全文获取类型
收费全文 | 220篇 |
免费 | 16篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 20篇 |
地球物理 | 51篇 |
地质学 | 104篇 |
海洋学 | 13篇 |
天文学 | 29篇 |
自然地理 | 17篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 13篇 |
2012年 | 2篇 |
2011年 | 14篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 11篇 |
2007年 | 16篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有239条查询结果,搜索用时 31 毫秒
231.
Martijn?KlaverEmail authorView authors OrcID profile Sergei?Matveev Jasper?Berndt C.?Johan?Lissenberg Pieter?Z.?Vroon 《Contributions to Mineralogy and Petrology》2017,172(11-12):95
Lavas and pyroclastic products of Nisyros volcano (Aegean arc, Greece) host a wide variety of phenocryst and cumulate assemblages that offer a unique window into the earliest stages of magma differentiation. This study presents a detailed petrographic study of lavas, enclaves and cumulates spanning the entire volcanic history of Nisyros to elucidate at which levels in the crust magmas stall and differentiate. We present a new division for the volcanic products into two suites based on field occurrence and petrographic features: a low-porphyricity andesite and a high-porphyricity (rhyo)dacite (HPRD) suite. Cumulate fragments are exclusively found in the HPRD suite and are predominantly derived from upper crustal reservoirs where they crystallised under hydrous conditions from melts that underwent prior differentiation. Rarer cumulate fragments range from (amphibole-)wehrlites to plagioclase-hornblendites and these appear to be derived from the lower crust (0.5–0.8 GPa). The suppressed stability of plagioclase and early saturation of amphibole in these cumulates are indicative of high-pressure crystallisation from primitive hydrous melts (≥ 3 wt% H2O). Clinopyroxene in these cumulates has Al2O3 contents up to 9 wt% due to the absence of crystallising plagioclase, and is subsequently consumed in a peritectic reaction to form primitive, Al-rich amphibole (Mg# > 73, 12–15 wt% Al2O3). The composition of these peritectic amphiboles is distinct from trace element-enriched interstitial amphibole in shallower cumulates. Phenocryst compositions and assemblages in both suites differ markedly from the cumulates. Phenocrysts, therefore, reflect shallow crystallisation and do not record magma differentiation in the deep arc crust. 相似文献
232.
Jasper Knight 《第四纪科学杂志》2001,16(5):405-418
Reconstructing the depositional processes and setting (marine or terrestrial depositional environment) of late Devensian age glacigenic sediments around the Irish Sea basin (ISB) is critical for developing an all‐embracing and consistent glacial model that can account for all observed field evidence. Identifying episodes of marine and terrestrial glacial deposition from field data is considered the first step in achieving this goal. Criteria for distinguishing marine and terrestrial glacial environments in the ISB include the geomorphology, sedimentology and faunal content (biofacies) of the associated deposits. Exposures of glacigenic sediments around the ISB are very diverse in terms of their morphosedimentary characteristics and associated biofacies, and thus inferred depositional processes and setting. Possible reasons for the diverse geological record include the differing geometry of eastern and western ISB coasts, time‐transgressive ice retreat, and differential land rebound effects as a result of forebulge collapse and neotectonics. Poor geochronometric control on ice sheet events has not helped the correlation of ISB events with glacial and climatic events elsewhere. Future investigations of glacial sites around the ISB should use an integrated methodological approach involving a range of geomorphological, sedimentary and biofacies data, and dating control where possible. This will help in developing a more precise and holistic late Devensian glacial model that is constrained rigorously by field geological evidence. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
233.
A simple model of the lower corona which allows for a possible difference in the electron and proton temperatures is analyzed. With the introduction of a phenomenological heating term, temperature and density profiles are calculated for several different cases. It is found that, under certain circumstances, the electron and proton temperatures may differ significantly. 相似文献
234.
G. Diego Gatta Romano Rinaldi K. S. Knight G. Molin G. Artioli 《Physics and Chemistry of Minerals》2007,34(3):185-200
The temperature induced structural evolution and thermoelastic behaviour of a natural (Pbca) orthopyroxene (Opx), with chemical formula M2(Mg0.856Ca0.025Fe2+
0.119) M1(Mg0.957Fe2+
0.011Fe3+
0.016Cr0.011Al0.005)Al0.032Si1.968O6, from a suite of high pressure ultramafic nodules of mantle origin, have been investigated by in-situ neutron powder diffraction
at several temperatures starting from 1,200°C down to 150°C. Unit-cell parameter variations as a function of T show no phase transition within this temperature range. The volume thermal expansion coefficient, α = V
−1(∂V/∂T) P0, varies linearly with T. The axial thermal expansion coefficients, αj = l
j−1(∂l
j/∂T)P0, increase non-linearly with T. The principal Lagrangian unit-strain coefficients (ɛ//a, ɛ//b, ɛ//c), increase continuously with T. However, the orientation of the unit-strain ellipsoid appears to change with T. With decreasing T, the values of the unit-strain coefficients along the b and c axes tend to converge. The orientation at ΔT = 1,080°C is maintained down to the lowest temperature (150°C). The two non-equivalent tetrahedral chains, TA
n
OA3n
and TB
n
OB3n
, are kinked differently. At room-T, the TB
n
OB3n
chain is more strongly kinked by about 23° than the TA
n
OA3n
chain. With increasing T, the difference decreases by 3° for the TB
n
OB3n
chain. The intersite cation exchange reaction between M1 and M2 (Mg2+ and Fe2+) shows a slight residual order at 1,200°C followed by reordering with decreasing temperature although seemingly not with
a definite progressive trend. At the lowest temperature reached (150°C), reordering has occurred with the same value of partitioning
coefficient K
D as that before heating. The absence of the expected phase transition is most likely due to the presence of minor amounts
of Fe3+, Al, Ca and Cr which must play a crucial role on the thermoelastic behaviour and phase stability fields in natural Opx, with
consequent important petrologic and geological implications. 相似文献
235.
