全文获取类型
收费全文 | 8116篇 |
免费 | 1209篇 |
国内免费 | 641篇 |
专业分类
电工技术 | 184篇 |
综合类 | 612篇 |
化学工业 | 398篇 |
金属工艺 | 1116篇 |
机械仪表 | 504篇 |
建筑科学 | 205篇 |
矿业工程 | 126篇 |
能源动力 | 47篇 |
轻工业 | 2714篇 |
水利工程 | 47篇 |
石油天然气 | 106篇 |
武器工业 | 51篇 |
无线电 | 601篇 |
一般工业技术 | 656篇 |
冶金工业 | 444篇 |
原子能技术 | 32篇 |
自动化技术 | 2123篇 |
出版年
2024年 | 59篇 |
2023年 | 177篇 |
2022年 | 272篇 |
2021年 | 285篇 |
2020年 | 323篇 |
2019年 | 304篇 |
2018年 | 284篇 |
2017年 | 325篇 |
2016年 | 332篇 |
2015年 | 347篇 |
2014年 | 440篇 |
2013年 | 522篇 |
2012年 | 574篇 |
2011年 | 641篇 |
2010年 | 522篇 |
2009年 | 510篇 |
2008年 | 496篇 |
2007年 | 567篇 |
2006年 | 494篇 |
2005年 | 425篇 |
2004年 | 377篇 |
2003年 | 269篇 |
2002年 | 215篇 |
2001年 | 183篇 |
2000年 | 176篇 |
1999年 | 116篇 |
1998年 | 117篇 |
1997年 | 103篇 |
1996年 | 90篇 |
1995年 | 94篇 |
1994年 | 59篇 |
1993年 | 62篇 |
1992年 | 55篇 |
1991年 | 24篇 |
1990年 | 32篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有9966条查询结果,搜索用时 15 毫秒
41.
低碳钢热变形过程中铁素体的织构形成规律 总被引:2,自引:0,他引:2
利用背散射电子衍射取向成像技术定量分析了热模拟单向压缩条件下Q235碳素钢热变形时铁素体的织构形成规律。结果表明,在710℃纯铁素体热压缩过程中,形成〈100〉和〈111〉方向的线织构。〈111〉方向织构增强的速度较快,到应变为1.0时达最大值,然后随应变的加大而减弱;〈100〉方向织构在形变量较小时增强的速度较慢,在大应变时增强的速度很快。大应变时虽导致一定程度的动态再结晶,使铁素体晶粒细化,但组织不均匀,织构过强,造成强烈的各向异性。在奥氏体与铁素体两相区变形时,先共析铁素体因形变同样产生强烈的织构。随着形变温度的提高和先共析铁素体的减少,织构减弱。 相似文献
42.
SEBASTIANO PORRETTA † GIUSEPPE CARPI GIANFRANCO DALL'AGLIO CLAUDIO GHIZZONI 《International Journal of Food Science & Technology》1992,27(4):427-433
The characteristics of high-quality tomato pulp (commercial def.: crushed or diced tomatoes with about 30% tomato juice as packing medium) canned with tomato juice pulp enriched by ultrafiltration as packing medium were compared with those covered with conventional vacuum-concentrated juice.
Both hot- and cold-break products were prepared and those containing 20% serum-reduced packing juice proved to be the best, showing no signs of syneresis on storage and with improvements in sensory properties, colour and non-enzymatic browning; some volatile components were reduced. 相似文献
Both hot- and cold-break products were prepared and those containing 20% serum-reduced packing juice proved to be the best, showing no signs of syneresis on storage and with improvements in sensory properties, colour and non-enzymatic browning; some volatile components were reduced. 相似文献
43.
Physical, Chemical and Sensory Changes in Irradiated Fresh Pork Packaged in Modified Atmosphere 总被引:3,自引:0,他引:3
The effects of irradiation dose (0, 0.5 and 1.0 kGy), headspace oxygen (0, 10 and 20% O2, balance nitrogen) and storage temperature (5, 15 and 25°C) on the physical, chemical and sensory changes in fresh pork were studied using factorial design experiments. Irradiation in the absence of oxygen extended the sensory shelf life of pork from 9 to 26 days at 5°C and from & lt; 2 to 2 days at 25°C. Oxygen in the package headspace combined with irradiation adversely affected physical, chemical and sensory characteristics of the end product. 相似文献
44.
