全文获取类型
收费全文 | 1943篇 |
免费 | 200篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 379篇 |
金属工艺 | 44篇 |
机械仪表 | 49篇 |
建筑科学 | 50篇 |
矿业工程 | 1篇 |
能源动力 | 50篇 |
轻工业 | 481篇 |
水利工程 | 12篇 |
石油天然气 | 10篇 |
无线电 | 73篇 |
一般工业技术 | 318篇 |
冶金工业 | 442篇 |
原子能技术 | 3篇 |
自动化技术 | 225篇 |
出版年
2024年 | 7篇 |
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 47篇 |
2020年 | 38篇 |
2019年 | 45篇 |
2018年 | 111篇 |
2017年 | 108篇 |
2016年 | 87篇 |
2015年 | 79篇 |
2014年 | 89篇 |
2013年 | 145篇 |
2012年 | 109篇 |
2011年 | 135篇 |
2010年 | 88篇 |
2009年 | 75篇 |
2008年 | 85篇 |
2007年 | 98篇 |
2006年 | 45篇 |
2005年 | 45篇 |
2004年 | 44篇 |
2003年 | 42篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 22篇 |
1999年 | 30篇 |
1998年 | 153篇 |
1997年 | 103篇 |
1996年 | 57篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 27篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1977年 | 3篇 |
1976年 | 17篇 |
1972年 | 1篇 |
排序方式: 共有2146条查询结果,搜索用时 15 毫秒
21.
Characterisation of greywater was conducted in two different greywater streams in the Netherlands (Groningen and Sneek). The concentrations of macropollutants and nutrients measured were very different in both streams; in particular the COD was 425 mg/L in Groningen's water whereas in Sneek it was 1,583 mg/L. The aerobic treatment of greywater in a fed-batch reactor led to a 90% removal of COD at different organic loading rates. Anaerobically, the removal reached 40% COD removal on average, the possible reason being the high amount of surfactants present in the influent. 相似文献
22.
OE Santana Rodríguez ML Malé Gil JF HernándezSantana JM Limi?ana Ca?al AM Martín Sánchez 《Canadian Metallurgical Quarterly》1998,14(6):555-561
Von Hippel-Lindau disease (VHL) is an autosomal dominant tumour syndrome caused by germline mutations of the VHL tumour suppressor gene located on chromosome 3p25-26. In VHL tumours may occur in 14 different target organs, including the eye. Retinal angiomas are considered the first manifestation of VHL disease in 43% of cases, and the cumulative probability of developing a retinal angioma in one or both eyes rises during each decade of life, reaching 80% for patients over 80 years old. Since 1976 patients with VHL at the University Hospital of Utrecht and their at-risk relatives have been screened periodically by a multidisciplinary team. Long-term follow-up ophthalmological data were analysed with special attention to natural course and results of treatment. In addition, we looked for a genotype-phenotype correlation. Retinal angiomas were found in all families. In one large family with a missense mutation (V170D) of the VHL gene, in which the complete spectrum of visceral- and central nervous system (CNS) features of VHL is present, macular, parapapillary, optic disc and ora serrata angiomas were also found. In general, however, a clear-cut genotype-phenotype correlation could not be found. Only early detection and treatment of peripheral retinal angiomas can be expected to decrease the percentage of patients with decreased visual acuity. Therefore, early detection and treatment of these tumours is of paramount importance. Ophthalmological screening of patients and persons at risk should start as early as possible. In patients with apparently sporadic retinal angiomas it is advisable to perform germline DNA analysis, since the risk of developing VHL is high, especially if the angiomas are bilateral, or unilateral and multifocal, if the patient is young, or if there is a family history suggestive of VHL. 相似文献
23.
L Bravo RJ Monté V Alfonso N Cabrera M Gómez R Hernández B García 《Canadian Metallurgical Quarterly》1995,47(3):215-216
One hundred and fifty-five strains of Aeromonas isolated in the stools of children under 5 years presenting with acute diarrheal disease were studied. Using the Aerokey II system for the identification of species, 47 strains were identified as Aeromonas caviae, 58 as Aeromonas hydrophila, 23 as Aeromonas veronii biovar sobria, 14 as Aeromonas trota, 9 as Aeromonas veronii biovar veronii, 2 as Aeromonas jandaei and 2 as Aeromonas shubertii, Emphasis is placed on the advantages of this method which allowed for the classification of new species not identified previously in our country. 相似文献
24.
Stefan K. Gehrig Hernán Badino Uwe Franke 《Computer Vision and Image Understanding》2012,116(1):16-24
Dense stereo algorithms are able to estimate disparities at all pixels including untextured regions. Typically these disparities are evaluated at integer disparity steps. A subsequent sub-pixel interpolation often fails to propagate smoothness constraints on a sub-pixel level.We propose to increase the sub-pixel accuracy in low-textured regions in four possible ways: First, we present an analysis that shows the benefit of evaluating the disparity space at fractional disparities. Second, we introduce a new disparity smoothing algorithm that preserves depth discontinuities and enforces smoothness on a sub-pixel level. Third, we present a novel stereo constraint (gravitational constraint) that assumes sorted disparity values in vertical direction and guides global algorithms to reduce false matches, especially in low-textured regions. Finally, we show how image sequence analysis improves stereo accuracy without explicitly performing tracking. Our goal in this work is to obtain an accurate 3D reconstruction. Large-scale 3D reconstruction will benefit heavily from these sub-pixel refinements.Results based on semi-global matching, obtained with the above mentioned algorithmic extensions are shown for the Middlebury stereo ground truth data sets. The presented improvements, called ImproveSubPix, turn out to be one of the top-performing algorithms when evaluating the set on a sub-pixel level while being computationally efficient. Additional results are presented for urban scenes. The four improvements are independent of the underlying type of stereo algorithm. 相似文献
25.
