全文获取类型
收费全文 | 4603篇 |
免费 | 359篇 |
国内免费 | 275篇 |
专业分类
电工技术 | 218篇 |
综合类 | 543篇 |
化学工业 | 27篇 |
金属工艺 | 12篇 |
机械仪表 | 130篇 |
建筑科学 | 321篇 |
矿业工程 | 50篇 |
能源动力 | 80篇 |
轻工业 | 81篇 |
水利工程 | 81篇 |
石油天然气 | 14篇 |
武器工业 | 11篇 |
无线电 | 813篇 |
一般工业技术 | 175篇 |
冶金工业 | 317篇 |
原子能技术 | 5篇 |
自动化技术 | 2359篇 |
出版年
2024年 | 17篇 |
2023年 | 35篇 |
2022年 | 63篇 |
2021年 | 81篇 |
2020年 | 132篇 |
2019年 | 66篇 |
2018年 | 96篇 |
2017年 | 111篇 |
2016年 | 121篇 |
2015年 | 155篇 |
2014年 | 297篇 |
2013年 | 333篇 |
2012年 | 307篇 |
2011年 | 350篇 |
2010年 | 328篇 |
2009年 | 312篇 |
2008年 | 437篇 |
2007年 | 426篇 |
2006年 | 338篇 |
2005年 | 297篇 |
2004年 | 226篇 |
2003年 | 155篇 |
2002年 | 98篇 |
2001年 | 72篇 |
2000年 | 72篇 |
1999年 | 52篇 |
1998年 | 33篇 |
1997年 | 28篇 |
1996年 | 27篇 |
1995年 | 31篇 |
1994年 | 20篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1973年 | 4篇 |
1966年 | 5篇 |
1956年 | 6篇 |
1955年 | 6篇 |
1954年 | 2篇 |
排序方式: 共有5237条查询结果,搜索用时 15 毫秒
91.
LIU Gang GOU Dingyong WU Shiqi 《中国电子科技》2003,1(1)
A new handover strategy named minimal-hops handover(MHH) strategy for the lowearth orbit(LEO) satellite constellations networks equipped with inter-satellite links(ISLs) is proposed.MHH strategy,which is based on the hops of the end-to-end connection paths and makes good use of theregularity of the constellation network topology,can appropriately combine the handover procedure withrouting and efficiently solve the inter-satellite handover issue.Moreover,MHH strategy can providequality of services(QoS) guarantees to some extent.The system performances of the MHH strategy,suchas time propagation delay and handover frequency,are evaluated and compared with that of otherprevious strategies.The simulation results show that MHH strategy performs better than other previoushandover strategies. 相似文献
92.
93.
Web services collaborative environments are highly automatic, dynamic, and heterogeneous. These characteristics always lead to high risks of services for interaction participants. Hence, it becomes one of the most important things to guarantee that the private information in cross-domain services is not illegally collected, used, disclosed or stored when the Web services are required to combine secure composition. This paper proposes the privacy-aware role based access control model for Web services composition (WSC-PRBAC), which provides protection for private data of users in composite service. The element services are divided into local services and outside services. Because the local service is authorized by users, it is exactly different from other services in the composition. To avoid sending private information to other outside services directly, we define global roles to help access these data in local service. Using global roles can realize a more strict control of the private data. In the end, the experiment and analysis of the proposed model show its and efficiency. 相似文献
94.
In passive optical networks (PONs), the low effectiveness in terms of service utilization and network evolution have been
important design issues. In this article, we introduce a hybrid access network architecture, so called scalable WDM-based
Ethernet hybrid-PON (SWE-PON), which features a wavelength-division-multiplexed (WDM) feeder network using a combination of
tunable laser device (TLD) and cyclic arrayed waveguide grating (AWG) and time-division-multiplexed (TDM) distribution network
based on a reflective transmission mode. Necessary conditions needed to guarantee flawless packet transmission through normal
WDM/TDM hierarchical PONs including the SWE-PON, are analyzed. We also propose a hierarchical fair time-window allocation
mechanism which coordinates wavelength assignment and time-window bandwidth allocation so that high link utilization and fair
bandwidth allocation are guaranteed in every multiplexing level.
相似文献
Minho KangEmail: |
95.
与移动网的结合是智能网研究的新方向。ETSI提出的CAMEL方案用来在GSM网络中提供智能业务。北京邮电大学程控交换与通信网国家重点实验室在其已成功应用的固定智能网CIN02系统的基础上,参照CAMEL方案推出了CMIN02移动智能网系统。现在该系统可提供预付费业务、移动虚拟专用网业务和通用接入码业务。 相似文献
96.
The problem of admission control in a DS-CDMA network carrying a heterogeneous mix of traffic is addressed. In an interference limited system such as DS-CDMA, admission of a new user impacts the performance of all other users, as well as the system capacity. The admission process is concerned with two factors: (1) maintaining the QoS of active users, (2) allocating bandwidth to new users. We propose a simple power control algorithm and prove that it is optimal in the sense of maintaining active link quality while maximizing free capacity for new admissions. The algorithm scales the powers of active links appropriately to achieve link protection and improved tolerance of the link to new interference from bursty sources. This algorithm can be used to overlay bursty packet data services without compromising QoS of active circuits. 相似文献
97.
随着高流量4G计划的普及以及在线游戏,在线视频,即时消息等移动互联网应用的快速发展,4G网络负载变得越来越繁重。在网络资源不足的情况下,电信运营商必须为不同类型的用户和服务提供差异化的网络服务,以吸引和留住高价值用户,提高网络的竞争力。本文尝试以无线资源利用率为触点,联动核心网与无线侧能力,通过实施基于Qo S(Quality Of Service)管控的差异化调度方案,在无线网络资源不足时,为不同类型的4G用户提供不同的网络感知服务。 相似文献
98.
Technology and innovation become more important determinants of corporate competitiveness, and the telecommunications sector is no exception. A good example is found in the development of the mobile phones. Technological development, embodied in innovative functions developed from the first (1G) to third generation (3G) systems, has played significantly important roles in the growth and upheavals of the Japanese mobile phone market. In addition, development in contents, value-added services which are supplied by related firms formed in the vertical structure, charging systems, handset development; all these have made this small gadget an increasingly important part of daily life. 相似文献
99.
分析了Web Services事务流处理中常用的FCFS技术,并对采用这种技术造成的服务类型不加区分,对不同事务不分轻重缓急统一处理,服务效率不高,服务质量不好的问题进行了探讨。然后提出了用优化的RR调度算法来解决该问题的想法,并将FCFS与优化后的RR调度算法的性能进行了比较,并证明了该算法解决Web Services事务流处理服务质量不好问题的有效性。 相似文献
100.
Unique Features of Mobile Commerce 总被引:1,自引:0,他引:1
While the market potentials and impacts of web-based e-commerce are still in the ascendant, the advances in wireless technologies and mobile networks have brought about a new business opportunity and research attention, what is termed mobile commerce. Commonly, mobile commerce is considered to be another new application of existing web-based e-commerce onto wireless networks, but as an independent business area, mobile commerce has its own advantages and challenges as opposed to traditional e-commerce applications. This paper focuses on exploring the unique features of mobile commerce as compared with traditional e-commerce. Also, there are still some limitations arisen in m-commerce in contrast to web-based e-commerce. Finally, current state of mobile commerce in Japan is presented in brief, with an introduction of several cases involving mobile commerce applications in today's marketplace. 相似文献