V Arvis B Michalet‐Doreau C Debain 《Journal of the science of food and agriculture》2004,84(14):1848-1854
We present a new computer vision method for measuring the physical characteristics of maize silages based on the extraction of image textural features, namely five Haralick features, the moments of order 1 and 2 on the grey levels of the image, and a fractal parameter. To show the effectiveness of these features for characterising the physical properties of the maize silage, a trial was performed on three maize cultivars (Zea mays L, a mid–early hybrid and an early hybrid) to study the effects of the ensiling process. The features could discern effects of the ensiling process on the physical properties of the maize silage. These effects were neither significant by comparing particle size distributions, nor with chemical compositions, whereas a biological response (degradation in the rumen) to the ensiling process exists. Thus image textural features seemed to give new and interesting measurements of the physical properties of the silage, explaining the biological response better than other methods. Furthermore, the ensiling effect was not the same with all the maize types and varied with the proportion of large particles in the silages. Linear relations between features before and after the ensiling process made it possible to predict a measure on a silage knowing its value on the parent forage. Copyright © 2004 Society of Chemical Industry 相似文献
45.
多相物质粉末衍射的物相检索 总被引:1,自引:1,他引:0
余焜 《理化检验(物理分册)》2003,39(2):92-95
讨论了多相物质粉末衍射的物相检索问题,介绍了XRDS的物相检索软件。这是一种智能型的物相检索程序,考虑了测试数据的不确定度,以及粉末样品和块状样品衍射图谱各自的特点,不仅注意到实际样品中微量物相存在的可能,也注意到块状样品结构有序性的可能。XRDS能够帮助材料工作者同时检出样品中所含的多种物相及其含量,操作简单、结果可靠。 相似文献
46.
47.
48.
Wood inspection with non-supervised clustering 总被引:9,自引:0,他引:9
Abstract. The appearance of sawn timber has huge natural variations that the human inspector easily compensates for mentally when determining
the types of defects and the grade of each board. However, for automatic wood inspection systems these variations are a major
source for complication. This makes it difficult to use textbook methodologies for visual inspection. These methodologies
generally aim at systems that are trained in a supervised manner with samples of defects and good material, but selecting
and labeling the samples is an error-prone process that limits the accuracy that can be achieved. We present a non-supervised
clustering-based approach for detecting and recognizing defects in lumber boards. A key idea is to employ a self-organizing
map (SOM) for discriminating between sound wood and defects. Human involvement needed for training is minimal. The approach
has been tested with color images of lumber boards, and the achieved false detection and error escape rates are low. The approach
also provides a self-intuitive visual user interface.
Received: 16 December 2000 / Accepted: 8 December 2001
Correspondence to: O. Silvén 相似文献
49.
50.
S. Zaefferer 《Advanced Engineering Materials》2003,5(8):607-613
In recent years the investigation of local texture and microstructure by analysis of electron backscatter diffraction patterns (EBSP) in the SEM has become a very powerful and popular method. With the introduction of SEM with field emission guns (FEG) the spatial resolution of EBSP measurements could be enhanced from 500 nm with a tungsten emitter to better than 50 nm. This evolution of SEM techniques raises the question whether transmission electron microscopy (TEM) still has fields of application in texture research. The present article answers this question with a clear “yes” and presents three examples of investigations where TEM is indispensable. The three examples comprise the investigation of the correlation between dislocation structure and deformation texture, a study on nucleation mechanisms of recrystallization in highly deformed metals and the investigation of microtexture and microstructure in nanocrystalline materials. Together with the presentation of these cases some of the necessary measurement techniques are described briefly. It is shown that TEM has to be applied when highest spatial resolution of orientation determination and imaging and high accuracy of orientation determination are to be reached, when the three‐dimensional and quantitative characterization of lattice defects is required or when materials with a high density of lattice defects are to be investigated. 相似文献