全文获取类型
收费全文 | 7626篇 |
免费 | 906篇 |
国内免费 | 474篇 |
专业分类
电工技术 | 574篇 |
技术理论 | 1篇 |
综合类 | 654篇 |
化学工业 | 1279篇 |
金属工艺 | 551篇 |
机械仪表 | 382篇 |
建筑科学 | 674篇 |
矿业工程 | 300篇 |
能源动力 | 195篇 |
轻工业 | 679篇 |
水利工程 | 159篇 |
石油天然气 | 397篇 |
武器工业 | 45篇 |
无线电 | 800篇 |
一般工业技术 | 848篇 |
冶金工业 | 324篇 |
原子能技术 | 112篇 |
自动化技术 | 1032篇 |
出版年
2024年 | 34篇 |
2023年 | 114篇 |
2022年 | 271篇 |
2021年 | 334篇 |
2020年 | 279篇 |
2019年 | 225篇 |
2018年 | 207篇 |
2017年 | 237篇 |
2016年 | 194篇 |
2015年 | 354篇 |
2014年 | 380篇 |
2013年 | 422篇 |
2012年 | 486篇 |
2011年 | 440篇 |
2010年 | 436篇 |
2009年 | 423篇 |
2008年 | 428篇 |
2007年 | 396篇 |
2006年 | 361篇 |
2005年 | 292篇 |
2004年 | 324篇 |
2003年 | 388篇 |
2002年 | 579篇 |
2001年 | 491篇 |
2000年 | 216篇 |
1999年 | 183篇 |
1998年 | 94篇 |
1997年 | 68篇 |
1996年 | 51篇 |
1995年 | 58篇 |
1994年 | 48篇 |
1993年 | 54篇 |
1992年 | 32篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有9006条查询结果,搜索用时 15 毫秒
2.
综述了铁素体与铁素体异种金属焊缝(dissimilar metal welds,DMWs)接头界面组织及其影响。结果表明,在焊后热处理或运行温度下的铁素体钢DMWs接头的不均匀界面组织中,通常会形成脱碳层和增碳层。在铁素体钢DMWs焊接接头界面组织影响因素中,焊缝金属的化学成分有重要影响;焊后热处理规范(温度和时间)、工作温度下运行时间的影响较为突出;焊接工艺参数的影响亦不可忽略。异种钢接头界面处近缝区裂纹的产生,以及接头的蠕变强度随Larson Miller 参数增大而下降等不利影响,均为异种钢界面碳迁移行为所导致。焊缝成分控制法是接头界面组织控制或改善的必要条件,而脱碳层部位转移法能有效防止裂纹发生,亦是接头安全运行的重要工艺措施之一。 相似文献
3.
Xian Suo Xili Cui Lifeng Yang Nan Xu Yuqi Huang Yi He Sheng Dai Huabin Xing 《Advanced materials (Deerfield Beach, Fla.)》2020,32(29):1907601
The design of highly stable and efficient porous materials is essential for developing breakthrough hydrocarbon separation methods based on physisorption to replace currently used energy-intensive distillation/absorption technologies. Efforts to develop advanced porous materials such as zeolites, coordination frameworks, and organic polymers have met with limited success. Here, a new class of ionic ultramicroporous polymers (IUPs) with high-density inorganic anions and narrowly distributed ultramicroporosity is reported, which are synthesized by a facile free-radical polymerization using branched and amphiphilic ionic compounds as reactive monomers. A covalent and ionic dual-crosslinking strategy is proposed to manipulate the pore structure of amorphous polymers at the ultramicroporous scale. The IUPs exhibit exceptional selectivity (286.1–474.4) for separating acetylene from ethylene along with high thermal and water stability, collaboratively demonstrated by gas adsorption isotherms and experimental breakthrough curves. Modeling studies unveil the specific binding sites for acetylene capture as well as the interconnected ultramicroporosity for size sieving. The porosity-engineering protocol used in this work can also be extended to the design of other ultramicroporous materials for the challenging separation of other key gas constituents. 相似文献
4.
结合广珠西高速路面超薄磨耗层的具体应用,论述了超薄磨耗层对原材料技术要求、配合比设计、施工工艺和施工关键技术控制等。 相似文献
5.
6.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
7.
Jiaao Yan Gao Zhiming Tan Qingchao Yang Xian Hu Wenbin 《Protection of Metals and Physical Chemistry of Surfaces》2020,56(5):965-972
Protection of Metals and Physical Chemistry of Surfaces - The Al2O3 powder was added as a filler to polyurea and the effect of doping amount on Shore hardness and wetting property were... 相似文献
8.
9.
贴片机脱机编程的快捷方法 总被引:7,自引:4,他引:3
SMT生产线中的大多数加工设备均为数控设备。它们编程所需要的大多数特征数据均可从CAD设计系统中得到。文章介绍了如何从CAD设计系统中导出X、Y坐标数据,并转换成贴片数据的方法和思路,以期引起更多的同行加入到这方面的研究中。 相似文献
10.