Synthesis of PGE sulfide standards for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) 总被引:1,自引:0,他引:1
Cora C. Wohlgemuth-Ueberwasser Chris Ballhaus Jasper Berndt Vaida Stotter née Paliulionyte Thomas Meisel 《Contributions to Mineralogy and Petrology》2007,154(5):607-617
Sulfide compositions with known Re, Os, Ir, Ru, Rh, Pt, and Pd contents are synthesized to be used as standards for noble
metal analysis in solid solution in sulfides. Major elements were added as metals and elemental S. The noble metals, i.e.
35 and 60 ppm each, were added as solutions by micro syringe. Following synthesis at 1 atm the sulfides were sintered at 1.5
to 2 GPa to obtain pellets with theoretical density. Aliquots of the pellets were analysed by isotope dilution ICP-MS for
bulk Re and platinum-group elements (PGE). The spatial noble metal distribution was investigated with an ArF excimer laser
coupled to a single collector ICP mass spectrometer. Sample homogeneity is shown to depend on the metal/S spectrum and the
major element composition of the sulfide, as well as on more subtle factors like oxygen partial pressure during synthesis,
run temperature, and degree of partial melting. The most homogeneous sulfide composition is a (Fe,Ni)1 − x
S monosulfide with 5 wt % Ni and 1-sigma variations in 34S-normalized noble metal count rates of <3.6%. Nearly as homogeneous is a pure Fe1 − x
S monosulfide with 1-sigma variations in 34S-normalized noble metal count rates of <5.8 %. A Cu-bearing Fe1 − x
S monosulfide with 2 wt % Cu was found to be considerably more heterogeneous, suggesting that Cu in solid solution in monosulfides
promotes noble metal heterogeneity. The sulfide composition least suitable for the synthesis of noble metal sulfide standards
is NiS. 相似文献
236.
Addi Bischoff Markus Patzek Tommaso Di Rocco Andreas Pack Aleksandra Stojic Jasper Berndt Stefan Peters 《Meteoritics & planetary science》2023,58(10):1385-1398
On February 13, 2023, a huge fireball was visible over Western Europe (fireball event 2023 CX1). After the possible strewn field was calculated, the first of several recovered samples, with a mass of about 100 g, was discovered just 2 days after the fireball event on the ground of the village of Saint-Pierre-le-Viger. Meanwhile, more than 60 samples with a total mass of more than 1 kg were recovered and a piece of one of these is studied here. The fall occurred 220 years after the historic meteorite fall of L'Aigle on April 26, 1803, <120 km south. L'Aigle is the closest meteorite fall to Saint-Pierre-le-Viger and belongs to the same chondrite group. Both meteorites are breccias containing only clasts of high metamorphic degree (type 5 and type 6). Since only 20% of the L chondrites are breccias this coincidence is remarkable. As just mentioned, both samples studied from these rocks in this work are ordinary chondrite breccias and consist of equilibrated and recrystallized lithologies of petrologic type 6. The brecciated texture in L'Aigle, resulting in a remarkable light–dark structure, is more pronounced than the brecciated features in Saint-Pierre-le-Viger, from which also type 5 fragments have been reported. The compositions of low-Ca pyroxene and olivine grains in Saint-Pierre-le-Viger (Fs21.2 and Fa23.4, respectively) clearly require an L-group classification. L'Aigle was classified as an L6 breccia in the past, and this has now been confirmed by new data on low-Ca pyroxene and olivine (Fs20.7 and Fa23.8, respectively). Saint-Pierre-le-Viger contains local thin shock veins, and both meteorites are moderately shocked. Most olivines in the studied samples have planar fractures, but the estimated abundance of mosaicized olivines of 30%–40% among the large grains require a S4 shock classification. Oxygen isotope and bulk chemical data of Saint-Pierre-le-Viger certainly support the L chondrite classification. Bulk spectral data of Saint-Pierre-le-Viger are dominated by silicate minerals, that is, Fe-bearing low-Ca pyroxene, olivine, and plagioclase. Isotopic, chemical, and spectral data of the L'Aigle meteorite are shown for comparison and are very similar, providing additional circumstantial evidence of Saint-Pierre-le-Viger's L chondritic nature. 相似文献
237.
