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   61篇
  免费   0篇
大气科学   2篇
地球物理   11篇
地质学   10篇
海洋学   29篇
自然地理   9篇
  2023年   1篇
  2020年   1篇
  2019年   1篇
  2016年   1篇
  2013年   1篇
  2012年   3篇
  2011年   2篇
  2010年   2篇
  2009年   3篇
  2008年   2篇
  2007年   12篇
  2006年   4篇
  2005年   2篇
  2004年   5篇
  2002年   1篇
  2001年   5篇
  2000年   2篇
  1998年   2篇
  1997年   2篇
  1996年   1篇
  1994年   2篇
  1993年   1篇
  1990年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
排序方式: 共有61条查询结果,搜索用时 343 毫秒
21.
Numerous cirques of the Lofoten–Vesterålen archipelago in northern Norway have distinct moraine sequences that previously have been assigned to the Allerød-Younger Dryas ( 13,400 to 11,700 yr BP) interval, constraining the regional distribution of the equilibrium-line altitude (ELA) of cirque and valley glaciers. Here we present evidence from a once glacier-fed lake on southern Andøya that contests this view. Analyses of radiocarbon dated lacustrine sediments including rock magnetic parameters, grain size, organic matter, dry bulk density and visual interpretation suggest that no glacier was present in the low-lying cirque during the Younger Dryas-Allerød. The initiation of the glacial retreat commenced with the onset of the Bølling warming ( 14,700 yr BP) and was completed by the onset of Allerød Interstade ( 13,400 yr BP). The reconstructed glacier stages of the investigated cirque coincide with a cool and dry period from  17,500 to 14,700 yr BP and a somewhat larger Last Glacial Maximum (LGM) advance possibly occurring between  21,050 and 19,100 yr BP.  相似文献   
22.
Why do fishers break rules? And why do they follow them? The answers to these pertinent questions could contribute to reducing overfishing, stock decimation, environmental degradation, economic losses and community failures. This explorative paper presents findings from a nationwide survey among Swedish fishers, who were asked what, in their opinion, would justify non-compliance, why fisheries management regulations are not being respected, and what might help improve the situation. The survey was conducted to test four inducements often suggested in the literature: Fishers’ compliance/non-compliance is based on (a) their own benefit, (b) whether they feel morally compelled to do one way or another, (c) whether compliance is believed to create a negative impression among peers and (d) whether they accept the justification given for introducing the rules. Among other things, the study finds that the moral motives of law-abidingness and peer group solidarity rank the highest among the reasons for compliance, that large-scale fishers are more concerned about deterrence than small- and medium-scale fishers and also that co-management experience makes fishers less inclined to accept non-compliance by fishers who seek to boost their income.  相似文献   
23.
In June/July 1994 a study was made of a small bloom of the coccolithophorid Emiliania huxleyi in an area of the North Sea to the east of the Shetland Islands. Observations on the hydrography of the study area indicated the bloom was associated with Atlantic water and was confined to an area in which a stable shallow mixed layer had formed. There was no evidence to suggest association of horizontal physical structure with the bloom development. High cell densities of >1– cells dm−3, together with low concentrations of PIC (<50 μg dm−3) and detached liths (2– liths cm−3) indicated that the bloom was studied at an early stage of development. Biochemical and physiological observations indicated active growth was taking place. The results presented are discussed in comparison with previous studies carried out in both oceanic and shelf seas.  相似文献   
24.
