全文获取类型
收费全文 | 12653篇 |
免费 | 871篇 |
国内免费 | 795篇 |
学科分类
工业技术 | 14319篇 |
出版年
2024年 | 20篇 |
2023年 | 76篇 |
2022年 | 138篇 |
2021年 | 221篇 |
2020年 | 263篇 |
2019年 | 181篇 |
2018年 | 243篇 |
2017年 | 334篇 |
2016年 | 402篇 |
2015年 | 530篇 |
2014年 | 805篇 |
2013年 | 650篇 |
2012年 | 944篇 |
2011年 | 1153篇 |
2010年 | 780篇 |
2009年 | 685篇 |
2008年 | 761篇 |
2007年 | 815篇 |
2006年 | 804篇 |
2005年 | 730篇 |
2004年 | 568篇 |
2003年 | 628篇 |
2002年 | 481篇 |
2001年 | 380篇 |
2000年 | 317篇 |
1999年 | 280篇 |
1998年 | 213篇 |
1997年 | 147篇 |
1996年 | 157篇 |
1995年 | 122篇 |
1994年 | 92篇 |
1993年 | 75篇 |
1992年 | 55篇 |
1991年 | 38篇 |
1990年 | 23篇 |
1989年 | 24篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
981.
《The Journal of Strategic Information Systems》2018,27(4):278-295
Digital ventures are formed around ideas that have digital artifacts at their core. We develop theory that explains how the composition of digital artifacts influences venture creation processes. First, we develop propositions that link differences in the embodiment and coupling of digital artifact components to tensions in venture creation process inputs, behaviors, and outputs. Second, we link compositional differences in digital artifacts to differences in venture creation process initiation, duration, and outcome. Our theorizing establishes a foundation for future research on digital artifacts within and beyond entrepreneurship contexts, and for future research on entrepreneurship within and beyond digital artifact contexts. 相似文献
982.
《Information and Software Technology》2014,56(11):1493-1507
BackgroundSoftware ecosystems emerged as means for several actors to jointly provide more value to the market than any of them can do on its own. Recently, software ecosystems are more often used to support the development of hardware-dependent solutions.ObjectivesThis work aims at studying barriers and bridges to participation in an ecosystem with substantial hardware dependencies.MethodWe conducted an interview-based case study of an ecosystem around Axis’ network video surveillance systems, interviewing 10 internal experts and 8 external representatives of 6 companies, complemented by document studies at Axis.ResultsMajor bridges to the ecosystem include end customer demands, open and transparent communication and relationship, as well as internal and external standardizations. Barriers include the two-tier business model, entry barriers and execution performance issues. Approximately half of the identified bridges and barriers could be considered hardware-dependent ecosystems specific.ConclusionOur results suggest that ecosystem leaders should share their sales channels with the ecosystem participants and focus on good communication and relationships as the dominant factors for the ecosystem participation. Moreover, we report that internal and external standardization can play a dual role, not only ease the development but also enable additional sales channels and new opportunities for the ecosystem participants. At the same time, the business model selected by the ecosystem leaders and performance, are identified as the main barriers to ecosystem participation. We believe that the business model barrier may be much more important for similar hardware-dependent software ecosystems. 相似文献
983.
目前,我国已基本具备进一步开展三网融合的技术条件、网络基础和市场空间,加快推进三网融合已进入关键时期。基于此,主要对三网融合技术的概念、关键技术以及广电网络的技术发展进行了分析探讨。 相似文献
984.
Francesca Arcelli Fontana 《Information Sciences》2011,181(7):1306-1324
It is well known that software maintenance and evolution are expensive activities, both in terms of invested time and money. Reverse engineering activities support the obtainment of abstractions and views from a target system that should help the engineers to maintain, evolve and eventually re-engineer it. Two important tasks pursued by reverse engineering are design pattern detection and software architecture reconstruction, whose main objectives are the identification of the design patterns that have been used in the implementation of a system as well as the generation of views placed at different levels of abstractions, which let the practitioners focus on the overall architecture of the system without worrying about the programming details it has been implemented with.In this context we propose an Eclipse plug-in called MARPLE (Metrics and Architecture Reconstruction Plug-in for Eclipse), which supports both the detection of design patterns and software architecture reconstruction activities through the use of basic elements and metrics that are mechanically extracted from the source code. The development of this platform is mainly based on the exploitation of the Eclipse framework and plug-ins as well as of different Java libraries for data access and graph management and visualization. In this paper we focus our attention on the design pattern detection process. 相似文献
985.
