全文获取类型
收费全文 | 339篇 |
免费 | 23篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 20篇 |
综合类 | 13篇 |
化学工业 | 51篇 |
金属工艺 | 22篇 |
机械仪表 | 4篇 |
建筑科学 | 54篇 |
矿业工程 | 17篇 |
能源动力 | 8篇 |
轻工业 | 3篇 |
水利工程 | 41篇 |
石油天然气 | 6篇 |
无线电 | 2篇 |
一般工业技术 | 9篇 |
冶金工业 | 122篇 |
原子能技术 | 4篇 |
自动化技术 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 24篇 |
2020年 | 17篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 16篇 |
2013年 | 18篇 |
2012年 | 38篇 |
2011年 | 28篇 |
2010年 | 17篇 |
2009年 | 16篇 |
2008年 | 25篇 |
2007年 | 26篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1979年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有380条查询结果,搜索用时 15 毫秒
41.
煤仓蓬煤是工业生产中普遍存在的问题,对生产的影响极大。通过对比目前一些解决蓬煤的方法,基于电厂煤仓,给出了一个实时监测解决蓬煤的设计方案。 相似文献
42.
The restoration of in‐stream habitats by structural improvement of stream beds is more and more frequent, but the ecological consequences of such works are still little known. We have examined the influence of the deposit of a 15 cm gravel layer over the stream bottom on the chemical characteristics of the interstitial water, the sediment grain size and the composition of the benthic assemblages. We have compared a restored reach to an upstream control over three years and at three seasons each year. Dissolved oxygen, ammonium, nitrite and nitrate contents were measured in both surface and interstitial (?15 cm deep) waters, together with the depth of anoxia estimated using wooden stakes and fine sediment content at the surface. During the same period and seasons, benthic invertebrates were sampled at five points in each reach. The restoration induced an increase in vertical exchanges of water between surface and interstitial habitats, with an increase in the depth of hypoxia. Changes were observed in the composition of invertebrate communities, but not in the density or in the taxonomic richness of assemblages. These changes in assemblages were fragile: a local disturbance (such as a drying period) diminished the beneficial effect of the restoration with the disappearance of several organisms. The viability of such restoration works may be associated with catchment management designed to reduce fine sediment inputs to the river. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
43.
44.
45.
蚯蚓改善垂直潜流人工湿地处理农村污水效能的研究 总被引:2,自引:0,他引:2
通过引入赤子爱胜蚓,构建蚯蚓垂直潜流人工湿地,比较了蚯蚓人工湿地与对照人工湿地去除污染物的特性,并分析了投加蚯蚓对改善湿地内微生物量的空间分布及提高湿地防堵塞的效果.结果表明,蚯蚓的引入提高了垂直潜流人工湿地对污染物的去除效果,与对照人工湿地相比,蚯蚓人工湿地对COD、NH_4~+-N、TN、TP的去除率分别提高了15.8%、23.2%、20.6%、16.2%;同时,还增加了人工湿地各层的微生物量.在表层,蚯蚓人工湿地的细菌总数、亚硝酸菌数、硝酸菌数、反硝化菌数分别为对照人工湿地的2.3、2.9、2.0、2.1倍;并且蚯蚓的引入还在一定程度上缓解了垂直潜流人工湿地的堵塞. 相似文献
46.
Understanding mechanisms of controlling the bacteria growth and degradation of pollutants is critical for effective improvements in water treatment and bioremediation in porous media. In this study, we developed an integrated model of individual-based model and multicomponent lattice Boltzmann method to study interactions of oxygen, bioclogging, chemical oxygen demand (COD) removal, and their influence on growth and permeability of microbial biofilms. We found biofilm growth to be very heterogeneous on the surface of the solid matrix and pores. There is a biofilm porosity threshold. Beyond this threshold, the porosity of biofilm has no obvious influence on the flow rate and COD removal. We also studied the influence of initial cell populations, bulk oxygen concentration and biofilm permeability on the flow rate and COD removal. It demonstrated the capability of the present model to investigate biofilm growth, clogging and contaminants degradation in porous media, and its potential applications in water treatment. 相似文献
47.
48.
Pina Nicoletta De Cicco Enio Paris Virginia Ruiz‐Villanueva Luca Solari Markus Stoffel 《河流研究与利用》2018,34(7):617-628
In‐channel wood is a key component in fluvial ecosystems; however, transport of in‐channel wood during floods can create hazards in urbanized areas. Among the main problems is wood accumulation at bridges, which reduces flow openings, causes blockage and inundation of nearby areas and, eventually, results in structures collapsing. Increasing awareness of the importance of the ecological role of wood in rivers calls for a compromise between the preservation of river ecosystems and management strategies for the prevention of wood‐related hazards. In recent years, knowledge related to in‐channel wood dynamics and hazards has notably increased, and a significant body of valuable information can be found in an extensive number of studies. This review provides a comprehensive summary of the most relevant advances regarding in‐channel wood‐bridge interactions. We review the factors controlling wood accumulation formation and summarize the different approaches used to analyse this process, namely, physical and numerical modelling. Finally, we conclude by highlighting the most important knowledge gaps, addressing particularly underresearched fields and stressing the remaining challenges. 相似文献
49.
由于施工工艺的原因,止水帷幕一般存在缝隙。在长期渗流的作用下,带缝隙的止水帷幕渗漏量如何发展需要进一步研究。因此,作者自行设计并制作了砂槽模型模拟带裂缝的止水帷幕,并开展了一系列的渗流试验。试验考虑了水力条件、砂样级配和缝隙尺度因素的影响。结果表明,在水头不变的情况下,各试验中均出现了渗漏量下降的现象,但水头升高则会破坏这一现象。缝隙渗漏量下降的实质是砂颗粒移动和聚集导致淤堵的产生,淤堵位置可能在上下游缝口、缝隙进出口或缝隙内。当砂样粒径较细时,缝隙渗漏量下降效果最为显著;当下游回填级配不稳定的砂样时,缝隙渗漏量下降效果不佳。 相似文献
50.
以碳酸钙水相合成为模型反应,借助对流动反应过程的放大观测,从沉淀悬浮液的流变特性分析了液相沉淀反应在毫米级管式微通道中的流动行为特征以及通道堵塞的过程机理。结果表明,碳酸钙-水悬浮体系的黏度在低剪切速率下随固含率的增加而飙升,而反应通道堵塞的本质可归因于在壁面和流动主体区形成了固含率较高的局部高黏区,使流动性严重恶化。提高反应的流速加快了壁面沉积层和沉淀颗粒团聚体的形成,反而加快了堵塞;其中团聚体的形成远快于沉积层的积累,使团聚体的“架桥”虽晚于沉积层出现,却成为管路堵塞的主要因素。基于破坏流动壁面和主体的局部高黏区,设计了两种新型的微通道反应器模型,有可能为解决反应通道堵塞这一难题提供新的思路。 相似文献