全文获取类型
收费全文 | 3436篇 |
免费 | 214篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 46篇 |
化学工业 | 925篇 |
金属工艺 | 62篇 |
机械仪表 | 142篇 |
建筑科学 | 156篇 |
矿业工程 | 10篇 |
能源动力 | 158篇 |
轻工业 | 553篇 |
水利工程 | 21篇 |
石油天然气 | 16篇 |
无线电 | 226篇 |
一般工业技术 | 495篇 |
冶金工业 | 155篇 |
原子能技术 | 17篇 |
自动化技术 | 670篇 |
出版年
2024年 | 13篇 |
2023年 | 42篇 |
2022年 | 94篇 |
2021年 | 175篇 |
2020年 | 131篇 |
2019年 | 156篇 |
2018年 | 137篇 |
2017年 | 131篇 |
2016年 | 153篇 |
2015年 | 111篇 |
2014年 | 169篇 |
2013年 | 298篇 |
2012年 | 215篇 |
2011年 | 274篇 |
2010年 | 203篇 |
2009年 | 195篇 |
2008年 | 158篇 |
2007年 | 153篇 |
2006年 | 136篇 |
2005年 | 99篇 |
2004年 | 77篇 |
2003年 | 66篇 |
2002年 | 64篇 |
2001年 | 40篇 |
2000年 | 42篇 |
1999年 | 31篇 |
1998年 | 38篇 |
1997年 | 38篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有3652条查询结果,搜索用时 15 毫秒
21.
Interfacial structure plays a great role in solder joint reliability. In solder joints on Cu, not only is Kirkendall voiding at the solder/Cu interface a concern, but also the growth of interfacial Cu–Sn intermetallic compounds (IMCs). In this work, evolution of microstructure in the interfacial region was studied after thermal aging at 100–150 °C for up to 1000 h. Special effort was made during sample preparation to reveal details of the interfacial structure. Thickness of the interfacial phases was digitally measured and the activation energy was deduced for the growth of Cu3Sn. Kirkendall voids formed at the Cu/Cu3Sn interface as well as within the Cu3Sn layer. The thickness of Cu3Sn significantly increased with aging time, but that of Cu6Sn5 changed a little. The interfacial Cu3Sn layer was found growing at the expense of Cu6Sn5. Evolution of the interfacial structure during thermal aging is discussed. 相似文献
22.
Denis Alcides Rezende Gilberto dos Santos Madeira Leonardo de Souza Mendes Gean Davis Breda Bruno Bogaz Zarpelão Frederico de Carvalho Figueiredo 《Telematics and Informatics》2014
Making information and telecommunications available is a permanent challenge for cities concerned to their social, urban and local planning and development, focused on life quality of their citizens and on the effectiveness of public management. Such a challenge requires the involvement of everyone in the city. The objective is to describe the information and telecommunications project from the planning of a digital city carried out in Vinhedo-SP, Brazil. It was built as a telecommunications infrastructure of the kind of “open access metropolitan area networks” which enables the integration of citizens in a single telecommunications environment. The research methodology was emphasized by a case study which turned to be a research-action, comprising the municipal administration and its local units. The results achieved describe, by means of a methodology, the phases, sub-phases, activities, approval points and resulting products, and formalize their respective challenges and difficulties. The contributions have to do with the practical feasibility of the project and execution of its methodology. The conclusion reiterates the importance of the project, collectively implemented and accepted, as a tool to help the management of cities, in the implementation of Strategic Digital City Projects, in the decisions of public administration managers, and in the quality of life of their citizens. 相似文献
23.
Castro Mateus B. Souza Raphael R. N. Junior Agord M. P. Lima Eduardo R. Manera Leandro T. 《Analog Integrated Circuits and Signal Processing》2021,109(3):647-656
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The... 相似文献
24.
Intelligent Monitoring for Adaptation in Grid Applications 总被引:1,自引:0,他引:1
Reed D.A. Mendes C.L. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2005,93(2):426-435
Grid applications access distributed, and often shared, resources. One consequence of this resource sharing is that measured application performance can vary widely and in unexpected ways. Determining the causes of poor performance, due to either anomalous application behavior or contention for shared resource use, and adapting to changing circumstances are critical to creation of robust Grid applications. Performance contracts and real-time adaptive control are two mechanisms to realize soft performance guarantees in Grid environments. Performance contracts formalize the relationship between application performance needs and resource capabilities. During execution, contract monitors use performance data to verify that expectations are met. When the contracted specifications are not satisfied, the system can choose to either adapt the application to available resources or reschedule the application on a new set of resources that can satisfy the original contract specifications. We describe an infrastructure for Grid application contract development and monitoring. This infrastructure, based on the Autopilot toolkit, provides flexible and scalable tools to assess both application and system behavior. 相似文献
25.
