全文获取类型
收费全文 | 515篇 |
免费 | 51篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 29篇 |
综合类 | 37篇 |
化学工业 | 118篇 |
金属工艺 | 15篇 |
机械仪表 | 20篇 |
建筑科学 | 47篇 |
矿业工程 | 98篇 |
能源动力 | 7篇 |
轻工业 | 15篇 |
水利工程 | 47篇 |
石油天然气 | 13篇 |
无线电 | 23篇 |
一般工业技术 | 19篇 |
冶金工业 | 36篇 |
原子能技术 | 2篇 |
自动化技术 | 53篇 |
出版年
2023年 | 6篇 |
2022年 | 22篇 |
2021年 | 53篇 |
2020年 | 33篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 34篇 |
2013年 | 71篇 |
2012年 | 69篇 |
2011年 | 65篇 |
2010年 | 50篇 |
2009年 | 47篇 |
2008年 | 25篇 |
2007年 | 33篇 |
2006年 | 20篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 2篇 |
1998年 | 2篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有579条查询结果,搜索用时 15 毫秒
1.
通过百泉泉区天然状态与超采状态下的水环境对比分析,并对岩溶水补给量和开采量进行计算,阐述恢复邢台百泉泉水流量的可行性,随着“引朱济邢”和“南水北调”供水工程的实施,邢台百泉水生态环境的恢复将变为现实。 相似文献
2.
《Applied catalysis. B, Environmental》2005,55(2):123-132
The photocatalytic oxidation of resorcinol, a potent endocrine disrupting chemical, in oxygenated aqueous suspensions of pure and cupric ions modified Degussa P25 titanium dioxide has been investigated at pH 3.0 ± 0.5. The initial rate of photocatalytic oxidation of resorcinol increased until an optimum dissolved cupric ions concentration was reached at 1.04 mM. At the optimum concentration of cupric ions, the initial rate of photocatalytic mineralisation and degradation of resorcinol was improved by 400%. The observed beneficial effect of cupric ions on the initial rate of resorcinol oxidation could be attributed to the formation of complex and its participation in the photoredox cyclic reaction.Two of the initial oxidation intermediates detected were 1,2,3-trihydroxybenzene and 1,2,4-trihydroxybenzene. These intermediates were formed via hydroxylation of the aromatic ring of resorcinol. Evidences have revealed that 1,2,4-trihydroxybenzene interacted strongly with cupric ions forming copper(II)-trihydroxybenzoate complexes that possessed good adsorption onto TiO2 surface. These dual-effects help to draw the metal ions closer to the photocatalyst surface and subsequently trigger the electron trapping mechanism by cupric ions. As a result, this improved the charge carriers’ separation. Furthermore, in the presence of oxygen, reoxidation of photoreduced cupric ions occurred and this eliminated the possibility of copper photodeposition, while inducing a photoredox cyclic reaction to regenerate copper species that may potentially act as co-catalyst for the oxidation of 1,2,4-trihydroxybenzene. In contrast, no obvious complex formation was seen between 1,2,3-trihydroxybenzene and cupric ions. This pointed to an intriguing finding which indicates that the positioning of functional group on benzene ring influences the role of cupric ions. 相似文献
3.
矿用隔爆兼本质安全型饮水机可以解决煤矿井下工作人员的饮水问题,提高井下工作人员的饮水条件和饮用水质量。介绍了矿用隔爆兼本质安全型饮水机的组成、各组成部分的设计与工作原理。 相似文献
4.
针对河套盆地开展了历时多年的水文地质环境地质调查,利用采集的298组浅层地下水样品以及收集并甄选的382个水文地质钻孔记录分析发现:河套盆地内95%的高砷地下水(As质量浓度10μg/L)集中在黄河决口、改道形成的古河道影响带及黄河决口扇裙带。其中,盆地南部首次发现了较为集中的高砷地下水,其分布范围与黄河北岸的晚更新世以来黄河决口、改道形成的4个大型决口扇,在空间上有着良好的对应关系。黄河古河道带及决口扇裙带表现为较强的还原环境及蒸发浓缩作用以及较弱的地表水补给强度。受pH值、含铁氧化物的还原性溶解等因素影响,决口扇裙带浅层地下水中砷的含量略低于平原中部黄河古河道带。结果表明:黄河古河道带及决口扇裙带特定的沉积环境控制着地下水的水文地球化学过程,进而对高砷地下水的分布具有决定性的作用。 相似文献
5.
