全文获取类型
收费全文 | 5909篇 |
免费 | 741篇 |
国内免费 | 91篇 |
学科分类
工业技术 | 6741篇 |
出版年
2024年 | 20篇 |
2023年 | 55篇 |
2022年 | 152篇 |
2021年 | 246篇 |
2020年 | 243篇 |
2019年 | 170篇 |
2018年 | 227篇 |
2017年 | 245篇 |
2016年 | 317篇 |
2015年 | 300篇 |
2014年 | 415篇 |
2013年 | 410篇 |
2012年 | 544篇 |
2011年 | 495篇 |
2010年 | 275篇 |
2009年 | 280篇 |
2008年 | 239篇 |
2007年 | 239篇 |
2006年 | 240篇 |
2005年 | 176篇 |
2004年 | 174篇 |
2003年 | 167篇 |
2002年 | 138篇 |
2001年 | 129篇 |
2000年 | 123篇 |
1999年 | 96篇 |
1998年 | 80篇 |
1997年 | 192篇 |
1996年 | 66篇 |
1995年 | 60篇 |
1994年 | 56篇 |
1993年 | 44篇 |
1992年 | 40篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有6741条查询结果,搜索用时 46 毫秒
51.
52.
53.
In order to extract froth morphological feature, a bubble image adaptive segmentation method was proposed. Considering the
image’s low contrast and weak froth edges, froth image was coarsely segmented by using fuzzy c means (FCM) algorithm. Through
the attributes of size and shape pattern spectrum, the optimal morphological structuring element was determined. According
to the optimal parameters, some image noises were removed with an improved area opening and closing by reconstruction operation,
which consist of image regional markers, and the bubbles were finely separated from each other by watershed transform. The
experimental results show that the structural element can be determined adaptively by shape and size pattern spectrum, and
the froth image is segmented accurately. Compared with other froth image segmentation method, the proposed method achieves
much high accuracy, based on which, the bubble size and shape features are extracted effectively. 相似文献
54.
Froth flotation is used widely for upgrading raw phosphate. The flotation recovery of coarse phosphate (-1.18+0.425 mm) is much lower than that achieved on the -0.425+0.15 mm size fraction. Enhanced recovery of coarse phosphate particles is of great economic and environmental importance for phosphate industry. In this investigation, four different phosphate samples were aquired, characterized and tested in a specially designed laboratory-scale flotation column. Significant recovery improvement of coarse phosphate flotation was achieved using cavitation-generated nanobubble though its effects differ among the four testing phosphate samples. The laboratory-scale flotation column test results indicate that nanobubble increased P2O5 recovery by up to 10%-30% for a given Acid Insoluble (A.I.) rejection, depending on the characteristic of phosphate samples. The improvement ef-fect of nanobubble on the hard-to-float particles was more significant than that on easy-to-float particles, especially at lower col-lector dosages. Nanobubbles reduced the collector dosage by 1/3 to 1/2. Nanobubbles almost doubled the coarse phosphate flotation rate constant and increased the flotation selectivity index by up to 25%. 相似文献
55.
The flotation of pure and natural carbonaceous iron ore samples in the oleate flotation system was investigated. Starch can
depress hematite effectively in a wide pH range, but cannot depress siderite efficiently in neutral conditions. The flotation
recovery of pure hematite, siderite, and quartz in the oleate-starch-CaCl2 system is significantly different when the slurry pH varies from 4 to 12. A novel two-step flotation process was developed
for the separation of iron concentrate from Donganshan carbonaceous iron ore through which the siderite concentrate is first
recovered and the high quality hematite concentrates with relative high iron recovery can be obtained in the second step flotation.
The siderite concentrate may be utilized directly or undergo further concentration steps to increase iron grade. 相似文献
56.
FCLS (Ferric Chromium Lignin Sulfonate) was used to aid the separation of chalcopyrite from marmatite. Flotation, adsorption and zeta-potential tests of treated marmatite and chalcopyrite were performed. The flotation of marmatite was strongly depressed, while that of chalcopyrite was only slightly depressed, over a wide range of pH values when FCLS was used as depressant in the presence of Butyl Xanthate (BX). The adsorption of BX onto chalcopyrite or marmatite takes place over a wide pH range. The adsorption density of BX on chalcopyrite and marmatite decreases as the pH increases. The adsorption density of FCLS onto marmatite is greater than the adsorption density onto chalcopyrite. The zeta potentials of chalcopyrite and marmatite become more negative due to the addition of xanthate and FCLS. 相似文献
57.
旋流-静态微泡浮选柱净化含油废水试验研究 总被引:1,自引:0,他引:1
为了提高含油废水处理效果、简化处理工艺,提出了以旋流一静态微泡浮选柱为核心的水处理工艺,在自行研制的试验装置系统上,研究了循环泵压力、柱体过流速度、混凝剂种类及投加量、表面活性剂投加量、油水pH值等主要工艺参数对模拟含油废水除油效果的影响.结果表明:以上因素均对脱油率有较大影响,在优化条件下,除油率可达95.7%,旋流-静态微泡浮选柱对含油废水有较高的净化能力. 相似文献
58.
59.
60.
几种常用捕收剂与红柱石作用机理的量子化学研究 总被引:1,自引:0,他引:1
运用量子化学中RHF(Hartree-Fock-Roothaan)方法,利用STO-3G基组,研究红柱石晶体中各离子电荷分布及4种捕收剂与红柱石作用的键级与能量变化。经对红柱石与捕收剂成键机理分析表明,十二烷基磺酸钠为化学吸附,十二胺为物理吸附,油酸钠和羟肟酸为物理吸附与化学吸附共存。4种捕收剂按捕收能力从强到弱的排序为:十二烷基磺酸钠〉十二胺〉羟肟酸〉油酸钠。该排序结果与浮选试验结果一致。 相似文献