全文获取类型
收费全文 | 7560篇 |
免费 | 1395篇 |
国内免费 | 631篇 |
专业分类
测绘学 | 303篇 |
大气科学 | 863篇 |
地球物理 | 4711篇 |
地质学 | 2064篇 |
海洋学 | 410篇 |
天文学 | 23篇 |
综合类 | 376篇 |
自然地理 | 836篇 |
出版年
2024年 | 30篇 |
2023年 | 75篇 |
2022年 | 182篇 |
2021年 | 213篇 |
2020年 | 199篇 |
2019年 | 266篇 |
2018年 | 218篇 |
2017年 | 252篇 |
2016年 | 215篇 |
2015年 | 271篇 |
2014年 | 411篇 |
2013年 | 370篇 |
2012年 | 420篇 |
2011年 | 455篇 |
2010年 | 408篇 |
2009年 | 469篇 |
2008年 | 496篇 |
2007年 | 456篇 |
2006年 | 454篇 |
2005年 | 426篇 |
2004年 | 363篇 |
2003年 | 328篇 |
2002年 | 290篇 |
2001年 | 271篇 |
2000年 | 270篇 |
1999年 | 267篇 |
1998年 | 263篇 |
1997年 | 197篇 |
1996年 | 214篇 |
1995年 | 228篇 |
1994年 | 138篇 |
1993年 | 127篇 |
1992年 | 86篇 |
1991年 | 47篇 |
1990年 | 46篇 |
1989年 | 28篇 |
1988年 | 50篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 25篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1954年 | 6篇 |
排序方式: 共有9586条查询结果,搜索用时 93 毫秒
81.
DMC+4小卫星在国际灾害监测中的应用与评价 总被引:8,自引:0,他引:8
针对国际灾害监测星座应用技术和中国各种自然灾害的现状,着重研究了DMC(DisasterMonitoringConstellation)星座应用技术和DMC 4小卫星的数据特点,研究了利用小卫星星座对防灾、抗灾救灾的突出作用,研究了小卫星地面系统集成技术和星地一体化运营、管理和控制体系,以便进一步推动国内小卫星技术、遥感应用技术、卫星星座技术、天地一体化运管控技术和机制创新的发展。促进中国灾害监测星座的研制,最终实现对各种自然灾害的实时、动态监测。 相似文献
82.
83.
徐汉斌 《地质灾害与环境保护》2002,13(1):26-28
成都外环路高速公路东半环超过有20km的路段处在成都粘土分布区,针对成都粘土的易滑性,本文提出了全封闭的浆砌片石护坡,土钉墙,非全封闭的锚杆框架护坡,钢纤维混凝土喷锚全封闭护坡,重力式挡土墙等五种方法处理成都粘土路堑边坡工程,施工实践表明,这些方法行之有效,在该类土的边坡防护中值得推广。 相似文献
84.
85.
The paper presents a numerical investigation aimed at evaluating the improvements achievable through devices for passive seismic protection of buildings based on the use of shape memory alloys (SMA) in place of conventional steel or rubber devices. To get some generality in the results, different resisting reinforced concrete plane frames were analysed, either protected or not. ‘New’ and ‘existing’ buildings were considered depending on whether seismic provisions are adopted in the building design or not. Base isolation and energy dissipation were equally addressed for both conventional and innovative SMA‐based devices. Fragility analyses were performed using specific damage measures to account for comparisons among different damage types; the results were then used to estimate quantitatively the effectiveness of the various protection systems. More specifically, the assessment involved a direct comparison of the damage reduction provided by each protection system with respect to the severe degradation experienced by the corresponding non‐protected frame. Structural damage, non‐structural damage and damage to contents were used on purpose and included in a subsequent phase of cost analysis to evaluate the expected gains also in terms of economic benefits and life loss prevention. The results indicate that base isolation, when applicable, provides higher degrees of safety than energy dissipation does; moreover, the use of SMA‐based devices generally brings about better performances, also in consideration of the reduced functional and maintenance requirements. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
86.
Natural Hazards - Strong earthquakes in the proximity of densely inhabited urban areas pose one ofthe most complicated disaster management situations faced by societies today. Herethe experience... 相似文献
87.
A major earthquake (M=6.6) occurred on 21 June 2000, in South Iceland. This paper presents an unusual example of left-lateral strike-slip displacement recorded in a newly asphalted car park surface through a mechanically consistent pattern of open fissures and pressure ridges resulting from simple shear and rotation. Measurement of these features allows accurate reconstruction of the local deformation. The behaviour of the asphalt layer resembles that of analogue physical models, especially in terms of rotations induced by shear deformation. It is finally shown that through a wide range of scales some basic patterns associating rotation and opposite senses of strike-slip exist in the South Iceland Seismic Zone. 相似文献
88.
Understanding the nature and impacts of tsunamis within the Aegean Sea region ofGreece is of importance to both the academic community and those organisationsconcerned with tsunami disaster management. In order to determine hazard and riskand consequently pre-plan mitigative strategies, it is necessary to analyse historical(documentary) and geological records of former tsunami events. Therefore, firstlythis paper provides a summary of the written sources of information on Aegeantsunamis paying particular attention to published catalogues. From the availabledata, it is noted that a large number of events have been reported during the last3500 years. Secondly, the paper provides a review of the published on-shore(terrestrial) geological records of tsunamis within the region. From this analysisit is seen that little geological evidence has been identified for the large numberof tsunamis reported in the catalogues. Thirdly, the paper considers the reliabilityof the written and geological records and how problems of accuracy, coverage,extent and reliability, may have potential implications for the estimation of hazardand risk. The paper concludes by making recommendations for disaster managers,geologists and historians to work closely together. 相似文献
89.
90.