全文获取类型
收费全文 | 3084篇 |
免费 | 867篇 |
国内免费 | 680篇 |
专业分类
电工技术 | 381篇 |
综合类 | 316篇 |
化学工业 | 53篇 |
金属工艺 | 41篇 |
机械仪表 | 242篇 |
建筑科学 | 30篇 |
矿业工程 | 54篇 |
能源动力 | 43篇 |
轻工业 | 43篇 |
水利工程 | 29篇 |
石油天然气 | 24篇 |
武器工业 | 33篇 |
无线电 | 479篇 |
一般工业技术 | 144篇 |
冶金工业 | 16篇 |
原子能技术 | 7篇 |
自动化技术 | 2696篇 |
出版年
2024年 | 14篇 |
2023年 | 38篇 |
2022年 | 96篇 |
2021年 | 121篇 |
2020年 | 148篇 |
2019年 | 148篇 |
2018年 | 129篇 |
2017年 | 182篇 |
2016年 | 203篇 |
2015年 | 268篇 |
2014年 | 315篇 |
2013年 | 261篇 |
2012年 | 428篇 |
2011年 | 445篇 |
2010年 | 322篇 |
2009年 | 326篇 |
2008年 | 330篇 |
2007年 | 301篇 |
2006年 | 233篇 |
2005年 | 152篇 |
2004年 | 95篇 |
2003年 | 43篇 |
2002年 | 22篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1997年 | 1篇 |
1986年 | 2篇 |
排序方式: 共有4631条查询结果,搜索用时 656 毫秒
91.
92.
93.
区域航空市场航线客流量预测研究 总被引:1,自引:0,他引:1
为了有效地控制和合理地分配区域航空市场航线客流量,提高航空机场的效率,为航管决策部门提供制定计划的理论依据,在深入研究国内外航空客流量预测研究成果基础之上,针对区域航空市场的特点,提出了一个自顶向下的航线客流量预测模型。它包括总体趋势预测、中长期预测模型和短期预测模型三部分;并将神经网络和支持向量机构成的组合模型引入中长期预测模型中,使用神经网络实现短期预测模型;并结合A公司实际进行了实证研究,证明了该预测模型的有效性。文中研究成果对所有航管部门具有一定的指导意义。 相似文献
94.
基于改进支持向量机的仿真电路故障诊断研究 总被引:5,自引:4,他引:1
研究电路的故障问题,应提高快速性和准确性。为提高仿真电路故障诊断效率,给出了一种基于改进支持向量机的仿真电路故障诊断方法。首先通过小波包变换实现了信号的能量特征提取,根据主元分析完成了特征压缩;其次针对支持向量机多分类一对一方法存在的不可分类区,将其与最近邻分类法相结合,实现了电路的故障诊断,并提出了一种混合遗传算法实现了小波函数和支持向量机参数的同步选择;最后通过一仿真电路的仿真实验,与BP,RBF和PNN等神经网络对比,结果显示基于支持向量机的方法诊断精度最高,达到98%,为设计提供参考依据。 相似文献
95.
96.
By introducing the rough set theory into the support vector machine (SVM), a rough margin based SVM (RMSVM) is proposed to deal with the overfitting problem due to outliers. Similar to the classical SVM, the RMSVM searches for the separating hyper-plane that maximizes the rough margin, defined by the lower and upper margin. In this way, more data points are adaptively considered rather than the few extreme value points used in the classical SVM. In addition, different support vectors may have different effects on the learning of the separating hyper-plane depending on their positions in the rough margin. Points in the lower margin have more effects than those in the boundary of the rough margin. From experimental results on six benchmark datasets, the classification accuracy of this algorithm is improved without additional computational expense compared with the classical ν-SVM. 相似文献
97.
Use of a dark object concept and support vector machines to automate forest cover change analysis 总被引:5,自引:0,他引:5
Chengquan Huang Kuan Song Sunghee Kim Paul Davis Jeffrey G. Masek 《Remote sensing of environment》2008,112(3):970-985
An automated method was developed for mapping forest cover change using satellite remote sensing data sets. This multi-temporal classification method consists of a training data automation (TDA) procedure and uses the advanced support vector machines (SVM) algorithm. The TDA procedure automatically generates training data using input satellite images and existing land cover products. The derived high quality training data allow the SVM to produce reliable forest cover change products. This approach was tested in 19 study areas selected from major forest biomes across the globe. In each area a forest cover change map was produced using a pair of Landsat images acquired around 1990 and 2000. High resolution IKONOS images and independently developed reference data sets were available for evaluating the derived change products in 7 of those areas. The overall accuracy values were over 90% for 5 areas, and were 89.4% and 89.6% for the remaining two areas. The user's and producer's accuracies of the forest loss class were over 80% for all 7 study areas, demonstrating that this method is especially effective for mapping major disturbances with low commission errors. IKONOS images were also available in the remaining 12 study areas but they were either located in non-forest areas or in forest areas that did not experience forest cover change between 1990 and 2000. For those areas the IKONOS images were used to assist visual interpretation of the Landsat images in assessing the derived change products. This visual assessment revealed that for most of those areas the derived change products likely were as reliable as those in the 7 areas where accuracy assessment was conducted. The results also suggest that images acquired during leaf-off seasons should not be used in forest cover change analysis in areas where deciduous forests exist. Being highly automatic and with demonstrated capability to produce reliable change products, the TDA-SVM method should be especially useful for quantifying forest cover change over large areas. 相似文献
98.
99.
100.