全文获取类型
收费全文 | 2744篇 |
免费 | 212篇 |
国内免费 | 160篇 |
专业分类
电工技术 | 186篇 |
综合类 | 492篇 |
化学工业 | 111篇 |
金属工艺 | 28篇 |
机械仪表 | 106篇 |
建筑科学 | 496篇 |
矿业工程 | 98篇 |
能源动力 | 48篇 |
轻工业 | 83篇 |
水利工程 | 126篇 |
石油天然气 | 55篇 |
武器工业 | 40篇 |
无线电 | 313篇 |
一般工业技术 | 212篇 |
冶金工业 | 87篇 |
原子能技术 | 31篇 |
自动化技术 | 604篇 |
出版年
2024年 | 7篇 |
2023年 | 13篇 |
2022年 | 28篇 |
2021年 | 36篇 |
2020年 | 45篇 |
2019年 | 47篇 |
2018年 | 40篇 |
2017年 | 65篇 |
2016年 | 71篇 |
2015年 | 75篇 |
2014年 | 195篇 |
2013年 | 145篇 |
2012年 | 173篇 |
2011年 | 215篇 |
2010年 | 156篇 |
2009年 | 170篇 |
2008年 | 161篇 |
2007年 | 252篇 |
2006年 | 225篇 |
2005年 | 161篇 |
2004年 | 143篇 |
2003年 | 148篇 |
2002年 | 81篇 |
2001年 | 76篇 |
2000年 | 50篇 |
1999年 | 47篇 |
1998年 | 47篇 |
1997年 | 39篇 |
1996年 | 39篇 |
1995年 | 32篇 |
1994年 | 28篇 |
1993年 | 17篇 |
1992年 | 21篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有3116条查询结果,搜索用时 15 毫秒
1.
Wei Xu Ziping Huang Weimin Han Wenbin Chen Cheng Wang 《Computers & Mathematics with Applications》2019,77(10):2596-2607
In this paper numerical approximation of history-dependent hemivariational inequalities with constraint is considered, and corresponding Céa’s type inequality is derived for error estimate. For a viscoelastic contact problem with normal penetration, an optimal order error estimate is obtained for the linear element method. A numerical experiment for the contact problem is reported which provides numerical evidence of the convergence order predicted by the theoretical analysis. 相似文献
2.
Nuclear power plant Safety analysis using coupled 3D neutron kinetics/thermal-hydraulic codes technique is increasingly used nowadays. Actually, the use of this technique allows getting less conservatism and more realistic simulations of the physical phenomena. The challenge today is oriented toward the application of this technique to the operating conditions of nuclear research reactors. In the current study, a three-Dimensional Neutron Kinetics and best estimate Thermal-Hydraulic model based upon the coupled PARCS/RELAP5 codes has been developed and applied for a heavy water research reactor. The objective is to perform safety analysis related to design accidents of this reactor types. In the current study two positive reactivity insertion transients are considered, SCRAM protected and self-limiting power excursion cases. The results of the steady state calculations were compared with results obtained from conventional diffusion codes, while transient calculations were assessed using the point kinetic model of the RELAP5 code. Through this study, the applicability and the suitability of using the coupled code technique with respect to the classical models are emphasized and discussed. 相似文献
3.
企业管理过程中,全面预算管理与成本管理相互促进、相辅相成。针对成本管理及全面预算管理的现状及存在的问题,以陕西某化学工业有限公司(XY公司)为案例,开展了优化成本管理及全面预算管理的对策探讨。首先介绍了全面预算管理和成本管理的基本理论及两者的关系,并针对公司现状及存在的问题,提出了优化全面预算管理和成本管控的思路和措施。通过两种管理相结合的方式,形成科学、健全的管理模式,使企业在市场竞争中获得有利地位,实现企业发展的良性循环。 相似文献
4.
彭威城 《电信工程技术与标准化》2019,32(10)
高铁移动网络覆盖是国内三大通信运营商的一个重点,而高铁隧道内移动网络覆盖更是运营商的一大难点痛点。文章根据我国中部省份某高铁线路覆盖规划实例,采用“设备+POI+泄漏电缆”模式,即三家运营商信号源设备通过同一POI(point of interface,多系统接入平台)接入,信号输出到泄漏电缆进行隧道覆盖,隧道口场坪站安装宽频切换天线对隧道外进行延伸覆盖,通过链路预算合理布置各运营商主设备信号源,从而实现隧道到室外的无缝覆盖。最后,根据已有成熟网络覆盖解决方案,对未来5G高铁隧道移动网络覆盖方案进行了探讨。 相似文献
5.
