全文获取类型
收费全文 | 16809篇 |
免费 | 1722篇 |
国内免费 | 1326篇 |
专业分类
电工技术 | 1278篇 |
综合类 | 1516篇 |
化学工业 | 1574篇 |
金属工艺 | 1540篇 |
机械仪表 | 1209篇 |
建筑科学 | 926篇 |
矿业工程 | 249篇 |
能源动力 | 229篇 |
轻工业 | 203篇 |
水利工程 | 303篇 |
石油天然气 | 454篇 |
武器工业 | 226篇 |
无线电 | 2788篇 |
一般工业技术 | 2608篇 |
冶金工业 | 376篇 |
原子能技术 | 176篇 |
自动化技术 | 4202篇 |
出版年
2024年 | 88篇 |
2023年 | 308篇 |
2022年 | 356篇 |
2021年 | 455篇 |
2020年 | 445篇 |
2019年 | 437篇 |
2018年 | 396篇 |
2017年 | 495篇 |
2016年 | 467篇 |
2015年 | 554篇 |
2014年 | 861篇 |
2013年 | 929篇 |
2012年 | 1071篇 |
2011年 | 1080篇 |
2010年 | 878篇 |
2009年 | 905篇 |
2008年 | 923篇 |
2007年 | 1191篇 |
2006年 | 1095篇 |
2005年 | 1032篇 |
2004年 | 891篇 |
2003年 | 804篇 |
2002年 | 656篇 |
2001年 | 579篇 |
2000年 | 520篇 |
1999年 | 405篇 |
1998年 | 371篇 |
1997年 | 311篇 |
1996年 | 253篇 |
1995年 | 233篇 |
1994年 | 186篇 |
1993年 | 183篇 |
1992年 | 128篇 |
1991年 | 83篇 |
1990年 | 73篇 |
1989年 | 57篇 |
1988年 | 45篇 |
1987年 | 14篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1959年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
《Expert systems with applications》2014,41(5):2574-2581
We describe in this paper a new methodology for blood alcohol content (BAC) estimation of a subject. Rather than using external devices to determine the BAC value of a subject, we perform a behaviour analysis of this subject using intelligent systems. We monitor the user’s actions in an ordinary task and label those data to various measured BAC values. The obtained data-set is then used to train learning systems to detect alcoholic consumption and perform BAC estimation. We obtain good results on a mono-user base, and lower results with multiple users. We improve the results by combining multiple classifiers and regression algorithms. 相似文献
82.
Fluid flow in coupled free and porous domain, particularly when the porous medium is heterogeneous, is encountered in many hydro-environmental conditions, e.g., leakage from underground pipe, combined groundwater lake-subsurface interactions. One of the most difficult problems in the study of coupled flow behaviour has been the development of a universally applicable modelling scheme for combining the flow regimes. This is because the free/porous interfacial properties (e.g., shear-stress; velocity slip) that govern the coupled flow behaviour are difficult to determine experimentally under hydro-environmental conditions. On the other hand, the implications of various forms of heterogeneity in the porous media properties can be very different on the fluid-flow behaviour. Difficulties may also arise in direct coupling of the model equations that govern the fluid flow in the individual regions (e.g., Navier-Stokes for free-flow region and the Darcy's equation for the porous flow region). Consequently, models of coupled free and porous flow for hydro-environmental conditions are not very well developed at the moment. While there are some indications that fluids in coupled free and porous domains may circulate (i.e., development of flow cells), there is a lack of appropriate 3D analysis on how heterogeneities in porous media may affect such flow patterns. In this paper, we aim to analyse how porous media heterogeneity affects the dynamics of flow circulation in the porous side of a coupled free and porous domain. For this purpose, we analyse flow patterns in several model domains made up of two porous layers with differing permeabilities. The governing model equations are discretised and solved using the standard finite volume method on a staggered cell-centred mesh. The temporal discretisation is done using the explicit method. An in-house graphical user interface (GUI) has been created specifically to aid in the visualisation of otherwise complex flow patterns. The GUI contains many post-processing options and provides a comprehensive tool for the analysis of hydrodynamics and contaminant motion (not discussed in this paper) in coupled free and porous flow domains. This GUI is described in this paper briefly. The effects of altering the aspect ratio (i.e., multi-scale) of the domain on the coupled flow pattern have also been discussed. 相似文献
83.
The modification of the interface in immiscible polymer blends is critical in order to optimize physical properties. Despite the great commercial importance of polymer blends, many aspects of the emulsification process remain unclear In this paper, it will be shown that an emulsification curve can be used to estimate the influence of the architecture molar mass of styrene/hydrogenated butadiene block copolymer interfacial modifiers on the emulsifion of polystyrene/ethylene-propylene rubber blends under melt processing conditions. An expression for eing the critical amount of copolymer to saturate the interface, as well as aspects concerning the localisation of the modifier in the blend system will also be addressed. 相似文献
84.
