全文获取类型
收费全文 | 1903篇 |
免费 | 287篇 |
国内免费 | 113篇 |
专业分类
电工技术 | 128篇 |
综合类 | 465篇 |
化学工业 | 123篇 |
金属工艺 | 192篇 |
机械仪表 | 261篇 |
建筑科学 | 33篇 |
矿业工程 | 12篇 |
能源动力 | 133篇 |
轻工业 | 9篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
武器工业 | 19篇 |
无线电 | 180篇 |
一般工业技术 | 264篇 |
冶金工业 | 32篇 |
原子能技术 | 2篇 |
自动化技术 | 445篇 |
出版年
2024年 | 17篇 |
2023年 | 58篇 |
2022年 | 84篇 |
2021年 | 101篇 |
2020年 | 104篇 |
2019年 | 70篇 |
2018年 | 50篇 |
2017年 | 71篇 |
2016年 | 56篇 |
2015年 | 81篇 |
2014年 | 152篇 |
2013年 | 170篇 |
2012年 | 282篇 |
2011年 | 303篇 |
2010年 | 173篇 |
2009年 | 173篇 |
2008年 | 46篇 |
2007年 | 121篇 |
2006年 | 67篇 |
2005年 | 79篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1994年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 2篇 |
排序方式: 共有2303条查询结果,搜索用时 78 毫秒
1.
The Friction Stir Welding process for producing corner and T-joints out of 6 mm Ti–6Al–4V was developed in this effort using previous work on butt weld joints as a starting point. A limited number of corner joints were also subjected to a bending fatigue test to preliminarily assess the applicability of the process in producing fatigue critical structures. These results were also compared to predictions made by applying stress concentration factors to previously generated uniaxial butt joint test data. While additional testing is still required to obtain a higher degree of confidence in the conclusions of this study, it was found that the performance of these corner joints in fatigue could be compared to butt joint data when a geometrically based stress concentration factor is applied. Furthermore, these welded joints possessed equivalent fatigue performance relative to identical test specimens machined from wrought product forms, both bar and extrusion. Thus, from the perspective of fatigue design, this study has shown that Friction Stir Welding is able to produce structures with the same performance as currently made from wrought materials. 相似文献
2.
Corncob liquefaction in supercritical ethanol–water was performed with and without the addition of an alkali catalyst by direct addition or biomass impregnation in a 250-cm3 batch reactor. The effects of temperature, solvent and alkali addition on the biomass conversion level and oil yield were investigated to find the optimum condition. For non-catalytic liquefaction using a 1:1 (v/v) ethanol: water ratio, a maximum oil yield and conversion level of 49.0% and 93.4%, respectively, were obtained at 340 °C. For alkali catalytic liquefaction, the oil yield with KOH addition (57.5%) was higher than that from KOH-impregnated corncob liquefaction (43.3%). The oil from liquefaction with KOH addition had higher heating value (26.7–35.3 MJ kg−1) than the corncob (19.1 MJ kg−1). The dominant components of the obtained oil were found by GC/MS analysis to be aldehyde, ester, phenol derivatives and aromatic compounds. 相似文献
3.
目前采用的视频流调度算法,没有充分利用补丁流满足服务率高而占用系统资源少的优势,系统效率较低.为了提高效率,提出了一种基于MFQ的补丁优先算法,并给出了该算法的系统流程。通过对实验结果的比较,该算法在用户请求撤销率、节目调度不公平性和用户等待时间方面有明显的优越性. 相似文献
4.
5.
6.
7.
标准的LDA方法通常有3个问题:1)为了确保类内散度矩阵的非奇异性,必须首先通过PCA进行维数约简,这限制了对更多维数空间的使用;2)当每人只有单个训练样本时,类内散度矩阵必然奇异,此时LDA无法工作;3)缺乏对像素间的局部相关性的考虑。为了解决这些问题,提出一种基于拉普拉斯方向的差值线性判别分析方法。该方法通过拉普拉斯方向实现更鲁棒的图像相异性测度,通过引入差值散度矩阵来避免类内散度矩阵的奇异性。实验结果显示,该算法对表情变化、光照改变及不同遮挡情况获得了更高的识别率,尤其针对光照变化,效果更加显著。 相似文献
8.
线性动态系统模型结合稀疏编码实现异常事件检测。线性动态系统可有效地捕捉动态纹理在时间和空间的转移信息,描述视频的时空小块。然而,线性动态系统属于非欧氏空间,无法直接用传统的稀疏编码进行异常检测。基于约束凸优化公式,将相似性变换与稀疏编码结合,可实现线性动态系统稀疏编码的优化求解。实验表明,所提出的方法具有更好的性能。 相似文献
9.
10.
SHI Xin 《计算机辅助绘图.设计与制造(英文版)》2014,(4):7-13
For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was taken as the data-exchanged interface and source. Based on depth analysis of DXF data structure, take one drawing of DXF lathe turning rotational part asthe test piece. By VC++6.0 programming, part's geometry information could be obtained. Through data processing, 3D data of the test piece could be generated, which is based on 2D data of DXF test piece. Then, OpenGL graphic processing technologies (light, material, texture, map, et al.) were applied on the 3D display of test piece from DXF files or program modules. Finally based on the test report, results of the system functions were shared to prove the realization of system design, and the feasibility of algorithms used. In the developed software, Machine Designers could get a full view of machine parts, and do some proper modifications. The study content and results of our work have some theory and practical significance on the application of program design in the practical projects. 相似文献