全文获取类型
收费全文 | 3963篇 |
免费 | 277篇 |
国内免费 | 170篇 |
专业分类
电工技术 | 128篇 |
综合类 | 191篇 |
化学工业 | 697篇 |
金属工艺 | 202篇 |
机械仪表 | 233篇 |
建筑科学 | 270篇 |
矿业工程 | 87篇 |
能源动力 | 107篇 |
轻工业 | 304篇 |
水利工程 | 55篇 |
石油天然气 | 270篇 |
武器工业 | 31篇 |
无线电 | 380篇 |
一般工业技术 | 543篇 |
冶金工业 | 320篇 |
原子能技术 | 26篇 |
自动化技术 | 566篇 |
出版年
2024年 | 13篇 |
2023年 | 50篇 |
2022年 | 102篇 |
2021年 | 129篇 |
2020年 | 102篇 |
2019年 | 100篇 |
2018年 | 106篇 |
2017年 | 95篇 |
2016年 | 108篇 |
2015年 | 124篇 |
2014年 | 146篇 |
2013年 | 226篇 |
2012年 | 223篇 |
2011年 | 230篇 |
2010年 | 208篇 |
2009年 | 207篇 |
2008年 | 222篇 |
2007年 | 204篇 |
2006年 | 217篇 |
2005年 | 202篇 |
2004年 | 141篇 |
2003年 | 123篇 |
2002年 | 120篇 |
2001年 | 124篇 |
2000年 | 115篇 |
1999年 | 92篇 |
1998年 | 134篇 |
1997年 | 99篇 |
1996年 | 75篇 |
1995年 | 70篇 |
1994年 | 54篇 |
1993年 | 40篇 |
1992年 | 36篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1978年 | 5篇 |
1973年 | 7篇 |
1971年 | 4篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有4410条查询结果,搜索用时 15 毫秒
61.
Face Detection: A Survey 总被引:5,自引:0,他引:5
In this paper we present a comprehensive and critical survey of face detection algorithms. Face detection is a necessary first-step in face recognition systems, with the purpose of localizing and extracting the face region from the background. It also has several applications in areas such as content-based image retrieval, video coding, video conferencing, crowd surveillance, and intelligent human–computer interfaces. However, it was not until recently that the face detection problem received considerable attention among researchers. The human face is a dynamic object and has a high degree of variability in its apperance, which makes face detection a difficult problem in computer vision. A wide variety of techniques have been proposed, ranging from simple edge-based algorithms to composite high-level approaches utilizing advanced pattern recognition methods. The algorithms presented in this paper are classified as either feature-based or image-based and are discussed in terms of their technical approach and performance. Due to the lack of standardized tests, we do not provide a comprehensive comparative evaluation, but in cases where results are reported on common datasets, comparisons are presented. We also give a presentation of some proposed applications and possible application areas. 相似文献
62.
重路由匿名通信系统中基于秘密共享的重路由算法 总被引:4,自引:0,他引:4
重路由匿名通信系统主要采用重路由机制来提供匿名保护.已有的下一跳重路由方式具有抗攻击能力弱且通信延时大等缺陷.提出基于秘密共享的重路由算法,用于在下一跳路由中实现端到端的加密,从而有效增大恶意成员的攻击难度.理论分析表明,抗攻击能力达到与源路由方式同等水平.并且,由于发送者能有效控制路由长度,因而能保证良好的通信性能. 相似文献
63.
计算机应用技术促进了流程工业的变革和发展,并日益渗透到流程工业的各个方面。文章以流程工业中的化工行业为重点,论述了计算机在流程工业自动控制、故障诊断与检测、软测量等领域的应用原理与方法,阐明了计算机是提高企业自动化和信息化水平的关键,阐述了化工流程工业中计算机的应用技术发展所面临的问题并就其发展提出若干建议。 相似文献
64.
65.
