全文获取类型
收费全文 | 272篇 |
免费 | 19篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 42篇 |
地球物理 | 66篇 |
地质学 | 99篇 |
海洋学 | 23篇 |
天文学 | 38篇 |
自然地理 | 24篇 |
出版年
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 16篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 19篇 |
2012年 | 21篇 |
2011年 | 14篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 11篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有295条查询结果,搜索用时 31 毫秒
201.
Benjamin M. Sleeter Terry L. Sohl Michelle A. Bouchard Ryan R. Reker Christopher E. Soulard William Acevedo Glenn E. Griffith Rachel R. Sleeter Roger F. Auch Kristi L. Sayler Stephen Prisley Zhiliang Zhu 《Global Environmental Change》2012,22(4):896-914
Global environmental change scenarios have typically provided projections of land use and land cover for a relatively small number of regions or using a relatively coarse resolution spatial grid, and for only a few major sectors. The coarseness of global projections, in both spatial and thematic dimensions, often limits their direct utility at scales useful for environmental management. This paper describes methods to downscale projections of land-use and land-cover change from the Intergovernmental Panel on Climate Change's Special Report on Emission Scenarios to ecological regions of the conterminous United States, using an integrated assessment model, land-use histories, and expert knowledge. Downscaled projections span a wide range of future potential conditions across sixteen land use/land cover sectors and 84 ecological regions, and are logically consistent with both historical measurements and SRES characteristics. Results appear to provide a credible solution for connecting regionalized projections of land use and land cover with existing downscaled climate scenarios, under a common set of scenario-based socioeconomic assumptions. 相似文献
202.
Colin A. Simpfendorfer Garin G. Freitas Tonya R. Wiley Michelle R. Heupel 《Estuaries and Coasts》2005,28(1):78-85
The distribution and salinity preference of immature bull sharks (Carcharhinus leucas) were examined based on the results of longline surveys in three adjacent estuarine habitats in southwest Florida: the Caloosahatchee
River, San Carlos Bay, and Pine Island Sound. Mean sizes were significantly different between each of these areas indicating
the occurrence of size-based habitat partitioning. Neonate and young-of-the-year animals occurred in the Caloosahatchee River
and juveniles older than 1 year occurred in the adjacent embayments. Habitat partitioning may reduce intraspecific predation
risk and increase survival of young animals. Classification tree analysis showed that both temperature and salinity were important
factors in determining the occurrence and catch per unit effort (CPUE) of immatureC. leucas. The CPUE of <1 year oldC. leucas was highest at temperatures over 29°C and in areas with salinities between 7‰ and 17.5‰ Although they are able to osmoregulate
in salinities from fresh to fully marine, youngC. leucas may have a salinity preference. Reasons for this preference are unknown, but need to be further investigated. 相似文献
203.
A. A. Peyve S. G. Skolotnev M. Ligi N. N. Turko E. Bonatti S. Yu. Kolodyazhnyi N. P. Chamov N. V. Tsukanov Yu. E. Baramykov A. E. Eskin N. Grindlay J. G. Sclater D. Brunelly A. N. Pertsev A. Cipriani G. Bortoluzzi R. Mercuri E. Paganelli F. Muccini Ch. Takeuchi F. Zaffagnini K. O. Dobrolyubova 《Doklady Earth Sciences》2007,416(1):991-994
204.
A. A. Peyve S. G. Skolotnev M. Ligi N. N. Turko E. Bonatti S. Yu. Kolodyazhnyi N. P. Chamov N. V. Tsukanov Yu. E. Baramykov A. E. Eskin N. Grindlay J. G. Sclater D. Brunelly A. N. Pertsev A. Cipriani G. Bortoluzzi R. Mercuri E. Paganelli F. Muccini Ch. Takeuchi F. Zaffagnini K. O. Dobrolyubova 《Doklady Earth Sciences》2007,416(7):991-994
205.
Seagrass population dynamics and water quality in the Great Barrier Reef region: a review and future research directions 总被引:6,自引:0,他引:6
Seagrasses in the Great Barrier Reef region, particularly in coastal habitats, act as a buffer between catchment inputs and reef communities and are important habitat for fisheries and a food source for dugong and green turtle. Within the Great Barrier Reef region there are four different seagrass habitat types now recognised. The spatial and temporal dynamics of the different types of seagrass habitat is poorly understood. In general seagrass growth is limited by light, disturbance and nutrient supply, and changes to any or all of these limiting factors may cause seagrass decline. The capacity of seagrasses to recover requires either recruitment via seeds or through vegetative growth. The ability of seagrass meadows to recover from large scale loss of seagrass cover observed during major events such as cyclones or due to anthropogenic disturbances such as dredging will usually require regeneration from seed bank. Limited research into the role of pollutants on seagrass survival suggests there may be ongoing impacts due to herbicides, pesticides and other chemical contaminants. Further research and monitoring of seagrass meadow dynamics and the influence of changing water quality on these is needed to enhance our ability to manage seagrasses on the Great Barrier Reef. 相似文献
206.
207.