Chengjun Yao Yixun Liu Jianhua Yao Dongxiao Zhuang Jinsong Wu Zhiyong Qin Ying Mao Liangfu Zhou 《Computer methods and programs in biomedicine》2014
Background
Preoperatively acquired diffusion tensor image (DTI) and blood oxygen level dependent (BOLD) have been proved to be effective in providing more anatomical and functional information; however, the brain deformation induced by brain shift and tumor resection severely impairs the correspondence between the image space and the patient space in image-guided neurosurgery.Method
To address the brain deformation, we developed a hybrid non-rigid registration method to register high-field preoperative MRI with low-field intra-operative MRI in order to recover the deformation induced by brain shift and tumor resection. The registered DTI and BOLD are fused with low-field intra-operative MRI for image-guided neurosurgery.Results
The proposed hybrid registration method was evaluated by comparing the landmarks predicted by the hybrid registration method with the landmarks identified in the low-field intra-operative MRI for 10 patients. The prediction error of the hybrid method is 1.92 ± 0.54 mm, and the compensation accuracy is 74.3 ± 5.0%. Compared to the landmarks far from the resection region, those near the resection region demonstrated a higher compensation accuracy (P-value = .003) although these landmarks had larger initial displacements.Conclusions
The proposed hybrid registration method is able to bring preoperatively acquired BOLD and DTI into the operating room and compensate for the deformation to augment low-field intra-operative MRI with rich anatomical and functional information. 相似文献85.
Angkoon Phinyomark Franck Quaine Sylvie Charbonnier Christine Serviere Franck Tarpin-Bernard Yann Laurillau 《Computer methods and programs in biomedicine》2014
This paper demonstrates the utility of a differencing technique to transform surface EMG signals measured during both static and dynamic contractions such that they become more stationary. The technique was evaluated by three stationarity tests consisting of the variation of two statistical properties, i.e., mean and standard deviation, and the reverse arrangements test. As a result of the proposed technique, the first difference of EMG time series became more stationary compared to the original measured signal. Based on this finding, the performance of time-domain features extracted from raw and transformed EMG was investigated via an EMG classification problem (i.e., eight dynamic motions and four EMG channels) on data from 18 subjects. The results show that the classification accuracies of all features extracted from the transformed signals were higher than features extracted from the original signals for six different classifiers including quadratic discriminant analysis. On average, the proposed differencing technique improved classification accuracies by 2–8%. 相似文献
86.
为制备强韧的共混材料,利用熔融接枝法研制了含有两种接技单体的新型聚丙烯接枝物,讨论了第二单体在接枝过程中的作用,并将其应用于尼龙6/聚丙烯(PA6/PP)共混体系,获得了使分散相粒径更细小、界面更模糊的增容效果。 相似文献
87.
在96℃水中,对开芙拉29(Kevlar29),开芙拉49(Kevlar49)和聚苯撑苯并唑(PBO)纤维束增强的环氧树脂和双马树脂基复合材料进行老化实验后,再在60℃下进行干燥脱水处理。实验测定了吸水和脱水阶段的含水率及热水老化试样和干燥试样的弯曲性能。结果表明:在热水作用下,复合材料的弯曲强度和模量随热水老化时间的延长呈下降趋势,纤维与树脂基体间的界面发生破坏;再干燥脱水后,材料的弯曲强度和模量恢复,但仍低于未老化试样的性能,纤维与树脂基体间的界面破坏情况也类似。 相似文献
88.
花岗岩残积土在华南、东南沿海、南岳、新疆等地区广泛分布,前人的研究多集中在结构性及微观特性上,后循环加载、位移演化、土壤密度等因素对筋-土界面的剪切特性及加筋作用效果的影响评估研究较少。从循环试验剪切刚度这一重要参数入手,以加载次数、加载频率值、位移振幅值、土壤重度值为自变量,应用控制变量法,通过设计循环直剪试验,得到加筋花岗岩残积土的剪切应力与剪切位移、垂直位移与剪切位移关系曲线进行观察对比,结果表明:花岗岩残积土土工格栅界面剪切刚度受位移半振幅、土壤干重度影响很大,受加载频率影响很小,循环加载并没有弱化后循环界面剪切强度,剪切位移与位移半振幅呈负相关关系。 相似文献
89.
The usefulness of Software Architecture (SA) documentation depends on how well its Architectural Knowledge (AK) can be retrieved by the stakeholders in a software project. Recent findings show that the use of ontology-based SA documentation is promising. However, different roles in software development have different needs for AK, and building an ontology to suit these needs is challenging. In this paper we describe an approach to build an ontology for SA documentation. This approach involves the use of typical questions for eliciting and constructing an ontology. We outline eight contextual factors, which influence the successful construction of an ontology, especially in complex software projects with diverse AK users. We tested our ‘typical question’ approach in a case study and report how it can be used for acquiring and modeling AK needs. 相似文献
90.
随着社会生产力的不断发展,越来越多的企业认识到了财务工作的重要性。企业要利用现代高效的运作方式来开发和管理组织中最重要、最昂贵的资源,实现财务管理的精细化、自动化,提高财务资源的利用率,促进企业的发展。 相似文献