全文获取类型
| 收费全文 | 555篇 |
| 免费 | 38篇 |
| 国内免费 | 16篇 |
专业分类
| 测绘学 | 12篇 |
| 大气科学 | 73篇 |
| 地球物理 | 139篇 |
| 地质学 | 225篇 |
| 海洋学 | 34篇 |
| 天文学 | 76篇 |
| 综合类 | 3篇 |
| 自然地理 | 47篇 |
出版年
| 2023年 | 4篇 |
| 2022年 | 3篇 |
| 2021年 | 18篇 |
| 2020年 | 18篇 |
| 2019年 | 20篇 |
| 2018年 | 26篇 |
| 2017年 | 20篇 |
| 2016年 | 31篇 |
| 2015年 | 25篇 |
| 2014年 | 29篇 |
| 2013年 | 33篇 |
| 2012年 | 32篇 |
| 2011年 | 43篇 |
| 2010年 | 27篇 |
| 2009年 | 28篇 |
| 2008年 | 31篇 |
| 2007年 | 26篇 |
| 2006年 | 16篇 |
| 2005年 | 8篇 |
| 2004年 | 14篇 |
| 2003年 | 12篇 |
| 2002年 | 7篇 |
| 2001年 | 8篇 |
| 2000年 | 6篇 |
| 1999年 | 7篇 |
| 1998年 | 6篇 |
| 1997年 | 5篇 |
| 1996年 | 8篇 |
| 1994年 | 2篇 |
| 1993年 | 4篇 |
| 1992年 | 3篇 |
| 1991年 | 3篇 |
| 1990年 | 3篇 |
| 1989年 | 2篇 |
| 1987年 | 5篇 |
| 1985年 | 5篇 |
| 1984年 | 5篇 |
| 1983年 | 7篇 |
| 1982年 | 11篇 |
| 1981年 | 6篇 |
| 1979年 | 5篇 |
| 1978年 | 6篇 |
| 1977年 | 6篇 |
| 1976年 | 6篇 |
| 1975年 | 2篇 |
| 1973年 | 3篇 |
| 1972年 | 3篇 |
| 1970年 | 2篇 |
| 1936年 | 1篇 |
| 1927年 | 1篇 |
排序方式： 共有609条查询结果，搜索用时 15 毫秒
181.
Jean-François Royer Daniel Cariolle Fabrice Chauvin Michel Déqué Hervé Douville Rong-Ming Hu Serge Planton Annie Rascol Jean-Louis Ricard David Salas Y Melia Florence Sevault Pascal Simon Samuel Somot Sophie Tyteca Laurent Terray Sophie Valcke 《Comptes Rendus Geoscience》2002,334(3):147-154
Two climate simulations of 150 years, performed with a coupled ocean/sea-ice/atmosphere model including stratospheric ozone, respectively with and without heterogeneous chemistry, simulate the tropospheric warming associated with an increase of the greenhouse effect of carbon dioxide and other trace gases since 1950 and their impact on sea–ice extent, as well as the stratospheric cooling and its impact on ozone concentration. The scenario with heterogeneous chemistry reproduces the formation of the ozone hole over the South Pole from the 1970s and its deepening until the present time, and shows that the ozone hole should progressively fill during the coming decades. To cite this article: J.-F. Royer et al., C. R. Geoscience 334 (2002) 147–154. 相似文献
182.
183.
184.
Intermediately complex models for the hydrological interactions in the atmosphere-vegetation-soil system 总被引：1，自引：0，他引：1
This paper investigates the hydrological interactions in the atmosphere-evegetation-soil system by using the bucket model and several new simplified intermediately complex models. The results of mathematical analysis and numerical simulations show that these models, despite their simplicity, can very clearly reveal the essential features of the rather complex hydrological system of atmosphere-ecosystem-soil. For given atmospheric variables, these models clearly demonstrate multiple timescales, the “red shift” of response spectra, multi-equilibria and limit cycles, bifurcation, abrupt change, self-organization, recovery, “desertification”, and chaos. Most of these agree with observations. Especially, the weakening of “shading effect” of living canopy and the wilted biomass might be a major mechanism leading to the desertification in a relatively short period due to overgrazing, and the desertification in a relatively long period or in climate of change might be due to both Charney’s mechanism and the shading effect. These ideas could be validated with further numerical simulations. In the paper, some methods for improving the estimation of timescales in the soil water evolution responding to the forcing are also proposed. 相似文献
185.
