全文获取类型
收费全文 | 12563篇 |
免费 | 1377篇 |
国内免费 | 1260篇 |
专业分类
电工技术 | 361篇 |
技术理论 | 4篇 |
综合类 | 2511篇 |
化学工业 | 283篇 |
金属工艺 | 65篇 |
机械仪表 | 393篇 |
建筑科学 | 3227篇 |
矿业工程 | 277篇 |
能源动力 | 133篇 |
轻工业 | 219篇 |
水利工程 | 158篇 |
石油天然气 | 132篇 |
武器工业 | 58篇 |
无线电 | 1879篇 |
一般工业技术 | 1139篇 |
冶金工业 | 198篇 |
原子能技术 | 4篇 |
自动化技术 | 4159篇 |
出版年
2024年 | 83篇 |
2023年 | 222篇 |
2022年 | 401篇 |
2021年 | 441篇 |
2020年 | 519篇 |
2019年 | 397篇 |
2018年 | 290篇 |
2017年 | 364篇 |
2016年 | 405篇 |
2015年 | 482篇 |
2014年 | 1024篇 |
2013年 | 927篇 |
2012年 | 1230篇 |
2011年 | 1104篇 |
2010年 | 922篇 |
2009年 | 868篇 |
2008年 | 838篇 |
2007年 | 1009篇 |
2006年 | 845篇 |
2005年 | 671篇 |
2004年 | 508篇 |
2003年 | 414篇 |
2002年 | 309篇 |
2001年 | 260篇 |
2000年 | 135篇 |
1999年 | 103篇 |
1998年 | 88篇 |
1997年 | 72篇 |
1996年 | 60篇 |
1995年 | 53篇 |
1994年 | 36篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1961年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
The recent trend of integration among new network services such as the long-term evolution (LTE) based on internet protocol (IP) needs reputable analyses and prediction information on the internet traffic. The IP along with increased internet traffics due to expanding new service platforms such as smartphones will reflect policies such as network QoS according to new services. The establishment of monitoring methods and analysis plans is thus required for the development of internet traffics that will analyze their status and predict their future. The paper with the speed of Internet traffic model is developed for monitoring the state of the experiment and verified. The problem is that the proposed service Internet service provider (ISP) to resolve the conflict between the occurrences can be considerably Internet traffic and that the state of data may be helpful in understanding. The paper advancement policy to reflect the network traffic volume of Internet services and users irradiation with increased traffic due to the development and management of the analysis was carried out experimental measurements. 相似文献
2.
The Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods simultaneously. The Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD) differs from the VRPSPD in that the customers may have either pickup or delivery demand. However, the solution approaches proposed for the VRPSPD can be directly applied to the VRPMPD. In this study, an adaptive local search solution approach is developed for both the VRPSPD and the VRPMPD, which hybridizes a Simulated Annealing inspired algorithm with Variable Neighborhood Descent. The algorithm uses an adaptive threshold function that makes the algorithm self-tuning. The proposed approach is tested on well-known VRPSPD and VRPMPD benchmark instances derived from the literature. The computational results indicate that the proposed algorithm is effective in solving the problems in reasonable computation time. 相似文献
3.
Drunk drivers are a menace to themselves and to other road users, as drunk driving significantly increases the risk of involvement in road accidents and the probability of severe or fatal injuries. Although injuries and fatalities related to road accidents have decreased in recent decades, the prevalence of drunk driving among drivers killed in road accidents has remained stable, at around 25% or more during the past 10 years. Understanding drunk driving, and in particular, recidivism, is essential for designing effective countermeasures, and accordingly, the present study aims at identifying the differences between non-drunk drivers, drunk driving non-recidivists and drunk driving recidivists with respect to their demographic and socio-economic characteristics, road accident involvement and other traffic and non-traffic-related law violations. This study is based on register-data from Statistics Denmark and includes information from 2008 to 2012 for the entire population, aged 18 or older, of Denmark. The results from univariate and multivariate statistical analyses reveal a five year prevalence of 17% for drunk driving recidivism, and a significant relation between recidivism and the drunk drivers’ gender, age, income, education, receipt of an early retirement pension, household type, and residential area. Moreover, recidivists are found to have a higher involvement in alcohol-related road accidents, as well as other traffic and, in particular, non-traffic-related offences. These findings indicate that drunk driving recidivism is more likely to occur among persons who are in situations of socio-economic disadvantage and marginalisation. Thus, to increase their effectiveness, preventive measures aiming to reduce drunk driving should also address issues related to the general life situations of the drunk driving recidivists that contribute to an increased risk of drunk driving recidivism. 相似文献
4.
