全文获取类型
收费全文 | 247篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 37篇 |
地球物理 | 52篇 |
地质学 | 90篇 |
海洋学 | 39篇 |
天文学 | 24篇 |
自然地理 | 12篇 |
出版年
2023年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 24篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 17篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 22篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有258条查询结果,搜索用时 15 毫秒
251.
Assessing climate change impacts on the Iberian power system using a coupled water-power model 总被引:1,自引:1,他引:0
Silvio J. Pereira-Cardenal Henrik Madsen Karsten Arnbjerg-Nielsen Niels Riegels Roar Jensen Birger Mo Ivar Wangensteen Peter Bauer-Gottwein 《Climatic change》2014,126(3-4):351-364
Climate change is expected to have a negative impact on the power system of the Iberian Peninsula; changes in river runoff are expected to reduce hydropower generation, while higher temperatures are expected to increase summer electricity demand, when water resources are already limited. However, these impacts have not yet been evaluated at the peninsular level. We coupled a hydrological model with a power market model to study three impacts of climate change on the current Iberian power system: changes in hydropower production caused by changes in precipitation and temperature, changes in temporal patterns of electricity demand caused by temperature changes, and changes in irrigation water use caused by temperature and precipitation changes. A stochastic dynamic programming approach was used to develop operating rules for the integrated system given hydrological uncertainty. We found that changes in precipitation will reduce runoff, decrease hydropower production (with accompanying increases in thermal generation), and increase irrigation water use, while higher temperatures will shift power demand from winter to summer months. The combined impact of these effects will generally make it more challenging to balance agricultural, power, and environmental objectives in the operation of Iberian reservoirs, though some impacts could be mitigated by better alignment between temporal patterns of irrigation and power demands. 相似文献
252.
ABSTRACTDue to more frequent extreme rainfall incidents in recent years, many large cities are considering the construction of new drainage systems to cope with rainfall in the order of 100-year events. In such cases, T-year point rainfall events should be supplemented with areal reduction factors (ARF) to avoid overdesign. To facilitate an initial design, a procedure based on using Chicago Design Storms (CDS) in combination with intensity–duration–area (IDA) curves was developed to produce CDS-ARF input rainfall. By means of the time of concentration, a specific instantaneous unit hydrograph (IUH) was obtained for each subcatchment. Combination of CDS-ARF rains and the subcatchment IUHs using convolution integrals was used to produce inflow hydrographs to the drainage system. A sequential design procedure that successively includes subcatchments for the entire drainage system in the downstream direction is implemented and exemplified ensuring a consistent initial design. 相似文献
253.
Polarized Fourier-transform infrared and Raman spectra were acquired on an elbaite sample previously characterized by electron- and ion microprobe analysis, X-ray diffraction and structure refinement. Spectra from the two vibrational spectroscopy techniques reveal a close similarity in the OH-stretching region, with three main absorption bands strongly polarized in the c-axis direction. By means of bond-valence theory arguments, the observed OH bands are interpreted and assigned to specific local cation arrangements around the O1 (≡W) and O3 (≡V) anion sites. In combination with the relatively simple composition of the studied sample, bond-valence constraints are used to identify stable anion-cation arrangements, which permit the occurrence of short-range ordering to be assessed. Evidence for nearly complete short-range order at the O1 site, with the stable arrangements Y(LiAlAl)0.6–W(OH)0.6 and Y(LiLiAl)0.4–W(F)0.4, are presented. These two local arrangements can be further expanded to obtain the larger ordered clusters [W(OH)–Y(LiAl2)–V(OH)3–Z(Al)6]0.6 and [W(F)–Y(Li2Al)–V(OH)3–Z(Al)6]0.4. 相似文献
254.
Claudia?Aparicio Jan?FilipEmail author Henrik?Skogby Zdenek?Marusak Miroslav?Mashlan Radek?Zboril 《Physics and Chemistry of Minerals》2012,39(4):311-318
The thermally induced reductive decomposition of a natural near end-member almandine [VIII(Fe2.85Mg0.11Ca0.05Mn0.02)VI(Al1.99)IV(Si2.99)O12] and possible hydrogen diffusion into its structure have been carried out at temperatures up to 1,200°C, monitored by simultaneous thermogravimetric analysis and differential scanning calorimetry (DSC), infrared and 57Fe Mössbauer spectroscopy and X-ray powder diffraction. Below 1,000°C, evidence for hydrogen diffusion into almandine structure was not observed. At temperatures above 1,000°C, reductive decomposition sets in, as displayed by a sharp endothermic peak at 1,055°C on the DSC curve accompanied by a total mass loss of 3.51%. We observe the following decomposition mechanism: almandine + hydrogen → α-Fe + cristobalite + hercynite + water. At higher temperatures, fayalite and sekaninaite are formed by consecutive reaction of α-Fe with cristobalite and water, and cristobalite with hercynite, respectively. The metallic α-Fe phase forms spherical and isolated particles (~1 μm). 相似文献
255.
