全文获取类型
收费全文 | 553496篇 |
免费 | 67395篇 |
国内免费 | 44339篇 |
专业分类
电工技术 | 49960篇 |
技术理论 | 6篇 |
综合类 | 61239篇 |
化学工业 | 68894篇 |
金属工艺 | 38550篇 |
机械仪表 | 40228篇 |
建筑科学 | 43417篇 |
矿业工程 | 24195篇 |
能源动力 | 14667篇 |
轻工业 | 58213篇 |
水利工程 | 18991篇 |
石油天然气 | 19936篇 |
武器工业 | 9198篇 |
无线电 | 58359篇 |
一般工业技术 | 45528篇 |
冶金工业 | 21554篇 |
原子能技术 | 8965篇 |
自动化技术 | 83330篇 |
出版年
2024年 | 1592篇 |
2023年 | 8634篇 |
2022年 | 21477篇 |
2021年 | 27517篇 |
2020年 | 19823篇 |
2019年 | 13884篇 |
2018年 | 14870篇 |
2017年 | 16907篇 |
2016年 | 15149篇 |
2015年 | 24570篇 |
2014年 | 31288篇 |
2013年 | 36469篇 |
2012年 | 46684篇 |
2011年 | 48627篇 |
2010年 | 46626篇 |
2009年 | 44263篇 |
2008年 | 45808篇 |
2007年 | 44591篇 |
2006年 | 38216篇 |
2005年 | 31073篇 |
2004年 | 22287篇 |
2003年 | 14689篇 |
2002年 | 13839篇 |
2001年 | 12620篇 |
2000年 | 9986篇 |
1999年 | 4232篇 |
1998年 | 1643篇 |
1997年 | 1296篇 |
1996年 | 1128篇 |
1995年 | 919篇 |
1994年 | 734篇 |
1993年 | 641篇 |
1992年 | 569篇 |
1991年 | 368篇 |
1990年 | 336篇 |
1989年 | 358篇 |
1988年 | 218篇 |
1987年 | 148篇 |
1986年 | 135篇 |
1985年 | 78篇 |
1984年 | 88篇 |
1983年 | 74篇 |
1982年 | 65篇 |
1981年 | 99篇 |
1980年 | 179篇 |
1979年 | 112篇 |
1965年 | 16篇 |
1964年 | 10篇 |
1959年 | 108篇 |
1951年 | 114篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The exosome-mediated response can promote or restrain the diseases by regulating the intracellular pathways, making the exosome become an effective marker for diagnosis and therapeutic control at the single-cell level. However, real-time analysis is hard to be achieved with traditional approaches because the exosomes usually need to be enriched by ultracentrifugation for a measurable signal-to-noise ratio. Recently developed label-free single-molecule imaging approaches may become an real-time quantitative tool for the analysis of single exosomes and related secretion behaviors of single living cells owing to their extreme sensitivity. 相似文献
3.
4.
Microbiologically influenced corrosion induced by bacteria has been studied for many years. Corrosion is known to be sensitive to the presence of microalgae, such as Phaeodactylum tricornutum. However, the life activity of P. tricornutum that influences the general and localized corrosion of carbon steel is not fully understood. The current study uses a combination of immersion tests and electrochemical experiments with a detailed surface characterization to reveal the naturally formed corrosion products with/without the presence of P. tricornutum. The results show that samples suffer from pitting corrosion and the averaged pit depths are approximately 15 μm under a light–dark cycle condition or a 24-h constant light condition. Meanwhile, the corrosion products are mainly comprised of γ-FeOOH and Fe3O4 in a constant light condition. However, γ-FeOOH, Fe3O4, and FeCO3 are found in a light–dark cycle. This study proposes the fundamental mechanisms of the effect of P. tricornutum life activities on the corrosion performance of Q235 carbon steel, to fulfill the knowledge gaps of the presence of microalgae inducing the general and pitting corrosion of carbon steel. 相似文献
5.
6.
目的 为了更科学地研究和检验可穿戴产品的适合性,提出一种适合性检验方法,能够精确保留现实环境中的产品佩戴关系,并能将现实与虚拟的适合性检验研究相结合,得到合理的适合性检验结果.方法 以虚拟现实眼镜的适合性检验为例,通过高精度的三维测量技术将现实环境中的人、产品以及人—产品佩戴关系转化为三维虚拟信息,并以人—产品佩戴三维模型为参考基准对齐人和产品的虚拟模型,得到保留现实佩戴关系的人—产品佩戴模型组,再应用偏差分析法得出人—机佩戴区域的可视化适合性结果和统计数据,结合主观评价方法进一步分析产品的适合性.结论 虚实结合的产品适合性检验方法可在虚拟环境中高精度地保留现实环境中的人—产品佩戴关系,并能得到可视化的适合性检验结果,为检验和指导产品的适合性提供依据. 相似文献
7.
To benefit from recent advances in modeling and computational algorithms,as well as the availability of new covariance data,sensitivity and uncertainty analyses are needed to quantify the impact of uncertain sources on the design parameters of small prismatic high-temperature gas-cooled reactors(HTGRs).In particular,the contribution of nuclear data to the keff uncertainty is an important part of the uncertainty analysis of small-sized HTGR physical calculations.In this study,a small-sized HTGR designed by China Nuclear Power Engineering Co.,Ltd.was selected for keff uncertainty analysis during full lifetime burnup calculations.Models of the cold zero power(CZP)condition and full lifetime burnup process were constructed using the Reactor Monte Carlo Code RMC for neutron transport calculation,depletion calculation,and sensitivity and uncertainty analysis.For the sensitivity analysis,the Contribution-Linked eigenvalue sensitivity/Uncertainty estimation via Track length importance Characterization(CLUTCH)method was applied to obtain sensitive infor-mation,and the"sandwich"method was used to quantify the keff uncertainty.We also compared the keff uncertainties to other typical reactors.Our results show that 235U is the largest contributor to keff uncertainty for both the CZP and depletion conditions,while the contribution of 239Pu is not very significant because of the design of low discharge burnup.It is worth noting that the radioactive capture reaction of 28Si significantly contributes to the keff uncer-tainty owing to its specific fuel design.However,the keff uncertainty during the full lifetime depletion process was relatively stable,only increasing by 1.12%owing to the low discharge burnup design of small-sized HTGRs.These numerical results are beneficial for neutronics design and core parameters optimization in further uncertainty prop-agation and quantification study for small-sized HTGR. 相似文献
8.
9.
VOCs是形成臭氧的重要前体物,加强VOCs治理是现阶段控制臭氧污染的有效途径.废气生物处理装置为满足新的排放要求改造前应先对废气组分进行分析,并筛选合适的菌种进行接种以降低后续提标装置的投资.可采用吸附技术或高级氧化技术对生物处理装置出气进行提标处理.提标工艺如采用吸附技术需考虑吸附剂脱附产生物质的再处理. 相似文献
10.