This paper addresses reliable and efficient calculation of the mode of a multivariate sample, which is a classical fusion function. In particular, we focus on the inputs given on the unit simplex, when aggregating elements of Atanassov intuitionistic fuzzy sets, interval-valued fuzzy sets and their extensions, as well as compositional data. We outline the use of a specially designed 2-additive fuzzy measures and the Choquet integral for the purposes of reducing computational complexity in higher dimensions. We present computational analysis and benchmark four different methods of density-based mode estimation. 相似文献
6.
Radial size estimation using radar high-resolution range profiles(HRRPs) and heading angle estimation are the main means for ship classification.The classification ability is closely related to the range resolution of the radar,precision of radial size estimation,and prior distribution of ship lengths in different offshore areas.We collected the AIS information on about 30 000 ships and their lengths in the four offshore areas of China in the ship information net of China.By fitting the data of ship lengths in each offshore area,it is found that the Weibull distributions provide good-of-fitness to the ship lengths and the parameters in individual area are rather different.Based on the prior distributions of ship lengths,we derived the quantitative relationship between the correct classification probability of big-moderate-small ships and the estimate error of ship radial size.The results indicate that the condition for the big-moderate-small correct classification probability in the offshore areas of China to be up to 90% is that the estimate errors of the ship radial size estimates falls into the interval(-12.67 m,9.41 m) when the heading angle of the ship is between ±75 degrees. 相似文献
7.
Virtual fencing technology uses a neckband-mounted device to deliver an audio cue when an animal nears a virtual boundary that is set via a global positioning system, followed by an electrical stimulus if it crosses the boundary. The flexibility offered by this technology could revolutionize grazing management on dairy farms, but its application and effects on lactating dairy cattle have not been assessed. This experiment reports on the effects of an electric or a virtual front-fence on dairy cow behavior and welfare. Two temporally separated treatments were applied to a herd of 30 multiparous cows. Cows were provided an estimated 14 to 15 kg of dry matter/cow of fresh pasture in a new paddock every 24 h. From d 1 to 10 cows were grazed using a conventional electric front-fence (control treatment) and from d 14 to 23 they were grazed using a virtual front-fence (eShepherd, Agersens Pty Ltd.). Cows were trained to the technology from d 11 to 13. The milk production and live weight of individual cows were recorded daily. Cortisol concentrations were obtained from milk samples collected from individual cows on 3 d during each of the control and the virtual fence grazing periods, plus the first day of training. From d 6 of the experiment, 6 focal cows were fitted with a RumiWatch (Itin + Hoch GmbH) noseband sensor to monitor grazing and ruminating time, and 8 focal cows were fitted with an IceTag (IceRobotics Ltd.) sensors to monitor activity. Milk production, live weight, and the time cows spent standing and lying did not differ between the electric and virtual fence periods. Milk cortisol concentrations, activity, and the times spent ruminating and grazing were comparable between the electric and early virtual fence periods (i.e., d 1–3 with a virtual fence). However, at d 4 to 6 with a virtual fence, activity (steps taken and motion index) and time spent grazing were lower, and time spent ruminating was greater, compared with an electric fence. Further, least significant difference tests suggest milk cortisol concentrations were higher at d 5 with a virtual fence than at d 8 with an electric fence and d 1 with a virtual fence. We conclude there is no evidence of behavioral and welfare effects of virtual fencing on dairy cows in the days immediately following implementation of the technology in a simple intensive grazing regimen, but a longer study is required to fully elucidate effects beyond this period. 相似文献
8.
针对油田企业预算管理存在的问题,阐述了加强预算管理的途径和措施:设置专门的预算管理机构,并建立预算工作岗位责任制;以油田企业战略为基础编制预算;设置弹性预算指标,建立预算预警机制和预算结果质询制度;适时调整、编制动态预算;采取有效的考核与激励措施,鼓励全员参与预算管理。 相似文献
9.
10.
介绍铜陵有色运输部实行全面预算管理的具体措施和所取得的实际效果。通过预算管理制度的建立、组织构架形成、指标体系的完善、责任中心的设置、预算的编制、预算的执行与监控、预算分析与考核等过程,运输部在安全生产,提高产能,降低成本,增加效益等方面取得了显著成绩,为建设节约型社会和构建和谐社会作出了努力。 相似文献