首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   86篇
  免费   11篇
  国内免费   24篇
测绘学   1篇
大气科学   1篇
地球物理   11篇
地质学   67篇
海洋学   22篇
综合类   5篇
自然地理   14篇
  2022年   1篇
  2021年   3篇
  2020年   1篇
  2019年   6篇
  2017年   3篇
  2016年   4篇
  2015年   6篇
  2014年   7篇
  2013年   8篇
  2012年   4篇
  2011年   6篇
  2010年   4篇
  2009年   5篇
  2008年   3篇
  2007年   8篇
  2006年   3篇
  2005年   5篇
  2004年   5篇
  2003年   3篇
  2002年   4篇
  2001年   3篇
  2000年   4篇
  1999年   3篇
  1997年   2篇
  1996年   2篇
  1995年   4篇
  1994年   1篇
  1993年   4篇
  1992年   1篇
  1991年   1篇
  1989年   2篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
排序方式: 共有121条查询结果,搜索用时 31 毫秒
1.
Karst researchers of the Karst Research Institute ZRC SAZU are regularly consulted during the planning of Slovenia’s motorways and invited to observe and monitor construction in the karst areas. More than 350 caves have been discovered in the course of building 60 km of new motorways over the past decade. Access to the most important caves is preserved by concrete tubes closed with metal covers at the roadside. The largest cave system in a tunnel, named LC-S647, is almost entirely preserved. The protection of this cave will serve as a good example for the preservation of natural heritage in the future. Construction work for the motorway uncovered a high degree of karstification. In particular, the discovery of this cave in the Kastelec tunnel LC-S647 showed the existence of a major cave system in the geological and speleological past. A number of unconnected passages have also been found. Caves discovered during highway construction have brought new knowledge about the cavernosity and the geological history of this part of the karst.  相似文献   
2.
Abstract. A new rhynchonellid brachiopod genus Tethyrhynchia , with type species Tethyrhynchia mediterranea n. sp., is described from specimens discovered in dark zones of submarine caves along the Mediterranean coast of France between Marseille and La Ciotat, and also at Zembra Island, off the Gulf of Tunis, Tunisia. Other brachiopods occurring with this diminutive rhynchonellid are also small and include the megathyridids Argyrotheca cistellula and Megathiris detruncata . This is the first recorded occurrence of a rhynchonellid from the Mediterranean Sea. The new form is apparently neotenous, in that the lophophore in adults never develops beyond the trocholophous stage. A new type of rhynchonellid crus, crescentic in profile and here named the lunifer type, is described. The new genus is assigned to the new family Tethyrhynchiidae , and comparisons are made with other extant rhynchonellid genera.  相似文献   
3.
南宁市麒麟山风景区的景观特色表现为山形如麒麟称之外表美 ,洞穴景观奇特称之内界美 ,交通便利、满山花果飘香 ,旧岜粒村村民热心办旅游 ,热情好客称之旅游环境美。该景观开发对发展旅游业 ,促进科研、教学 ,加速南宁旅游城的建设进程具有重要意义 ,呼吁有关部门给予大力扶持。  相似文献   
4.
Rock salt is approximately 1000 times more soluble than limestone and thus displays high rates of geomorphic evolution. Cave stream channel profiles and downcutting rates were studied in the Mount Sedom salt diapir, Dead Sea rift valley, Israel. Although the area is very arid (mean annual rainfall ≈ 50 mm), the diapir contains extensive karst systems of Holocene age. In the standard cave profile a vertical shaft at the upstream end diverts water from a surface channel in anhydrite or clastic cap rocks into the subsurface route in the salt. Mass balance calculations in a sample cave passage yielded downcutting rates of 0–2 mm s?1 during peak flood conditions, or about eight orders of magnitude higher than reported rates in any limestone cave streams. However, in the arid climate of Mount Sedom floods have a low recurrence interval with the consequence that long-term mean downcutting rates are lower: an average rate of 8·8 mm a?1 was measured for the period 1986–1991 in the same sample passage. Quite independently, long-term mean rates of 6·2mm a?1 are deduced from 14C ages of driftwood found in upper levels of 12 cave passages. These are at least three orders of magnitude higher than rates established for limestone caves. Salt cave passages develop in two main stages: (1) an early stage characterized by high downcutting rates into the rock salt bed, and steep passage gradients; (2) a mature stage characterized by lower downcutting rates, with establishment of a subhorizontal stream bed armoured with alluvial detritus. In this mature stage downcutting rates are controlled by the uplift rate of the Mount Sedom diapir and changes of the level of the Dead Sea. Passages may also aggrade. These fast-developing salt stream channels may serve as full-scale models for slower developing systems such as limestone canyons.  相似文献   
5.