The Bam Earthquake of 26 December 2003   总被引:3,自引:0,他引:3  
The devastating earthquake of 26 December 2003 claimed more than 26,000 lives in the city of Bam and surrounding towns and villages in Southeast Iran, and left the majority of the Bam population homeless. The reason for this tragedy was an unfortunate combination of geological, social and human circumstances. The causative fault practically traversed the city of Bam and the earthquake occurred at a shallow depth. The residential buildings were completely inappropriate for a seismic region, being extremely vulnerable to earthquake shaking, and the earthquake occurred early in the morning when most people were still sleeping. The damage pattern was nearly symmetric about a line 3 km to the west of the surface expression of the Bam fault, and the damage attenuated rapidly with distance from this line. The industrial facilities and the lifelines performed relatively well and experienced slight to moderate damage, but this might have been due to their distance from the earthquake epicentre. However, many of the qanat (traditional subterranean irrigation channels) chains that served the twin cities of Bam and Baravat collapsed. Emergency facilities (hospitals, police and fire stations), schools and the university were destroyed and/or heavily damaged during the earthquake. The geotechnical effects of the earthquake were not significant. There was little evidence that site response effects played a major role in the damage pattern in the city. There were no reports of liquefaction and only minor sliding activity took place during the event. A unique set of strong motion acceleration recordings were obtained at the Bam accelerograph station. The highest peak ground acceleration (nearly 1g) was recorded for the vertical component of the motion. However, the longitudinal component (fault-parallel motion in N–S direction) clearly had the largest energy flux, as well as the largest maximum velocity and displacement.  相似文献   
25.
26.
Dried samples of the red algae Solieria filiformis and Agardhiella subulata from Mar Piccolo, Taranto, were extracted by stirring in water at 25 (Cold), 85 (Hot) and 120 (pressure) °C. For each species, six successive cold, three hot and two pressure extractions were performed and analyzed separately. Water-soluble polysaccharides were isolated after treatment with amylase, alcohol precipitation, dialysis and freeze drying. The total, starch-free yields were 27 and 24% of the dry weight for S. filiformis (SF) and A. subulata (AS), respectively. FTIR and NMR spectroscopic analysis showed that the different cold and hot water extracts had a similar structural backbone, which can be characteristic of gelling type carrageenans with a dominant iota repeating structure (DA2S-G4S). However, some irregularities were detected by NMR, which may be attributed to 6-sulphated 4-linked precursor units. The occurrence of such and other irregularities was more frequent in the SF samples, giving a possible explanation for the enhanced extractability in cold water of carrageenan polymers from this species.  相似文献   
27.
28.
Marine Protected Areas (MPAs) are established for various purposes. Some are aimed at protection, some are intended as resource management tools, while others imply both of these objectives, as well as others. Regardless of the stated goals, the same MPA can mean different things to different people, and these meanings may be inconsistent. In practice, MPA goals are not always stated clearly, and even if they are, they do not necessary align well with what the different actors have in mind. Moreover, the stated goals are not always those that govern the actual operation of MPAs. The priorities of goals may also change over time for stakeholders and for MPAs. In this paper we argue that the goals of MPAs should not be assumed a priori but should be researched empirically. Thus, before we can answer why MPAs succeed or fail in reaching their goals, we must ask what these goals are in the first place and how they came into existence. How are they, for instance, established, negotiated and agreed upon among stakeholders? How do they reflect particular interests, perspectives and power differentials of those involved? Here, we provide a framework for how to analyze the formation, complexity, and displacement of goals in MPAs, presenting three case studies as illustration.  相似文献   
29.
30.
High‐resolution loss‐on‐ignition analyses of lacustrine sediment cores from both proglacial and non‐glacial lakes in southern Norway have revealed a specific pattern characterised by a significant, two‐peaked reduction of the loss‐on‐ignition values in the basal half of the cores. In non‐glacier‐fed lakes, the loss‐on‐ignition variations are interpreted to reflect mainly lake productivity and hence variability in surface summer air temperature. Sediments deposited in proglacial lakes, however, reflect mainly the glacier activity in the lake catchment. Bulk AMS radiocarbon dates from the core sequences and the loss‐on‐ignition curve pattern suggest that this event correlates with the ‘8200 cal. yr BP event’ recorded in the GRIP and GISP2 Greenland ice‐cores, termed the Finse event in southern Norway. Copyright © 2001 John Wiley & Sons, Ltd.  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