全文获取类型
收费全文 | 87451篇 |
免费 | 7303篇 |
国内免费 | 3818篇 |
专业分类
电工技术 | 3754篇 |
技术理论 | 8篇 |
综合类 | 7861篇 |
化学工业 | 15656篇 |
金属工艺 | 1595篇 |
机械仪表 | 1972篇 |
建筑科学 | 13367篇 |
矿业工程 | 5085篇 |
能源动力 | 5184篇 |
轻工业 | 5285篇 |
水利工程 | 18778篇 |
石油天然气 | 7738篇 |
武器工业 | 200篇 |
无线电 | 1248篇 |
一般工业技术 | 3981篇 |
冶金工业 | 3311篇 |
原子能技术 | 1458篇 |
自动化技术 | 2091篇 |
出版年
2024年 | 252篇 |
2023年 | 945篇 |
2022年 | 1904篇 |
2021年 | 2331篇 |
2020年 | 2597篇 |
2019年 | 2134篇 |
2018年 | 2089篇 |
2017年 | 2554篇 |
2016年 | 2867篇 |
2015年 | 2825篇 |
2014年 | 5353篇 |
2013年 | 5449篇 |
2012年 | 6598篇 |
2011年 | 6569篇 |
2010年 | 4864篇 |
2009年 | 5073篇 |
2008年 | 4472篇 |
2007年 | 5938篇 |
2006年 | 5530篇 |
2005年 | 5074篇 |
2004年 | 3968篇 |
2003年 | 3620篇 |
2002年 | 3156篇 |
2001年 | 2548篇 |
2000年 | 2125篇 |
1999年 | 1623篇 |
1998年 | 1183篇 |
1997年 | 982篇 |
1996年 | 749篇 |
1995年 | 681篇 |
1994年 | 499篇 |
1993年 | 395篇 |
1992年 | 303篇 |
1991年 | 237篇 |
1990年 | 181篇 |
1989年 | 189篇 |
1988年 | 118篇 |
1987年 | 137篇 |
1986年 | 102篇 |
1985年 | 105篇 |
1984年 | 91篇 |
1983年 | 54篇 |
1982年 | 31篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1959年 | 4篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
介孔碳材料是指孔径介于2 nm-50 nm的一类多孔碳材料。有序介孔碳材料,具有比表面积高、孔道结构规则有序、孔径分布狭窄、孔径大小可调控、表面易于修饰等结构特点和高机械强度、强吸附能力、化学惰性等性能特点,在诸多领域得到了广泛应用,特别是其作为新型吸附剂在水处理领域具有广阔的发展前景。有序介孔炭材料的制备方法主要有硬模板法和软模板法。模板和碳源的选择是控制有序介孔碳材料结构和性能的关键因素。本文从有序介孔硅、天然矿物、MOFs材料、嵌段共聚物等不同模板的角度对有序介孔碳、多级有序微/介孔碳、多级有序大/介孔碳的制备方法进行综述,并对有序介孔碳材料在水处理领域的应用进行简单介绍。 相似文献
992.
Renan Felicio dos Reis Joao Sergio Cordeiro Xavier Font Cali Laguna Achon 《Drying Technology》2020,38(10):1247-1260
AbstractSewage treatment can be classified into three phases: liquid, gaseous, and solid. Treatment of solids is performed in several steps, and the greatest difficulty in removing water from sewage sludge is due to the bound water present in the sludge. Thus, biodrying, a drying method that can be classified as biological, has been recently applied to treat this type of waste. This review paper aims to report and compile data from 49 biodrying assays of sewage sludge found in the literature (through the present, 2019) into one synthesis table, to discuss and compare the numerous variables found in these papers and their implications for biodrying, and to suggest possibilities for future research. This paper additionally intends to improve knowledge of biodrying and to consequently contribute to the monitoring and understanding of the process. 相似文献
993.
994.