Colby A. Smith Martin Sundh Henrik Mikko 《International Journal of Earth Sciences》2014,103(6):1711-1724
In Sweden, knowledge of the location and timing of glacially induced faulting and seismicity is critical to effective engineering of a long-term nuclear disposal facility. To improve understanding and modeling of the complex ice-induced and tectonic stresses associated with glacially induced faulting, field studies detailing the location and timing of movement of such structures are required. Although the fault has not been confirmed in the bedrock, multi-proxy surficial geologic evidence indicates that the recently discovered scarp in Bollnäs is such a structure. Machine-excavated trenches across the scarp reveal landsliding down the scarp and, in one location, faulted and vertically offset fine-grained glacial sediments. The presence of water-escape structures in trenches excavated on a topographic high strongly suggests a co-seismic origin derived from earthquake magnitudes >5.5. Numerous landslides in till exist in the region as well. Four slopes with landslides were examined in detail, and the factors of safety for these slopes indicate stable conditions and suggest a seismic trigger. Basal radiocarbon dates from peat bogs located stratigraphically above the landslides provide minimum limiting ages for the co-seismic landslides. The oldest date indicates sliding prior to 10,180 calendar years before the present. The proposed Bollnäs Fault is 400 km south of the so called Lapland Fault Province. To date, it is the southernmost confirmed glacially induced fault in Sweden. The results of this study are consistent with existing modeling results that indicate fault instability in this region of central Sweden following deglaciation. 相似文献
256.
Fifty interconnecting loops (ILs) that are induced by new-born active regions are investigated. The formation period of four
ILs including two same-hemisphere interconnecting loops (HILs) and two transequatorial loops (TLs) are analyzed. The magnetic
flux related with these loops is studied. Considering the active region pairs related with the IL as a magnetic system, the
total magnetic flux has a tendency of increasing for this system, the signs of net magnetic flux tend to be opposite for the
active region pairs. There is no difference between HILs and TLs in this aspect. 相似文献
257.
258.
Jussi Hovikoski Alfred Uchman Rikke Weibel Henrik Nøhr-Hansen Emma Sheldon Jon Ineson Morten Bjerager Jens Therkelsen Mette Olivarius Michael Larsen Peter Alsen Jørgen Bojesen-Koefoed 《Sedimentology》2020,67(7):3619-3654
Reported ancient bottom current deposits in deep marine settings are scarce and most of them remain contentious. This study describes sedimentological, ichnological and petrographical characteristics of a drill core that covers ca 10 Myr of Upper Cretaceous stratigraphy at Hold with Hope, north-east Greenland. The core is divided into four facies associations, which are interpreted to reflect deposition from bottom currents, turbidity flows and hemipelagic settling in slope and/or near slope environments. The evidence for bottom current influence is three-fold. Firstly, pervasive indications of winnowing such as marine bioclast-rich lags and outsized clasts on ‘mud on mud’ contacts are suggestive of low-sediment concentration flows capable of transporting up to pebble-sized clasts. Common Mn–Fe–Mg rich carbonate matrix cements and various types of hiatal chemogenic lag deposits showing glauconite, apatite and carbonate clasts also point to condensation, prolonged exposure at the sediment–water interface and recurrent phases of sea-floor erosion. Secondly, such deposits can show indicators for tidal processes such as double mud-drapes, tangential bottom sets in dune-scale cross-bedding and cyclic rhythmites. Thirdly, inverse to normal grading at various scales is common in fully marine, commonly seafloor-derived sediments. Ichnological data indicate considerable taxonomic variability in the bottom current deposits, but recurrent fabrics are characteristically dominated by morphologically simple burrows such as Thalassinoides and Planolites, with secondary Phycosiphon, Nereites, Zoophycos and/or Chondrites. In general, opportunistic taxa are common whereas mature composite ichnofabrics are rare. The omission surfaces are locally burrowed with stiffground to firmground trace fossil suites. The results contribute to establishing sedimentological, ichnological and mineralogical criteria for recognition of bottom current deposits as well as to the understanding of the Late Cretaceous palaeoenvironmental evolution of the Arctic region. 相似文献