全文获取类型
收费全文 | 2291篇 |
免费 | 112篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 23篇 |
综合类 | 4篇 |
化学工业 | 546篇 |
金属工艺 | 48篇 |
机械仪表 | 62篇 |
建筑科学 | 44篇 |
矿业工程 | 8篇 |
能源动力 | 59篇 |
轻工业 | 120篇 |
水利工程 | 9篇 |
石油天然气 | 40篇 |
武器工业 | 1篇 |
无线电 | 196篇 |
一般工业技术 | 686篇 |
冶金工业 | 63篇 |
原子能技术 | 122篇 |
自动化技术 | 377篇 |
出版年
2024年 | 7篇 |
2023年 | 16篇 |
2022年 | 74篇 |
2021年 | 105篇 |
2020年 | 73篇 |
2019年 | 66篇 |
2018年 | 80篇 |
2017年 | 72篇 |
2016年 | 81篇 |
2015年 | 51篇 |
2014年 | 116篇 |
2013年 | 153篇 |
2012年 | 155篇 |
2011年 | 208篇 |
2010年 | 95篇 |
2009年 | 104篇 |
2008年 | 100篇 |
2007年 | 120篇 |
2006年 | 92篇 |
2005年 | 72篇 |
2004年 | 79篇 |
2003年 | 57篇 |
2002年 | 72篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 28篇 |
1998年 | 33篇 |
1997年 | 26篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1987年 | 8篇 |
1985年 | 7篇 |
1983年 | 6篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1977年 | 14篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1970年 | 6篇 |
1968年 | 9篇 |
1966年 | 4篇 |
1965年 | 5篇 |
1964年 | 6篇 |
排序方式: 共有2408条查询结果,搜索用时 203 毫秒
71.
Igor D.D. Curcio Antonio Puliafito Salvatore Riccobene Lorenzo Vita 《Multimedia Systems》1998,6(6):367-381
The relative simplicity of access to digital communications nowadays and the simultaneous increase in the available bandwidth
are leading to the definition of new telematic services, mainly oriented towards multimedia applications and interactivity
with the user. In the near future, a decisive role will be played in this scenario by the providers of interactive multimedia
services of the on-demand type, which will guarantee the end user a high degree of flexibility, speed and efficiency. In this
paper, some of the technical aspects regarding these service providers are dealt with, paying particular attention to the
problems of storing information and managing service requests. More specifically, the paper presents and evaluates a new storage
technique based on the use of disk array technology, which can manage both typical multimedia connections and traditional
requests. The proposed architecture is based on the joint use of the partial dynamic declustering and the information dispersal
algorithm, which are employed for the allocation and retrieval of the data stored on the disk array. We also define efficient
strategies for request management in such a way as to meet the time constraints imposed by multimedia sessions and guarantee
good response times for the rest of the traffic. The system proposed is then analyzed using a simulation approach. 相似文献
72.
The Semantic Web envisions a World Wide Web in which data is described with rich semantics and applications can pose complex queries. To this point, researchers have defined new languages for specifying meanings for concepts and developed techniques for reasoning about them, using RDF as the data model. To flourish, the Semantic Web needs to provide interoperability—both between sites with different terminologies and with existing data and the applications operating on them. To achieve this, we are faced with two problems. First, most of the world’s data is available not in RDF but in XML; XML and the applications consuming it rely not only on the domain structure of the data, but also on its document structure. Hence, to provide interoperability between such sources, we must map between both their domain structures and their document structures. Second, data management practitioners often prefer to exchange data through local point-to-point data translations, rather than mapping to common mediated schemas or ontologies.This paper describes the Piazza system, which addresses these challenges. Piazza offers a language for mediating between data sources on the Semantic Web, and it maps both the domain structure and document structure. Piazza also enables interoperation of XML data with RDF data that is accompanied by rich OWL ontologies. Mappings in Piazza are provided at a local scale between small sets of nodes, and our query answering algorithm is able to chain sets mappings together to obtain relevant data from across the Piazza network. We also describe an implemented scenario in Piazza and the lessons we learned from it. 相似文献
73.
We propose a numerical simulation technique to model the process of diffusional creep and stress relaxation that occurs in
Cu-damascene interconnects of integrated circuit devices in processing stage. The mass flow problem is coupled to the stress
analysis through vacancy flux and equilibrium vacancy concentration. The technique is implemented in a software package that
seamlessly integrates the problem-oriented code with commercially available finite element program MSC.Marc. It is utilized
to model the Coble creep phenomenon by introducing the nanoscale grain boundary region having the thickness on the order of
several layers of atoms. As an illustration, the two-dimensional problem of stress relaxation in a single grain subjected
to prescribed displacements and tractions is examined. 相似文献
74.
