全文获取类型
收费全文 | 4107篇 |
免费 | 70篇 |
国内免费 | 78篇 |
专业分类
电工技术 | 79篇 |
综合类 | 111篇 |
化学工业 | 630篇 |
金属工艺 | 83篇 |
机械仪表 | 323篇 |
建筑科学 | 230篇 |
矿业工程 | 21篇 |
能源动力 | 37篇 |
轻工业 | 579篇 |
水利工程 | 3篇 |
石油天然气 | 30篇 |
武器工业 | 10篇 |
无线电 | 711篇 |
一般工业技术 | 532篇 |
冶金工业 | 640篇 |
原子能技术 | 18篇 |
自动化技术 | 218篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 41篇 |
2021年 | 57篇 |
2020年 | 55篇 |
2019年 | 29篇 |
2018年 | 49篇 |
2017年 | 53篇 |
2016年 | 72篇 |
2015年 | 125篇 |
2014年 | 175篇 |
2013年 | 190篇 |
2012年 | 142篇 |
2011年 | 365篇 |
2010年 | 266篇 |
2009年 | 232篇 |
2008年 | 234篇 |
2007年 | 273篇 |
2006年 | 306篇 |
2005年 | 265篇 |
2004年 | 203篇 |
2003年 | 176篇 |
2002年 | 187篇 |
2001年 | 92篇 |
2000年 | 86篇 |
1999年 | 92篇 |
1998年 | 67篇 |
1997年 | 90篇 |
1996年 | 90篇 |
1995年 | 43篇 |
1994年 | 40篇 |
1993年 | 31篇 |
1992年 | 28篇 |
1991年 | 32篇 |
1990年 | 25篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有4255条查询结果,搜索用时 46 毫秒
101.
通过对一起有载调压变压器直流电阻不平衡故障分析,总结经验,提出解决措施以便更好地做好有载调压变压器的检修工作。 相似文献
102.
将百里香酚蓝固定在Nafion膜上,以此为敏感膜研制的光导纤维酸度传感器,具有响应迅速可逆、稳定性好、选择性高的优点,适用于pH3.7~0范围酸度的传感监测及0.001-mol/L以上HF浓度的快速测定. 相似文献
103.
104.
特高压环境下OPGW耐雷性能分析 总被引:4,自引:1,他引:4
我国目前正在开展的特高压电网,由于线路参数发生变化,对OPGW的耐雷性能将提出更高的要求,在实践工程中应重点考虑。文章首先简要介绍了特高压电网的基本概念,分析了在特高压环境下OPGW在雷击性能方面与超高压环境的主要区别,并通过一些计算比较得出在特高压环境下由于引雷概率增大,则相应地提高OPGW耐雷能力的结论。 相似文献
105.
OPGW的热稳定性分析 总被引:3,自引:0,他引:3
OPGW(Composite Fiber Optic Overhead Ground Wire)又称为光纤架空复合地线,它是利用高压输电线路的一根地线(避雷线)复合组成OPGW来传输光信息。文中阐述了短路电流引起OPGW温升的机理,讨论了OPGW在发生接地故障时的温升和短路电流计算方法,建立了一种完整的计算方法。对OPGW的热稳定性进行了探讨,提出了降低OPGW中的短路电流与热容量的几种措施。 相似文献
106.
107.
碳纤维加固混凝土外伸梁斜截面破坏形态浅析 总被引:2,自引:2,他引:2
采用对比试验方法分别研究了混凝土外伸梁负弯矩区段应用U形粘贴进行抗剪加固时,在不同粘贴高度和有无压条情况下,梁斜截面的受力性能和破坏特征。在对比破坏特征的基础上,对混凝土梁负弯矩区段抗剪加固机理进行了分析,并指出了在加固设计和工程应用中应注意的问题。 相似文献
108.
Insect cuticle as a natural biocomposite includes many favored microstructures which have been refined over centuries and endow the cuticle eminent mechanical properties. This paper first studies the microstructures of chafer cuticle through SEM observations. Several peculiar fiber configurations and fiber-ply arrangements such as branched fiber, acanth-fiber and helicoid plies are observed. These microstructures are useful for man-made fiber-reinforced composites to improve their mechanical properties. Then, a special configuration of the branched fiber found in chafer cuticle is in details analyzed through a mechanical model and experimental verification. The pullout force of fibers as an index is firstly studied through parameter study. The factors, which can improve the pullout forces, are identified. Finally, the maximal pullout force of the branched fiber is experimentally tested and compared with that of plain straight fiber. It is proved that the maximal pullout force of branched fibers is obviously greater than that of the plain straight fibers. 相似文献
109.
D. Ryan Breese Gregory Beaucage 《Current Opinion in Solid State & Materials Science》2004,8(6):439-448
Modeling changes in the physical properties of oriented semi-crystalline polymer films is beneficial for understanding the fundamentals associated with structure property relationships and could be used for developing new polymer films with significantly enhanced physical properties. Relating the molecular changes observed in oriented polymer films to inherent polymer characteristics provides valuable insight for the development of new polymers which exhibit enhanced physical properties upon orientation. Modeling efforts will be reviewed that have attempted to use fiber composite theory to explain the transitions seen during the orientation process. 相似文献
110.
Catalin Gheorghiu Pierre Labossière Alexandre Ra?che 《Canadian Metallurgical Quarterly》2004,8(3):211-218
Many countries around the world have tremendous needs to repair and strengthen their transportation infrastructure. Almost everywhere, traffic loads have reached levels largely exceeding design expectations. Northern countries also experience severe winter conditions that are combined with an extensive use of deicing salts and accelerate structural deterioration. In Canada, the extent of deterioration has prompted many authorities, including the federal and provincial governments, to investigate the potential use of fiber-reinforced polymer products to extend the life of their existing structures. However, it is widely recognized that the large-scale implementation of these products is often impaired by the lack of data on their durability. This paper presents an experimental project undertaken in order to assess the durability of reinforced concrete beams externally strengthened with two types of carbon-fiber-reinforced polymer (CFRP). The beams were first exposed to either wet-dry cycles or continuous immersion in water and then were loaded in fatigue. Finally, they were tested quasi-statically under four-point bending up to failure. The test results presented here provide some insights on the potential long-term performance of CFRP-strengthened beams exposed to severe environmental conditions. 相似文献