全文获取类型
| 收费全文 | 296篇 |
| 免费 | 13篇 |
| 国内免费 | 3篇 |
专业分类
| 测绘学 | 9篇 |
| 大气科学 | 10篇 |
| 地球物理 | 55篇 |
| 地质学 | 124篇 |
| 海洋学 | 27篇 |
| 天文学 | 23篇 |
| 综合类 | 4篇 |
| 自然地理 | 60篇 |
出版年
| 2021年 | 3篇 |
| 2020年 | 4篇 |
| 2019年 | 5篇 |
| 2018年 | 4篇 |
| 2017年 | 10篇 |
| 2016年 | 7篇 |
| 2015年 | 3篇 |
| 2014年 | 14篇 |
| 2013年 | 26篇 |
| 2012年 | 9篇 |
| 2011年 | 15篇 |
| 2010年 | 15篇 |
| 2009年 | 19篇 |
| 2008年 | 13篇 |
| 2007年 | 17篇 |
| 2006年 | 16篇 |
| 2005年 | 4篇 |
| 2004年 | 13篇 |
| 2003年 | 11篇 |
| 2002年 | 4篇 |
| 2001年 | 8篇 |
| 2000年 | 2篇 |
| 1999年 | 8篇 |
| 1998年 | 7篇 |
| 1997年 | 4篇 |
| 1996年 | 2篇 |
| 1995年 | 7篇 |
| 1994年 | 2篇 |
| 1992年 | 2篇 |
| 1991年 | 2篇 |
| 1990年 | 3篇 |
| 1987年 | 6篇 |
| 1986年 | 2篇 |
| 1985年 | 4篇 |
| 1984年 | 4篇 |
| 1983年 | 3篇 |
| 1982年 | 4篇 |
| 1981年 | 3篇 |
| 1980年 | 2篇 |
| 1979年 | 2篇 |
| 1977年 | 2篇 |
| 1975年 | 2篇 |
| 1972年 | 2篇 |
| 1969年 | 1篇 |
| 1968年 | 1篇 |
| 1967年 | 2篇 |
| 1966年 | 2篇 |
| 1964年 | 1篇 |
| 1954年 | 1篇 |
| 1951年 | 2篇 |
排序方式： 共有312条查询结果，搜索用时 46 毫秒
141.
Valentin R. Troll Jane P. Chadwick Ester M. Jolis Frances M. Deegan David R. Hilton Lothar M. Schwarzkopf Lara S. Blythe Martin Zimmer 《Geology Today》2013,29(3):96-101
High‐temperature gas in volcanic island arcs is widely considered to originate predominantly from the mantle wedge and from subducted sediments of the down‐going slab. Over the decade (1994–2005) prior to the 2006 eruption of Merapi volcano, summit fumarole CO2 gas δ13C ratios are relatively constant at ?4.1 ± 0.3‰. In contrast, CO2 samples taken during the 2006 eruption and after the May 26th 2006 Yogyakarta earthquake (M6.4) show a dramatic increase in carbon isotope ratios to ?2.4 ± 0.2‰. Directly following the earthquake (hypocentre depth 10–15 km), a 3–5‐fold increase in eruptive intensity was observed. The elevated carbon isotope gas data and the mid‐crustal depth of the earthquake source are consistent with crustal volatile components having been added during the 2006 events, most probably by the thick local limestone basement beneath Merapi. This ‘extra’ crustal gas likely played an important role in modifying the 2006 eruptive behaviour at Merapi and it appears that crustal volatiles are able to intensify and maintain eruptions independently of traditional magmatic recharge and fractionation processes. 相似文献
142.
143.
Twenty high Arctic lakes and ponds were sampled for water chemistry and modern diatom assemblages in two distinct physiographic
sectors of Sirmilik National Park, Nunavut, Canada. Sites on southwestern Bylot Island were warmer, more alkaline, less dilute,
and had higher concentrations of nutrients, DOC and Chl-a (mesotrophic to oligo-mesotrophic), whereas sites on Qorbignaluk Headland on northern Baffin Island were deeper, very dilute,
mostly oligotrophic and had lower pH. Diatom assemblages differed markedly between these two regions as a consequence of limnological
differences between them. Paleolimnological records, spanning > 200 years and dated by 210Pb activity, were produced from each region to compare biological responses to recent warming inferred from glaciological
studies on Bylot Island and regional syntheses for the Arctic. Diatom assemblages began to change around AD 1900 at both sites.
At Qorbignaluk Headland, marked shifts in diatom community composition occurred during the twentieth century, with large increases
in the abundance of planktonic diatoms. At Bylot Island, diatom community changes began around the same time, and involved
modest decreases in planktonic diatoms and increases in inferred specific conductance, likely because of a decrease in the
areal extent of the small lake as a response to warming. The study confirms that responses of freshwater ecosystems to climate
warming vary depending on local physiographic factors. 相似文献
144.
This study uses a combination of evidence from ground penetrating radar, borehole, video, and wireless probe data to assess temporal changes in englacial water content associated with Briksdalsbreen, a rapidly retreating Norwegian glacier. Over a 13 day period in 2006, ice radar‐wave velocity varied between 0·135 m/ns (± 0·009) and 0·159 m/ns (± 0·003), and water content from 7·8% (+2·6, ?2·8) to 2·5% (+0·9, ?1·1) [derived from the Looyenga (Physica 31 (3): 401–406, 1965) formula]. It is suggested that during warm precipitation free days, void spaces within the glacier become filled with water, resulting in low radar‐wave velocity. This stored water then drained during cold, high precipitation days, allowing the radar‐wave velocity to rise. These changes in englacial storage were caused by the enhanced crevassing generated by the newly floating ice margin, and were associated with accelerated glacier retreat. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
145.
