全文获取类型
收费全文 | 557886篇 |
免费 | 65356篇 |
国内免费 | 45351篇 |
专业分类
电工技术 | 49987篇 |
技术理论 | 4篇 |
综合类 | 60937篇 |
化学工业 | 69234篇 |
金属工艺 | 39110篇 |
机械仪表 | 40544篇 |
建筑科学 | 43344篇 |
矿业工程 | 24341篇 |
能源动力 | 14688篇 |
轻工业 | 58664篇 |
水利工程 | 19119篇 |
石油天然气 | 20248篇 |
武器工业 | 9229篇 |
无线电 | 58458篇 |
一般工业技术 | 46190篇 |
冶金工业 | 22013篇 |
原子能技术 | 9119篇 |
自动化技术 | 83364篇 |
出版年
2024年 | 2936篇 |
2023年 | 8605篇 |
2022年 | 21436篇 |
2021年 | 27670篇 |
2020年 | 19816篇 |
2019年 | 13923篇 |
2018年 | 14952篇 |
2017年 | 16949篇 |
2016年 | 15269篇 |
2015年 | 24604篇 |
2014年 | 31389篇 |
2013年 | 36644篇 |
2012年 | 46874篇 |
2011年 | 48927篇 |
2010年 | 46646篇 |
2009年 | 44290篇 |
2008年 | 45763篇 |
2007年 | 44729篇 |
2006年 | 38223篇 |
2005年 | 31223篇 |
2004年 | 22454篇 |
2003年 | 14942篇 |
2002年 | 14024篇 |
2001年 | 12811篇 |
2000年 | 10081篇 |
1999年 | 4269篇 |
1998年 | 1595篇 |
1997年 | 1225篇 |
1996年 | 1055篇 |
1995年 | 924篇 |
1994年 | 646篇 |
1993年 | 638篇 |
1992年 | 534篇 |
1991年 | 348篇 |
1990年 | 326篇 |
1989年 | 314篇 |
1988年 | 236篇 |
1987年 | 136篇 |
1986年 | 150篇 |
1985年 | 75篇 |
1984年 | 89篇 |
1983年 | 69篇 |
1982年 | 60篇 |
1981年 | 94篇 |
1980年 | 172篇 |
1979年 | 118篇 |
1975年 | 14篇 |
1965年 | 17篇 |
1959年 | 106篇 |
1951年 | 113篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
One-dimensional, diluted magnetic semiconductor nanofibers have attracted increasing attention for their unique magnetic properties, large specific surface area, and high porosity. These qualities lead to excellent performance in magneto-optical devices, magnetic resonance imaging, ferrofluids and magnetic separation. The purpose of this study is to fabricate P-type one dimensional CuAlO2-based diluted magnetic semiconductor nanofibers. First, we fabricated Cu Al0.95Co0.05O2 nanofibers with an average diameter of 1 μm with the electrospinning method. The annealed nanofibers were thermally treated at a temperature of 1 100 ℃ and then shrunk to a diameter of about 650 nm. We used X-ray diffraction measurements and Raman spectra to confirm that the Cu Al0.95Co0.05O2 nanofibers had a single impurity free delafossite phase. The X-ray photoelectron spectroscopy analysis indicates that Co was present in the +2 oxidation state, resulting in an room temperature ferromagnetism in the Cu Al0.95Co0.05O2 fiber. This contrasts with nonmagnetism in pristine CuAlO2 fiber. The coercivity(Hc) value of 65.26 Oe and approximate saturation magnetization(Ms) of 0.012 emu/g demonstrate good evidence of ferromagnetism at room temperature for Cu Al0.95Co0.05O2 nanofibers. 相似文献
92.
93.
面部运动单元检测旨在让计算机从给定的人脸图像或视频中自动检测需要关注的运动单元目标。经过二十多年的研究,尤其是近年来越来越多的面部运动单元数据库的建立和深度学习的兴起,面部运动单元检测技术发展迅速。首先,阐述了面部运动单元的基本概念,介绍了已有的常用面部运动单元检测数据库,概括了包括预处理、特征提取、分类器学习等步骤在内的传统检测方法;然后针对区域学习、面部运动单元关联学习、弱监督学习等几个关键研究方向进行了系统性的回顾梳理与分析;最后讨论了目前面部运动单元检测研究存在的不足以及未来潜在的发展方向。 相似文献
94.
In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria 下载免费PDF全文
Su Chul Jang Sae Rom Kim Yae Jin Yoon Kyong‐Su Park Ji Hyun Kim Jaewook Lee Oh Youn Kim Eun‐Jeong Choi Dae‐Kyum Kim Dong‐Sic Choi Yoon‐Keun Kim Jaesung Park Dolores Di Vizio Yong Song Gho 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(4):456-461
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo. 相似文献
95.
思维可视化是利用图形化、形象化的形式来表达人们头脑中形成的概念、知识、思想等,把隐性知识显性化、可视化,方便人们思考、表达、理解并能促进交流的一种图形技术。该文在阐述思维可视化定义的基础上,研究了思维可视化工具在教学中的应用。 相似文献
96.
不同折流板结构螺旋折流板换热器传热性能的比较(英文) 总被引:1,自引:0,他引:1
Numerical simulations were performed on flow and heat transfer performances of heat exchangers having six helical baffles of different baffle shapes and assembly configurations, i.e., two trisection baffle schemes, two quadrant baffle schemes, and two continuous helical baffle schemes. The temperature contour or the pressure contour and velocity contour plots with superimposed velocity vectors on meridian, transverse and unfolded concentric hexagonal slices are presented to obtain a full angular view. For the six helix baffled heat exchangers, the different patterns of the single vortex secondary flow and the shortcut leakage flow were depicted as wel as the heat transfer properties were compared. The results show that the optimum scheme among the six configurations is a circumferential overlap trisection helix baffled heat exchanger with a baffle incline angle of 20° (20°TCO) scheme with an anti-shortcut baffle structure, which exhibits the second highest pressure dropΔpo, the highest overal heat transfer coefficient K, shel-side heat transfer coefficient ho and shel-side average comprehensive index ho/Δpo. 相似文献
97.
王玮 《上海第二工业大学学报》2015,(2):173-176
从探讨郭沫若的生平背景入手,介绍了他的翻译成就,并对郭沫若的翻译理论和翻译思想做出了初步的剖析。郭沫若的翻译实践主要可以从郭沫若译著《英诗译稿》和《浮士德》窥见一斑,而郭沫若的翻译理论则可从罗新璋所著的《翻译论集》和方克平所著的《溯洄从美:从批判理论到文学翻译》中探出精髓。对郭沫若翻译实践和理论的研究可以发现郭沫若的"创作论"的地位固然不可撼动,但其中对于创作的维度却并没有提出很好的标准。 相似文献
98.
99.
100.