Jean-Pierre Girard Ren Flicoteaux Anne-Vronique Walter Samuel M. Savin Daniel Nahon 《Applied Geochemistry》1993,8(6)
The oxygen (δ18Oc) and carbon (δ13Cc) isotope compositions of the structural carbonate group (CO3) in apatites from lateritic profiles were investigated. The weathering profiles, located in southern Brazil and in western Senegal, are developed on three different types of apatite-rich parent rock: carbonatite, metamorphosed marine phosphorite and sedimentary marine phosphorite. The parent rock apatites are of magmatic, hydrothermal, metamorphic and sedimentary origins. The in situ formation of apatite of weathering origin in the profiles is well documented petrographically and geochemically.The overall range of measured δ18Oc and δ13Cc values of apatites of weathering origin (22 to 27 SMOW for δ18Oc and −15 to −10 PDB for δ13Cc) is much smaller than the range of measured and/or published isotope compositions of parent rock apatites (4–35 for δ18Oc and −11 to +1 for δ13Cc). In any profile, the apatites of weathering origin can exhibit lower, similar or higher δ18Oc values than parent rock apatites. In contrast, their δ13Cc values are systematically and significantly lower than those of the parent rock apatites. Apatites formed as a result of weathering in laterites can therefore be readily distinguished from apatites of other origin on the basis of their isotope composition.Assuming that apatite CO3 fractionates O in a way similar to calcite CO3, the structural carbonate group of the apatites of weathering origin appears to form in approximate isotopic equilibrium with the weathering solutions. The very low δ13Cc values exhibited by these apatites indicate that the dominant sources of dissolved CO2 in the soil water are organic. The isotope composition of structural carbonate in apatite of weathering origin in lateritic profiles may provide useful information for paleoenvironmental studies. 相似文献
186.
Christopher Hamann Agnese Fazio Matthias Ebert Lutz Hecht Richard Wirth Luigi Folco Alex Deutsch Wolf Uwe Reimold 《Meteoritics & planetary science》2018,53(8):1594-1632
We have investigated silicate emulsions in impact glasses and impact melt rocks from the Wabar (Saudi Arabia), Kamil (Egypt), Barringer (USA), and Tenoumer (Mauritania) impact structures, and in experimentally generated impact glasses and laser-generated glasses (MEMIN research unit) by scanning electron microscopy, electron microprobe analysis, and transmission electron microscopy. Textural evidence of silicate liquid immiscibility includes droplets of one glass disseminated in a chemically distinct glassy matrix; sharp phase boundaries (menisci) between the two glasses; deformation and coalescence of droplets; and occurrence of secondary, nanometer-sized quench droplets in Si-rich glasses. The compositions of the conjugate immiscible liquids (Si-rich and Fe-rich) are consistent with phase separation in two-liquid fields in the general system Fe2SiO4–KAlSi3O8–SiO2–CaO–MgO–TiO2–P2O5. Major-element partition coefficients are well correlated with the degree of polymerization (NBO/T) of the Si-rich melt: Fe, Ca, Mg, and Ti are concentrated in the poorly polymerized, Fe-rich melt, whereas K, Na, and Si prefer the highly polymerized, Si-rich melt. Partitioning of Al is less pronounced and depends on bulk melt composition. Thus, major element partitioning between the conjugate liquids closely follows trends known from tholeiitic basalts, lunar basalts, and experimental analogs. The characteristics of impact melt inhomogeneity produced by melt unmixing in a miscibility gap are then compared to impact melt inhomogeneity caused by incomplete homogenization of different (miscible or immiscible) impact melts that result from shock melting of different target lithologies from the crater's melt zone, which do not fully homogenize and equilibrate due to rapid quenching. By taking previous reports on silicate emulsions in impact glasses into account, it follows that silicate impact melts of variable composition, cooling rate, and crystallization history might readily unmix during cooling, thereby rendering silicate liquid immiscibility a much more common process in the evolution of impact melts than previously recognized. 相似文献
187.
V. Bhalerao D. Bhattacharya A. Vibhute P. Pawar A. R. Rao M. K. Hingar Rakesh Khanna A. P. K. Kutty J. P. Malkar M. H. Patil Y. K. Arora S. Sinha P. Priya Essy Samuel S. Sreekumar P. Vinod N. P. S. Mithun S. V. Vadawale N. Vagshette K. H. Navalgund K. S. Sarma R. Pandiyan S. Seetha K. Subbarao 《Journal of Astrophysics and Astronomy》2017,38(2):31
The Cadmium Zinc Telluride Imager (CZTI) is a high energy, wide-field imaging instrument on AstroSat. CZTI’s namesake Cadmium Zinc Telluride detectors cover an energy range from 20 keV to \(>200\) keV, with 11% energy resolution at 60 keV. The coded aperture mask attains an angular resolution of 17\(^\prime \) over a 4.6\(^\circ \) \(\times \) 4.6\(^\circ \) (FWHM) field-of-view. CZTI functions as an open detector above 100 keV, continuously sensitive to GRBs and other transients in about 30% of the sky. The pixellated detectors are sensitive to polarization above \(\sim \)100 keV, with exciting possibilities for polarization studies of transients and bright persistent sources. In this paper, we provide details of the complete CZTI instrument, detectors, coded aperture mask, mechanical and electronic configuration, as well as data and products. 相似文献
188.