Maize and beans were grown on a ferralsol at Kiboko, Kenya, with up to 120 kg N ha–1. Within the 10 kg N ha–1 plots,15N labelled fertilizer was applied in microplots. There was no significant response in yield to fertilizer N and labelled N recovery was low, being 7.5% or less in one season and 17.7% or less in the second season. Samples of Kiboko soil at four different water contents were incubated and the rate of gross N mineralization over 7 days was calculated, utilizing15N labelling of the mineral N. Gross N mineralization increased greatly with soil moisture and a fitted relationship between gross N mineralization rate and soil water content was obtained. Using measurements of soil water content at the field site, daily values of the soil N supply by gross mineralization were calculated. On average, modelled gross soil N mineralized could supply much (> 69%) of the N removed from the plots. It is suggested that the lack of response to fertilizer N may be explained by the coincidence of a high rate of N mineralization, and increased crop demand, caused by the onset of rain. 相似文献
995.
黄坚萍 《化学推进剂与高分子材料》2007,5(4):57-59
运用钽平台石墨管测定基体成分复杂的废水样品中的Cd、Pb元素,基本消除了基体残留影响和记忆效应,降低了背景吸收,提高了灵敏度。样品经超声波仪粉碎后直接进样,用校正曲线法测定,简化了操作步骤,减少了测定时间,延长了石墨管使用寿命。其测定值与石墨平台标准加入法测定值结果一致。样品回收率:Cd为96.9%~104%,Pb为98.2%~106%,Cd的相对标准偏差(RSD)为3.04%~4.24%,Pb的RSD为2.93%~6.53%。 相似文献
996.
The synthesis of super-microporous aluminosilicate with a pore diameter of 14.6 Å has been achieved, by means of synthesis under specified conditions with a skeletal material comprising TMOS and a small quantity of sodium aluminate, and a conventional alkyl-trimethylammonium halide (C10TMABr) as a template. This super-microporous aluminosilicate has an adsorption capacity of 0.2 ml/g at a relative water vapor pressure of 0.2, and thus is promising as an adsorbent for an adsorption heat-pump. 相似文献
997.
本文介绍了一种新型的能在较高压力环境下进行细过滤的PE井口高压滤芯的结构特征、关键技术研究、技术特性,以及应用效果。 相似文献
998.
Effect of operating conditions in removal of arsenic from water by nanofiltration membrane 总被引:2,自引:0,他引:2
The removal of arsenic from synthetic waters and surface water by nanofiltration (NF) membrane was investigated. In synthetic solutions, arsenic rejection experiments included variation of arsenic retentate concentration, transmembrane pressure, crossflow velocity and temperature. Arsenic rejection increased with arsenic retentate concentration. Arsenic was removed 93-99% from synthetic feed waters containing between 100 and 382 μg/L as V, resulting in permeate arsenic concentrations of about 5 μg/L. Under studied conditions, arsenic rejection was independent of transmembrane pressure, crossflow velocity and temperature. In surface water, the mean rejection of As V was 95% while the rejection of sulfate was 97%. The co-occurrence of dissolved inorganics does not significantly influence arsenic rejection. The mean concentration of As in collected permeated was 8 μg/L. The mean rejection of TDS, total hardness and conductivity were 75, 88 and 75% respectively. 相似文献
999.
1000.
介绍了污酸污水处理装置的工艺流程、工艺特点和主要设备。来自净化工序的污酸脱出二氧化硫后进行两级石灰石乳中和生成石膏浆;石膏浆经浓密机沉降,底液经hrox压滤机脱水,浓密机上清液和压滤机滤液汇入石膏滤液槽与硫化钠反应生成硫化物沉淀;硫化物沉淀经浓密机沉降,底流经陶瓷过滤机过滤,滤液和浓密机上清液自流到污水处理工序进一步处理。来自污酸处理工序和各车间的污水混合后进行一级石灰乳中和、硫酸亚铁除砷、二级石灰乳中和,实现达标排放。运行3年来,污酸污水处理装置各项指标均达到设计要求。 相似文献