Because the spatial pattern of plant communities in garden landscapes usually exhibits highly non-random distribution characteristics, the accuracy of the analysis results is not high. For this purpose, a spatial ecological distribution model of landscape landform plant communities is designed. Based on the remote sensing images of landscape plant communities, the study area was obtained. The grassland communities in this area were classified and calculated by geostatistics, and the semi variogram values of typical samples of different vegetation types were obtained. According to the calculation results, the spatial terrain factors of landscape plant community are extracted, and the annual NDVI value is taken as the ecological vitality index of landscape green vegetation, the NDVI level is divided, the spatial ecological distribution model of landscape plant community is constructed, and the evaluation index system is generated, so as to complete the spatial ecological distribution model analysis of landscape plant community. The results show that the method of this study accurately analyzes the area of coniferous and broad-leaved mixed forest, mountain meadow, road, construction land, water area land and slope grade, which is slightly different from the actual value, indicating that the method has certain reliability. 相似文献
6.
With the advent of the governance economy era, traditional government governance models face enormous challenges. Governance management is the source of power to enter the era of the knowledge economy. This is a profound change that governments have needed to implement innovative government governance models, methods of social organization, and management. Governments in many countries are now adopting the construction of e-government as a strategy and response to demonstrate their priority development competitive advantage over the international competition and the challenges of the knowledge economy that spreads around the world. Therefore, the establishment of a new model of government governance has great theoretical and practical significance for impulse and government management innovation. The Dynamic Image Classification Algorithm (DICA) system is introduced in the implementation of the image processing technology and global disaster detection proposed here, and of this dynamic image classification algorithm (DICA) of the government, sector to extract more effectively. DICA is the most important task, or it is a strong shadow, proper access to the characteristics of the disaster area, and a false impact on the impact of the disaster, overcoming false alarms. It creates patches of post-disaster aerial image data from pre-tailoring and pre-adjustment training and satellite imagery. DICA training, all patches to government-managed data modified without delay or image data extraction. Two types of proposed systems are high-speed operation and accuracy (96.6%) and detection of earth disasters. 相似文献
7.
研究了硅酸盐对软聚氯乙烯(PVC)的阻燃作用。通过热分析法研究了经阻燃处理后软PVC从室温到800℃的热降解过程;通过剩炭率的测定,结合用扫描电子显微镜(SEM)对样品燃烧后剩炭结构的观察,探讨了硅酸盐的阻燃机理。结果表明:经硅酸盐处理的样品具有较高的氧指数(OI)和剩炭率,与未处理的样品相比具有较好的阻燃性能。硅酸盐的加入可改变PVC的热降解过程,使起始降解温度降低,最大失重速率加快,硅酸盐对软PVC的阻燃主要是由于凝聚相的Lewis酸催化作用以及高温下生成的玻璃体对剩炭的保护作用造成的。 相似文献
8.
本试验采用污水快速净化器,以硫酸铝(AS)和聚合氯化铝(PAC)为混凝剂处理乳品废水,研究其投加量与浊度和COD去除率之间的关系,确定出硫酸铝的最佳投加量为390mg/L,聚合氯化铝的最佳投加量为320 mg/L。同时研究了最佳无机混凝剂(PAC)与有机助凝剂聚丙烯酰胺(PAM)在废水处理中的协同作用,得出PAC(240 mg/L) PAM(0.5mg/L)是最佳、最经济的组合方式。 相似文献
9.
邢台市主要农作物为冬小麦-夏玉米,种植冬小麦-夏玉米粮食作物,在平水年只有8月、9月份的降水能满足作物生长需水量,其他10个月缺水368.4mm。在平水年,种植棉花一年中有5个月缺水,缺水量为79.6mm,由于棉花生长期需水量与降水季节同步,缺水量较小。利用邢台市2001~2012年棉花种植面积资料,与种植粮食作物进行对比分析,平均每年可节约灌溉用水3.161 2亿m3。 相似文献
10.