全文获取类型
收费全文 | 186篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 18篇 |
地球物理 | 42篇 |
地质学 | 82篇 |
海洋学 | 13篇 |
天文学 | 25篇 |
综合类 | 2篇 |
自然地理 | 10篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 15篇 |
2010年 | 14篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 5篇 |
2006年 | 8篇 |
2005年 | 3篇 |
2004年 | 7篇 |
2003年 | 1篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1969年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有196条查询结果,搜索用时 15 毫秒
91.
M. F. Correia M. A. F. da Silva Dias M. R. da Silva Aragão 《Meteorology and Atmospheric Physics》2006,94(1-4):103-113
Summary Sobradinho Lake lies in the S?o Francisco River Basin, in one of the most arid regions in Northeastern Brazil, within a land
stretch categorized as the Lower-middle S?o Francisco, situated at about 40 km away from the municipality of Petrolina (09°23′S–40°30′W)
in the state of Pernambuco. The dam, in its full capacity, consists of a lake of approximately 4,214 km2; 280 km in length, the width of which varies from 5 to 50 km. The dam storage capacity is that of 34.1 billion m3 of water. Being situated in a semi-arid region, the dam brought about significant development to local irrigated agriculture.
The caatinga ecosystem has, for that matter, undergone considerable changes. Statistical analysis techniques applied to data collected
before and after the filling of the lake, made it possible both to make an assessment of the impact of the dam construction
on the region meteorology and to diagnose the variability of such an impact on environmental conditions. Results showed that
the dam has brought about considerable changes to regional meteorology. The alterations were observed to be more significant
as regards atmospheric humidity and wind speed. 相似文献
92.
Degeneracy effects for bosons are more important for smaller particle mass, smaller temperature and higher number density. Bose condensation requires that particles be in the same lowest energy quantum state. We propose a cosmic background Bose condensation, present everywhere, with its particles having the lowest quantum energy state, ?c/λ, with λ about the size of the visible universe, and therefore unlocalized. This we identify with the quantum of the self gravitational potential energy of any particle, and with the bit of information of minimum energy. The entropy of the universe (~10122 bits) has the highest number density (~1036 bits/cm3) of particles inside the visible universe, the smallest mass, ~10?66 g, and the smallest temperature, ~10?29 K. Therefore it is the best candidate for a Cosmic Background Bose Condensation (CBBC), a completely calmed fluid, with no viscosity, in a superfluidity state, and possibly responsible for the expansion of the universe. 相似文献
93.
Charles S. Cockell Matt Balme John C. Bridges Alfonso Davila Susanne P. Schwenzer 《Icarus》2012,217(1):184-193
Investigations of Mars as a potential location for life often make the assumption that where there are habitats, they will contain organisms. However, the observation of the ubiquitous distribution of life in habitable environments on the Earth does not imply the presence of life in martian habitats. Although uninhabited habitats are extremely rare on the Earth, a lack of a productive photosynthetic biosphere on Mars to generate organic carbon and oxygen, thus providing a rapidly available redox couple for energy acquisition by life and/or a lack of connectivity between habitats potentially increases the scope and abundance of uninhabited habitats for much of the geological history of the planet. Uninhabited habitats could have existed on Mars from the Noachian to the present-day in impact hydrothermal systems, megaflood systems, lacustrine environments, transient melted permafrost, gullies and local regions of volcanic activity; and there may be evidence for them in martian meteorites. Uninhabited habitats would provide control habitats to investigate the role of biology in planetary-scale geochemical processes on the Earth and they would provide new constraints on the habitability of Mars. Future robotic craft and samples returned from Mars will be able to directly show if uninhabited habitats exist or existed on Mars. 相似文献
94.
