全文获取类型
收费全文 | 40668篇 |
免费 | 4847篇 |
国内免费 | 2251篇 |
专业分类
电工技术 | 1673篇 |
综合类 | 2759篇 |
化学工业 | 5488篇 |
金属工艺 | 2123篇 |
机械仪表 | 3082篇 |
建筑科学 | 2785篇 |
矿业工程 | 1442篇 |
能源动力 | 1083篇 |
轻工业 | 1124篇 |
水利工程 | 888篇 |
石油天然气 | 1086篇 |
武器工业 | 258篇 |
无线电 | 5252篇 |
一般工业技术 | 8450篇 |
冶金工业 | 844篇 |
原子能技术 | 481篇 |
自动化技术 | 8948篇 |
出版年
2024年 | 28篇 |
2023年 | 995篇 |
2022年 | 970篇 |
2021年 | 1538篇 |
2020年 | 1720篇 |
2019年 | 1648篇 |
2018年 | 1386篇 |
2017年 | 1611篇 |
2016年 | 1781篇 |
2015年 | 1959篇 |
2014年 | 2519篇 |
2013年 | 2465篇 |
2012年 | 2528篇 |
2011年 | 3308篇 |
2010年 | 2468篇 |
2009年 | 2610篇 |
2008年 | 2283篇 |
2007年 | 2450篇 |
2006年 | 2063篇 |
2005年 | 2065篇 |
2004年 | 1833篇 |
2003年 | 1720篇 |
2002年 | 1555篇 |
2001年 | 843篇 |
2000年 | 740篇 |
1999年 | 610篇 |
1998年 | 405篇 |
1997年 | 356篇 |
1996年 | 282篇 |
1995年 | 203篇 |
1994年 | 195篇 |
1993年 | 116篇 |
1992年 | 88篇 |
1991年 | 69篇 |
1990年 | 49篇 |
1989年 | 59篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 28篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 23篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Retrieving 3D shapes with 2D images has become a popular research area nowadays, and a great deal of work has been devoted to reducing the discrepancy between 3D shapes and 2D images to improve retrieval performance. However, most approaches ignore the semantic information and decision boundaries of the two domains, and cannot achieve both domain alignment and category alignment in one module. In this paper, a novel Collaborative Distribution Alignment (CDA) model is developed to address the above existing challenges. Specifically, we first adopt a dual-stream CNN, following a similarity guided constraint module, to generate discriminative embeddings for input 2D images and 3D shapes (described as multiple views). Subsequently, we explicitly introduce a joint domain-class alignment module to dynamically learn a class-discriminative and domain-agnostic feature space, which can narrow the distance between 2D image and 3D shape instances of the same underlying category, while pushing apart the instances from different categories. Furthermore, we apply a decision boundary refinement module to avoid generating class-ambiguity embeddings by dynamically adjusting inconsistencies between two discriminators. Extensive experiments and evaluations on two challenging benchmarks, MI3DOR and MI3DOR-2, demonstrate the superiority of the proposed CDA method for 2D image-based 3D shape retrieval task. 相似文献
2.
3.
针对货运列车在神华铁路日常的运营过程中,车辆车体受外界及自身磨耗等因素的影响,而造成车体破损、车体仓门缝隙过大,甚至出现严重破损等故障。而故障诊断是实现铁路科学维修决策的重要依据。本文提出了一种利用3D图像检测技术,进行货车车体故障数据处理和诊断的方法。引入主流成像技术,提出一种采用三维图像采集方式,用于覆盖车体整个侧部表明图像的拍摄。进行了车体数据采集、3D深度数据分析、数据测试,并通过实验验证了方法的有效性。 相似文献
4.
5.
6.