George W. Luther Shufen Ma Robert Trouwborst Brian Glazer Michelle Blickley Robert W. Scarborough Michael G. Mensinger 《Estuaries and Coasts》2004,27(3):551-560
In 2001, the development of seasonal anoxia was studied in two waterways located at the head of Delaware’s northern inland
bay, Rehoboth Bay. Bald Eagle Creek is a northern tributary of the bay, which has tidal exchange with Torquay Canal (a dead-end
canal) via a short channel with a 1.4 m sill. Mean low water depth in Torquay Canal is about 2 m, but dredging produced over
a dozen depressions with a total water depth of 5.5 m. During the summer of 2000, four major fish kills were reported in Torquay
Canal and Bald Eagle Creek with more than 2.5 million juvenile menhaden (Brevoortia tyrannus) killed. Low O2 concentration was assumed to be the problem but production of toxic H2S is more likely. From late spring 2001, we conducted in situ determination of temperature, salinity, pH, dissolved O2, and H2S in Torquay Canal and Bald Eagle Creek. During spring, water column stratification began in the depressions with warmer and
less salty water observed in the upper layer, and cooler, saltier water below 2 m. O2 was at saturation levels in the surface waters but was not detectable below 2 m by the end of May. The depressions were anoxic
with H2S accumulating to mM concentrations in June. A storm event prior to July 12 mixed these two layers with a subsequent loss
of H2S. The H2S levels again increased in the deep water due to stratification and reached another maximum in late August. Another storm
event occurred at this time resulting in no detectable O2 and up to 400 μM H2S in surface waters. H2S appears to be the primary reason for fish kills in these tributaries. Aerators installed in Torquay Canal on June 21 had
no significant effect on abating stratification and anoxic conditions beyond their immediate area. 相似文献
208.
Late Cretaceous and Cenozoic sea-level estimates: backstripping analysis of borehole data, onshore New Jersey 总被引:1,自引:0,他引:1
William A. Van Sickel Michelle A. Kominz Kenneth G. Miller† James V. Browning† 《Basin Research》2004,16(4):451-465
Backstripping analysis of the Bass River and Ancora boreholes from the New Jersey coastal plain (Ocean Drilling Project Leg 174AX) provides new Late Cretaceous sea‐level estimates and corroborates previously published Cenozoic sea‐level estimates. Compaction histories of all coastal plain boreholes were updated using porosity–depth relationships estimated from New Jersey coastal plain electric logs. The new porosity estimates are considerably lower than those previously calculated at the offshore Cost B‐2 well. Amplitudes and durations of sea‐level variations are comparable in sequences that are represented at multiple boreholes, suggesting that the resultant curves are an approximation of regional sea level. Both the amplitudes and durations of third‐order (0.5–5 Myr) cycles tend to decrease from the Late Cretaceous to the late Miocene. Third‐order sea‐level amplitudes in excess of 60 m are not observed. Long‐term (108–107 years) sea level was approximately constant at 30–80 m in the Late Cretaceous, rose to a maximum early Eocene value of approximately 100–140 m, and then fell through the Eocene and Oligocene. 相似文献
209.
Antonio Tadeu dos Reis Christian Gorini Alain Mauffret Michelle Mepen 《Comptes Rendus Geoscience》2004,336(2):125-133
The Pyreneo-Languedocian submarine sediment body, located in the western sector of the Gulf of Lions, is an example of a fan-like depositional system essentially controlled by salt tectonics. The area was subjected to a combined effect of overburden subsidence into the evacuated salt layer and a significant distal salt thickening, due to preferential basinward salt migration. This mode of salt migration impacted the Quaternary sea-bottom morphology by creating a large midslope topographic low, providing space accommodation for the Pyreneo-Languedocian fan. At gulf scale, the fan is a unique feature because unchannelized sedimentary environment in the area occurs at slope level, thus in minor water depth in relation to all other deep-water sedimentary systems offshore Gulf of Lions. To cite this article: A.T. dos Reis et al., C. R. Geoscience 336 (2004). 相似文献
210.
Variations in Alpine white mica 40Ar/39Ar dates from the cover units of the Siviez-Mischabel Nappe relate to regional variations in the thermal history of the nappe. We focus on three regions within the nappe: the central Siviez-Mischabel (CSM), the southern Siviez-Mischabel (SSM), and the eastern Siviez-Mischabel (ESM). Our approach weaves together observations of quartz and mica textures in thin section, the variation of 40Ar/39Ar date with grain size, considerations of the effective diffusion dimension (EDD) of argon in white mica, and a comparison of dates with diffusion model results. In the CSM, pressure solution of quartz and dislocation glide in mica accommodated Alpine deformation. Dates record mica growth during nappe emplacement from 40 to 36 Ma and do not vary with grain size. In the SSM and ESM, both mica and quartz show textures associated with dynamic recrystallization, and dates decrease with grain size. In the SSM, dates also agree with the timing of nappe emplacement, but in the ESM, dates significantly post-date the timing of nappe emplacement. A comparison of dates with diffusion model results supports inferences from rock fabrics that the SSM experienced higher peak temperatures than the CSM, even though dates from both units approximate the timing of mica growth. Dates obtained from the ESM, however, do not compare well with simple models, and the thermal evolution of this region of the nappe, in the neighborhood of the Simplon Fault Zone, is not well understood. 相似文献