Sadek Joseph R.; Johnson Shannon A.; White Desirée A.; Salmon David P.; Taylor Kirsten I.; DeLaPena Jody H.; Paulsen Jane S.; Heaton Robert K.; Grant Igor 《Canadian Metallurgical Quarterly》2004,18(4):692
Remote memory was assessed in persons with HIV-associated dementia (HIV-D), probable Alzheimer's disease (AD), and Huntington's disease (HD) and in healthy controls. The clinical groups were similar in overall dementia severity. Each clinical group exhibited impairments on remote memory tests relative to controls; however, temporally graded memory loss with selective preservation of older information was observed in the AD group but not the HD or HIV-D group. Analysis of cued retrieval indicated a preferential cuing benefit for the HIV-D and HD groups relative to the AD group. The similar pattern of remote memory performance demonstrated by the HIV-D and HD groups is a novel finding and suggests a subcortically mediated retrograde amnesia in HIV-D. The temporally graded pattern and the abnormal cued retrieval performance in the AD group are consistent with a consolidation deficit associated with extrahippocampal (cortical) and hippocampal damage. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
Hydraulic resistance of fluids flowing in channels at supercritical pressures (survey) 总被引:3,自引:0,他引:3
Igor L. Pioro Romney B. Duffey Tyler J. Dumouchel 《Nuclear Engineering and Design》2004,231(2):187-197
This literature survey is devoted to hydraulic resistance of water and carbon dioxide flows at supercritical pressures. The objectives are to assess previous studies that were done in the area of hydraulic resistance of fluids at supercritical pressures flowing in channels of various geometries and to understand the specifics of pressure drop at these conditions. The literature search showed that the majority of experimental data were obtained in vertical tubes, some data were obtained in horizontal tubes and just a few of them in other flow geometries including bundles. In general, hydraulic resistance data are limited compared to the heat transfer data at supercritical pressures. Differences in pressure drop between supercritical and subcritical forced convection seem to be related to significant variations in thermophysical properties near the critical and pseudocritical points. Due to these variations, satisfactory analytical and numerical methods have not yet been developed especially in turbulent flows and at high heat fluxes. In general, the pressure drop in supercritical fluid flow consists of four components: pressure drop due to frictional resistance, due to local flow obstruction, due to acceleration of flow and due to gravity. The total pressure drop at supercritical pressures can be estimated using general correlations for pressure drop at subcritical pressures with correction factors for the effect of significant thermophysical properties variations and high heat fluxes. Only one paper was devoted to pressure drop in tight short bundles cooled with water at supercritical pressures. Therefore, more experimental work is needed to estimate the total pressure drop in various bundle designs with the objective of providing reliable information for designing supercritical water nuclear reactors. 相似文献
76.
Igor Maciejewski Tomasz Krzyzynski 《Journal of Mechanical Science and Technology》2018,32(11):5163-5170
A generalized model of vibration isolation systems with a human body in a seated position is developed. The system dynamics is modeled for a single-axis transmission of vibration, that is, longitudinal x, lateral y and vertical z, to limit whole-body vibration exposure. The developed model can be successfully employed to describe the propagation of vibration waves from the source to a vibrating object. The proposed mathematical model can be widely used to protect a human body against vibration. 相似文献
77.
78.
The paper focuses on quantitative evaluation of the microstructural changes - growth of the dislocation density - in stainless steel specimens subjected to fatigue loading. We propose to use electrical resistivity measurements for this goal. Change in electrical resistance of the specimens has been monitored in dependence on the number of fatigue cycles and the relative growth of the dislocation density was calculated from these data and known values of the specific resistivity of dislocations for iron. We also estimated the growth of dislocation density using analysis of Scanning Electron Microscopy (SEM) images of etched specimens. This estimate however appears to be unreasonably low, so that SEM may be used for qualitative analysis only. 相似文献
79.
80.
Romário Mauricio Urbanetto Nogueira Carlos Enrique Niño Bohórquez Igor Giacomelli Zanella 《Welding International》2017,31(3):161-172
Despite their similarity, the MIG/MAG and Tubular Electrode processes display particular features with regard to arc stability and variability in the characteristics of the beads. Thus, selection of one of these processes for a specific application will have to consider how these particular features affect the quality of the welds. To support this choice, the present study aimed to investigate how changing the average current affects the stability and regularity of metal transfer in welds carried out with constant voltage and pulsed current and compare the variability in the geometry and dilution of these welds. To achieve these aims, automatic welding was carried out, with steel ABNT 1020 as base metal and wire AWS ER70S-6 and AWS E71T-1 as filler metals. Besides the welds with variation in the average current, the tests involved determination of the parameters for occurrence of stable short circuiting, drop and pulsed transfer. The results showed that the voltage that gives the highest stability in short circuiting transfer is independent of the welding speed and increases with the wire speed, and also showed that welds made with hollow wire displayed greater variability compared to solid wire. 相似文献