Assessing Groundwater Depletion and Dynamics Using GRACE and InSAR: Potential and Limitations
下载免费PDF全文
![点击此处可从《Ground water》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pascal Castellazzi Richard Martel Devin L. Galloway Laurent Longuevergne Alfonso Rivera 《Ground water》2016,54(6):768-780
In the last decade, remote sensing of the temporal variation of ground level and gravity has improved our understanding of groundwater dynamics and storage. Mass changes are measured by GRACE (Gravity Recovery and Climate Experiment) satellites, whereas ground deformation is measured by processing synthetic aperture radar satellites data using the InSAR (Interferometry of Synthetic Aperture Radar) techniques. Both methods are complementary and offer different sensitivities to aquifer system processes. GRACE is sensitive to mass changes over large spatial scales (more than 100,000 km2). As such, it fails in providing groundwater storage change estimates at local or regional scales relevant to most aquifer systems, and at which most groundwater management schemes are applied. However, InSAR measures ground displacement due to aquifer response to fluid‐pressure changes. InSAR applications to groundwater depletion assessments are limited to aquifer systems susceptible to measurable deformation. Furthermore, the inversion of InSAR‐derived displacement maps into volume of depleted groundwater storage (both reversible and largely irreversible) is confounded by vertical and horizontal variability of sediment compressibility. During the last decade, both techniques have shown increasing interest in the scientific community to complement available in situ observations where they are insufficient. In this review, we present the theoretical and conceptual bases of each method, and present idealized scenarios to highlight the potential benefits and challenges of combining these techniques to remotely assess groundwater storage changes and other aspects of the dynamics of aquifer systems. 相似文献
95.
Anoop S. Mahajan Lisa K. Whalley Elena Kozlova Hilke Oetjen Luis Mendez Kate L. Furneaux Andrew Goddard Dwayne E. Heard John M. C. Plane Alfonso Saiz-Lopez 《Journal of Atmospheric Chemistry》2010,66(3):167-178
Measurements of formaldehyde (HCHO) were made at the Cape Verde Atmospheric Observatory between November 2006 and June 2007 using the Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) technique. Observations show that typical HCHO mixing ratios ranged between 350 and 550 pptv (with typical 2-σ uncertainties of ~110 pptv), with several events of high HCHO, the maximum being 1,885?±?149 pptv. The observations indicate a lack of strong seasonal or diurnal variations, within the uncertainty of the measurements. A box model is employed to test whether the observations can be explained using known hydrocarbon photochemistry; the model replicates well the typical diurnal profile and monthly mean values. The model results indicate that on average 20% of HO2 production and 10% of OH destruction can be attributed to the mean HCHO levels, suggesting that even at these low average mixing ratios HCHO plays an important role in determining the HOx (HO2+OH) balance of the remote marine boundary layer. 相似文献
96.
97.
98.
Herbert W. Schnopper Eric Silver Stephen Murray Suzanne Romaine Simon Bandler Christine Jones William Forman Norman Madden Jeffery Beeman Eugene Haller Finn Christensen Niels Westergaard Juan Fabregat Victor Reglero Alvaro Gimenez Noah Brosch Elia Liebowitz Hagai Netzer Marco Barbera Alfonso Collura Salvatore Sciortino 《Astrophysics and Space Science》2001,276(1):49-65
The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2 . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations. 相似文献
99.
The position of the titanomagnetite subsolidus stability field boundaries, within the Fe-Ti-O ternary, above 1,000° C, has been calculated from chemical equilibrium considerations, using experimental data for the calibrated buffers of end member compositions. The relationship between chemical composition and intrinsic oxygen fugacity, within the single phase spinel field, has been investigated with a Frenkel cation point defect model. With this calculation scheme, conditions for departure from strict metal-oxygen stoichiometry to stable cation rich or deficient phases can be predicted.
相似文献100.
The solubilities of synthetic, natural and biogenic aragonite and calcite, in natural seawater of 35%. salinity at 25°C and 1 atm pressure, were measured using a closed system technique. Equilibration times ranged up to several months. The apparent solubility constant determined for calcite of 4.39(±0.20) × 10?7 mol2 kg?2 is in good agreement with other recent solubility measurements and is constant after 5 days equilibration. When we measured aragonite solubility we observed that it decreased with increasing time of equilibration. The value of 6.65(±0.12) × 10?7 mol2 kg?2, determined for equilibration times in excess of 2 months, is significantly less than that found in other recent measurements, which employed equilibration times of only a few hours to days. No statistically significant difference was found among the synthetic, natural and biogenic material. Solid to solution ratio, contamination of aragonite with up to 10 wt% calcite and recycling of the aragonite made no statistically significant difference in solubility when long equilibration times were used.Measured apparent solubility constants of aragonite and calcite are respectively 22( ± 3)% and 20( ± 2)% less than apparent solubility constants calculated from thermodynamic equilibrium constants and seawater total activity coefficients. These large differences in measured and calculated apparent solubility constants may be the result of the formation of surface layers of lower solubility than the bulk solid. 相似文献