Addi Bischoff Mike Komnik Jakob Storz Jasper Berndt 《Meteoritics & planetary science》2023,58(9):1260-1273
The lunar regolith breccia Dhofar 1769, which was found in 2012 as a single 125 g piece in the Zufar desert area of Oman, contains a relatively large, dark-colored impact melt breccia embedded in a fine-grained clastic matrix. The internal texture of the fragment indicates the repeated melt breccia formation on the lunar surface, their repeated brecciation, and mixing in second, third, and fourth generations of brecciated rock types. The chemical and mineralogical data reveal the incorporation of a feldspar-rich subophitic crystalline melt within a feldspar-rich microporphyritic crystalline melt breccia. This lithic paragenesis itself is embedded within a mafic, crystalline melt breccia. The entire breccia with the three different impact melts has been finally incorporated into the whole rock breccia. The three impact melts are mixtures of different source rocks and impact projectiles, based on the obtained minor and trace element compositions (in particular of Ni and the rare earth elements [REE]) of the impact melt lithologies. For all processes of impact melt formation, additional steps of their brecciation and re-lithification require a minimum number of seven impact processes. 相似文献
238.
Aneesh Soman Thorsten Geisler Frank Tomaschek Marion Grange Jasper Berndt 《Contributions to Mineralogy and Petrology》2010,160(6):909-930
A natural, altered zircon crystal from an alkaline pegmatite from the Zomba–Malosa Complex of the Chilwa Alkaline Province
in Malawi has been studied by a wide range of analytical techniques to understand the alteration process. The investigated
zircon shows two texturally and chemically different domains. Whereas the central parts of the grain (zircon I) appear homogeneous
in backscattered electron images and are characterised by high concentrations of trace elements, particularly Th, U, and Y,
the outer regions (zircon II) contain significantly less trace elements, numerous pores, and inclusions of thorite, ytttrialite,
and fergusonite. Zircon II contains very low or undetectable concentrations of non-formula elements such as Ca, Al, and Fe,
which are commonly observed in high concentrations in altered radiation-damaged zircon. U–Pb dating of both zircon domains
by LA-ICPMS and SHRIMP yielded statistically indistinguishable U–Pb weighted average ages of 119.3 ± 2.1 (2σ) and 118 ± 1.2
(2σ) Ma, respectively, demonstrating that the zircon had not accumulated a significant amount of self-irradiation damage at
the time of the alteration event. Electron microprobe dating of thorite inclusions in zircon II yielded a Th–U-total Pb model
age of 122 ± 5 (2σ) Ma, supporting the age relationship between both zircon domains. The hydrothermal solution responsible
for the alteration of the investigated zircon was alkaline and rich in CO3
2−, as suggested by the occurrence of REE carbonates and CO2-bearing fluid inclusions. The alteration of the crystalline, trace element-rich zircon is explained by an interface-coupled
dissolution-reprecipitation mechanism. During such a process, the congruent dissolution of the trace element-rich parent zircon
I was spatially and temporally coupled to the precipitation of the trace element-poor zircon II at an inward moving dissolution-precipitation
front. The driving force for such a process was merely the difference between the solubility of the trace element-rich and
-poor zircon in the hydrothermal solution. The replacement process and the occurrence of mineral inclusions and porosity in
the product zircon II is explained by the thermodynamics of solid solution-aqueous solution systems. 相似文献
239.
In the Omagh Basin, north central Ireland, subglacial diamict ridges lie transverse to southwestward Late Devensian (ca. 23–13 ka) ice flow. These ridges (0.5–2.5 km long, 100–450 m wide, 15–35 m high), are similar morphologically to Rogen moraines, which have not been described previously from the British Isles. The crests of some transverse ridges are streamlined, cross-cut or overprinted by drumlins, whereas other ridges are unmodified and were not affected by later drumlinisation. At Kilskeery, west–east trending eskers overlying unmodified transverse ridges post-date drumlinisation (17–14 14C ka). Esker formation shows that the subglacial thermal regime changed from cold-based, favouring bedform preservation, to warm-based with meltwater flowing through enclosed subglacial channels. Patterns of flow-transverse-ridges and spatial variations in the degree of bedform modification record dynamic changes in regional subglacial environments during the last deglacial cycle. This ice-mass variability cannot be reconciled with current Irish glacial models, which are based on immobile ice centres and ordered stages of ice retreat. In a wider context, these changes in bedform patterns and basal ice regimes have a similar signature to millennial-scale ice-mass oscillations recorded by dated proxy evidence elsewhere in the amphi-North Atlantic. © 1997 John Wiley & Sons, Ltd. 相似文献