全文获取类型
收费全文 | 5588篇 |
免费 | 704篇 |
国内免费 | 292篇 |
专业分类
电工技术 | 557篇 |
综合类 | 300篇 |
化学工业 | 930篇 |
金属工艺 | 397篇 |
机械仪表 | 443篇 |
建筑科学 | 454篇 |
矿业工程 | 204篇 |
能源动力 | 309篇 |
轻工业 | 731篇 |
水利工程 | 124篇 |
石油天然气 | 11篇 |
武器工业 | 4篇 |
无线电 | 309篇 |
一般工业技术 | 661篇 |
冶金工业 | 126篇 |
原子能技术 | 43篇 |
自动化技术 | 981篇 |
出版年
2024年 | 30篇 |
2023年 | 193篇 |
2022年 | 288篇 |
2021年 | 304篇 |
2020年 | 299篇 |
2019年 | 206篇 |
2018年 | 189篇 |
2017年 | 162篇 |
2016年 | 183篇 |
2015年 | 146篇 |
2014年 | 307篇 |
2013年 | 408篇 |
2012年 | 705篇 |
2011年 | 636篇 |
2010年 | 437篇 |
2009年 | 495篇 |
2008年 | 245篇 |
2007年 | 493篇 |
2006年 | 381篇 |
2005年 | 128篇 |
2004年 | 43篇 |
2003年 | 27篇 |
2002年 | 28篇 |
2001年 | 31篇 |
2000年 | 30篇 |
1999年 | 35篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 28篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有6584条查询结果,搜索用时 0 毫秒
1.
从退火态原位TiCp/Fe复合材料的切削力和切屑形状方面分析了其切削性能。研究结果表明其切削力及切削力的波动范围都小于铸态45钢,其切削性能比45钢好。TiCp/Fe复合材料的切屑为C形屑、长紧卷屑和发条状卷屑,在机加工中,产生这几种切屑是比较理想的。从切屑方面看,TiCp/Fe复合材料的切削性能较好。 相似文献
2.
《Hydrometallurgy》2006,81(3-4):234-240
The oxidation of glucose during the reductive leaching of pure MnO2 and manganese ore in sulphuric acid at 90 °C MnO2 was investigated. The aim was to identify the derivatives and the chemical pathway of glucose oxidation. Organic derivatives were monitored by HPLC using an Aminex HPX-78H column and UV detection. Chromatographic patterns of leaching solutions showed that major compound formed was formic acid. Minor quantities of glycolic, glyceric and traces of gluconic acids were identified. Results suggest that during the leaching reaction, the carbon chain of glucose is shortened by detachment of one carbon atom as formic acid. 相似文献
3.
《Intermetallics》2007,15(12):1497-1503
The coherent precipitate γ1-Ti4Nb3Al9 in the Nb-modified TiAl-based intermetallic compound with a nominal composition of Ti–48 at% Al–10 at% Nb was investigated by transmission electron microscopy. The crystallographic and morphologic characteristics of the precipitating phase have been calculated based on invariant line theory. It is revealed that in the γ-TiAl(Nb)/γ1-Ti4Nb3Al9 couples, both the morphological and crystallographical characteristics of the precipitate γ1-Ti4Nb3Al9 could be predicted by the three-dimensional phase transformation invariant line model. The needle direction of [001] at the early stage for coherent precipitate γ1-Ti4Nb3Al9 and [111] for equilibrium phase γ1-Ti4Nb3Al9 have both been explained well. The characterization of morphology and crystallography of the precipitate reaction in γ-TiAl/γ1-Ti4Nb3Al9 system sustain the postulate that precipitates are bounded by unrotated planes (eigenplanes) when three real eigenvalues exist. 相似文献
4.
喻桂兰 《电脑与微电子技术》2012,(19):7-10
介绍一种分析时序逻辑电路的补充方法,并应用于教学实践中。其特点是原理简单、易于理解、直观方便,相对于传统的分析方法,避免了对次状态方程的分析处理计算,有时比传统方法简便、快捷。通过两个示例展示其优越性。 相似文献
5.
6.
7.
《Fuel》2006,85(14-15):2187-2194
In this present investigation deccan hemp oil, a non-edible vegetable oil is selected for the test on a diesel engine and its suitability as an alternate fuel is examined. The viscosity of deccan hemp oil is reduced first by blending with diesel in 25/75%, 50/50%, 75/25%, 100/0% on volume basis, then analyzed and compared with diesel. Further blends are heated and effect of viscosity on temperature was studied. The performance and emission characteristics of blends are evaluated at variable loads of 0.37, 0.92, 1.48, 2.03, 2.58, 3.13 and 3.68 kW at a constant rated speed of 1500 rpm and results are compared with diesel. The thermal efficiency, brake specific fuel consumption (BSFC), and brake specific energy consumption (BSEC) are well comparable with diesel, and emissions are a little higher for 25% and 50% blends. At rated load, smoke, carbon monoxide (CO), and unburnt hydrocarbon (HC) emissions of 50% blend are higher compared with diesel by 51.74%, 71.42% and 33.3%, respectively. For ascertaining the validity of results obtained, pure deccan hemp oil results are compared with results of jatropha and pongamia oil for similar works available in the literature and were well comparable. From investigation it has been established that, up to 25% of blend of deccan hemp oil without heating and up to 50% blend with preheating can be substituted for diesel engine without any engine modification. 相似文献
8.
Gan-Ji Huang Wu-Hua Chen 《International Journal of Control, Automation and Systems》2014,12(5):954-962
This paper revisits the problem of designing switched observers for switched linear systems with unknown inputs. By performing a state and output coordinates transformation that decouples the unknown input, a novel piecewise time-varying Lyapunov function is introduced to analyze the stability of the switched error dynamics. Compared with the existing time-invariant Lyapunov function method, the proposed time-varying Lyapunov function method is more suitable to exploit the structural characteristics of switched linear systems. New conditions are derived that guarantee the exponential stability of the switched error dynamics. These conditions are formulated in term of linear matrix inequalities (LMIs). By solving a set of LMIs, the switched observers can be designed. Two numerical examples are provided to illustrate the effectiveness of the proposed method. 相似文献
9.
10.