全文获取类型
收费全文 | 1076篇 |
免费 | 47篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 182篇 |
地球物理 | 256篇 |
地质学 | 440篇 |
海洋学 | 37篇 |
天文学 | 124篇 |
综合类 | 6篇 |
自然地理 | 59篇 |
出版年
2023年 | 6篇 |
2022年 | 2篇 |
2021年 | 27篇 |
2020年 | 27篇 |
2019年 | 25篇 |
2018年 | 38篇 |
2017年 | 30篇 |
2016年 | 62篇 |
2015年 | 46篇 |
2014年 | 61篇 |
2013年 | 81篇 |
2012年 | 61篇 |
2011年 | 77篇 |
2010年 | 60篇 |
2009年 | 68篇 |
2008年 | 60篇 |
2007年 | 45篇 |
2006年 | 59篇 |
2005年 | 48篇 |
2004年 | 33篇 |
2003年 | 23篇 |
2002年 | 27篇 |
2001年 | 23篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1951年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有1134条查询结果,搜索用时 0 毫秒
121.
Holtstam Dan Cámara Fernando Skogby Henrik Karlsson Andreas Langhof Jörgen 《Mineralogy and Petrology》2019,113(1):7-16
Mineralogy and Petrology - Potassic-richterite, ideally AKB(NaCa)CMg5TSi8O22W(OH)2, is recognized as a valid member of the amphibole supergroup (IMA-CNMNC 2017–102). Type material is from the... 相似文献
122.
Andreas Dietrich Ronald Gutierrez Eric P. Nelson Paul W. Layer 《Mineralium Deposita》2012,47(3):233-249
The San José district is located in the northwest part of the Deseado massif and hosts a number of epithermal Ag–Au quartz
veins of intermediate sulfidation style, including the Huevos Verdes vein system. Veins are hosted by andesitic rocks of the
Bajo Pobre Formation and locally by rhyodacitic pyroclastic rocks of the Chon Aike Formation. New 40Ar/39Ar constraints on the age of host rocks and mineralization define Late Jurassic ages of 151.3 ± 0.7 Ma to 144.7 ± 0.1 Ma for
volcanic rocks of the Bajo Pobre Formation and of 147.6 ± 1.1 Ma for the Chon Aike Formation. Illite ages of the Huevos Verdes
vein system of 140.8 ± 0.2 and 140.5 ± 0.3 Ma are 4 m.y. younger than the volcanic host rock unit. These age dates are among
the youngest reported for Jurassic volcanism in the Deseado massif and correlate well with the regional context of magmatic
and hydrothermal activity. The Huevos Verdes vein system has a strike length of 2,000 m, with several ore shoots along strike.
The vein consists of a pre-ore stage and three main ore stages. Early barren quartz and chalcedony are followed by a mottled
quartz stage of coarse saccharoidal quartz with irregular streaks and discontinuous bands of sulfide-rich material. The banded
quartz–sulfide stage consists of sulfide-rich bands alternating with bands of quartz and bands of chlorite ± illite. Late-stage
sulfide-rich veinlets are associated with kaolinite gangue. Ore minerals are argentite and electrum, together with pyrite,
sphalerite, galena, chalcopyrite, minor bornite, covellite, and ruby silver. Wall rock alteration is characterized by narrow
(< 3 m) halos of illite and illite/smectite next to veins, grading outward into propylitic alteration. Gangue minerals are
dominantly massive quartz intergrown with minor to accessory adularia. Epidote, illite, illite/smectite, and, preferentially
at deeper levels, Fe-chlorite gangue indicate near-neutral pH hydrothermal fluids at temperatures of >220°C. Kaolinite occurring
with the late sulfide-rich veinlet stage indicates pH < 4 and a temperature of <200°C. The Huevos Verdes system has an overall
strike of 325°, dipping on average 65° NE. The orientations of individual ore shoots are controlled by vein strike and intersecting
north-northwest-striking faults. We propose a structural model for the time of mineralization of the San José district, consisting
of a conjugate shear pair of sinistral north-northwest- and dextral west-northwest-striking faults that correspond to R and R′ in the Riedel shear model and that are related to master faults (M) of north-northeast-strike. Veins of 315° strike can
be interpreted as nearly pure extensional fractures (T). Variations in vein strike predict an induced sinistral shear component
for strike directions of >315°, whereas strike directions of <315° are predicted with an induced dextral strike–slip movement.
