全文获取类型
收费全文 | 258542篇 |
免费 | 20591篇 |
国内免费 | 10552篇 |
专业分类
电工技术 | 15162篇 |
技术理论 | 19篇 |
综合类 | 15119篇 |
化学工业 | 43689篇 |
金属工艺 | 13579篇 |
机械仪表 | 15136篇 |
建筑科学 | 21261篇 |
矿业工程 | 6334篇 |
能源动力 | 7402篇 |
轻工业 | 16018篇 |
水利工程 | 4215篇 |
石油天然气 | 13919篇 |
武器工业 | 1810篇 |
无线电 | 31967篇 |
一般工业技术 | 32819篇 |
冶金工业 | 13238篇 |
原子能技术 | 2807篇 |
自动化技术 | 35191篇 |
出版年
2024年 | 1147篇 |
2023年 | 4126篇 |
2022年 | 7329篇 |
2021年 | 10065篇 |
2020年 | 7345篇 |
2019年 | 6289篇 |
2018年 | 6862篇 |
2017年 | 7852篇 |
2016年 | 7148篇 |
2015年 | 9335篇 |
2014年 | 11974篇 |
2013年 | 15323篇 |
2012年 | 15540篇 |
2011年 | 17445篇 |
2010年 | 14893篇 |
2009年 | 14491篇 |
2008年 | 14092篇 |
2007年 | 13552篇 |
2006年 | 13902篇 |
2005年 | 12196篇 |
2004年 | 8407篇 |
2003年 | 7448篇 |
2002年 | 7034篇 |
2001年 | 6313篇 |
2000年 | 6206篇 |
1999年 | 7068篇 |
1998年 | 6350篇 |
1997年 | 5286篇 |
1996年 | 4882篇 |
1995年 | 4046篇 |
1994年 | 3380篇 |
1993年 | 2641篇 |
1992年 | 2093篇 |
1991年 | 1580篇 |
1990年 | 1224篇 |
1989年 | 1051篇 |
1988年 | 829篇 |
1987年 | 592篇 |
1986年 | 447篇 |
1985年 | 384篇 |
1984年 | 244篇 |
1983年 | 221篇 |
1982年 | 195篇 |
1981年 | 162篇 |
1980年 | 149篇 |
1979年 | 104篇 |
1978年 | 65篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Ming-Puu Chen Asta Y. Z. Lord Yu-Yao Cheng Ku-Chou Tai Wen-Harn Pan 《Journal of Computer Assisted Learning》2020,36(3):383-396
Reflective judgement is crucial for medical-related practitioners in dealing with controversial issues. However, the conformity phenomenon is likely to occur and interfere with reflective judgement learning during interactive activities. Effective strategies are required to moderate the conformity behaviour tendency (CBT) and improve reflective judgement performance (RJP). This study demonstrates two significant results: (a) Compared with the guided self-reflection learning strategy, the online collective reflection (OCR) learning strategy effectively weakened the learners' general CBT while dealing with professional controversial issues; and (b) a significantly negative correlation between the RJP achieved and the change of CBT in online environment was detected in the OCR group. The implications and potential applications in higher education were discussed. Further studies are needed to confirm the long-term effects and the extending application to other professional studies. 相似文献
32.
Kai He Zhe Li Longfei Liu Mengxi Zheng Prof. Chengde Mao 《Chembiochem : a European journal of chemical biology》2020,21(15):2132-2136
As a giant leap in DNA self-assembly, DNA origami has exhibited an unprecedented ability to construct nanostructures with arbitrary shapes and sizes. In typical DNA origami, hundreds of short DNA staple strands fold a long, single-stranded (ss) DNA scaffold cooperatively into designed nanostructures. However, large numbers of DNA strands are expensive and would hinder applications such as pharmaceutical investigations because of the complicated components. Therefore, one challenge is how to reduce the number of staple strands needed to construct DNA origami. For a DNA origami structure, the scale-free folding pattern of the scaffold strand is determined by staple strands at the branching vertexes. Simple duplex regions help to define the size-related features of the origami geometry. In this study, we hypothesized that a scaffold strand can be correctly folded into a designed topology by using only staple strands involved in branching vertexes. After assembly, any remaining, flexible, single-stranded regions of the scaffold could be converted into rigid duplexes by DNA polymerase to achieve the designed geometric structures. To demonstrate the concept, we used only 18 staple strands (covering 15 % of the scaffold strand) to assemble a porous DNA nanostructure, which was visualized by atomic force microscopy (AFM). This study helps understanding of the role of cooperativity in origami folding, and provides a cost-effective approach for small-scale prototyping DNA origami. 相似文献
33.
Wei Mengnan Ban Boyuan Li Jingwei Sun Jifei Li Feifei Jiang Xuesong Chen Jian 《SILICON》2020,12(2):327-338
Silicon - A novel green cationic surfactant Poly (propylene glycol) bis (2-aminopropyl ether) (PEA) with multiple amine groups was utilized as a collector for flotation separation of quartz from... 相似文献
34.
35.
36.
Ionomics is a novel multidisciplinary field that uses advanced techniques to investigate the composition and distribution of all minerals and trace elements in a living organism and their variations under diverse physiological and pathological conditions. It involves both high-throughput elemental profiling technologies and bioinformatic methods, providing opportunities to study the molecular mechanism underlying the metabolism, homeostasis, and cross-talk of these elements. While much effort has been made in exploring the ionomic traits relating to plant physiology and nutrition, the use of ionomics in the research of serious diseases is still in progress. In recent years, a number of ionomic studies have been carried out for a variety of complex diseases, which offer theoretical and practical insights into the etiology, early diagnosis, prognosis, and therapy of them. This review aims to give an overview of recent applications of ionomics in the study of complex diseases and discuss the latest advances and future trends in this area. Overall, disease ionomics may provide substantial information for systematic understanding of the properties of the elements and the dynamic network of elements involved in the onset and development of diseases. 相似文献
37.
使用气-质联用仪测定餐饮废油生物柴油(WCME)和-10号柴油(-10PD)的组成,使用冷滤点试验器和运动黏度试验器测定WCME的低温流动性,同时使用调合、添加低温流动性改进剂的方法改进WCME的低温流动性。实验结果表明,WCME主要由饱和脂肪酸甲酯和不饱和脂肪酸甲酯组成,质量分数分别为27.63%和71.81%;WCME冷滤点为0℃,运动黏度(40℃)为4.41mm2/s;WCME与-10PD调合后,冷滤点降低,其中B20的冷滤点最低,为-13℃,运动黏度随着WCME的体积分数的减少,逐渐接近-10PD的运动黏度。通过添加低温流动性改进剂,WCME,B10,B20的冷滤点分别从0,-8,-13℃降至-4,-26,-25℃。 相似文献
38.
39.
在分析单一MU(Most Uncertainty)采样缺陷的基础上,提出一种"全局最优搜寻"方法 GOS(Global Optimal Search),并结合MU共同完成查询选择。GOS+MU方法中,GOS着眼全局寻找目标,在应用环境能提供的训练样本数量有限、分类器受训不充分时,该方法选择的对象学习价值高,能快速推进分类器学习进程;MU则能够在GOS采样失效情形下,利用分类器当前训练成果,选择查询不确定性最强的样本补充训练集。通过对网络商品的用户评论进行分类仿真,并比较其他采样学习方法的效果,证明了GOS+MU方法在压缩学习成本、提高训练效率方面的有效性。 相似文献
40.