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   79篇
  免费   2篇
测绘学   1篇
大气科学   6篇
地球物理   23篇
地质学   29篇
海洋学   8篇
天文学   7篇
自然地理   7篇
  2021年   1篇
  2019年   3篇
  2018年   2篇
  2017年   2篇
  2016年   1篇
  2015年   2篇
  2014年   2篇
  2013年   8篇
  2012年   2篇
  2011年   3篇
  2010年   3篇
  2009年   7篇
  2008年   3篇
  2007年   4篇
  2006年   5篇
  2005年   2篇
  2004年   7篇
  2003年   2篇
  2000年   4篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1995年   2篇
  1992年   1篇
  1990年   1篇
  1987年   5篇
  1986年   2篇
  1985年   1篇
  1980年   1篇
  1977年   1篇
排序方式: 共有81条查询结果,搜索用时 15 毫秒
31.
Abstract:  Current curriculum developments will provide a new framework for the teaching of social sciences, including geography, in New Zealand secondary schools. This article outlines recent challenges faced by the subject, and the development and likely nature of the new curriculum. Some ways in which teachers can plan and implement innovative programmes within the framework of the existing syllabus and the new curriculum are suggested.  相似文献   
32.
The volcanic island of Milos, Greece, comprises an Upper Pliocene –Pleistocene, thick (up to 700 m), compositionally and texturally diverse succession of calc-alkaline, volcanic, and sedimentary rocks that record a transition from a relatively shallow but dominantly below-wave-base submarine setting to a subaerial one. The volcanic activity began at 2.66±0.07 Ma and has been more or less continuous since then. Subaerial emergence probably occurred at 1.44±0.08 Ma, in response to a combination of volcanic constructional processes and fault-controlled volcano-tectonic uplift. The architecture of the dominantly felsic-intermediate volcanic succession reflects contrasts in eruption style, proximity to source, depositional environment and emplacement processes. The juxtaposition of submarine and subaerial facies indicates that for part of the volcanic history, below-wave base to above-wave base, and shoaling to subaerial depositional environments coexisted in most areas. The volcanic facies architecture comprises interfingering proximal (near vent), medial and distal facies associations related to five main volcano types: (1) submarine felsic cryptodome-pumice cone volcanoes; (2) submarine dacitic and andesitic lava domes; (3) submarine-to-subaerial scoria cones; (4) submarine-to-subaerial dacitic and andesitic lava domes and (5) subaerial lava-pumice cone volcanoes. The volcanic facies are interbedded with a sedimentary facies association comprising sandstone and/or fossiliferous mudstone mainly derived from erosion of pre-existing volcanic deposits. The main facies associations are interpreted to have conformable, disconformable, and interfingering contacts, and there are no mappable angular unconformities or disconformities within the volcanic succession.Electronic Supplementary Material Supplementary material is available for this article at  相似文献   
33.
A new approach to the parametrization of the cumulus-capped boundary layer is described. It combines a traditional higher-order turbulence closure, appropriate for boundary layers where the skewness of thermodynamic variable probability distributions is low (typically stratocumulus-capped), with non-local scaled similarity functions. These are introduced in order to represent explicitly that part of the distribution arising from skewed cumulus elements and the scalings are found to work very well against equilibrium shallow cumulus large-eddy simulations. Results from a wide range of single column model simulations, from stratocumulus to shallow cumulus to cumulus rising into stratocumulus, are presented that demonstrate the validity of the approach as a means of parametrizing the cloudy boundary layer. Sensitivity tests show that enhancement of the turbulence length scales and the buoyancy production of TKE are especially important.  相似文献   
34.
Momo-iwa, Rebun Island, Hokkaido, Japan, is a dacite cryptodome 200–300 m across and 190 m high. The dome is inferred to have intruded wet, poorly consolidated sediment in a shallow marine environment. The internal structure of the dome is concentric, with a massive core, banded rim, and narrow brecciated border, all of which are composed of compositionally uniform feldspar-phyric dacite. Boundaries between each of the zones are distinct but gradational. The massive core consists of homogeneous coherent (unfractured) dacite and is characterized by radial columnar joints 60–200 cm across. The banded rim encircles the massive core and is 40 m wide. It is characterized by large-scale flow banding parallel to the dome surface. The flow banding comprises alternating partly crystalline and more glassy bands 80–150 cm thick. The outermost brecciated border is up to 80 cm thick, and consists of in situ breccia and blocky peperite. The in situ breccia comprises polyhedral dacite clasts 5–20 cm across and a cogenetic granular matrix. The blocky peperite consists of polyhedral dacite clasts 0.5–2 cm across separated by the host sediment (mudstone). The internal structures of the dome suggest endogenous growth involving a continuous magma supply during a single intrusive phase and simple expansion from the interior. Although much larger, the internal structures of Momo-iwa closely resemble those of lobes in subaqueous felsic lobe-hyaloclastite lavas.  相似文献   
35.
