全文获取类型
收费全文 | 842篇 |
免费 | 82篇 |
专业分类
公路运输 | 156篇 |
综合类 | 344篇 |
水路运输 | 219篇 |
铁路运输 | 143篇 |
综合运输 | 62篇 |
出版年
2024年 | 5篇 |
2023年 | 11篇 |
2022年 | 17篇 |
2021年 | 24篇 |
2020年 | 26篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 26篇 |
2016年 | 24篇 |
2015年 | 52篇 |
2014年 | 53篇 |
2013年 | 66篇 |
2012年 | 80篇 |
2011年 | 70篇 |
2010年 | 65篇 |
2009年 | 54篇 |
2008年 | 60篇 |
2007年 | 58篇 |
2006年 | 65篇 |
2005年 | 42篇 |
2004年 | 37篇 |
2003年 | 17篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
排序方式: 共有924条查询结果,搜索用时 31 毫秒
581.
为了判定技术直达去向的合理性,提出静态条件和动态条件2种判定方法。静态条件方法是指:根据铁路运输组织学中的必要条件生成车流强度标准的计算公式,以列车平均编组辆数作为表格的横向表头,以运行里程作为纵向表头,形成技术直达去向的车流强度标准汇总表。动态条件方法是指:根据铁路运输组织学中的充分条件生成车流强度标准的计算公式,结合现场的最远站改编法则确定技术直达去向的车流强度标准。结合实例阐述静态条件和动态条件的计算过程及使用方法。通过对比分析得知,静态条件方法适用于评价规划技术直达去向的合理性,动态条件方法适用于评价既有技术直达去向的合理性。 相似文献
582.
船舶管道在气囊作用下往往形成空气塞,阻碍燃油等液体的流通,对柴油机的正常工作带来不利影响。作者根据长期工作经验,分析了空气塞的成因,提出了消除空气塞的若干措施。 相似文献
583.
This paper is part of ongoing research on incorporating environmental aspects in microscopic integrated land use/transport models. The long-term goal is to add scenario sensitivity for noise emissions in a new modeling suite. Therefore, as a first step, the influence of simulated car traffic noise on real rent prices in the study area in question is analyzed and compared to existing studies. It is shown that modeled noise values from the transportation model are able to explain significant impacts on rent prices when using a hedonic pricing regression. When using noise as a continuous variable, price discounts of 0.4% per dB(A) are found. A discount of up to 9.6% for particularly loud locations is estimated when noise is used as a categorical variable. Care should be taken when controlling for accessibilities that may correlate with noise. The results are in line with results of previous studies and confirm that environmental aspects can and should be considered in integrated models. 相似文献
584.
The characteristics and interannual variability of the deep water masses in the North and Central Aegean Sea are being investigated through the data sets of the Hellenic Navy Hydrographic Service (HNHS) and the MEDATLAS 1997 project. In the period between 1987 and 1993, the densest deep water in the Mediterranean has been produced in the Aegean Sea (with σθ densities reaching up to 29.6 kg/m3), contributing to what has been called the Eastern Mediterranean Transient. The examination of time series of mean integrated values of θ, S and σθ below the depth of 500 dbar reveals the significant deep water density increase after 1987 in all of the deep basins in the area. Data suggest that the density increase of 1987–1988 is mainly attributed to a temperature drop, while in 1993, an even more intense density increase is observed, characterized this time by an abrupt salinity increase. We assume that the increased salinity necessary to produce deep water masses with the observed characteristics was not locally produced but rather advected from the Levantine through the South Aegean. After 1993, no new deep water formation episodes have been observed. A series of Θ–S diagrams derived from HNHS CTD casts covering the period between 1993 and 2000, depict the different characteristics of the deep water masses in the area. As 1993 marks the end of the formation period, observed differences between basins in that year must be attributed to different deep water formation sites. Thereafter, the stagnating deep water in the North and Central Aegean basins has been slowly gaining buoyancy by losing salt and gaining heat. The rate at which this phenomenon takes place varies between different deep basins. It is suggested that these variations are linked to the different volumes of each basin as well as to the general circulation features of the Aegean Sea. 相似文献
585.
586.
587.
588.
金沙洲居住新城位于广州市白云区,在2004年经过调整的《广州市城市总体规划(2001-2010)》中,金沙洲地区被列入广州市今后重点发展的新居住区之一,规划本居住新城人口数为11.4万人。现时市政配套设施较缺乏,雨污水通过排水明渠汇集排入白沙河。综合金沙洲防洪排涝规划及现有排水现状,本文仅对金沙洲居住新城市政雨水系统进行简要概述。 相似文献
589.
通过对水泥混凝土灌注桩缺陷产生原因的分析,提出了避免产生缺陷及处理的方法,从而提高了混凝土灌注桩的质量。 相似文献
590.