Mohamed Feredj Author Vitae Frédéric Boulanger Author Vitae 《Journal of Systems and Software》2009,82(1):112-120
Heterogeneous systems mix different technical domains such as signal processing, analog and digital electronics, software, telecommunication protocols, etc. Heterogeneous systems are composed of subsystems that are designed using different models of computation (MoC). These MoCs are the laws that govern the interactions of the components of a subsystem. The design of heterogeneous systems includes the design of each part of the system according to its specific MoC, and the connection of the parts in order to build the model representing the system. Indeed, this model allows the MoCs that govern different parts of system to coexist and interact.To be able to use a component which is specified according to a given MoC, under other, different MoCs, we can use either a hierarchical or a non-hierarchical approach, or we can build domain-specific components (DSC). However, these solutions present several disadvantages. This paper presents a new model of component, called domain-polymorph component (DPC). Such a component is atomic and is able to execute its core behavior, specified under a given MoC, under different host MoCs. This approach is not a competitor to the approaches above but is complementary. 相似文献
986.
Junfeng Jiang Zhigang Cao 《Frontiers of Electrical and Electronic Engineering in China》2009,4(2):145-148
The acknowledged mode radio link control (AM-RLC) protocol is one of the most important radio protocols in wideband code division
multiple access (WCDMA) and time division-synchronization code division multiple access (TD-SCDMA) mobile communication systems.
A modified AM-RLC scheme with adaptive acknowledgement interval is proposed. At the receiver, the acknowledgement interval
is dynamically changed according to the channel status. The simulation results show that the proposed AM-RLC scheme outperforms
the fixed acknowledgement interval AM-RLC scheme in terms of frame delivery delay and protocol overhead.
__________
Translated from Journal on Communications, 2008, 29(3): 119–122 [译自: 通信学报] 相似文献
987.
本文主要研究了民航无线电导航信号监测方法,结合日常监测的工作经验,以乌鲁木齐国际机场NDB导航台为例多次测试分析,详细给出了针对NDB系统导航信号进行监测的技术方法。 相似文献
988.
介绍了一种基于频分复用信号的宽带数字收发设计。根据软件无线电基本理论给出了系统的硬件具体实现和软件处理流程,描述了基于FPGA平台的并行FIR滤波器和并行CIC滤波器的高效实现方法。给出了宽带数字收发系统的仿真和测试结果。该系统硬件结构简洁,逻辑资源开销小,通用性和扩展性强。 相似文献
989.
针对宽带频谱认知无线电环境中,传统能量检测法在信噪比较低时,容易出现误检而使系统的检测性能下降的问题,文中提出了一种新型高性能的协作频谱感知算法,它是基于压缩理论的多节点频谱感知方法,各节点之间采用基于双判决门限的协作方式。仿真结果显示,双门限协作压缩频谱感知算法在低信噪比的情况下,检测性能明显优于传统能量检测法。 相似文献
990.
现今,大型的射电望远镜项目在各个国家都得到了普遍的重视。但是,市场上需求越来越多的是小型的射电望远镜或者科普类的射电望远镜。大型的射电望远镜天线,指向精度要求高,观测的过程中需要做各种实时修正,允许投资较多于控制模块,大多采用计算机闭环程序控制。虽然在大型的射电望远镜上这样的控制方法取得了很好的效果,但是对于小型的射电望远镜来说昂贵和复杂的闭环控制方式并不是适用。所以,本文通过实践调研,通过按键控制电路来控制单片机的工作模式来代替原来庞大的控制台,并经过大量的调试,实现了可适用于小型天线的控制系统。 相似文献