全文获取类型
收费全文 | 7623篇 |
免费 | 206篇 |
专业分类
公路运输 | 2084篇 |
综合类 | 2108篇 |
水路运输 | 2067篇 |
铁路运输 | 1313篇 |
综合运输 | 257篇 |
出版年
2024年 | 10篇 |
2023年 | 33篇 |
2022年 | 123篇 |
2021年 | 243篇 |
2020年 | 169篇 |
2019年 | 73篇 |
2018年 | 108篇 |
2017年 | 97篇 |
2016年 | 119篇 |
2015年 | 204篇 |
2014年 | 249篇 |
2013年 | 417篇 |
2012年 | 465篇 |
2011年 | 584篇 |
2010年 | 564篇 |
2009年 | 543篇 |
2008年 | 592篇 |
2007年 | 760篇 |
2006年 | 711篇 |
2005年 | 480篇 |
2004年 | 159篇 |
2003年 | 177篇 |
2002年 | 208篇 |
2001年 | 189篇 |
2000年 | 141篇 |
1999年 | 70篇 |
1998年 | 53篇 |
1997年 | 43篇 |
1996年 | 52篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 24篇 |
1992年 | 21篇 |
1991年 | 27篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 4篇 |
排序方式: 共有7829条查询结果,搜索用时 46 毫秒
231.
232.
本文详细介绍了等截面多风口等量排风长管道内压力分布基本式理论推导和风口开度调节计算方法,并根据实际地下工程测定数据验证其理论计算可靠性,可以供地下工程设计计算和工程调试中作借鉴和参考。 相似文献
233.
234.
235.
地铁设计需要多种岩土参数,这些参数可通过室内试验及现场原位测试获得。文章以西安市城市快速轨道交通Ⅱ号线B标岩土工程勘察为例,不仅总结了B标岩土的一些总体工程特征及有关参数的统计数据,为结构设计、降水设计提供了必要的依据;而且在方法上也可为西安地铁岩土工程勘察提供借鉴。同时,这些岩土工程特征及岩土参数,还可为西安城区同类或相似场地岩土工程设计提供参考,也可为丰富西安市城市环境地质内容提供补充资料。 相似文献
236.
Recent work on risky choice modelling has sought to address the shortcomings of expected utility theory (EUT) by using non-expected utility theoretic (non-EUT) approaches. However, to date these approaches have been merely tested on stated choice data which is flexible and cheap. In this study, we empirically investigate the feasibility and validity of non-EUT approaches in a revealed preference (RP) context in which travel time distribution is extracted from observed historical travel time data, and subsequently present systematic comparisons between EUT, weighted utility theory, rank-dependent expected utility theory, and prospect theory (PT). The empirical evidence indicates that each non-EUT model has important behavioural insights to offer, moreover, EUT as well as non-EUT models can be applied to the RP context. However, the EUT and non-EUT model fits are generally similar with only PT providing a marginally improved model fit over EUT. The key findings presented in this study reinforce the importance of exploring non-EUT models within a revealed preference context before they can be applied reliably to modelling risky choices in the real world. 相似文献
237.
238.
In 2013, the concept of the ‘Silk Road Economic Belt and the 21st-Century Maritime Silk Road (Belt and Road)’ was initiated by the Chinese government, which involves Asian, European and African continents and their adjacent seas. Logistics plays a core role in such a large framework of economy and trade. In recent years, China, European Union, and Southeast Asia pay much attention to the design and development of the intermodal transportation network towards both economic and environmental efficiency. In this paper, we propose an empty container repositioning model in the intermodal transportation network of Belt and Road (B&R) Initiative by considering both standard and foldable containers. In this model, empty containers are repositioned from the inland of the original area, such as China, to other areas of B&R Initiative related countries and regions, such as European Union and Southeast Asia. We develop a mixed integer linear programming model to determine the optimal repositioning of empty containers via the intermodal transportation network. An Artificial Bee Colony algorithm is developed to solve large size problems in practice and numerical experiments are conducted to show the efficiency of our proposed algorithm. We provide managerial insights regarding the impact on the network performance of foldable containers transportation. 相似文献
239.
With the growth of maritime transportation, seaports have become critical to the world economy as linking nodes between shipping and inland transport. However, the port system is fragile under certain unconventional emergency events. This study addresses the issue of investment on disaster prevention within the port competition context. The present model discusses and compares four situations of different relationships and strategies of pre-disaster prevention between two adjacent ports. Results indicate that both ports increase the disaster prevention investment under the cooperation scenario compared with that in the case of non-cooperation wherein they are complementary ports. Meanwhile, a numerical simulation is conducted to examine the collective and individual rationality of both ports. Although cooperation strategy decreases the total risk cost of two ports, one of the two ports may profit, whereas the other may suffer losses. 相似文献
240.