The components of the structural model appear to be present on a regional scale and are not restricted to the San José district. 相似文献
123.
Urban water demand (UWD) is highly dependent on interacting natural and socio-economic factors, and thus a wide range of data analysis and forecasting methods are required to fully understand the issue. This study applies, for the first time, the continuous wavelet transform to determine changes in the temporal pattern of UWD and its potential meteorological drivers for three major Canadian cities: Calgary, Montreal, and Ottawa. This analysis is complemented by Fourier and cross-spectral analysis to determine inter-relationships and the significance of the patterns detected. The results show that the annual (365 days) cycle provides the most consistent and significant relationship between UWD and meteorological drivers. Wavelet analysis shows that UWD is only sensitive to air temperature in the summer months when mean daily temperatures are greater than 10 to 12 °C. For the three cities studied, the UWD increases by between 10 ML (Montreal) and 50 ML (Calgary) per day with every 1 °C increase in air temperature. In an area with low precipitation (Calgary), there is an inverse relationship between UWD and precipitation during summer months. Wavelet transform and Fourier analysis also detected a 7-day cycle in UWD, particularly in the more industrialized city of Montreal, which is related to the working week. In general, applying the season dependent linear relationships between UWD and temperature is suggested as perhaps being more appropriate and potentially successful for forecasting, rather than continuous complex nonlinear algorithms that are designed to explain variability in the entire UWD record. 相似文献
124.
Andreas Ertl Gerald Giester Ulrich Schüssler Helene Brätz Martin Okrusch Ekkehart Tillmanns Hermann Bank 《Mineralogy and Petrology》2013,107(2):265-279
Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounced positive correlation between the <Y-O> distances and the (Li + Mn2+ + Cu + Fe2+) content (apfu) at this site with R 2 = 0.90. An excellent negative correlation exists between the <Y-O> distances and the Al2O3 content (R 2 = 0.94). The samples at each locality generally show a strong negative correlation between the X-site vacancies and the (MnO + FeO) content. The Mn content in these tourmalines depends on the availability of Mn, on the formation temperature, as well as on stereochemical constraints. Because of a very weak correlation between MnO and CuO we believe that the Cu content in tourmaline is essentially dependent on the availability of Cu and on stereochemical constraints. 相似文献
125.
Lise Byskov Herslund Fatemeh Jalayer Nathalie Jean-Baptiste Gertrud Jørgensen Sigrun Kabisch Wilbard Kombe Sarah Lindley Patrik Karlsson Nyed Stephan Pauleit Andreas Printz Trond Vedeld 《Natural Hazards》2016,82(2):149-172
In this paper, we develop and apply a multi-dimensional vulnerability assessment framework for understanding the impacts of climate change-induced hazards in Sub-Saharan African cities. The research was carried out within the European/African FP7 project CLimate change and Urban Vulnerability in Africa, which investigated climate change-induced risks, assessed vulnerability and proposed policy initiatives in five African cities. Dar es Salaam (Tanzania) was used as a main case with a particular focus on urban flooding. The multi-dimensional assessment covered the physical, institutional, attitudinal and asset factors influencing urban vulnerability. Multiple methods were applied to cover the full range of vulnerabilities and to identify potential response strategies, including: model-based forecasts, spatial analyses, document studies, interviews and stakeholder workshops. We demonstrate the potential of the approach to assessing several dimensions of vulnerability and illustrate the complexity of urban vulnerability at different scales: households (e.g., lacking assets); communities (e.g., situated in low-lying areas, lacking urban services and green areas); and entire cities (e.g., facing encroachment on green and flood-prone land). Scenario modeling suggests that vulnerability will continue to increase strongly due to the expected loss of agricultural land at the urban fringes and loss of green space within the city. However, weak institutional commitment and capacity limit the potential for strategic coordination and action. To better adapt to urban flooding and thereby reduce vulnerability and build resilience, we suggest working across dimensions and scales, integrating climate change issues in city-level plans and strategies and enabling local actions to initiate a ‘learning-by-doing’ process of adaptation. 相似文献
126.
127.
Andreas G. Mueller Gregory C. Hall Alexander A. Nemchin Holly J. Stein Robert A. Creaser Douglas R. Mason 《Mineralium Deposita》2008,43(3):337-362
The Granny Smith (37 t Au production) and Wallaby deposits (38 t out of a 180 t Au resource) are located northeast of Kalgoorlie,
in 2.7 Ga greenstones of the Eastern Goldfields Province, the youngest orogenic belt of the Yilgarn craton, Western Australia.