任岐山 ' target='_blank'> 徐伟瑜 ' target='_blank'> 邢中海 ' target='_blank'> 皮伟 ' target='_blank'> 张震润 ' target='_blank'> 《中州煤炭》2022,(8):97-103
三维地震技术作为煤矿生产中必不可少的工作手段,有效解决了煤层赋存地质问题,对巷道布设和煤矿安全生产具有重要意义。通过对赵楼煤矿八采区和十采区三维地震资料进行精细解译,识别了新生界与奥灰顶界面形态,主要褶皱、断裂和岩浆岩的展布形态以及异常体、异常区的分布及导致因素;阐述了主采3煤层的深度、厚度和起伏形态变化,否定和修正了部分断层的形态和位置;新发现断层35条,并进行了勘探前后地层和构造变化对比。 相似文献
7.
为解决引江济淮跌水、跌井汇流口水流水力特性模拟问题,采用基于 VOF 法的 RNG k-ε 双方程紊流数学模型对杨大庄跌水工程进行三维数值模拟研究,通过计算结果与已经完成的水工模型试验结果相对比,验证该模型模拟杨大庄跌水工程水流的水力特性的可行性。 研究结果表明:通过合理的处理网格及计算参数,杨大庄跌水水流入渠的流态、流速分布及水位数值模拟结果整体与试验值吻合较好,说明利用该模型模拟杨大庄跌水工程水流的水力特性是可行的,数学模型可用于指导和解决类似工程问题。 相似文献
8.
以碳纤维的三维编织架构为增强体,经镀铜预处理后,置于铝合金熔体中施加压力成形,得到三维编织碳纤维增强铝基复合材料。探究大气和氩气气氛下不同三维纤维架构挤压成型的复合材料的界面特征与结构。通过拉伸试验及扫描电镜检测,对材料性能进行表征。结果表明:紧密编织的三维编织碳纤维较宽松结构的三维编织碳纤维,与铝合金基材的浸润性和相容性更好,铝合金在与三维编织碳纤维复合后拉伸强度与硬度均提升。 相似文献
9.
《International Journal of Hydrogen Energy》2022,47(26):12903-12913
Oxygen evolution reaction (OER) plays a decisive role in electrolytic water splitting. However, it is still challengeable to develop low-cost and efficient OER electrocatalysts. Herein, we present a combination strategy via heteroatom doping, hetero-interface engineering and introducing conductive skeleton to synthesize a hybrid OER catalyst of CNT-interconnected iron-doped NiP2/Ni2P (Fe-(NiP2/Ni2P)@CNT) heterostructural nanoflowers by a simple hydrothermal reaction and subsequent phosphorization process. The optimized Fe-(NiP2/Ni2P)@CNT catalyst delivers an ultralow Tafel slope of 46.1 mV dec?1 and overpotential of 254 mV to obtain 10 mA cm?2, which are even better than those of commercial OER catalyst RuO2. The excellent OER performance is mainly attributed to its unique nanoarchitecture and the synergistic effects: the nanoflowers constructed by a 2D-like nanosheets guarantee large specific area and abundant active sites; the highly conductive CNT skeleton and the electronic modulation by the heterostructural NiP2/Ni2P interface and the hetero-atom doping can improve the catalytic activity; porous nanostructure benefits electrolyte penetration and gas release; most importantly, the rough surface and rich defects caused by phosphorization process can further enhance the OER performance. This work provides a deep insight to boost catalytic performance by heteroatom doping and interface engineering for water splitting. 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(91):38721-38735
Proper management of the liquid water and heat produced in proton exchange membrane (PEM) fuel cells remains crucial to increase both its performance and durability. In this study, a two-phase flow and multicomponent model, called two-fluid model, is developed in the commercial COMSOL Multiphysics® software to investigate the liquid water heterogeneities in large area PEM fuel cells, considering the real flow fields in the bipolar plate. A macroscopic pseudo-3D multi-layers approach has been chosen and generalized Darcy's relation is used both in the membrane-electrode assembly (MEA) and in the channel. The model considers two-phase flow and gas convection and diffusion coupled with electrochemistry and water transport through the membrane. The numerical results are compared to one-fluid model results and liquid water measurements obtained by neutron imaging for several operating conditions. Finally, according to the good agreement between the two-fluid and experimentation results, the numerical water distribution is examined in each component of the cell, exhibiting very heterogeneous water thickness over the cell surface. 相似文献