In North Africa, the Algerian margin is made of basement blocks that drifted away from the European margin, namely the Kabylia, and docked to the African continental crust in the Early Miocene. This young margin is now inverted, as dated Miocene (17 Ma) granites outcrop alongshore, evidencing kilometre‐scale exhumation since their emplacement. Age of inversion is actually unknown, although Pliocene is often considered in the offshore domain. To decipher the exhumation history of the margin between 17 and 5 Ma, we performed a coupled apatite fission track (AFT) and (U–Th–Sm)/He (AHe) study in the Cap Bougaroun Miocene granite. AFT dates range between 7 ± 1 and 10 ± 1 Ma, and mean AHe dates between 8 ± 2 and 10 ± 1 Ma. These data evidence rapid and multi‐kilometre exhumation during Tortonian times. This event cannot be related to slab break‐off but instead to the onset of margin inversion that has since developed as an in‐sequence north‐verging deforming prism.  相似文献   
36.
A geological /geophysical survey of the western Solomon Sea and Manus Basin, northeastern Bismarck Sea, was carried out in 1983-84. The results of the survey and associated studies are reported in this issue and a later issue ofGeo-Marine Letters.  相似文献   
37.
Pioneer is an open‐air, stratified, multicomponent archaeological site located in the upper Snake River Plain of southeastern Idaho, USA. Block excavations provided an opportunity to contribute to the Late Quaternary geomorphic history of the Big Lost River drainage and provide geochronological context of archaeological components at the site. The stratigraphic sequence is interpreted as reflecting multiple depositional episodes and five soil‐formation periods beginning pre‐7200 cal. yr B.P. and lasting to the historic period. The stratigraphic sequence contains an archaeological component dated to ∼3800 cal. yr B.P. and several other components post‐800 cal. yr B.P. Major site formation processes include fluvial deposition and erosion, pedogenesis (accumulation of secondary carbonates), and bioturbation. Periods of increased deposition at Pioneer and elsewhere along the Big Lost River are inferred to have occurred between ∼8400–6500 cal. yr B.P. and ∼2700–400 cal. yr B.P., potentially related to cooler/wetter episodes of the mid‐to‐late Holocene, including increased precipitation during the Medieval Climatic Anomaly (post‐750 cal. yr B.P.). There is also evidence of a high‐energy erosional event at ∼3800 cal. yr B.P. indicating a large middle Holocene flood. Pioneer provides an example of the archaeological and paleoclimatic value of studying alluvial buried soil stratigraphic sequences in arid environments.  相似文献   
38.
The structural signature in the area between the Baguio mineral district and Ansagan, Tuba, Benguet in the South Central Cordillera, northern Luzon, Philippines, is dominated by northeast- to ENE-trending faults, contained within a NNW–SSE-trending transtensional strip. This 50-km-long, 25-km-wide elongated tectonic zone is bounded to the west by the Pugo Fault and to the east by the Tebbo Fault, both being branches of the Philippine Fault System. Detailed structural geological (particularly microtectonic) analysis of fracture and mineral vein systems indicates strong conformity with the regional structural direction. Computed extensional stress axis σ3 directions are oriented N150° on average, sub-parallel to the strike of the bounding faults. The existence of known mineral deposits and prospects within the tectonic strip implies an intimate relationship between transtension and mineral occurrence.  相似文献   
39.
The Volcanic Sedimentary Complex (VSC) of the Iberian Pyrite Belt (IPB) in southern Portugal and Spain, comprises an Upper Devonian to Lower Carboniferous submarine succession with a variety of felsic volcanic lithofacies. The architecture of the felsic volcanic centres includes felsic lavas/domes, pyroclastic units, intrusions and minor mafic units that define lava–cryptodome–pumice cone volcanoes. The diversity of volcanic lithofacies recognized in different areas of the IPB mainly reflects variations in proximity to source, but also differences in the eruption style. The IPB volcanoes are intrabasinal, range in length from 2 km to > 8 km and their thickest sections vary from ∼ 400 m to > 800 m. These volcanoes are dominated by felsic lavas/domes that occur at several stratigraphic positions within the volcanic centre, however the pyroclastic units are also abundant and are spatially related to the lavas/domes. The intrusions are minor, and define cryptodomes and partly-extrusive cryptodomes. The hydrothermal systems that formed the Neves Corvo and Lousal massive sulfide ore deposits are associated with effusive units of felsic volcanic centres. At Neves Corvo, the massive sulfide orebodies are associated to rhyolitic lavas that overlie relatively thick fiamme-rich pyroclastic unit. In several other locations within the belt, pyroclastic units contain sulfide clasts that may have been derived from yet to be discovered coeval massive sulfide deposits at or below the sea floor, which enhances the exploration potential of these pyroclastic units and demonstrates the need for volcanic facies analysis in exploration.  相似文献   
40.
A geological /geophysical survey of the western Solomon Sea and Manus Basin, northeastern Bismarck Sea, was carried out in 1983-84. The results of the survey and associated studies are reported in this issue and a later issue ofGeo-Marine Letters.  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