全文获取类型
收费全文 | 322篇 |
免费 | 16篇 |
国内免费 | 18篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 18篇 |
地球物理 | 106篇 |
地质学 | 121篇 |
海洋学 | 14篇 |
天文学 | 64篇 |
综合类 | 10篇 |
自然地理 | 19篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 27篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 27篇 |
2014年 | 20篇 |
2013年 | 31篇 |
2012年 | 22篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
Measurement of ecological, climatic and anthropogenic changes underpins the formulation of effective management strategies for sustainable use and protection of the marine environment. Sensors are traditionally used in marine studies to determine physical parameters, but there is increasing demand for real-time information about chemical and biological parameters. These parameters are currently measured in samples collected at sea and subsequently analysed in the laboratory. Biosensors fuse the exquisite sensitivity and specificity of living systems with the processing power of microelectronics to deliver simple, inexpensive measurement systems for use in the field or deployment in situ. While their potential for use in the marine environment is enormous, much published work to date has focussed on applications in freshwater and wastewater. Marine applications pose a substantial challenge in the robustness required for remote application, but recent developments in portable medical devices and receptor design suggest that these demands can now be realistically tackled. 相似文献
95.
Sergey R. Kotov 《Mathematical Geology》2003,35(4):477-491
Records from the Greenland Ice Sheet Project Two ice core are considered in terms of dynamical systems theory and nonlinear prediction. Dynamical systems theory allows us to reconstruct some properties of a phenomenon based only on past behavior without any mechanistic assumptions or deterministic models. A near-term prediction of temperature, including a mean estimate and confidence interval, is made for 800 years into the future. The prediction suggests that the present short-time global warming trend will continue for at least 200 years and be followed by a reverse in the temperature trend. 相似文献
96.
Role of water in the origin of podiform chromitite deposits 总被引:2,自引:0,他引:2
We report experiments in basalt oversaturated with water to duplicate the nodular ore textures of podiform chromitite ores. In immiscible basalt-water systems saturated with olivine and chromite, olivine will reside in the melt while chromite will collect in the fluid phase. Fractionation is physical and is driven by differential wetting properties of melt and fluid against silicate and oxide surfaces. There is no need to suppress olivine from the liquidus of a primitive basaltic melt as suggested by Irvine [Irvine, T.N., Geology 5 (1977) 273-277], to achieve chromite accumulations as observed in natural podiform ore deposits. The results imply that podiform chromitite ores will form where a primitive olivine-chromite-saturated mantle melt is sufficiently water-rich to exsolve a fluid phase during passage through the uppermost mantle. The most likely geodynamic environment for podiform chromite mineralization to take place is a supra-subduction zone setting. 相似文献
97.
Ryszard Kryza Jan Zalasiewicz Stanisław Mazur Paweł Aleksandrowski Sergey Sergeev Alexander Larionov 《International Journal of Earth Sciences》2007,96(6):1153-1162
SHRIMP dating of detrital zircons from sandstones of the Gackowa Formation (Kaczawa Complex, Sudetes, SW Poland) indicates
input from late (550–750 Ma) and early Proterozoic to Archaean sources (∼2.0–3.4 Ga, the latter being the oldest recorded
age from the Sudetic region). These dates preclude within-terrane derivation from seemingly correlatory acid volcanic rocks
of early Palaeozoic age. Rather, they indicate provenance from Cadomian and older rocks that currently form part of other,
geographically distant terranes; the most likely source identified to date is the Lusatian Block in the Saxothuringian Zone.
Hence, the Gackowa Formation may be late Proterozoic rather than early Palaeozoic in depositional age, possibly coeval with
the late Proterozoic (pre-Cadomian) greywackes of Lusatia, being subsequently tectonically interleaved with early Palaeozoic
volcanic rocks into the Kaczawa accretionary prism during the Variscan orogeny. However, correlation with the lithologically
similar early Ordovician Dubrau Quartzite of Saxothuringia, and so assignation to the early Paleozoic (post-Cadomian) rift
succession deposited at the northern margin of Gondwana, cannot yet be precluded. 相似文献
98.
Sergey V. Marchenko Gregor Rauw Eleonora A. Antokhina Igor I. Antokhin Dominique Ballereau Jacques Chauville Michael F. Corcoran Rafael Costero Juan Echevarria Thomas Eversberg Ken G. Gayley Gloria Koenigsberger Anatoly S. Miroshnichenko Anthony F. J. Moffat Nidia I. Morrell Nancy D. Morrison Christopher L. Mulliss Julian M. Pittard Ian R. Stevens Jean-Marie Vreux Jean Zorec 《Monthly notices of the Royal Astronomical Society》2000,317(2):333-342
With the objective of investigating the windwind collision phenomenon and supporting contemporaneous X-ray observations, we have organized a large-scale, coordinated optical monitoring campaign of the massive, highly eccentric O9 III+B1 III binary Iota Orionis. Successfully separating the spectra of the components, we refine the orbital elements and confirm the rapid apsidal motion in the system. We also see strong interaction between the components during periastron passage and detect phase-locked variability in the spectrum of the secondary star. However, we find no unambiguous signs of the bow shock crashing on the surface of the secondary, despite the predictions of hydrodynamic simulations. Combining all available photometric data, we find rapid, phase-locked variations and model them numerically, thus restricting the orbital inclination to 50° i 70°. 相似文献
99.
Shallow groundwater dynamics and its driving forces in extremely arid areas: a case study of the lower Heihe River in northwestern China
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ping Wang Jingjie Yu Sergey P. Pozdniakov Sergey O. Grinevsky Changming Liu 《水文研究》2014,28(3):1539-1553
Shallow groundwater is an important source of water for the maintenance and restoration of ecosystems in arid environments, which necessitates a deeper understanding of its complex spatial and temporal dynamics driven by hydrological processes. This study explores the dominant hydrological processes that control the shallow groundwater dynamics in the Gobi Desert‐riparian‐oasis system of the lower Heihe River, a typical arid inland river basin located in northwestern China. The groundwater level and temperature were monitored in 14 shallow wells at 30‐min intervals during the 2010–2012 period. After combining this information with meteorological and hydrological data, a comprehensive analysis was conducted to understand the dynamic behaviour of the shallow groundwater system and to determine the dominant factors that control the groundwater flow processes. The results of the study indicate notably large temporal and spatial variations in both the groundwater level and temperature. Noticeable fluctuations in the groundwater level (0.5–1 m) and temperature (4–8 °C) were observed in the riparian zone, evidencing a clear river influence. In comparison, the groundwater fluctuations in the Gobi Desert were more stable (the annual variations of the water table were less than 0.5 m, and the water temperature varied by no more than 2 °C). Strong variations in the groundwater table (1.5–5.0 m/year) and temperature (1.5–6.5 °C), mainly caused by surface flood irrigation and groundwater pumping, were observed in the oasis area. The investigated sites were categorized into three types that reflect the dominant hydrological processes: (1) the riparian zone, dominated by riverbank filtration and groundwater evapotranspiration; (2) the Gobi Desert area, controlled by groundwater evaporation and lateral recharge; and (3) the oasis area, dominated by groundwater evapotranspiration as well as surface–groundwater interactions caused by human activities. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
100.