146.
147.
Wentao Cao Jane A. Gilotti Hans‐Joachim Massonne Simona Ferrando Charles T. Foster 《Journal of Metamorphic Geology》2019,37(1):15-39
In the North‐East Greenland Caledonides, P–T conditions and textures are consistent with partial melting of ultrahigh‐pressure (UHP) eclogite during exhumation. The eclogite contains a peak assemblage of garnet, omphacite, kyanite, coesite, rutile, and clinozoisite; in addition, phengite is inferred to have been present at peak conditions. An isochemical phase equilibrium diagram, along with garnet isopleths, constrains peak P–T conditions to be subsolidus at 3.4 GPa and 940°C. Zr‐in‐rutile thermometry on inclusions in garnet yields values of ~820°C at 3.4 GPa. In the eclogite, plagioclase may exhibit cuspate textures against surrounding omphacite and has low dihedral angles in plagioclase–clinopyroxene–garnet aggregates, features that are consistent with former melt–solid–solid boundaries and crystallized melt pockets. Graphic intergrowths of plagioclase and amphibole are present in the matrix. Small euhedral neoblasts of garnet against plagioclase are interpreted as formed from a peritectic reaction during partial melting. Polymineralic inclusions of albite+K‐feldspar and clinopyroxene+quartz±kyanite±plagioclase in large anhedral garnet display plagioclase cusps pointing into the host, which are interpreted as crystallized melt pockets. These textures, along with the mineral composition, suggest partial melting of the eclogite by reactions involving phengite and, to a large extent, an epidote‐group mineral. Calculated and experimentally determined phase relations from the literature reveal that partial melting occurred on the exhumation path, at pressures below the coesite to quartz transition. A calculated P–T phase diagram for a former melt‐bearing domain shows that the formation of the peritectic garnet rim occurred at 1.4 GPa and 900°C, with an assemblage of clinopyroxene, amphibole, and plagioclase equilibrated at 1.3 GPa and 720°C. Isochemical phase equilibrium modelling of a symplectite of clinopyroxene, plagioclase, and amphibole after omphacite, combined with the mineral composition, yields a P–T range at 1.0–1. 6 GPa, 680–1,000°C. The assemblage of amphibole and plagioclase is estimated to reach equilibrium at 717–732°C, calculated by amphibole–plagioclase thermometry for the former melt‐bearing domain and symplectite respectively. The results of this study demonstrate that partial melt formed in the UHP eclogite through breakdown of an epidote‐group mineral with minor involvement of phengite during exhumation from peak pressure; melt was subsequently crystallized on the cooling path. 相似文献
148.
The non-thermal escape of neutral O atoms from Mars at the current epoch is largely due to dissociative recombination of :
149.
We analyze here the behavior of the magnitudes of the F1 and E peaks of the electron density profiles measured by the Radio Science Subsystem of the Mars Global Surveyor spacecraft, as a function of solar zenith angle χ and solar flux. For each of the 658 days of data in the six occultation seasons in the northern hemisphere, we choose one profile to analyze, which is that for which the F1 peak is the median value. We assume that the variations of the measured peak densities can be represented as Aa(cosχ) and as Bb(F10.7), where F10.7 is the usual solar flux proxy, appropriately shifted to the orbital position of Mars. To minimize the effect of solar activity, we divide the data into 6 F10.7 bins, fit the data in each bin, and derive the values of the exponent a and the coefficient AF10.7 for each bin. The median values that we derive for the exponent a is 0.46 for the F1 peak, and 0.395 for the E peak. To minimize the effect of SZA, we divide the data into eight SZA bins, and derive the exponent b and the coefficient Bχ for each SZA bin. We argue that the last three SZA bins should be excluded because the fits were poor, due partly to the small number of data points in each of these bins. If we do so, the median values of b that we derive are 0.27 and 0.40 for the F1 and E peaks, respectively. Finally we derive a 3-parameter fit to all the data, which expresses the variability of the peak densities as a function of a′(cosχ) and b′(F10.7) simultaneously. The fitted values of the exponents a′ and b′ for the F1 peak are 0.45 and 0.26, respectively; for the E peak, the values are 0.39 and 0.46, respectively. We compare our results to Chapman theory, and to those of other investigators. 相似文献
150.
Englacial and subglacial water flow at Skálafellsjökull,Iceland derived from ground penetrating radar,in situ Glacsweb probe and borehole water level measurements 
下载免费PDF全文
下载免费PDF全文 We reconstruct englacial and subglacial drainage at Skálafellsjökull, Iceland, using ground penetrating radar (GPR) common offset surveys, borehole studies and Glacsweb probe data. We find that englacial water is not stored within the glacier (water content ~0–0.3%). Instead, the glacier is mostly impermeable and meltwater is able to pass quickly through the main body of the glacier via crevasses and moulins. Once at the glacier bed, water is stored within a thin (1 m) layer of debris‐rich basal ice (2% water content) and the till. The hydraulic potential mapped across the survey area indicates that when water pressures are high (most of the year), water flows parallel to the margin, and emerges 3 km down glacier at an outlet tongue. GPR data indicates that these flow pathways may have formed a series of braided channels. We show that this glacier has a very low water‐storage capacity, but an efficient englacial drainage network for transferring water to the glacier bed and, therefore, it has the potential to respond rapidly to changes in melt‐water inputs. © 2015 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. 相似文献