全文获取类型
收费全文 | 3000篇 |
免费 | 98篇 |
国内免费 | 39篇 |
专业分类
电工技术 | 93篇 |
综合类 | 39篇 |
化学工业 | 755篇 |
金属工艺 | 67篇 |
机械仪表 | 136篇 |
建筑科学 | 115篇 |
矿业工程 | 23篇 |
能源动力 | 98篇 |
轻工业 | 276篇 |
水利工程 | 26篇 |
石油天然气 | 10篇 |
武器工业 | 2篇 |
无线电 | 263篇 |
一般工业技术 | 411篇 |
冶金工业 | 261篇 |
原子能技术 | 44篇 |
自动化技术 | 518篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 50篇 |
2021年 | 69篇 |
2020年 | 28篇 |
2019年 | 57篇 |
2018年 | 68篇 |
2017年 | 45篇 |
2016年 | 58篇 |
2015年 | 66篇 |
2014年 | 87篇 |
2013年 | 170篇 |
2012年 | 143篇 |
2011年 | 212篇 |
2010年 | 192篇 |
2009年 | 203篇 |
2008年 | 213篇 |
2007年 | 178篇 |
2006年 | 143篇 |
2005年 | 163篇 |
2004年 | 96篇 |
2003年 | 102篇 |
2002年 | 101篇 |
2001年 | 61篇 |
2000年 | 54篇 |
1999年 | 41篇 |
1998年 | 53篇 |
1997年 | 45篇 |
1996年 | 49篇 |
1995年 | 34篇 |
1994年 | 32篇 |
1993年 | 46篇 |
1992年 | 33篇 |
1991年 | 23篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 9篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 19篇 |
1982年 | 8篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有3137条查询结果,搜索用时 0 毫秒
1.
Ken Takagi 《Journal of Engineering Mathematics》2004,48(3-4):339-352
The numerical accuracy of the displacement potential approach for a three-dimensional water-impact problem is investigated. An examination of the elliptic paraboloid shows that the boundary-value problem for the displacement potential, as well as the velocity potential, can be solved accurately, even if the panel size of the numerical scheme is no small enough. The numerical accuracy of the position of the contact line is poor. However, the accuracy of the virtual mass is good because of the averaging effect along the contact line. A comparison with Scolan and Korobkin's designed body confirms the accuracy of the drop speed and the penetration displacement. The displacement potential approach is extended to the case of water impact with trapped air. The numerical accuracy of the calculated air pressure in the cavity is confirmed by comparison with an experimental result. With these results, the suitability of the displacement potential approach to the ship-slamming problem is demonstrated. 相似文献
2.
3.
4.
5.
The breakdown processes of oil films under quasi-static loading have been investigated by using a newly developed steel-oil-mercury system. The relationship between the thickness and breakdown ratio of a hexadecane film is represented by a single master curve independently of the indentation speed, indentation load, and temperature. The master curve shows that the breakdown process of hexadecane includes two stages; one is the decrement of the thickness without breakdown and the other is the decrement of the thickness with a drastic progress of breakdown. By solving a small amount of fatty acid in hexadecane, the thickness increases and the breakdown ratio decreases noticeably; a multilayer residual film supporting normal load is formed between two metal surfaces. Experiments at different temperatures reveal a negative relationship between the temperature and thickness of residual film, which indicates that the residual film is organized by physical interaction rather than chemical interaction. At least under a lower concentration, the residual film appears to consist of not only fatty acid molecules but also hexadecane molecules. 相似文献
6.
7.
I Frías MT Caldeira JR Pérez-Casti?eira JP Navarro-Avi?ó FA Culia?ez-Maciá O Kuppinger H Stransky M Pagés A Hager R Serrano 《Canadian Metallurgical Quarterly》1996,8(9):1533-1544
The plasma membrane (PM) H(+)-ATPase has been proposed to play important transport and regulatory roles in plant physiology, including its participation in auxin-induced acidification in coleoptile segments. This enzyme is encoded by a family of genes differing in tissue distribution, regulation, and expression level. A major expressed isoform of the maize PM H(+)-ATPase (MHA2) has been characterized. RNA gel blot analysis indicated that MHA2 is expressed in all maize organs, with highest levels being in the roots. In situ hybridization of sections from maize seedlings indicated enriched expression of MHA2 in stomatal guard cells, phloem cells, and root epidermal cells. MHA2 mRNA was induced threefold when nonvascular parts of the coleoptile segments were treated with auxin. This induction correlates with auxin-triggered proton extrusion by the same part of the segments. The PM H(+)-ATPase in the vascular bundies does not contribute significantly to auxin-induced acidification, is not regulated by auxin, and masks the auxin effect in extracts of whole coleoptile segments. We conclude that auxin-induced acidification in coleoptile segments most often occurs in the nonvascular tissue and is mediated, at least in part, by increased levels of MHA2. 相似文献
8.
9.
10.
Hitoshi Kurokawa Taku Nakayama Yasunori Kobayashi Ken Suzuki Mutsumi Takahashi Seiichi Takami Momoji Kubo Naotsugu Itoh Parasuraman Selvam Akira Miyamoto 《Catalysis Today》2003,82(1-4):233-240
A modified Monte Carlo (MC) simulation was performed to investigate the hydrogen absorption behavior in Pd and Pd–Ag alloys of the composition PdxAg1−x (x=0.7–0.8) under H2 pressure (0.1 MPa) at different temperatures. The present method employed can consider the dissociative adsorption of hydrogen molecule and the subsequent absorption of hydrogen atom by formalizing the relationship between the pressure of hydrogen molecule and hydrogen atom. The potential parameters were determined to reproduce the solution enthalpy of hydrogen in pure metals. The results are in good agreement with experimental findings as well as previous theoretical studies. We confirmed that our method is useful to simulate the absorption of hydrogen in metals and alloys. 相似文献