全文获取类型
收费全文 | 3432篇 |
免费 | 196篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 42篇 |
化学工业 | 868篇 |
金属工艺 | 46篇 |
机械仪表 | 84篇 |
建筑科学 | 137篇 |
矿业工程 | 5篇 |
能源动力 | 122篇 |
轻工业 | 573篇 |
水利工程 | 38篇 |
石油天然气 | 19篇 |
无线电 | 214篇 |
一般工业技术 | 509篇 |
冶金工业 | 142篇 |
原子能技术 | 13篇 |
自动化技术 | 824篇 |
出版年
2024年 | 10篇 |
2023年 | 45篇 |
2022年 | 127篇 |
2021年 | 144篇 |
2020年 | 115篇 |
2019年 | 134篇 |
2018年 | 122篇 |
2017年 | 110篇 |
2016年 | 143篇 |
2015年 | 113篇 |
2014年 | 151篇 |
2013年 | 292篇 |
2012年 | 244篇 |
2011年 | 267篇 |
2010年 | 219篇 |
2009年 | 206篇 |
2008年 | 194篇 |
2007年 | 161篇 |
2006年 | 130篇 |
2005年 | 109篇 |
2004年 | 84篇 |
2003年 | 76篇 |
2002年 | 74篇 |
2001年 | 41篇 |
2000年 | 34篇 |
1999年 | 32篇 |
1998年 | 41篇 |
1997年 | 27篇 |
1996年 | 26篇 |
1995年 | 25篇 |
1994年 | 15篇 |
1993年 | 22篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1967年 | 2篇 |
排序方式: 共有3636条查询结果,搜索用时 0 毫秒
161.
Ignacio Sánchez-González Arantxa Rodríguez-Casado Mercedes Careche Pedro Carmona 《Food chemistry》2009
Raman analysis has been carried out to study the effects of Vitacel® wheat dietary fibre (WDF) during gelation of surimi. The main results reveal the following: (a) Vitacel® comprises natural cellulose I as major component; (b) hydration of WDF leads to νCH frequency upshifting and decreasing intensity. On the basis of these spectral features it is suggested that water transfer from protein to WDF can occur in surimi gels. WDF hydration can be interpreted in the sense that this fibre either takes water that is delivered from the gel protein upon heat-mediated formation of β-sheets and hydrophobic contacts and/or or acts as an active dehydrating agent. An increase of solvent-exposed hydrophobic side chains is observed in the sol phase, upon the addition of WDF, which may cause breaking of intermolecular protein hydrophobic contacts; a subsequent change upon WDF-containing gel formation is the reduction in the νCH intensity, which may be indicative of increasing hydrophobic WDF-protein contacts. Interestingly, these results constitute molecular data, to be considered when designing restructured fish products with these fibre ingredients. 相似文献
162.
163.
Eduardo Gomes Salgado Luiz Alberto Beijo Paulo Sampaio Carlos Henrique Pereira Mello Pedro Saraiva 《国际生产研究杂志》2016,54(18):5416-5433
The ISO 9001 standard is considered as an effective tool to support a quality management system (QMS). A steady growth in the number of ISO 9001 issued certificates is observed worldwide, confirming the interest of companies in this approach. However, information regarding this behaviour over time in the American Continent is scarce. This paper presents a set of qualitative and quantitative analyses related to the ISO 9001 certification (globally and at the country level of the Americas), the use of this standard in countries that were part of the ISO Survey 2011 and modelling the ISO 9001 certification for American countries, in order to characterise through mathematical models, the evolution of the certification process and to identify factors that influence the ISO 9001 issued certificates in the various countries analysed. Based on the work developed, a positive relationship was found between the number of issued certificates in each country per 1000 inhabitants and the indicators of economic development (Gross National Income Per Capita). It is determined that the total reserves of a country is an economic variable that directly affects the number of issued certificates, a finding not observed in other forecasting models. 相似文献
164.
Pedro Barahona Gemma Bel-Enguix Veronica Dahl M. Dolores Jiménez-López Ludwig Krippahl 《Natural computing》2014,13(2):169-177
Trees are a useful framework for classifying entities whose attributes are, at least partially, related through a common ancestry, such as species of organisms, family members or languages. In some common applications, such as phylogenetic trees based on DNA sequences, relatedness can be inferred from the statistical analysis of unweighted attributes. The vast majority of mutations that survive across generations are evolutionarily neutral, which means that most genetic differences between species will have accumulated independently and randomly. In these cases, it is possible to calculate the tree from a precomputed matrix of distances. In other cases, such as with anatomical traits or languages, the assumption of random and independent differences does not hold, making it necessary to consider some traits to be more relevant than others for determining how related two entities are. In this paper, we present a constraint programming approach that can enforce consistency between bounds on the relative weight of each trait and tree topologies, so that the user can best determine which sets of traits to use and how the entities are likely to be related. 相似文献
165.
