全文获取类型
收费全文 | 2481篇 |
免费 | 526篇 |
国内免费 | 772篇 |
专业分类
测绘学 | 62篇 |
大气科学 | 139篇 |
地球物理 | 1191篇 |
地质学 | 1356篇 |
海洋学 | 810篇 |
天文学 | 8篇 |
综合类 | 75篇 |
自然地理 | 138篇 |
出版年
2024年 | 9篇 |
2023年 | 76篇 |
2022年 | 108篇 |
2021年 | 107篇 |
2020年 | 146篇 |
2019年 | 165篇 |
2018年 | 150篇 |
2017年 | 116篇 |
2016年 | 165篇 |
2015年 | 141篇 |
2014年 | 189篇 |
2013年 | 182篇 |
2012年 | 147篇 |
2011年 | 170篇 |
2010年 | 144篇 |
2009年 | 188篇 |
2008年 | 179篇 |
2007年 | 180篇 |
2006年 | 162篇 |
2005年 | 130篇 |
2004年 | 112篇 |
2003年 | 137篇 |
2002年 | 99篇 |
2001年 | 74篇 |
2000年 | 70篇 |
1999年 | 69篇 |
1998年 | 58篇 |
1997年 | 65篇 |
1996年 | 62篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有3779条查询结果,搜索用时 15 毫秒
81.
82.
83.
珊瑚礁工程地质研究的内容和方法 总被引:3,自引:0,他引:3
珊瑚礁工程地质研究的主要内容为珊瑚礁自然地质条件、珊瑚礁岩土物理力学性质和珊瑚礁混凝土料问题。除了通常的工程地质研究方法外, 着重介绍珊瑚礁工程地质研究的钻探、触探和地球物理勘测方法。 相似文献
84.
85.
86.
近断层地震动对地表结构物造成严重的破坏,它具有明显的方向性和脉冲型特征. 在速度时程中含有大幅值、长周期的脉冲波,对结构响应影响很大. 为简化计算和分析的需要,在既有的等效速度脉冲模型的基础上,建议了较为合理等效速度脉冲模型. 在充分收集脉冲型近断层地震记录的基础上,对等效速度脉冲模型的脉冲周期、脉冲强度及卓越脉冲数等参数进行了研究,并与以往研究者的结果进行比较,以利于近断层区结构的抗震设计. 相似文献
87.
The geography information system of the 1303 Hongton M=8 earthquake has been established. Using the spatial analysis function of GIS, the spatial distribution characteristics of
damage and isoseismal of the earthquake are studies. By comparing with the standard earthquake intensity attenuation relationship,
the abnormal damage distribution of the earthquake is found, so the relationship of the abnormal distribution with tectonics,
site condition and basin are analyzed. In this paper, the influence on the ground motion generated by earthquake source and
the underground structures near source also are studied. The influence on seismic zonation, anti-earthquake design, earthquake
prediction and earthquake emergency responding produced by the abnormal density distribution are discussed.
Foundation item: National important fundamental research “The Basic Research of Important Project in Damage Environment” and The important
project “The Seismic Hazard Assessment Research and Anti-earthquake Structure Research” from China Earthquake Administration
during the 10th Five-year Plan.
Contribution No. 04FE1008, Institute of Geophysics, China Earthquake Administration. 相似文献
88.
89.
While laboratory and analytical studies can provide valuable information about earthquake hazard mitigation, the most effective educator is the impact of a full-scale earthquake on a full-scale city. The recent earthquakes in Turkey showed that the governmental as well as individual attitudes towards earthquakes did not represent proportionate responses to the risk levels concerned. Turkey had weaknesses in preparing, planning, mitigating and responding to disasters in spite of the known seismic vulnerability of the country. Many steps have been taken after 1999 earthquakes in Turkey, however, the preparations largely concentrate on the response and recovery phases and a fundamental step to reform the current disaster management system and steps to rehabilitate the vulnerable building stock has not been undertaken until today. This would involve changing the present laws and regulations and de-centralising the disaster management system. The aim of this paper is to propose a national mitigation strategy for Turkey for a time-frame of 10 years. The model proposed is a very comprehensive model for earthquake risk reduction in Turkey and within this context, the legislative and technical aspects of mitigation will be discussed in detail. Strategies for mitigating and retrofitting the existing building stock will also be proposed. 相似文献
90.
A common assumption in the geological analysis of modern reefs is that coral community zonation seen on the surface should also be found in cores from the reef interior. Such assumptions not only underestimate the impact of tropical storms on reef facies development, but have been difficult to test because of restrictions imposed by narrow‐diameter cores and poor recovery. That assumption is tested here using large‐diameter cores recovered from a range of common zones across three Campeche Bank reefs. It is found that cores from the reef‐front, crest, flat and rubble‐cay zones are similar in texture and coral composition, making it impossible to recognize coral assemblages that reflect the surface zonation. Taphonomic signatures imparted by variations in encrustation, bioerosion and cementation, however, produce distinct facies and delineate a clear depth zonation. Cores from the reef‐front zone (2–10 m depth) are characterized by sections of Acropora palmata cobble gravel interspersed with sections of in‐place (but truncated) A. palmata stumps. Upper surfaces of truncated colonies are intensely bioeroded by traces of Entobia isp. and Gastrochaenolites isp. and encrusted by mm‐thick crustose corallines before colony regeneration and, therefore, indicate punctuated growth resulting from a hurricane‐induced cycle of destruction and regeneration. Cores from the reef crest/flat (0–2 m depth) are also characterized by sections of hurricane‐derived A. palmata cobble‐gravels as well as in‐place A. palmata colonies. In contrast to the reef front, however, these cobble gravels are encrusted by cm‐thick crusts of intergrown coralline algae, low‐relief Homotrema and vermetids, bored by traces of Entobia isp. and Trypanites isp. and coated by a dense, peloidal, micrite cement. Cores from the inter‐ to supratidal rubble‐cay zone (+0–5 m) are only composed of A. palmata cobble gravels and, although clasts show evidence of subtidal encrustation and bioerosion, these always represent processes that occurred before deposition on the cay. Instead, these gravels are distinguished on the basis of their limited bioerosion and marine cements, which exhibit fabrics formed in the intertidal zone. These results confirm that hurricanes have a major influence on facies development in Campeche Bank reefs. Instead of reflecting the surface coral zonation, each facies records a distinctive, depth‐related set of taphonomic processes, which reflect colonization, alteration and stabilization following the production of new substrates by hurricanes. 相似文献