文章介绍了新一代IP骨干网上的IP QoS实现技术,论述了集成业务(IntServ)与差分业务(DiffServ)解决方案的特点,详细介绍了相关的队列管理与排队机制。并结合多协议标签交换(MPLS)技术的最新发展,阐述了综合多协议标签交换流量工程与DiffServ技术体系端到端IP QoS的实现。 相似文献
5.
降低成品油二次物流运输成本的思考 总被引:4,自引:0,他引:4
介绍了传统成品油进货和管理模式存在的诸如成品油物流以行政区划、中问环节多、信息化程度不高、运输路线未优化造成物流成本提高等问题。提出要降低成品油二次物流运输成本,当务之急是加强成品油物流的信息化建设;调整管理模式,打破行政区域界限,开展经济辐射半径内的库站物流配送;引进竞争机制,打破运输垄断,一、二次物流结合,大、小车型搭配,提高运营效率;做好运杂费全面预算、核算及运行费用的过程控制。 相似文献
6.
7.
可持续发展战略指导下的轨道交通规划与评价 总被引:9,自引:0,他引:9
提出了轨道交通规划与评价在实施可持续发展战略过程中需要研究的问题,研究重点是轨道交通规划与评价方法体系和环境对策,研究了轨道交通规划目标的变化、轨道交通规划优化决策理论与方法、轨道交通规划中的环境影响评价、城市轨道交通网络的合理规划、城际轨道交通——客运专线/高速铁路线路基本走向的规划、轨道交通规划可持续发展的评价指标体系概念框架、轨道交通系统可持续发展的能力建设问题等,并通过实例验证了所建立的理论方法体系和模型体系;不仅进行了有关理论和方法的探讨,而且以面向实际应用为目标,开发了相应的软件系统,为轨道交 相似文献
8.
首先简单叙述了C3I系统在军事上的应用,然后针对我国各类大中型城市的交通现状及特点,涉及到城市交通管理、道路管理、车辆管理和城市交通管理指挥中心站、区域指挥站及各交叉路口控制站,提出将C3I系统体系结构运用到民用城市交通管理中去的构想。 相似文献
9.
长输管道工程是以线路管道与沿途站场为主要内容的建设工程,其物资配送有着不同于一般物流管理的特点,点多线长,且交通不便.文章结合西南成品油管道建设工程的物资配送实践,总结出长输管道物资配送的类型,并从机构设置、计划编制、台账和报表管理等方面介绍了物资配送的管理内容及经验,实践证明,这种物资配送方法不但使业主的物资管理人员大为减少,而且使长输管道工程的物资供应更加及时有序. 相似文献
10.
Disassembly sequence planning in a disassembly cell context 总被引:2,自引:0,他引:2
In this paper a two-phase approach is proposed for determining the optimal disassembly sequence when the disassembly system has a cellular configuration. Operations are first grouped into cells based on the resources they require with the goal of minimizing machine acquisition costs. The aim is to group together those operations that use similar equipment in order to achieve good utilization levels of such equipment. A maximum cell size may be imposed. Once the cells have been formed and the operations have been assigned to them, a metaheuristic algorithm (namely GRASP) is used to search for the disassembly sequence for each product that leads to the minimum number of intercellular movements. To account for uncertainty regarding the condition in which the product may arrive, each disassembly task is assumed to be required with a certain probability, regardless of the other tasks. AND/OR precedence relations among the disassembly tasks are also considered. The proposed approach is illustrated on a randomly generated disassembly problem. 相似文献