全文获取类型
收费全文 | 8489篇 |
免费 | 1104篇 |
国内免费 | 1411篇 |
专业分类
电工技术 | 235篇 |
综合类 | 1095篇 |
化学工业 | 140篇 |
金属工艺 | 65篇 |
机械仪表 | 100篇 |
建筑科学 | 3747篇 |
矿业工程 | 1315篇 |
能源动力 | 254篇 |
轻工业 | 56篇 |
水利工程 | 2330篇 |
石油天然气 | 489篇 |
武器工业 | 12篇 |
无线电 | 268篇 |
一般工业技术 | 278篇 |
冶金工业 | 225篇 |
原子能技术 | 12篇 |
自动化技术 | 383篇 |
出版年
2024年 | 10篇 |
2023年 | 105篇 |
2022年 | 263篇 |
2021年 | 297篇 |
2020年 | 294篇 |
2019年 | 261篇 |
2018年 | 266篇 |
2017年 | 362篇 |
2016年 | 390篇 |
2015年 | 380篇 |
2014年 | 633篇 |
2013年 | 489篇 |
2012年 | 718篇 |
2011年 | 774篇 |
2010年 | 680篇 |
2009年 | 659篇 |
2008年 | 577篇 |
2007年 | 704篇 |
2006年 | 584篇 |
2005年 | 549篇 |
2004年 | 422篇 |
2003年 | 331篇 |
2002年 | 275篇 |
2001年 | 189篇 |
2000年 | 154篇 |
1999年 | 144篇 |
1998年 | 106篇 |
1997年 | 88篇 |
1996年 | 69篇 |
1995年 | 53篇 |
1994年 | 50篇 |
1993年 | 35篇 |
1992年 | 35篇 |
1991年 | 13篇 |
1990年 | 5篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Transfer learning between crop types for semantic segmentation of crops versus weeds in precision agriculture 总被引:1,自引:0,他引:1
Agricultural robots rely on semantic segmentation for distinguishing between crops and weeds to perform selective treatments and increase yield and crop health while reducing the amount of chemicals used. Deep‐learning approaches have recently achieved both excellent classification performance and real‐time execution. However, these techniques also rely on a large amount of training data, requiring a substantial labeling effort, both of which are scarce in precision agriculture. Additional design efforts are required to achieve commercially viable performance levels under varying environmental conditions and crop growth stages. In this paper, we explore the role of knowledge transfer between deep‐learning‐based classifiers for different crop types, with the goal of reducing the retraining time and labeling efforts required for a new crop. We examine the classification performance on three datasets with different crop types and containing a variety of weeds and compare the performance and retraining efforts required when using data labeled at pixel level with partially labeled data obtained through a less time‐consuming procedure of annotating the segmentation output. We show that transfer learning between different crop types is possible and reduces training times for up to 80%. Furthermore, we show that even when the data used for retraining are imperfectly annotated, the classification performance is within 2% of that of networks trained with laboriously annotated pixel‐precision data. 相似文献
3.
南海北部陆坡区域构造地质控制着气源、流体疏导体系、富集空间及储层物性特征,因此,东沙海域、神狐海域、西沙海槽和琼东南盆地的水合物成藏条件及控制因素具有明显差异性。东沙海域深部气体可沿断层、裂缝、不整合面、砂岩疏导层和气烟囱等通道向上运移,并形成天然气水合物,具有渗漏型水合物产出特征;神狐海域水合物成藏与规模巨大的泥底辟活动相关,并与布莱克海台天然气水合物产出特征具有相似性;琼东南盆地中央坳陷带内为天然气水合物发育的重点区,底辟、泥火山或麻坑构造与天然气水合物发育密切相关。 相似文献
4.
《Geotextiles and Geomembranes》2020,48(6):802-811
Construction of this 67 m high RSS was completed in December 2006. After seven years in-service, a tension crack was observed at the top of the slope. In March 2015 this RSS structure catastrophically collapsed. This RSS structure collapsed in a compound failure mode; as the failure plane passed beneath, partially behind, and partially through the reinforced soil mass. The failure plane beneath the RSS was along a shale-claystone interface. The failure surface partially behind the RSS was along sandstone bedrock with water-seeping bedding planes dipping out of the rock mass. The failure surface through the upper portion of the RSS is where the geogrid reinforcement was overwhelmed by stresses originating from underlying deformation. The RSS collapse occurred after 8.3 years in-service as the shear strength along the shale-claystone interface decreased and approached the fully softened strength. The primary causative factors of this failure are: (i) an insufficient subsurface investigation program and interpretation of data for design and detailing; (ii) insufficient specifications and construction plan details for both foundation preparation and rock backcut benching; (iii) insufficient foundation preparation and rock backcut benching during construction; and (iv) adaptations to the design made during construction. 相似文献
5.
6.
7.
The assessment of soil slope stability is an important task in geotechnical designs. This study uses finite element upper bound (UB) and lower bound (LB) limit analysis (LA) methods to investigate inhomogeneous soil slope stability on the basis of the conventional Mohr–Coulomb parameters. The obtained stability numbers are presented in inhomogeneous soil slope stability charts. In order to minimize manual reading errors when using the chart solutions, an artificial neural network (ANN) is employed to develop a stability assessment tool for the slopes investigated in this paper. The slope stability analysis using the ANN-based tool is convenient, and the predictions it provides are highly accurate. 相似文献
8.
Daniele Viciani Lorella Dell’Olmo Antonio Gabellini Daniela Gigante Lorenzo Lastrucci 《Landscape Research》2018,43(7):952-964
Widespread trends of abandonment have strongly affected Mediterranean mountains after the Second World War, triggering spontaneous recolonisation of forests. A diachronic analysis of the landscape in a Natura 2000 site (Tuscany, Italy) was carried out using digital aerial photographs (1954, 2013) and a GIS-based methodology, focusing on territories above 1300 m a.s.l. The detected variations of total areas, patch shape, patch dimensions and selected metrics showed a notable shift of the vegetation towards woody types and a drastic reduction of open grasslands, some with high conservation value, accompanied by a strong increase in patch number, surface and edge. A decrease of SDI and SEI diversity indices was also observed. Considering that fragmentation is one of the main causes threatening habitats and species, our results point out a clear necessity for a monitoring programme and suitable actions aimed at improving the status of biodiversity-rich montane grasslands. 相似文献
9.
对高速路建设中高边坡病害的成因展开分析,并对高边坡病害的治理提出对策,希望对高边坡病害治理有一定的促进作用。 相似文献
10.
四川省植被覆盖时空演变及未来变化趋势分析 总被引:2,自引:0,他引:2
四川省地处长江上游,是长江流域重要的生态屏障;解析该区域植被覆盖的时空演变特征,对长江上游的生态环境修护与治理具有重要意义。基于长时间序列的MODIS NDVI数据,解析2000~2016年间四川省植被的空间分布格局与时间变化特征;采用趋势分析法和Hurst指数,预测未来植被的变化趋势及持续性。结果表明:(1)四川省NDVI多年平均值为0.50,植被覆盖整体上呈现川东高于川西的空间分布特征;(2)2000~2016年间,四川省的NDVI值在0.48至0.53之间波动,整体呈上升趋势,增长率为0.002 5/a;(3)植被覆盖度在未来变化将呈现改善大于退化的趋势;植被持续性改善的面积大于持续性退化的面积。 相似文献