全文获取类型
收费全文 | 8873篇 |
免费 | 401篇 |
专业分类
公路运输 | 3263篇 |
综合类 | 3623篇 |
水路运输 | 1300篇 |
铁路运输 | 878篇 |
综合运输 | 210篇 |
出版年
2024年 | 27篇 |
2023年 | 33篇 |
2022年 | 106篇 |
2021年 | 188篇 |
2020年 | 172篇 |
2019年 | 100篇 |
2018年 | 79篇 |
2017年 | 86篇 |
2016年 | 87篇 |
2015年 | 201篇 |
2014年 | 540篇 |
2013年 | 493篇 |
2012年 | 749篇 |
2011年 | 810篇 |
2010年 | 720篇 |
2009年 | 676篇 |
2008年 | 770篇 |
2007年 | 989篇 |
2006年 | 903篇 |
2005年 | 503篇 |
2004年 | 311篇 |
2003年 | 210篇 |
2002年 | 197篇 |
2001年 | 126篇 |
2000年 | 66篇 |
1999年 | 29篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 18篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
排序方式: 共有9274条查询结果,搜索用时 812 毫秒
721.
特殊桥梁结构应用于京沪高速铁路沪宁段的设置条件 总被引:1,自引:0,他引:1
谢维鎏 《铁道标准设计通讯》2002,(2):7-10
结合京沪高速铁路几个特殊工点的桥式设计 ,对京沪高速铁路特殊桥梁结构的技术、经济条件进行探讨 ,初步提出斜拉桥、系杆拱桥、斜交桥梁这几种桥式应用于高速铁路的设置条件。 相似文献
722.
Laurence C. Breaker David B. Gilhousen Hendrik L. Tolman Lawrence D. Burroughs 《Journal of Marine Systems》1998,16(3-4)
Measurements of boundary layer moisture have been acquired from Rotronic MP-100 sensors deployed on two NDBC buoys in the northern Gulf of Mexico from June through November 1993. For one sensor, which was retrieved approximately 8 months after deployment, the post- and precalibrations agreed closely and fell well within WMO specifications for accuracy. The second sensor operated continuously from June 1993 to February 1997 (3.5 years). Buoy observations of relative humidity and supporting data were used to calculate specific humidity and the surface fluxes of latent and sensible heat. Specific humidities from the buoys were compared with observations of moisture obtained from nearby ship reports, and the correlations were generally high (0.7–0.9). Surface gravity wave spectra were also acquired. The time series of specific humidity and the other buoy parameters revealed three primary scales of variability, small (h), synoptic (days), and seasonal (months). The synoptic variability was clearly dominant and occurred primarily during September, October, and November. Most of the synoptic variability was due to frontal systems that dropped down into the Gulf of Mexico from the continental US followed by air masses which were cold and dry. Cross-correlation analyses of the buoy data indicated that: (1) the moisture field was highly coherent over distances of 800 km or more in the northern Gulf of Mexico; and (2) both specific humidity and air temperature served as tracers of the motion associated with propagating atmospheric disturbances. These correlation analyses also revealed that the prevailing weather systems generally entered the buoy domain from the South prior to September, but primarily from the North thereafter. Spectra of the various buoy parameters indicated strong diurnal and semidiurnal variability for barometric pressure and sea surface temperature (SST) and lesser variability for air temperature, wind speed and significant wave height. The surface fluxes of latent and sensible heat were dominated by the synoptic events which took place from September through November with the transfer of latent heat being primarily from the ocean to the atmosphere. Finally, an analysis of the surface wave observations from each buoy, which included calculations of wave age and estimates of surface roughness, indicate that major heat and moisture flux events coincide with periods of active wave growth, although the data were insufficient to identify any causal relationships. 相似文献
723.
钢筋混凝土拱桥多节段吊装主扣塔合用的设计及施工技术 总被引:2,自引:0,他引:2
六圭河大桥是净跨为195m普通钢筋混凝土箱形拱公路桥,该桥在主拱箱吊装施工中采用主扣塔合用的施工技术,节约了成本,缩短了工期,该方法可供多节段拱桥吊装施工参考和借鉴。 相似文献
724.
725.
赵军丽 《内蒙古公路与运输》2005,(3):22-24
旧油石沥青再生利用在国内外已广泛应用于旧路改造中,取得了良好的技术效果及经济效益。文章通过102国道三河段大修工程中对旧油石沥青再生利用施工技术的实践,总结了旧油石再生利用施工技术的强度形成机理及施工工艺,并就其工程造价与传统工艺造价进行了比较。 相似文献
726.
727.
728.
通过室内试验,研究了贫混凝土道路基层材料的温度收缩和干燥收缩特性。试验结果为贫混凝土基层路面温度应力的计算提供了重要的参数,并对进一步研究贫混凝土基层干缩裂缝的防止具有重要的意义。 相似文献
729.
730.
通过查阅有关混凝土内部应力方面的专著,结合现场观察,对混凝土温度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施等进行阐述。 相似文献