Summary Copolymeric poly(acrylic acid-co-methyl methacrylate) hydrogels for three different compositions: (90/10), (80/20) and (60/40),
have been studied. Drug release has been examined as a function of the hydrogel composition by HPLC (High Pressure Liquid
Cromatography). The release experiments were carried out at 37 °C. The fraction of available drug release was linear in t1/2. The values of the diffusional coefficient (0.50<n<1.0) indicate that the nafcillin release mechanism from the hydrogels
in study is non-Fickian. The diffusion coefficients for this drug release have been calculated. The molecular diffusion of
nafcillin through hydrogels is controlled by the swelling. 相似文献
26.
David F. Barrero Julio César Hernández‐Castro Pedro Peris‐Lopez David Camacho María D. R‐Moreno 《Expert Systems》2014,31(1):9-19
Radio frequency identification (RFID) is a powerful technology that enables wireless information storage and control in an economical way. These properties have generated a wide range of applications in different areas. Due to economic and technological constrains, RFID devices are seriously limited, having small or even tiny computational capabilities. This issue is particularly challenging from the security point of view. Security protocols in RFID environments have to deal with strong computational limitations, and classical protocols cannot be used in this context. There have been several attempts to overcome these limitations in the form of new lightweight security protocols designed to be used in very constrained (sometimes called ultra‐lightweight) RFID environments. One of these proposals is the David–Prasad ultra‐lightweight authentication protocol. This protocol was successfully attacked using a cryptanalysis technique named Tango attack. The capacity of the attack depends on a set of boolean approximations. In this paper, we present an enhanced version of the Tango attack, named Genetic Tango attack, that uses Genetic Programming to design those approximations, easing the generation of automatic cryptanalysis and improving its power compared to a manually designed attack. Experimental results are given to illustrate the effectiveness of this new attack. 相似文献
27.
M. Manzano M. Urueña M. Sužnjević E. Calle J. A. Hernández M. Matijasevic 《Multimedia Systems》2014,20(5):451-470
Cloud gaming is a new paradigm that is envisaged to play a pivotal role in the video game industry in forthcoming years. Cloud gaming, or gaming on demand, is a type of online gaming that allows on-demand streaming of game content onto non-specialised devices (e.g. PC, smart TV, etc.). This approach requires no downloads or game installation because the actual game is executed on the game company’s server and is streamed directly to the client. Nonetheless, this revolutionary approach significantly affects the network load generated by online games. As cloud gaming presents new challenges for both network engineers and the research community, both groups need to be fully conversant with these new cloud gaming platforms. The purpose of this paper is to investigate OnLive, one of the most popular cloud gaming platforms. Our key contributions are: (a) a review of the state-of-the-art of cloud gaming; (b) reverse engineering of the OnLive protocol; and (c) a synthetic traffic model for OnLive. 相似文献
28.
Maritza F. Díaz José A. Gavín Magali Gómez Vicente Curtielles Frank Hernández 《臭氧:科学与工程》2006,28(1):59-63
Prior studies have proven that ozonated vegetable oils present a high germicidal power. Ozonation of sunflower oil at different applied ozone dosage was carried out and peroxide and aldehydes indices along with antimicrobial activity were determined. The reaction products were identified using Proton Nuclear Magnetic Resonance Spectroscopy (1H NMR). The principal signals intensity values were used for following the reaction course between ozone and sunflower oil. The reaction was following up to peroxide index values of 1202 mmol-equi/kg. The intensities of olefinic proton signals decreased with the gradual increase in ozone concentration but without disappearing completely. The Criegee ozonides obtained at 107.1 mg/g of ozone doses were approximately 3.9-fold higher than that at beginning of the reaction. The aldehyde protons were observed as a weak intensity signal in all the spectra. The signals belonging to olefinic protons from hydroperoxides appeared weak and increased with the increase in ozone doses. Signals from other oxygenated groups were assigned. The highest action spectrum of antimicrobial activity was obtained with the higher peroxide index. It was concluded that at higher applied ozone doses, the higher the antimicrobial activity potential of ozonized sunflower oil 相似文献
29.
Sang Hern Kim Won Keun Son Yong Joo Kim Eu‐Gene Kang Dong‐Won Kim Chang Woo Park Whan‐Gi Kim Hyung‐Joong Kim 《应用聚合物科学杂志》2003,88(3):595-601
A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The Tg's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003 相似文献
30.
R. A. Torres J. Arellano-Ceja M. E. Hernández-Hernández R. González-Núñez 《Polymer Bulletin》2007,59(2):251-260
Summary The effects of blending sequence and the addition of an interfacial agent (triblock copolymer styrene-butylene ethylene/styrene,
Kraton G1652) on the morphology and the mechanical properties of Polycarbonate (PC)/Polypropylene (PP) blends prepared by
injection molding were studied. This study presents an analysis of impact resistance, tensile properties and morphology of
the raw materials and the blends at different compositions. The blends, before being injected, were prepared in a twin-screw
extruder by different sequences of blending. The results indicate that the blending sequence and the presence of humidity
significantly affect the properties and morphology of the blends. For ternary blends (PC/PP/Kraton), only one-step mixing
before injection molding proved to be sufficient to improve mechanical properties. Increasing the amount of blending steps
did not present a significant change in properties. With the addition of the interfacial agent, higher impact resistance and
particle size reduction were observed. 相似文献