全文获取类型
收费全文 | 1926篇 |
免费 | 149篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 14篇 |
化学工业 | 570篇 |
金属工艺 | 14篇 |
机械仪表 | 24篇 |
建筑科学 | 108篇 |
矿业工程 | 5篇 |
能源动力 | 44篇 |
轻工业 | 477篇 |
水利工程 | 21篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 101篇 |
一般工业技术 | 298篇 |
冶金工业 | 132篇 |
原子能技术 | 2篇 |
自动化技术 | 244篇 |
出版年
2024年 | 3篇 |
2023年 | 27篇 |
2022年 | 46篇 |
2021年 | 141篇 |
2020年 | 37篇 |
2019年 | 51篇 |
2018年 | 57篇 |
2017年 | 65篇 |
2016年 | 84篇 |
2015年 | 73篇 |
2014年 | 83篇 |
2013年 | 153篇 |
2012年 | 134篇 |
2011年 | 162篇 |
2010年 | 112篇 |
2009年 | 105篇 |
2008年 | 106篇 |
2007年 | 90篇 |
2006年 | 72篇 |
2005年 | 66篇 |
2004年 | 63篇 |
2003年 | 53篇 |
2002年 | 52篇 |
2001年 | 19篇 |
2000年 | 22篇 |
1999年 | 21篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 21篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1969年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有2077条查询结果,搜索用时 234 毫秒
101.
102.
Nearest neighbour search is a widely used technique in pattern recognition. During the last three decades a large number of fast algorithms have been proposed. In this work we are interested in algorithms that can be used with any dissimilarity function provided that it fits the mathematical notion of distance.Some of such algorithms organize, in preprocessing time, the data in a tree structure that is traversed in search time to find the nearest neighbour. The speedup is obtained using some pruning rules that avoid the traversal of some parts of the tree.In this work two new decomposition methods to build the tree and three new pruning rules are explored. The behaviour of our proposal is studied through experiments with synthetic and real data. 相似文献
103.
Asger Hobolth Jan Pedersen Eva B. Vedel Jensen 《Journal of Mathematical Imaging and Vision》2002,17(2):131-137
This paper suggests a high-level continuous image model for planar star-shaped objects. Under this model, a planar object is a stochastic deformation of a star-shaped template. The residual process, describing the difference between the radius-vector function of the template and the object, is allowed to be non-stationary. Stationarity is obtained by a time change. A parametric model for the residual process is suggested and straightforward parameter estimation techniques are developed. The deformable template model makes it possible to detect pathologies as demonstrated by an analysis of a data set of cell nuclei from a benign and a malignant tumour, using stochastic deformations of ellipses. 相似文献
104.
105.
Accurate assessment of human intake of mutagenic/carcinogenic heterocyclic amines (HAs) is necessary for epidemiological studies and future risk assessment. Using questionnaires, the frequency of consumption of specific dishes can be obtained at an individual level and linked to analyzed concentrations of different compounds in corresponding dishes. Some typical Swedish cooked meat dishes, hamburgers and kebab, industrially prepared or from fast food outlets and restaurants, were analyzed regarding their content of 11 different HAs. The amount of each of these compounds was below 0.1 ng/g cooked weight in most of the industrially prepared products. The total amount of HAs was highest in the kebab samples. The intake of HAs from 200 g of the dishes was estimated to range from not detectable levels to 0.6 microg. The results of the present study indicate that the content of HAs in a specific dish may vary with origin, and that the concentrations of HAs in commercial fried meat products are generally low, although some of these food items may contain elevated amounts. 相似文献
106.
Technological development and increased international competition have imposed a significant burden on the product development function of many companies. The growing complexity of products demands a larger product development team with people having various competencies. Simultaneously the importance of good quality, usability and customisation of products is growing, and many companies want to involve customers and users directly in the development work. Both the complexity and quality demand new ways of working that support collaboration between people with various competencies, interests and responsibilities both inside and outside the company. This paper reports experiences from using action research to introduce new user-centred work practices in two commercial product development projects. The interventions varied. In the first project it was found rewarding to engage customers and users in workshops based on participatory inquiry and collaborative design. The design process was iterative and the workshops took place several times involving concept through detailed design. In the second project, new design representations are introduced. The experiences highlight the importance of creating and reifying insights in design representations and using these to both support collaboration, and create continuity in the project. The paper ends with a discussion of scientific rigor in action research and what the new work practices imply for the development team. 相似文献
107.
Hypoxia occurs over large areas in aquatic systems worldwide, and there is growing concern that hypoxia may affect aquatic animals, leading to population decline and changes in community by elimination of sensitive species. For the first time, we report that sublethal levels of hypoxia can significantly increase (+77.4%) malformation in fish embryonic development. Disruption of apoptotic pattern was clearly evident at 24 h post-fertilization, which may be a major cause of malformation. Furthermore, embryonic development was delayed, and balance of sex hormones (testosterone and estradiol) was disturbed during embryonic stages, implicating that subsequent sexual development may also be affected. Overall, our results imply that hypoxia may have a teratogenic effect on fish and delay fish embryonic development, which may subsequently impair species fitness leading to natural population decline. 相似文献
108.
109.
The samples are digested in nitric acid and evaporated to near dryness. Hydrogen peroxide is then added for complete oxidation of fat residues. Determination of metals is performed by flameless AAS with graphite furnace and results evaluated by the method of standard addition. The method is suitable for the determination of some non-volatile metals in fish livers in which the amount of available sample is limited; Pb, Cd, Cu and Zn have been determined in such samples. 相似文献
110.
Environmental exposure assessment of fluoroquinolone antibacterial agents from sewage to soil 总被引:7,自引:0,他引:7
Golet EM Xifra I Siegrist H Alder AC Giger W 《Environmental science & technology》2003,37(15):3243-3249
The behavior of fluoroquinolone antibacterial agents (FQs) during mechanical-biological wastewater treatment was studied by mass flow analysis. In addition, the fate of FQs in agricultural soils after sludge application was investigated. Concentrations of FQs in filtered wastewater (raw sewage, primary, secondary, and tertiary effluents) were determined using solid-phase extraction with mixed phase cation exchange disk cartridges and reversed-phase liquid chromatography with fluorescence detection. FQs in suspended solids, sewage sludge (raw, excess, and anaerobically digested sludge), and sludge-treated soils were determined as described for the aqueous samples but preceded by accelerated solvent extraction. Wastewater treatment resulted in a reduction of the FQ mass flow of 88-92%, mainly due to sorption on sewage sludge. A sludge-wastewater partition coefficient (log Kd approximately 4) was calculated in the activated sludge reactors with a hydraulic residence time of about 8 h. No significant removal of FQs occurred under methanogenic conditions of the sludge digesters. These results suggest sewage sludge as the main reservoir of FQ residues and outline the importance of sludge management strategies to determine whether most of the human-excreted FQs enter the environment. Field experiments of sludge-application to agricultural land confirmed the long-term persistence of trace amounts of FQs in sludge-treated soils and indicated a limited mobility of FQs into the subsoil. 相似文献