全文获取类型
收费全文 | 1227篇 |
免费 | 84篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
综合类 | 5篇 |
化学工业 | 397篇 |
金属工艺 | 23篇 |
机械仪表 | 16篇 |
建筑科学 | 56篇 |
矿业工程 | 1篇 |
能源动力 | 23篇 |
轻工业 | 232篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
无线电 | 53篇 |
一般工业技术 | 160篇 |
冶金工业 | 170篇 |
原子能技术 | 1篇 |
自动化技术 | 151篇 |
出版年
2023年 | 10篇 |
2022年 | 63篇 |
2021年 | 92篇 |
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 31篇 |
2016年 | 37篇 |
2015年 | 36篇 |
2014年 | 46篇 |
2013年 | 78篇 |
2012年 | 61篇 |
2011年 | 111篇 |
2010年 | 52篇 |
2009年 | 57篇 |
2008年 | 58篇 |
2007年 | 59篇 |
2006年 | 57篇 |
2005年 | 56篇 |
2004年 | 47篇 |
2003年 | 18篇 |
2002年 | 28篇 |
2001年 | 16篇 |
2000年 | 24篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 20篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1968年 | 3篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1313条查询结果,搜索用时 31 毫秒
21.
22.
This research study analysed the interaction between people's postures and activities while in semi-public/leisure situations and during transportation (journey by train). In addition, the use of small electronic devices received particular emphasis. Video recordings in German trains and photographs in Dutch semi-public spaces were analysed using a variation of Branton and Grayson's (An evaluation of train seats by observation of sitting behaviour. Ergonomics, 10 (1), (1967), 35-51) postural targeting forms and photos. The analysis suggests a significant relationship between most activities and the position of the head, trunk and arms during transportation situations. The relationship during public situations is less straightforward. Watching, talking/discussing and reading were the most observed activities for the transportation and leisure situations combined. Surprisingly, differences in head, trunk, arm and leg postures were not significant when using small electronic devices. Important issues not considered in this study include the duration of the activities, the gender and age of observed subjects and the influence of the time of day. These are interesting issues to consider and include for future research. STATEMENT OF RELEVANCE: This study shows what activities people choose to carry out and their related postures when not forced to a specific task (e.g. driving). The results of this study can be used for designing comfortable seating in the transportation industry (car passenger, train, bus and aircraft seats) and semi-public/leisure spaces. 相似文献
23.
24.
Mid-level processes on images often return outputs in functional form. In this context the use of functional data analysis (FDA) in image analysis is considered. In particular, attention is focussed on shape analysis, where the use of FDA in the functional approach (contour functions) shows its superiority over other approaches, such as the landmark based approach or the set theory approach, on two different problems (principal component analysis and discriminant analysis) in a well-known database of bone outlines. Furthermore, a problem that has hardly ever been considered in the literature is dealt with: multivariate functional discrimination. A discriminant function based on independent component analysis for indicating where the differences between groups are and what their level of discrimination is, is proposed. The classification results obtained with the methodology are very promising. Finally, an analysis of hippocampal differences in Alzheimer’s disease is carried out. 相似文献
25.
26.
Irene M. C. Lo Chester S. C. Lam Keith C. K. Lai 《Canadian Metallurgical Quarterly》2005,131(11):1598-1606
Eleven columns were set up under various groundwater geochemistry conditions to investigate the competitive effect of trichloroethylene (TCE) on hexavalent chromium [Cr(VI)] removal by zero-valent iron (Fe0). They were found to be electron competitors in the redox reactions. In the presence of TCE, the Cr(VI) removal capacities of Fe0 were decreased by about 40% when compared with their respective Cr(VI) removal capacities with identical groundwater geochemistry but without TCE. The specific reaction rate constant (kSA) of TCE was decreased by about 50% when Cr(VI) was singly applied. The kSA of TCE was further decreased by 75% in the presence of both Cr(VI) and carbonate. However, there was no apparent effect on the kSA of TCE when Cr(VI), hardness and carbonate were all present. It revealed that TCE was a stronger electron competitor of Cr(VI) and the degradation of TCE became more favorable when both hardness and carbonate were present. This suggests that the passivated precipitates formed on the Fe0 surface in the presence of both hardness and carbonate may significantly affect the Cr(VI) removal by Fe0 but has insignificant effect on the TCE removal. 相似文献
27.
We provide analytical forms for the plastic deformation and velocity gradients associated with a single pass of equal channel angular extrusion (ECAE). Three cases of plastic deformation are considered: ideal simple shear, a plastic deformation zone (PDZ) in the shape of a central fan of angle βm, and a two-part PDZ consisting of a central fan in the ‘upper’ region and a low intensity shear deformation in the ‘lower’ region. The analysis for simple shear considers a general die angle Φ, whereas the other two cases only consider Φ=90°. The tensors for deformation and velocity gradients completely describe the deformation, such as the directions and magnitudes of material stretching and rotations. From this analysis, one can calculate deformation and texture evolution. Texture evolution during flow through the central fan zone involves continuous rotation of the texture components causing the texture developed at the end of the extrusion to be rotated relative to the ideal simple shear case. The analysis of the two-part zone suggests inhomogeneity in texture evolution, in which features of the initial texture are retained and rotated in the lower region, while they are nearly erased in the upper region. These analytical flow patterns for a single pass can be repeatedly applied for any number of passes of any ECAE route. 相似文献
28.
Process waters obtained from hydrothermal carbonization (HTC) of wheat straw, a biogas digestate derived thereof, and four woody biomass feedstocks were quantified regarding the total organic carbon (TOC) and selected organic compounds. HTC runs revealed that TOC loads were largely unaffected by process severity or type of feedstock whereas the C2–C6 fatty acids, determined by GC, displayed clear effects of temperature and feedstock. HPLC demonstrated simultaneously the initial increase and subsequent consumption of cellulose‐derived furfural and 5‐hydroxymethylfurfural as well as the increase of the lignin‐derived 2‐methoxyphenol. 2‐Methylbenzofuran, an example for a substance potentially harmful to aquatic biota, was observed in high concentration in the HTC liquor from wheat straw‐based feedstocks. 相似文献
29.
30.
Robert Van Dam Irene Langkilde-Geary Dan Ventura 《Knowledge and Information Systems》2013,35(3):525-552
The ADtree, a data structure useful for caching sufficient statistics, has been successfully adapted to grow lazily when memory is limited and to update sequentially with an incrementally updated dataset. However, even these modified forms of the ADtree still exhibit inefficiencies in terms of both space usage and query time, particularly on datasets with very high dimensionality and with high-arity features. We propose four modifications to the ADtree, each of which can be used to improve size and query time under specific types of datasets and features. These modifications also provide an increased ability to precisely control how an ADtree is built and to tune its size given external memory or speed requirements. 相似文献