Lauren D. Somers Jeffrey M. McKenzie Samuel C. Zipper Bryan G. Mark Pablo Lagos Michel Baraer 《水文研究》2018,32(3):318-331
As Andean glaciers rapidly retreat due to climate change, the balance of groundwater and glacial meltwater contributions to stream discharge in tropical, proglacial watersheds will change, potentially increasing vulnerability of water resources. The Shullcas River Watershed, near Huancayo, Peru, is fed only partly by the rapidly receding Huaytapallana glaciers (<20% of dry season flow). To potentially increase recharge and therefore increase groundwater derived baseflow, the government and not‐for‐profit organizations have installed trenches along large swaths of hillslope in the Shullcas Watershed. Our study focuses on a nonglacierized subcatchment of the Shullcas River Watershed and has 2 objectives: (a) create a model of the Shullcas groundwater system and assess the controls on stream discharge and (b) investigate the impact of the infiltration trenches on recharge and baseflow. We first collected hydrologic data from the field including a year‐long hydrograph (2015–2016), meteorological data (2011–2016), and infiltration measurements. We use a recharge model to evaluate the impact of trenched hillslopes on infiltration and runoff processes. Finally, we use a 3‐dimensional groundwater model, calibrated to the measured dry season baseflow, to determine the impact of trenching on the catchment. Simulations show that trenched hillslopes receive approximately 3.5% more recharge, relative to precipitation, compared with unaltered hillslopes. The groundwater model indicates that because the groundwater flow system is fast and shallow, incorporating trenched hillslopes (~2% of study subcatchment area) only slightly increases baseflow in the dry season. Furthermore, the location of trenching is an important consideration: Trenching higher in the catchment (further from the river) and in flatter terrain provides more baseflow during the dry season. The results of this study may have important implications for Andean landscape management and water resources. 相似文献
189.
Application of geochemical and stable isotopic tracers to investigate groundwater salinity in the Ochi-Narkwa Basin,Ghana 总被引：1，自引：1，他引：0
Samuel Y. Ganyaglo Shiloh Osae Tetteh Akiti Thomas Armah Laurence Gourcy Tomas Vitvar 《水文科学杂志》2017,62(8):1301-1316
Rainwater, groundwater and soil-water samples were analysed to assess groundwater geochemistry and the origin of salinity in the Ochi-Narkwa basin of the Central Region of Ghana. The samples were measured for major ions and stable isotopes (δ18O, δ2H and δ13C). The Cl? content in rainwater decreased with distance from the coast. The major hydrochemical facies were Na-Cl for the shallow groundwaters and Ca-Mg-HCO3, Na-Cl and Ca-Mg-Cl-SO4 for the deep groundwaters. Groundwater salinization is caused largely by halite dissolution and to a minor extent by silicate weathering and seawater intrusion. Stable isotope composition of the groundwaters followed a slope of 3.44, suggesting a mixing line. Chloride profiles in the soil zone revealed the existence of salt crusts, which support halite dissolution in the study area. A conceptual flow model developed to explain the mechanism of salinization showed principal groundwater flow in the NW–SE direction.
EDITOR D. KoutsoyiannisASSOCIATE EDITOR K. Heal 相似文献
190.
Colin F. Byrne Gregory B. Pasternack Hervé Guillon Belize A. Lane Samuel Sandoval-Solis 《地球表面变化过程与地形》2020,45(9):2179-2200
Reach-scale morphological channel classifications are underpinned by the theory that each channel type is related to an assemblage of reach- and catchment-scale hydrologic, topographic, and sediment supply drivers. However, the relative importance of each driver on reach morphology is unclear, as is the possibility that different driver assemblages yield the same reach morphology. Reach-scale classifications have never needed to be predicated on hydrology, yet hydrology controls discharge and thus sediment transport capacity. The scientific question is: do two or more regions with quantifiable differences in hydrologic setting end up with different reach-scale channel types, or do channel types transcend hydrologic setting because hydrologic setting is not a dominant control at the reach scale? This study answered this question by isolating hydrologic metrics as potential dominant controls of channel type. Three steps were applied in a large test basin with diverse hydrologic settings (Sacramento River, California) to: (1) create a reach-scale channel classification based on local site surveys, (2) categorize sites by flood magnitude, dimensionless flood magnitude, and annual hydrologic regime type, and (3) statistically analyze two hydrogeomorphic linkages. Statistical tests assessed the spatial distribution of channel types and the dependence of channel type morphological attributes by hydrologic setting. Results yielded 10 channel types. Nearly all types existed across all hydrologic settings, which is perhaps a surprising development for hydrogeomorphology. Downstream hydraulic geometry relationships were statistically significant. In addition, cobble-dominated uniform streams showed a consistent inverse relationship between slope and dimensionless flood magnitude, an indication of dynamic equilibrium between transport capacity and sediment supply. However, most morphological attributes showed no sorting by hydrologic setting. This study suggests that median hydraulic geometry relations persist across basins and within channel types, but hydrologic influence on geomorphic variability is likely due to local influences rather than catchment-scale drivers. © 2020 John Wiley & Sons, Ltd. 相似文献