全文获取类型
收费全文 | 13129篇 |
免费 | 804篇 |
国内免费 | 317篇 |
专业分类
电工技术 | 592篇 |
技术理论 | 1篇 |
综合类 | 559篇 |
化学工业 | 2895篇 |
金属工艺 | 703篇 |
机械仪表 | 522篇 |
建筑科学 | 662篇 |
矿业工程 | 263篇 |
能源动力 | 388篇 |
轻工业 | 1439篇 |
水利工程 | 172篇 |
石油天然气 | 508篇 |
武器工业 | 61篇 |
无线电 | 1160篇 |
一般工业技术 | 1973篇 |
冶金工业 | 526篇 |
原子能技术 | 154篇 |
自动化技术 | 1672篇 |
出版年
2025年 | 46篇 |
2024年 | 274篇 |
2023年 | 290篇 |
2022年 | 527篇 |
2021年 | 677篇 |
2020年 | 535篇 |
2019年 | 444篇 |
2018年 | 471篇 |
2017年 | 604篇 |
2016年 | 572篇 |
2015年 | 514篇 |
2014年 | 699篇 |
2013年 | 1014篇 |
2012年 | 817篇 |
2011年 | 854篇 |
2010年 | 687篇 |
2009年 | 608篇 |
2008年 | 500篇 |
2007年 | 400篇 |
2006年 | 372篇 |
2005年 | 279篇 |
2004年 | 284篇 |
2003年 | 335篇 |
2002年 | 462篇 |
2001年 | 385篇 |
2000年 | 196篇 |
1999年 | 179篇 |
1998年 | 174篇 |
1997年 | 118篇 |
1996年 | 97篇 |
1995年 | 85篇 |
1994年 | 71篇 |
1993年 | 67篇 |
1992年 | 43篇 |
1991年 | 41篇 |
1990年 | 29篇 |
1989年 | 26篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 31篇 |
1984年 | 35篇 |
1983年 | 30篇 |
1982年 | 29篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 22篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1974年 | 20篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
为解决PROTOS M5卷接机组梗签输送装置中输送管道容易堵塞问题,通过Solid Works建立管道模型,利用Fluent分析软件模拟空气在管道中流动的形态,对流体在管道中的压力和流线进行分析,得到梗签输送管道的堵塞原因并对该装置进行了优化设计:将封闭式弯管改为开放式振槽,缩短输送管道长度;增加切碎梗签功能,将较长梗签切断,避免过长梗签卡在管道弯曲处;采用直管连接梗签箱与集中负压源,减少负压损失。结果表明:1管道在最大弯曲处、同一截面上出现螺旋式流动时,或在最大弯曲处出现流速为零时,以及管道压力损失过大时,均容易造成管道堵塞。2改进后管道压力和流线分布均匀,管道压力损失由452.8 Pa减小到245.5 Pa,有效解决了梗签输送管道堵塞问题。 相似文献
112.
Image processing has become a tremendous tool for various fields of applications as well as for textile manufacturing industry in recent years. Inspection of fabric density is one of the major issues for fabric manufacturers in textile industries. In this study, an image processing method comprising of linear and nonlinear techniques for automatic inspection of warp and weft yarn density of fabrics has been proposed. By avoiding common problems of linear filtering such as blurring and localization, anisotropic diffusion filtering has been applied as preprocessing operation to enhance the edge region/boundaries between adjacent yarns of the fabric images. We conjecture that given a skewed gray level image, the number of peaks in the gray line profile of the image is minimized if the image is rotated in such a way that the inter-spaces between yarns are aligned with the vertical axis. Gabor filter, an orientation-sensitive filter, is applied to the skewed image at that angle to boost the edges between inter-spaces. The number of warp and weft yarn density has been inspected by applying gray line profile method. Simulations have been done on a wide range of fabric image data set. The results have shown that nonlinear and steered filters made a contribution to the performance of the method. The number warp and weft yarn densities are determined with an accuracy rates above 90%. 相似文献
113.
114.
115.
Seok Hyun Nam Sun Phil Choi Mi Young Kang Hee Jong Koh Nobuyuki Kozukue Mendel Friedman 《Food chemistry》2006
Ethanol–water (70:30, v/v) extracts from the bran of rice seeds from twenty one pigmented and one nonpigmented rice cultivars were evaluated for antioxidative activities using the following tests: inhibition of peroxidation of linoleic acid; inhibition of peroxidation of rabbit lipid erythrocyte membranes; reduction of potassium ferricyanide, and scavenging of superoxide anions and hydroxyl radicals. With some exceptions, extracts from the pigmented rice seeds had higher antioxidative activity than did the nonpigmented variety. The following pigmented cultivars had the highest antioxidative activities in all tests: Jumlalocal-1, Parnkhari 203, DZ78, LK1-3-6-12-1-1, and Elwee. A significant correlation was also noted between reducing power, inhibition of erythrocyte ghost membrane peroxidation, and superoxide anion and hydroxyl radical scavenging. The results suggest that: (a) ferricyanide reducing power might be a useful and simple index for large-scale evaluation of antioxidative potencies of natural products present in rice; (b) pigmented rice varieties with high antioxidative activities provide a source of antioxidants and a genetic resource to develop new health-promoting rice cultivars. 相似文献
116.
117.
A regression model composed of two sigmoid functions with variable asymptotes was developed and used to analyse the dietary fibre supplement behaviour during bread dough mixing. Using eight commercial dietary fibres of different botanical origin and model wheat starch-gluten flour, farinograph curves for fibre-flour blends and for the flour only were performed. After smoothing of the curves with the regression model, difference farinograms as the fibre supplementation effects were determined. The results showed that the difference farinograms had two peaks, whose shape was strongly differentiated by the studied supplements. The presence of both peaks allowed distinguishing two kinds of the rheological activity of each fibre supplement: weakening and strengthening of the consistency of bread dough during its development. The carrot, oat, cranberry, and cacao fibres exhibited dominance of strengthening over weakening action. While chokeberry, carob, apple, and flax fibres were characterised by dominance of weakening over strengthening action. The analysis of both position and height of the peaks in the difference farinogram can be also helpful for determination of hydration kinetics of the fibres used for bread supplementation. 相似文献
118.
通过试验研究了大港油田4个区块的稠油在不同温度、不同剪切速率及不同含水条件下的充变体性。结果表明,大港油田稠油在油层中具有半顿流体的特性;而在井筒中,将会出现非牛顿流体的流动特性。含水原油在井筒中流动时将不会出现明显的乳化现象,粘度将随含水率增加而降低。 相似文献
119.
120.