全文获取类型
收费全文 | 20867篇 |
免费 | 1540篇 |
国内免费 | 761篇 |
专业分类
电工技术 | 979篇 |
技术理论 | 3篇 |
综合类 | 1245篇 |
化学工业 | 3797篇 |
金属工艺 | 1002篇 |
机械仪表 | 1274篇 |
建筑科学 | 1597篇 |
矿业工程 | 435篇 |
能源动力 | 557篇 |
轻工业 | 1494篇 |
水利工程 | 330篇 |
石油天然气 | 1052篇 |
武器工业 | 153篇 |
无线电 | 2170篇 |
一般工业技术 | 3111篇 |
冶金工业 | 1151篇 |
原子能技术 | 251篇 |
自动化技术 | 2567篇 |
出版年
2024年 | 59篇 |
2023年 | 280篇 |
2022年 | 446篇 |
2021年 | 586篇 |
2020年 | 491篇 |
2019年 | 446篇 |
2018年 | 475篇 |
2017年 | 590篇 |
2016年 | 536篇 |
2015年 | 709篇 |
2014年 | 848篇 |
2013年 | 1107篇 |
2012年 | 1178篇 |
2011年 | 1273篇 |
2010年 | 1083篇 |
2009年 | 1052篇 |
2008年 | 1113篇 |
2007年 | 1069篇 |
2006年 | 1149篇 |
2005年 | 1131篇 |
2004年 | 703篇 |
2003年 | 661篇 |
2002年 | 612篇 |
2001年 | 528篇 |
2000年 | 681篇 |
1999年 | 727篇 |
1998年 | 630篇 |
1997年 | 555篇 |
1996年 | 490篇 |
1995年 | 453篇 |
1994年 | 333篇 |
1993年 | 247篇 |
1992年 | 207篇 |
1991年 | 169篇 |
1990年 | 133篇 |
1989年 | 116篇 |
1988年 | 89篇 |
1987年 | 43篇 |
1986年 | 45篇 |
1985年 | 43篇 |
1984年 | 18篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
Tingting Gu Jesper Just Katrine Tang Stenz Yan Yan Peter Sieljacks Jakob Wang Thomas Skjaerlund Groennebaek Jesper Emil Jakobsgaard Emil Rindom Jon Herskind Anders Gravholt Thomas Ravn Lassen Mathias Jrgensen Rikke Bk Eugenio Gutirrez-Jimnez Nina Kerting Iversen Peter Mondrup Rasmussen Jens Randel Nyengaard Malene Mller Jrgensen Frank de Paoli Hans Erik Btker Jrgen Kjems Kristian Vissing Kim Ryun Drasbek 《International journal of molecular sciences》2022,23(6)
Ischemic conditioning and exercise have been suggested for protecting against brain ischemia-reperfusion injury. However, the endogenous protective mechanisms stimulated by these interventions remain unclear. Here, in a comprehensive translational study, we investigated the protective role of extracellular vesicles (EVs) released after remote ischemic conditioning (RIC), blood flow restricted resistance exercise (BFRRE), or high-load resistance exercise (HLRE). Blood samples were collected from human participants before and at serial time points after intervention. RIC and BFRRE plasma EVs released early after stimulation improved viability of endothelial cells subjected to oxygen-glucose deprivation. Furthermore, post-RIC EVs accumulated in the ischemic area of a stroke mouse model, and a mean decrease in infarct volume was observed for post-RIC EVs, although not reaching statistical significance. Thus, circulating EVs induced by RIC and BFRRE can mediate protection, but the in vivo and translational effects of conditioned EVs require further experimental verification. 相似文献
922.
The microstructure and anti-corrosion behavior of Mg–Mn alloys by magnesium scrap have been investigated in this study.The results show that the size of the Fe-rich particles in magnesium scrap decreases but the quantity increases with the Mn addition.Although the presence of Mn-containing Fe-rich particles with unique symbiotic structure can eff ectively weaken the micro-galvanic corrosion,the presence of more free Fe(Fe-rich particles) does not necessarily lead to severe corrosion of the alloy.The corrosion susceptibility of Mg–Mn–Fe alloy primarily depends on the solubility of iron in the Mg matrix,while it can be significantly reduced by suitable Mn addition.Besides,the tolerance limit of the Fe impurity can be expressed as Fe_(max) = 0.0083 Mn(relative to the iron solubility).Only when the Fe/Mn ratio is below 0.0083 can the alloy have excellent corrosion resistance,with the corrosion rate changing in the scope of 0.38 ± 0.09 to 0.54 ± 0.15 mg/cm~2 day and i_(corr) from 3 to 9 × 10~(–4) A/cm~2. 相似文献
923.
High pressure pipeline transportation has been an established technology for economically transporting large amounts of CO_2. However, there are still issues and associated risks that have to be effectively addressed and adequately understood. It is well known that a strong Joule-Thomson Cooling effect can occur when pressurized CO_2 flows through a choke valve. Thus, to investigate the choking characteristics especially the temperature drop of high pressure CO_2, a new laboratory scale experimental setup(total length of 14.85 m and the inner diameter of 15 mm) was constructed. Steady choked flow and transient choked flow tests were carried out respectively for pressurized CO_2 in various initial phases. The phase transitions and temperature drop characteristics were then studied following the choked flow and the results show that the phase transitions in steady choked flow differs significantly from that in transient choked flow. For transient choked flow of various initial phases, all the flows downstream would transfer from single phase to gas–liquid two-phase flow. Furthermore, the effect of water on transient choked flow of supercritical CO_2 pipeline was investigated, and the phenomena of solid particles deposition was captured which was paramount importance of ensuring the safety operation of CO_2 pipelines when throttling by the choke valves. 相似文献
924.
工业建筑设计要遵循现代建筑设计理念,昆明光电子产业基地项目设计,充分体现大工业集约化、以人为本、可持续发展、保护生态的建筑本质;强调由内到外的理性构成、组合,应用新技术、新材料创造简捷明快的几何形体,体现现代工业建筑时代气息。 相似文献
925.
顾军 《国外电子测量技术》2007,26(5):39-42
随着通信技术的不断发展,信号复杂程度越来越高.本文借助软件无线电的思想,以现场可编程逻辑门阵列(FPGA)和直接数字频率合成(DDS)为中心,构成通用的硬件平台,通过更换软件的方法模拟各种复杂信号.采用该方案可实现信号模拟,且电路简单易于实现.最后,本文提供了脉冲压缩雷达(PCR)信号模拟的硬件设计.实际测试结果表明,本文给出的设计方法合理有效,有较高的实用价值. 相似文献
926.
基于PT2262/PT2272的机器人遥控系统的设计 总被引:2,自引:0,他引:2
本文通过对PT2262/PT2272工作原理的分析,结合凌阳SPCE061A单片机提出了一种机器人遥控系统.电路易于实现、性价比高,所涉及的电路及参数均经过测试,可广泛使用于从玩具机器人到科学研究机器人中.实际应用表明,本文给出的设计方法合理有效,有效遥控距离长,具有较高的实用价值. 相似文献
927.
928.
929.
进行了一种称为交替式数据采集及实时监控系统的研究。该系统不仅能实现以较高频率进行任意时间的数据采集,还能在放电过程中以图形方式实时显示等离子体的各种参数供实验人员在线分析及控制。 相似文献
930.