全文获取类型
收费全文 | 25951篇 |
免费 | 3604篇 |
国内免费 | 2856篇 |
专业分类
电工技术 | 3172篇 |
技术理论 | 4篇 |
综合类 | 3124篇 |
化学工业 | 755篇 |
金属工艺 | 304篇 |
机械仪表 | 1130篇 |
建筑科学 | 1999篇 |
矿业工程 | 509篇 |
能源动力 | 796篇 |
轻工业 | 564篇 |
水利工程 | 478篇 |
石油天然气 | 484篇 |
武器工业 | 219篇 |
无线电 | 5287篇 |
一般工业技术 | 1467篇 |
冶金工业 | 565篇 |
原子能技术 | 65篇 |
自动化技术 | 11489篇 |
出版年
2024年 | 131篇 |
2023年 | 460篇 |
2022年 | 698篇 |
2021年 | 883篇 |
2020年 | 940篇 |
2019年 | 685篇 |
2018年 | 663篇 |
2017年 | 861篇 |
2016年 | 974篇 |
2015年 | 1203篇 |
2014年 | 1979篇 |
2013年 | 1722篇 |
2012年 | 2134篇 |
2011年 | 2185篇 |
2010年 | 1890篇 |
2009年 | 1964篇 |
2008年 | 1936篇 |
2007年 | 2049篇 |
2006年 | 1907篇 |
2005年 | 1636篇 |
2004年 | 1292篇 |
2003年 | 1110篇 |
2002年 | 819篇 |
2001年 | 658篇 |
2000年 | 494篇 |
1999年 | 279篇 |
1998年 | 197篇 |
1997年 | 130篇 |
1996年 | 111篇 |
1995年 | 97篇 |
1994年 | 75篇 |
1993年 | 51篇 |
1992年 | 43篇 |
1991年 | 33篇 |
1990年 | 22篇 |
1989年 | 19篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1977年 | 3篇 |
1972年 | 2篇 |
1964年 | 1篇 |
1962年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
概述了美国国家材料咨询委员会报告《未来加工工业的材料技术-管理战略和研究机会》要点,对比了美国“未来工业”与中国“传统产业”,鉴于两者的诸多相似特征,指出了该报告中所提出的“市场推动”和“共性技术”开发策略对于中国传统产业改造的借鉴意义,并探讨了报告中所建议的项目管理战略对于中国新材料研发工作的启示。 相似文献
102.
风险评估在加氢装置的应用 总被引:1,自引:0,他引:1
广州石化加氢(二)B装置采用基于风险的检测(RBI)技术,对装置的静设备与管道使用RBI软件RB—eye进行定量、定性分析以及失效概率、失效后果的评价,评估了装置的风险情况,制定了装景基于风险分析的检验策略。 相似文献
103.
多跳无线网路由协议研究进展 总被引:13,自引:0,他引:13
移动计算和无线通信的飞速发展为无线网络的应用开辟了美好前景.作为一种没有基础设施的无线网络,多跳无线网在战场、紧急救援等场合具有得天独厚的优势。多跳无线网路由协议的主要作用是监控网络拓扑变化、交换路由信息、产生和维护路由,它是目前的研究热点之一。本介绍了该领域的研究进展,首先叙述多跳无线网的8个特点及其对路由协议的7个要求.然后描述21种路由协议的原理并比较它们的特性,最后阐述了10个研究方向。 相似文献
104.
In this paper we propose a new protocol called time-space label switching protocol (TSL-SP) in optical burst switching (OBS), and define the terms time-space label (TSL) and time-space routing (TSR). An important concept of response time is introduced in the time label mechanism. The TSL-SP is a new technology that can quickly and efficiently forward data with a label on the optical networks. A two-dimension label switched path (TD-LSP) can be set up, that is maintained and deleted by the TSL-SP. For clearly illuminating the operation principles of the TSL-SP, we propose a new approach of orthogonal time-space coordinates in which the vertical coordinate is the space label and the horizontal coordinate is the time label. The proposed TD-LSP can dramatically reduce the routing failure probability and greatly improve the link network efficiency compared with other signaling protocols. Moreover, we define the time-space label control plane that can achieve the higher efficiency. When the TSL-SP is applied to networks, switching performance can be improved by two orders compared to the switching performance with the conventional OBS signaling protocols. The fundamental goal of TSL-SP is to band the signaling and routing functions together closely. Also, the TSL-SP can reduce the complexity of the network, support automatic service offering, and provide traffic engineering. 相似文献
105.
106.
XU Li~ 《中国邮电高校学报(英文版)》2004,11(4)
MANET(Mobile Ad Hoc Network)is a collection of wireless mobile nodes forming a temporary communica-tion network without the aid of any established infrastructure or centralized administration.The lifetime of a MANETdepends on the battery resources of the mobile nodes.So energy consumption may one of important design criterions forMANET.With changing the idle model to sleep model in the grid environment,this paper proposes a new energy-awarerouting protocol.Performance simulation results show that the proposed strategy can dynamic balance the traffic load in-side the whole network,extend the lifetime of a MANET,and without decreasing the throughput ratio. 相似文献
107.
多协议标记交换MPLS通过在传统的IP包里加入标记,使原来依赖于IP头标分析的路由转发转变为依赖于标记的转发,这不仅可以大大地提高IP包的转发速度,更可使传统IP网络具有QoS能力。本文深入分析了标记转发的思想.并指出了MPLS实现其优点所用的机制与原理。 相似文献
108.
A routing framework for providing robustness to node failures in mobile ad hoc networks 总被引:2,自引:0,他引:2
Nodes in a mobile ad hoc network are often vulnerable to failures. The failures could be either due to fading effects, battery drainage, or as a result of compromised nodes that do not participate in network operations. Intermittent node failures can disrupt routing functionalities. As such, it is important to provide redundancy in terms of providing multiple node-disjoint paths from a source to a destination. In line with this objective, we first propose a modified version of the widely studied ad hoc on-demand distance vector routing protocol to facilitate the discovery of multiple node-disjoint paths from a source to a destination. We find that very few of such paths can be found. Furthermore, as distances between sources and destinations increase, bottlenecks inevitably occur and thus, the possibility of finding multiple paths is considerably reduced. We conclude that it is necessary to place what we call reliable nodes (in terms of both being robust to failure and being secure) in the network to support efficient routing operations. We propose a deployment strategy that determines the positions and the trajectories of these reliable nodes such that we can achieve a framework for reliably routing information. We define a notion of a reliable path which is made up of multiple segments, each of which either entirely consists of reliable nodes, or contains a preset number of multiple paths between the end points of the segment. We show that the probability of establishing a reliable path between a random source and destination pair increases tremendously even with a small number of reliable nodes when we use our algorithm to appropriately position these reliable nodes. 相似文献
109.
北电网络提供的Contivity解决方案不仅可以使用户建立各种类型的VPN,而且还可以把这些VPN集成到未来的融合话音和数据的网络中。该方案已实现了安全路由选择;可通过多种技术支持鉴权功能,从而实现安全接入;允许用户使用其各自的安全性配置文件设置;其设计中没有“后门”,重点介绍了Contivity 2700网关的主要特征及其优势。 相似文献
110.