The Otranto–Leuca coastal tract is marked by the presence of numerous sea caves placed close to present sea level. They are located generally at the back of a shore platform covered by a sequence of breccia deposits, marine sediments and speleothems. At Grotta di Masseria dell'Orte, marine cemented sands rest on a narrow shore platform at about 6.2 m above mean sea level and are covered by speleothems older than 185 ka. At Grotta del Diavolo, which is mostly filled by breccia deposits, three beach levels have been detected at about 3.0, 3.5 and 5.9 m above msl. They are either covered by or overlie speleothems that yield an U/Th age of 340, 78 ka and between 170.3 and 146.5, respectively. Geomorphological evidence and radiometric ages indicate that the area after a period of uplift has been tectonically stable since the last part of the Middle Pleistocene so that marine landforms close to the present shoreline underwent a polycyclic evolution. The sedimentary fills of sea caves formed during Middle-Late Pleistocene glacial stages, when arid or semiarid conditions promoted the removal of regolith and the development of thick breccia deposits. During Marine Isotope Stages (MIS) 9.3, 5.5 and 5.1, cave sediments were partially eroded whereas beach layers and related speleothems developed. These are, in fact, the only marine isotope stages marked by a sea level position which in this Mediterranean region was either close to, or slightly higher than, the present one.  相似文献   
6.
7.
The caves of the Umbria and Marche regions in central Italy are made up of three-dimensional maze systems that display different general morphologies due to the various geological and structural contexts. At the same time, the internal morphologies of the passages, galleries, and shafts present some similarity, with solutional galleries characterized by cupolas and blind pits, anastamotic passages, roof pendants, and phreatic passages situated at different levels. Some of these caves are still active, as is the case for Frassassi Gorge, Parrano Gorge, and Acquasanta Terme, with galleries that reach the phreatic zone, where there is a rising of highly mineralized water, rich in hydrosulfydric acid, and with erosion of limestone walls and the formation of gypsum. Elsewhere there are fossil caves, such as Monte Cucco and Pozzi della Piana, where large speleothems of gypsum are present 500 m or more above the regional water table. In all of these important karst systems it is possible to recognize basal input points through fracture and intergranular porosity networks at the base of the oxidizing zone in the core of the anticline, where mineralized water rises up from the Triassic evaporitic layers in small hydrogeological circuits. Different underground morphologies can derive from the presence of a water table related to an external stream or from the confined setting of the carbonate rocks, underlying low permeable sedimentary cover, where artesian conditions can occur.  相似文献   
8.
塘坝子-葛仙山景点,地处举世瞩目的龙门山推覆-滑覆构造带上,已成为拟建中的“龙门山地质公园”的重要组成部分。其独特的石灰岩岩溶地貌和溶洞景观,是成都旅游区和彭县景区内宝贵的旅游景观配套资源,除旅游开发价值较高外,亦是离成都市区较近较理想的人防各战疏散基地,因而具有一定的资源综合开发潜力。对该景点的尽早开发,还可缓解邻区旅游热点的人满之患。  相似文献   
9.
Biostratinomic analysis (processes acting between death and burial) of Lateglacial mammal bone assemblages from three caves in northern England demonstrates the value of re‐examining archived assemblages. With AMS radiocarbon dating of key specimens, these assemblages shed light on the ecology of a region at the northern limit of Lateglacial human activity in Britain. During the Lateglacial Interstadial bears, wolves and humans expanded into the region, bears by around 12 500 14C yr BP, and the earliest evidence for human presence is around 12 300 14C yr BP. At Victoria Cave, wolf activity included predation and scavenging of large ungulates and scavenging bear carcasses apparently resulting from hibernation deaths. The scavenging of bear carcasses is possibly confined to the first part of the Lateglacial Interstadial, whereas evidence for wolf scavenging large ungulates increases later in the Interstadial, after about 11 800 14C yr BP, perhaps reflecting changes in the productivity of the Lateglacial ecosystem, and in human subsistence patterns. The assemblage from Sewell's Cave is wolf den debris from the very end of the Lateglacial Interstadial around 10 800 14C yr BP, whilst that from Kinsey Cave is dominated by large‐bodied carnivores, and is argued to have a quite different taphonomic history. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
10.
模糊评判法在公路黄土洞穴发育程度分区中的应用   总被引:1,自引:1,他引:0  
阐述了影响黄土洞穴形成的黄土湿陷性、崩解性、地质构造、节理裂隙、微地形地貌和水文及气候条件等工程地质特性和地质因素;在公路沿线地区,公路工程质量及人类活动也是黄土洞穴形成的影响因素。洞穴发育程度分区预测和评价极具复杂性、随机性和模糊性,为此,在对各影响因素分析的基础上,借助模糊综合评判法,对黄土区公路沿线洞穴发育程度分区进行了研究。与实际情况对比分析表明,预测评价结果合理可靠,可作为黄土区已建公路洞穴灾害的防治依据。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号