The tweens are a transitional age group undergoing deep physical and psychological transformations. Based on a thirteen-focus group research design involving 103 students, and applying a tweens-centered approach, the characteristics of SMS, IM, Internet, digital photos, electronic games, and email were analyzed. Categories such as moral issues, psychological and social consequences, problems/drawbacks, general benefits, and technical attributes synthesized the main characteristics attached to each form of digital technology. Their relative relevance was not gender dependent. Furthermore, tweens exhibited both metacognitive knowledge and personal epistemological observations associated with most of the digital technologies. 相似文献
166.
Xesús Feás José Pires María Letícia Estevinho Antonio Iglesias José Pedro Pinto De Araujo 《International Journal of Food Science & Technology》2010,45(6):1255-1262
Honey legislation has been addressed to establish the minimum marketing level of the product and the need for consumer protection through correct denominations. Research oriented toward assessment of floral origin and physicochemical properties may increase the commercial value of these products. The characteristics of thirty‐one honeys produced in the Entre‐Douro e Minho region in Portugal were studied. Pollen features and some physicochemical parameters (moisture, ash, pH, free acidity, electrical conductivity, hydroxymethylfurfural contain, apparent sucrose, reducing sugars and diastase activity) were determined. The samples were found to meet international honey specifications. The present study found a linear regression between the ash content of honeys and their specific conductivity. Five samples are listed as Eucalyptus honey, one sample as Citrus honey, and twenty‐five samples as multifloral honeys. Of the total, 87.1% exceeded the quality parameters and should be labelled as ‘virgin’ honey. 相似文献
167.
Estíbaliz Sánchez-González Pedro Miranda Fernando Guiberteau Antonia Pajares 《Journal of the European Ceramic Society》2009,29(12):2635-2641
The elasto-plastic properties and contact damage evolution of a commercial polycrystalline silicon nitride are evaluated as a function of temperature up to 1000 °C, using a recently developed method combining Hertzian indentation and FEM simulation. The results of the study are compared to existing data for other ceramic materials such as alumina and zirconia. Silicon nitride is found to exhibit an excellent combination of elasto-plastic properties in the pre-creep temperature range and good contact damage resistance. These qualities make this material ideal for high temperature applications in general, and in particular to be used in spherical indenters for the evaluation of mechanical properties of other materials at elevated temperature using the procedure applied in this work. 相似文献
168.
Fabricio J. Pontes João R. Ferreira Messias B. Silva Anderson P. Paiva Pedro Paulo Balestrassi 《The International Journal of Advanced Manufacturing Technology》2010,49(9-12):879-902
In recent years, several papers on machining processes have focused on the use of artificial neural networks for modeling surface roughness. Even in such a specific niche of engineering literature, the papers differ considerably in terms of how they define network architectures and validate results, as well as in their training algorithms, error measures, and the like. Furthermore, a perusal of the individual papers leaves a researcher without a clear, sweeping view of what the field’s cutting edge is. Hence, this work reviews a number of these papers, providing a summary and analysis of the findings. Based on recommendations made by scholars of neurocomputing and statistics, the review includes a set of comparison criteria as well as assesses how the research findings were validated. This work also identifies trends in the literature and highlights their main differences. Ultimately, this work points to underexplored issues for future research and shows ways to improve how the results are validated. 相似文献
169.
170.
Energy is essential for present societies. In particular, transportation systems depend on petroleum-based fuels. That world oil production is set to pass a peak is now a reasonably accepted concept, although its date is far from consensual. In this work, we analyze the true expectations of the oil market participants about the future availability of this fundamental energy source. We study the evolution through time of the curves of crude oil futures prices, and we conclude that the market participants, among them the crude oil producers, already expect a near-term peak of oil production. This agrees with many technical predictions for the date of peak production, including our own, that point to peak dates around the end of the present decade. If this scenario is confirmed, it can cause serious social and economical problems because societies will have little time to perform the necessary adjustments. 相似文献