全文获取类型
收费全文 | 2476篇 |
免费 | 267篇 |
国内免费 | 59篇 |
专业分类
电工技术 | 11篇 |
综合类 | 318篇 |
化学工业 | 1223篇 |
金属工艺 | 14篇 |
机械仪表 | 14篇 |
建筑科学 | 427篇 |
矿业工程 | 20篇 |
能源动力 | 264篇 |
轻工业 | 250篇 |
水利工程 | 52篇 |
石油天然气 | 49篇 |
武器工业 | 4篇 |
无线电 | 19篇 |
一般工业技术 | 25篇 |
冶金工业 | 21篇 |
原子能技术 | 7篇 |
自动化技术 | 84篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 48篇 |
2021年 | 67篇 |
2020年 | 85篇 |
2019年 | 50篇 |
2018年 | 41篇 |
2017年 | 58篇 |
2016年 | 92篇 |
2015年 | 80篇 |
2014年 | 167篇 |
2013年 | 143篇 |
2012年 | 188篇 |
2011年 | 189篇 |
2010年 | 153篇 |
2009年 | 171篇 |
2008年 | 149篇 |
2007年 | 155篇 |
2006年 | 180篇 |
2005年 | 131篇 |
2004年 | 97篇 |
2003年 | 73篇 |
2002年 | 63篇 |
2001年 | 63篇 |
2000年 | 39篇 |
1999年 | 38篇 |
1998年 | 22篇 |
1997年 | 33篇 |
1996年 | 22篇 |
1995年 | 19篇 |
1994年 | 23篇 |
1993年 | 29篇 |
1992年 | 17篇 |
1991年 | 22篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 13篇 |
1986年 | 14篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1961年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有2802条查询结果,搜索用时 31 毫秒
1.
Deep geological repositories for radioactive waste contain metallic materials, either used to construct disposal canisters or as low-/intermediate-level waste (L/ILW). The safety relevance of corrosion is linked to canister lifetime in the former case and gas generation in the latter. More specifically, the Belgian “supercontainer” concept envisages mild steel for the used fuel disposal canister, and in the case of the Swiss L/ILW repository, mild steels are the largest metallic waste component due to the decommissioning of civilian power-generating facilities. For these circumstances, the corrosion environment is dominated by the chemistry of cement, which is used as buffer or backfill material. The corrosion behaviour of mild steel in anoxic environments was studied through the analysis of the hydrogen end-product. Hydrogen analysis was conducted by periodically purging the cell head-space and analysing the gas using a solid-state hydrogen sensor. While this method is limited to providing only uniform corrosion rates averaged over periods of time, ranging from weeks to months, it provides excellent resolution and sensitivity. The test cell environments were matched against the anticipated Belgian high-level waste and Swiss L/ILW repository environments, and also against experiments that have been conducted by other researchers for comparative purposes. Samples were exposed to synthetic cement pore waters, representing fresh and degraded cement. In young cement waters, the formation of initial corrosion products resulted in steel wire corrosion rates of the order of µm/year, which, at 80°C rapidly declined to ∼10 nm/year. In contrast, SA516 grade 70 steel plate corroded much more slowly under similar conditions. In aged cement waters, initial corrosion rates were higher but declined faster towards a longer-term rate of ∼10 nm/year. 316L stainless steel, embedded in cementitious material, corroded at a rate of <1 nm/year at 50°C. 相似文献
2.
玄武岩纤维填料应用于两种混合生长反应器的评价 总被引:1,自引:0,他引:1
采用单丝直径微米级的伞状玄武岩纤维(BF)作为填料,将其引入序批式反应器(SBR)和后置缺氧反硝化SBR外聚合物(EPS)含量和扫描电子显微镜形貌图,考察了两种SHBR的污水处理效果。试验结果表明:基于SBR的SHBR的出水COD、氨氮、总氮去除率分别为83.2%、89.9%、86.8%;基于后置缺氧反硝化SBR的SHBR优良,而基于后置缺氧反硝化SBR的SHBR的脱氮效果得到进一步的优化和提升。两种SHBR的BF填料中EPS含量分析结果显示:在好氧环境下,蛋白质(PN)的含量高于多糖(PS)的含量;在缺氧条件下,PS的含量明显高于PN的含量。 相似文献
3.
为满足后续生物处理单元对固体悬浮物(SS)和铁浓度的进水要求,采用磁絮凝强化技术对厌氧消化污泥脱水液进行预处理。通过正交试验和单因素试验,本文考察了混凝水力条件、聚合氯化铝(PAC)投加量、聚丙烯酰胺(PAM)投加量、磁粉投加量及药剂投加顺序对磁絮凝效果的影响。试验结果表明:磁絮凝强化技术在快搅300r/min(2min)、慢搅100r/min(15min)、静置10min时,依次投加磁粉(40mg/L)、PAC(30mg/L)、PAM(4mg/L)时处理效果最好。在此运行条件下,SS和Fe3+去除率分别为97.61%、98.24%、絮凝指数(FI值)取得最大值、zeta电位绝对值最小,絮凝效果最佳。与对照相比,磁絮凝强化技术对SS和Fe3+去除率分别可提高3.70%和10.82%,同时絮体最大沉降速度可提高33%。磁絮凝技术处理后的出水不仅可以满足后续生物处理单元对SS和铁浓度的要求,还可以有效提高磁絮凝体的沉降速度,减小沉淀时间,具有较好的实用价值。 相似文献
4.
5.
6.
以特定污泥挂膜的自制厌氧生物滤床系统具有良好的去铬(VI)能力。恒流泵最佳流量为47mL/min,外加碳源使废水COD约140mg/L,铬(VI)的浓度由60mg/L左右降到0.5mg/L以下(一级排放标准),需要4h,而对照组(未加碳源)需要14h。铬(VI)浓度由64.66mg/L提高到75.53mg/L时,对系统负面影响甚微,提高到95.47mg/L时,系统出水达标所需时间延长到7.5h。添加微量金属离子与未添加微量金属离子的情况相比,处理效率提高21.26%。分析试验表明:铬(VI)的去除途径可能是由生物还原作用将六价铬还原为三价铬,形成氢氧化铬沉积于微生物表面。 相似文献
7.
8.
9.
10.
P. S. Lawson 《Biomass & bioenergy》1992,2(1-6):319-330
In recent years it has been recognised by an increasing number of nations that there is considerable energy potential within MSW. As a result many countries have established R,D& D programmes to examine methods of exploiting this potential. The IEA's MSW Conversion Activity was set up in 1986 to provide an infrastructure for sharing information and co-ordinating work in this area internationally. This Activity was extended in 1989 and currently a total of 9 nations participate in it.
To cope with the wide scope of the area (encompassing both biological and thermal processing of MSW) the Activity was divided into three subgroups or Expert Working Groups (EWGs). Each of these dealt with a distinct area of expertise:
- 1. •Downstream effects of source separation and screening of MSW
- 2. •Sampling and analytical protocols
- 3. •Landfill gas
In addition to these groups a central secretariat based at Harwell (UK) has provided guidance, established and administered databases of contacts and produced a series of national reports.
This paper describes the achievements of the Activity and discusses work proposed for the future. 相似文献