoed teleoperated microassembly assisted by virtual reality techniques. It is composed of two micromanipulators equipped with microtools operating under a light microscope. Visual servoing techniques are applied for efficient and reliable position/force feedback during microassembly tasks. First, a pushing-based micromanipulation strategy for the microobject to follow a planned trajectory is proposed under vision based-position control. Then, we present the cooperation control strategy of the microhandling operation under vision-based force control integrating a sensor fusion framework approach. A guiding-system based on virtual microworld exactly reconstructed from the CAD-CAM databases of the real environment being considered is presented for the imprecisely calibrated microworld. Finally, a planned scenario is executed and experimental results of microassembly tasks performed on millimeter-sized components are provided. 相似文献
84.
85.
Jessica Maiuolo Francesca Oppedisano Cristina Carresi Micaela Gliozzi Vincenzo Musolino Roberta Macrì Federica Scarano Annarita Coppoletta Antonio Cardamone Francesca Bosco Rocco Mollace Carolina Muscoli Ernesto Palma Vincenzo Mollace 《International journal of molecular sciences》2022,23(24)
Reduced bioavailability of the nitric oxide (NO) signaling molecule has been associated with the onset of cardiovascular disease. One of the better-known and effective therapies for cardiovascular disorders is the use of organic nitrates, such as glyceryl trinitrate (GTN), which increases the concentration of NO. Unfortunately, chronic use of this therapy can induce a phenomenon known as “nitrate tolerance”, which is defined as the loss of hemodynamic effects and a reduction in therapeutic effects. As such, a higher dosage of GTN is required in order to achieve the same vasodilatory and antiplatelet effects. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is a cardioprotective enzyme that catalyzes the bio-activation of GTN to NO. Nitrate tolerance is accompanied by an increase in oxidative stress, endothelial dysfunction, and sympathetic activation, as well as a loss of the catalytic activity of ALDH2 itself. On the basis of current knowledge, nitrate intake in the diet would guarantee a concentration of NO such as to avoid (or at least reduce) treatment with GTN and the consequent onset of nitrate tolerance in the course of cardiovascular diseases, so as not to make necessary the increase in GTN concentrations and the possible inhibition/alteration of ALDH2, which aggravates the problem of a positive feedback mechanism. Therefore, the purpose of this review is to summarize data relating to the introduction into the diet of some natural products that could assist pharmacological therapy in order to provide the NO necessary to reduce the intake of GTN and the phenomenon of nitrate tolerance and to ensure the correct catalytic activity of ALDH2. 相似文献
86.
Paola Zanetta Diletta Francesca Squarzanti Alessia di Coste Roberta Rolla Paolo Aluffi Valletti Massimiliano Garzaro Valeria DellEra Angela Amoruso Marco Pane Barbara Azzimonti 《International journal of molecular sciences》2022,23(24)
The human oral pathobionts Aggregatibacter actinomycetemcomitans, Streptococcus mitis and Streptococcus mutans, in dysbiosis-promoting conditions, lead to oral infections, which also represent a threat to human systemic health. This scenario may be worsened by antibiotic misuse, which favours multi-drug resistance, making the research on pathogen containment strategies more than crucial. Therefore, we aimed to in vitro select the most promising probiotic strains against oral pathogen growth, viability, biofilm formation, and co-aggregation capacity, employing both the viable probiotics and their cell-free supernatants (CFSs). Interestingly, we also assessed probiotic efficacy against the three-pathogen co-culture, mimicking an environment similar to that in vivo. Overall, the results showed that Lactobacillus CFSs performed better than the Bifidobacterium, highlighting Limosilactobacillus reuteri LRE11, Lacticaseibacillus rhamnosus LR04, Lacticaseibacillus casei LC04, and Limosilactobacillus fermentum LF26 as the most effective strains, opening the chance to deeper investigation of their action and CFS composition. Altogether, the methodologies presented in this study can be used for probiotic efficacy screenings, in order to better focus the research on a viable probiotic, or on its postbiotics, suitable in case of infections. 相似文献
87.
It has been found that carbon dioxide gas is an efficient acid-catalyst to promote hydrolysis of a solution of sucrose. The conditions for this reaction to proceed have been found to be dependent on the partial pressure of the gas. 相似文献
88.
Zinc Oxide Nanoparticles: Synthesis,Antimicrobial Activity and Food Packaging Applications 总被引:2,自引:0,他引:2
Paula Judith Perez Espitia Nilda de Fátima Ferreira Soares Jane Sélia dos Reis Coimbra Nélio José de Andrade Renato Souza Cruz Eber Antonio Alves Medeiros 《Food and Bioprocess Technology》2012,5(5):1447-1464
Zinc oxide (ZnO) is an inorganic compound widely used in everyday applications. ZnO is currently listed as a generally recognized
as safe (GRAS) material by the Food and Drug Administration and is used as food additive. The advent of nanotechnology has
led the development of materials with new properties for use as antimicrobial agents. Thus, ZnO in nanoscale has shown antimicrobial
properties and potential applications in food preservation. ZnO nanoparticles have been incorporated in polymeric matrices
in order to provide antimicrobial activity to the packaging material and improve packaging properties. This review presents
the main synthesis methods of ZnO nanoparticles, principal characteristics and mechanisms of antimicrobial action as well
as the effect of their incorporation in polymeric matrices. Safety issues such as exposure routes and migration studies are
also discussed. 相似文献
89.
Isabel Ferreira Ana Catarina Baptista Joaquim Pratas Leitão Jorge Soares Elvira Fortunato Rodrigo Martins João Paulo Borges 《大分子材料与工程》2013,298(2):174-180
Electrospun fibers of poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] (F8T2) with exceptional electro‐optical performance are obtained. The I/T characteristics measured in fibers with 7–15 µm diameter and 1 mm length show a semiconductor behavior; their thermal activation energy is 0.5 eV and the dark conductivity at RT is 5 × 10?9 (Ω cm)?1. Besides exhibiting a photosensitivity of about 60 under white light illumination with a light power intensity of 25 mW · cm?2, the fibers also attain RT photoluminescence in the cyan, yellow, and red wavelength range under ultraviolet, blue, and green light excitation, respectively. Optical microscope images of F8T2 reveal homogeneous electrospun fibers, which are in good agreement with the uniformly radial fluorescence observed.
90.
Mario Gleria Roberta Bertani Roger De Jaeger 《Journal of Inorganic and Organometallic Polymers》2004,14(1):1-28
A general survey of fluorinated phosphazene polymers starting from their synthesis in 1965 to recent times is presented. Various types of fluorinated phosphazenes are described depending on the way fluorine atoms are connected to the polyphosphazene skeleton. The characterization, properties and practical utilization of these compounds in different domains are critically discussed. 相似文献