Xuejiao Liu Zhixin Xu Asma Iqbal Ming Chen Nazakat Ali CheeTongJohn Low Rongrong Qi Jiantao Zai Xuefeng Qian 《纳微快报(英文)》2021,(3):197-208
Huge volume changes of Si during lithiation/delithiation lead to regeneration of solid-electrolyte interphase(SEI)and consume electrolyte.In this article,γ-glycidoxypropyl trimethoxysilane(GOPS)was incorporated in Si/PEDOT:PSS electrodes to construct a flexible and conductive artificial SEI,effectively suppressing the consumption of electrolyte.The optimized electrode can maintain 1000 mAh g^−1 for nearly 800 cycles under limited electrolyte compared with 40 cycles of the electrodes without GOPS.Also,the optimized electrode exhibits excellent rate capability.The use of GOPS greatly improves the interface compatibility between Si and PEDOT:PSS.XPS Ar+etching depth analysis proved that the addition of GOPS is conducive to forming a more stable SEI.A full battery assembled with NCM 523 cathode delivers a high energy density of 520 Wh kg^−1,offering good stability. 相似文献
66.
67.
电控安溢活门由主阀和指挥阀构成,指挥阀由压力传感器、控制系统、比例电磁阀以及相关接线等附件组成,用来控制主阀背压腔的压力,从而实现主阀的启闭.控制系统采用PID控制原理,控制器由比例(P)电路、积分(I)电路和微分(D)电路线性纽合而成,对主阈背压腔压力和气枕压力这两个控制对象进行调节.试验表明,在小流量工况下,相对于机械式指挥阀,该控制系统调节下的气枕压力更平稳,控制精度更高. 相似文献
68.
Sui Lay Xavier Pearce Oana Sanislav Paul Robert Fisher Sarah Jane Annesley 《International journal of molecular sciences》2022,23(9)
Mitochondrial Complex II is composed of four core subunits and mutations to any of the subunits result in lowered Complex II activity. Surprisingly, although mutations in any of the subunits can yield similar clinical outcomes, there are distinct differences in the patterns of clinical disease most commonly associated with mutations in different subunits. Thus, mutations to the SdhA subunit most often result in mitochondrial disease phenotypes, whilst mutations to the other subunits SdhB-D more commonly result in tumour formation. The reason the clinical outcomes are so different is unknown. Here, we individually antisense-inhibited three of the Complex II subunits, SdhA, SdhB or SdhC, in the simple model organism Dictyostelium discoideum. Whilst SdhB and SdhC knockdown resulted in growth defects on bacterial lawns, antisense inhibition of SdhA expression resulted in a different pattern of phenotypic defects, including impairments of growth in liquid medium, enhanced intracellular proliferation of the bacterial pathogen Legionella pneumophila and phagocytosis. Knockdown of the individual subunits also produced different abnormalities in mitochondrial function with only SdhA knockdown resulting in broad mitochondrial dysfunction. Furthermore, these defects were shown to be mediated by the chronic activation of the cellular energy sensor AMP-activated protein kinase. Our results are in agreement with a role for loss of function of SdhA but not the other Complex II subunits in impairing mitochondrial oxidative phosphorylation and they suggest a role for AMP-activated protein kinase in mediating the cytopathological outcomes. 相似文献
69.
利用普通针孔成象的双摄像模型对双眼立体感知几何模型进行了研究,详细讨论了体视象空间的视觉重构,最后通过实验分析了影响体视的因素。 相似文献
70.
The efficacy of using polymers in cylindrical applications depends closely on its surface friction and wear characteristics. In this regard, a surface modification technique through plastic deformation has been implemented. Roller burnishing is commonly used to improve the surface quality of non-ferrous surfaces, but no work showed concern about roller burnishing as a polymer surface treatment process. The objective of the present work is to investigate the influence of burnishing force and burnishing speed on the friction and wear performance of acetal homopolymer and polyurethane under dry and lubricated sliding conditions. The results reveal that the coefficient of friction and wear rate decreased to a minimum value and then increased as higher burnishing force and speed were applied. It was shown that roller burnishing had favourable prospective to be utilized as a valuable polymer surface treatment technique. 相似文献