Eduardo Augusto Bezerra Fabian Vargas Michael Paul Gough 《Journal of Electronic Testing》2001,17(2):163-174
This paper revises and introduces to the field of reconfigurable computer systems, some traditional techniques used in the fields of fault-tolerance and testing of digital circuits. The target area is that of on-board spacecraft electronics, as this class of application is a good candidate for the use of reconfigurable computing technology. Fault tolerant strategies are used in order for the system to adapt itself to the severe conditions found in space. In addition, the paper describes some problems and possible solutions for the use of reconfigurable components, based on programmable logic, in space applications. 相似文献
26.
The concentrations of individual and total glucosinolates were measured in four types of Portuguese cabbage and in one hybrid white cabbage before and after cooking. Typical Portuguese culinary procedures include boiling the cabbage for 10 min but for particular kale types the leaves are first shredded then boiled for 5 min (Caldo verde). Analysis of the fresh cabbage, cooked leaves and cooking water showed that the glucosinolate content of the cabbages is reduced by more than 50%. Almost all of this loss is accounted for as intact glucosinolates in the cooking water, normally used for soups in Portugal. 相似文献
27.
Luis E. Juanicó Fabián Rinalde Eduardo Taglialavore Marcelo Molina 《Journal of Electronic Materials》2013,42(7):1789-1795
This paper presents a new thermogenerator based on moderate-temperature (up to 175°C) BiTe modules available on the open market. Despite this handicap relative to commercial thermogenerators based on high-temperature proprietary-technology PbBi modules (up to 560°C), this new design may become economically competitive due to its innovative thermal sink. Our thermal sink is based on a free-convection water loop built with standard tubing and household hot-water radiators, leading to a more practical, modular design. So, the specific cost of about 55,000 USD/kW obtained for this 120-W prototype is improved to 33,000 USD/kW for a 1-kW unit, which represents about half the price of commercial thermogenerators. Moreover, considering recently launched BiTe modules (that withstand up to 320°C), our proposition could have an even more favorable outlook. 相似文献
28.
Claudio Ferraro Esther Garcia‐Tuñon Victoria G. Rocha Suelen Barg Maria Dolores Fariñas Tomas E. Gomez Alvarez‐Arenas Giorgio Sernicola Finn Giuliani Eduardo Saiz 《Advanced functional materials》2016,26(10):1636-1645
The directional freezing of microfiber suspensions is used to assemble highly porous (porosities ranging between 92% and 98%) SiC networks. These networks exhibit a unique hierarchical architecture in which thin layers with honeycomb‐like structure and internal strut length in the order of 1–10 μm in size are aligned with an interlayer spacing ranging between 15 and 50 μm. The resulting structures exhibit strengths (up to 3 MPa) and stiffness (up to 0.3 GPa) that are higher than aerogels of similar density and comparable to other ceramic microlattices fabricated by vapor deposition. Furthermore, this wet processing technique allows the fabrication of large‐size samples that are stable at high temperature, with acoustic impedance that can be manipulated over one order of magnitude (0.03–0.3 MRayl), electrically conductive and with very low thermal conductivity. The approach can be extended to other ceramic materials and opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions. 相似文献
29.
Recently, preemption techniques have attracted considerable attention as a means to provide differentiated quality of service
in optical burst switching (OBS) networks. This paper is focused on the analysis of preemption probabilities for bursts within
the same priority class. As proposed by Vokkarane and Jue ((2003)* IEEE J Select Areas Commun 21(7): 1198–1209) an incoming
burst will preempt the burst in service, within the same priority class, if the residual length of the burst in service is
smaller than the incoming burst length. For a general case with wavelength conversion, the preemption probability of contending
bursts with a generic service distribution, not necessarily exponential, is analyzed. First, we show that the size distribution
for the preempting bursts is shifted to larger values, in comparison to the original burst size distribution. Second, we obtain
an upper and lower bound for the preemption probability. Finally, the asymptotic behavior of the OBS switch is analyzed showing
that preemption will always occur for a very large number of wavelengths. 相似文献
30.
The degradation of end-to-end quality of service (QoS) on mobile users is becoming a common issue for IEEE 802.11 infrastructure-based networks in crowded areas. This research tackles the issue by employing an SDN framework on an integrated wireless/wired environment. Thereby, we present the development and implementation of a system that performs user management by analyzing the network load from the OpenFlow statistics, as well as the wireless information collected from the associated users. In order to analyse the behaviour of the proposed user migration algorithm, we evaluate the system under scenarios with different traffic load and user session duration. From the experiments, we observed that in several cases wireless users get a considerable QoS improvement at the application layer (up to 30% improvement in throughput and up to 20% in delay in our simulations) once the system is activated. Based on the results, we present an analysis on how and when user migration in multi-access point IEEE 802.11 networks can be most effective. 相似文献