全文获取类型
收费全文 | 17389篇 |
免费 | 1488篇 |
国内免费 | 698篇 |
专业分类
电工技术 | 715篇 |
技术理论 | 13篇 |
综合类 | 2314篇 |
化学工业 | 233篇 |
金属工艺 | 23篇 |
机械仪表 | 77篇 |
建筑科学 | 9072篇 |
矿业工程 | 267篇 |
能源动力 | 584篇 |
轻工业 | 34篇 |
水利工程 | 4635篇 |
石油天然气 | 175篇 |
武器工业 | 5篇 |
无线电 | 189篇 |
一般工业技术 | 317篇 |
冶金工业 | 153篇 |
原子能技术 | 12篇 |
自动化技术 | 757篇 |
出版年
2024年 | 90篇 |
2023年 | 268篇 |
2022年 | 462篇 |
2021年 | 569篇 |
2020年 | 550篇 |
2019年 | 570篇 |
2018年 | 414篇 |
2017年 | 639篇 |
2016年 | 585篇 |
2015年 | 565篇 |
2014年 | 1246篇 |
2013年 | 1196篇 |
2012年 | 1169篇 |
2011年 | 1319篇 |
2010年 | 1150篇 |
2009年 | 1051篇 |
2008年 | 1041篇 |
2007年 | 1082篇 |
2006年 | 1044篇 |
2005年 | 871篇 |
2004年 | 710篇 |
2003年 | 554篇 |
2002年 | 532篇 |
2001年 | 499篇 |
2000年 | 384篇 |
1999年 | 258篇 |
1998年 | 165篇 |
1997年 | 146篇 |
1996年 | 85篇 |
1995年 | 80篇 |
1994年 | 72篇 |
1993年 | 56篇 |
1992年 | 50篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1969年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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
12.
During the day, there are considerable variations in the climatic factors prevailing in these regions. This is especially so during the 24-hour daily cycle of the long, hot and dry summer (mid-May to midOctober). Such climatic conditions have had a considerable impact on the daily living pattern of family life in the same season, particularly in the urban areas. During the same 24-hour cycle, they have compelled the inhabitants to shift their living activities both vertically in section and horizontally in plan; they do this in pursuit of more acceptable, if not, desirable internal thermal environmental ambience. 相似文献
13.
14.
This article is the second of two papers that review the field of spatially sensitive social scientific research into the links between social status and transport disadvantage. The first paper undertook a comprehensive review of the social scientific and transport planning literature to mark the level of development in the field and identify conceptual and methodological issues and constraints in this field of inquiry. The present article supports the advancement of socially and geographically sensitive transport research by opportunities for the development of more sophisticated spatial analytical methodologies. The approach we present is able to account for factors not previously addressed in either social or transport planning research, in particular the temporal dimensions of transport service accessibility. The article articulates the methodology through an empirical case study of socio-spatial transport disadvantage within the Gold Coast City. The article demonstrates that there are important theoretical and practical lessons to be gained for researchers and policy makers in addressing the social dimensions of transport and infrastructure provision. Further, the article argues that an attentiveness to new ways of combining and representing social and transport data-sets can promote policy relevant empirical social inquiry. The article also contributes in a productive way to the empirical knowledge of Australia's sixth-largest metropolitan area, which is often overlooked by urban scholars. 相似文献
15.
洪水预报调度决策系统近年来在全国各地得到广泛的应用。简单介绍了洪水预报系统的系统组成及功能,分析了系统在抗击台风过程中的作用与效益,总结了系统多年的运行和维护经验。根据多年的运行经验,系统能及时提供雨、水情数据和高效的调度会商决策,提高防御台风、突发性暴雨等自然灾害的能力。 相似文献
16.
17.
揭示了城市环境的基本性质的基本特征,研究了城市环境对人的心理影响和生理影响。指出城市环境建设不公要满足人的物质需要,还要满足人的精神需要。 相似文献
18.
Open window buses without air-conditioning are a major mode of urban and inter-city transport in most countries. High occupancy
combined with hot and humid conditions makes travel in these buses quite uncomfortable. In this study air flow through a bus
has been studied that could be the basis for low cost and eco-friendly methods of increasing passenger comfort and possibly
reduce drag. The aerodynamics of such a road vehicle has not been studied as previous investigations have been confined to
vehicles with closed windows that present a smooth exterior to air flow. Using a 1:25 scaled Perspex model of an urban bus
in Delhi, flow visualization was performed in a water channel. The Reynolds numbers were one-tenth of a real bus moving at
10 m/s. Smoke and tuft visualizations were also performed on an urban bus at 40 km/h. Numerical simulations were performed
at the actual Reynolds number. Even though there were Reynolds number differences, the broad features were similar. Air enters
the bus from the rear windows, moves to the front (relative to the bus) and exits from the front windows. Inside air velocity
relative to the bus is about one-tenth of the free-stream velocity. The flow is highly three-dimensional and unsteady. 相似文献
19.
城市化进程中的小城镇交通初探 总被引:4,自引:0,他引:4
通过对小城镇城市结构、路网结构、交通结构和交通管理特征进行详细分析,得出小城镇交通问题症结所在,并初步提出小城镇交通规划和交通治理的对策。 相似文献
20.
Fisher最优分割法在星星哨水库汛期分期划分中的应用 总被引:1,自引:0,他引:1
Fisher最优分割法是对有序样本进行最优化分段的一种数学方法。本文利用该方法对星星哨水库汛期进行相应的划分,结果表明该方法是可行的。因此,可利用该结果对分期实施不同的汛限水位,使水库的防洪和兴利效益达到最大。 相似文献