At Granny Smith, a zoned monzodiorite–granodiorite stock, dated by a concordant titanite–zircon U–Pb age of 2,665 ± 3 Ma,
cuts across east-dipping thrust faults. The stock is fractured but not displaced and sets a minimum age for large-scale (1 km)
thrust faulting (D2), regional folding (D1), and dynamothermal metamorphism in the mining district. The local gold–pyrite
mineralization, controlled by fractured fault zones, is younger than 2,665 ± 3 Ma. In augite–hornblende monzodiorite, alteration
progressed from a hematite-stained alkali feldspar–quartz–calcite assemblage and quartz–molybdenite–pyrite veins to a late
reduced sericite–dolomite–albite assemblage. Gold-related monazite and xenotime define a U–Pb age of 2,660 ± 5 Ma, and molybdenite
from veins a Re–Os isochron age of 2,661 ± 6 Ma, indicating that mineralization took place shortly after the emplacement of
the main stock, perhaps coincident with the intrusion of late alkali granite dikes. At Wallaby, a NE-trending swarm of porphyry
dikes comprising augite monzonite, monzodiorite, and minor kersantite intrudes folded and thrust-faulted molasse. The conglomerate
and the dikes are overprinted by barren (<0.01 g/t Au) anhydrite-bearing epidote–actinolite–calcite skarn, forming a 600-m-wide
and >1,600-m-long replacement pipe, which is intruded by a younger ring dike of syenite porphyry pervasively altered to muscovite
+ calcite + pyrite. Skarn and syenite are cut by pink biotite–calcite veins, containing magnetite + pyrite and subeconomic
gold–silver mineralization (Au/Ag = 0.2). The veins are associated with red biotite–sericite–calcite–albite alteration in
adjacent monzonite dikes. Structural relations and the concordant titanite U–Pb age of the skarn constrain intrusion-related
mineralization to 2,662 ± 3 Ma. The main-stage gold–pyrite ore (Au/Ag >10) forms hematite-stained sericite–dolomite–albite
lodes in stacked D2 reverse faults, which offset skarn, syenite, and the biotite–calcite veins by up to 25 m. The molybdenite
Re–Os age (2,661 ± 10 Ma) of the ore suggests a genetic link to intrusive activity but is in apparent conflict with a monazite–xenotime
U–Pb age (2,651 ± 6 Ma), which differs from that of the skarn at the 95% confidence level. The time relationships at both
gold deposits are inconsistent with orogenic models invoking a principal role for metamorphic fluids released during the main
phase of compression in the fold belt. Instead, mineralization is related in space and time to late-orogenic, magnetite-series,
high-Mg monzodiorite–syenite intrusions of mantle origin, characterized by Mg/(Mg + FeTOTAL) = 0.31–0.57, high Cr (34–96 ppm), Ni (22–63 ppm), Ba (1,056–2,321 ppm), Sr (1,268–2,457 ppm), Th (15–36 ppm), and rare earth
elements (total REE: 343–523 ppm). At Wallaby, shared Ca–K–CO2 metasomatism and Th-REE enrichment (in allanite) link Au–Ag mineralization in biotite–calcite veins to the formation of the
giant epidote skarn, implicating a Th + REE-rich syenite pluton at depth as the source of the oxidized hydrothermal fluid.
At Granny Smith, lead isotope data and the Rb–Th–U signature of early hematite-bearing wall-rock alteration point to fluid
released by the source pluton of the differentiated alkali granite dikes. 相似文献
128.
Chondritic Mg isotope composition of the Earth 总被引:2,自引:0,他引:2
The processes of planetary accretion and differentiation have potentially been recorded as variations in the stable isotope ratios of the major elements between planetary objects. However, the magnitude of observed isotopic variations for several elements (Mg, Fe, Si) is at the limit of what current analytical precision and accuracy are able to resolve. Here, we present a comprehensive data set of Mg isotope ratios measured in ocean island and mid-ocean ridge basalts, peridotites and chondrites. The precision and accuracy were verified by isotopic standard addition for two samples, one carbonaceous chondrite (Murchison) and one continental flood basalt (BCR-1). In contrast with some previous studies, our data from terrestrial and chondritic materials have invariant Mg isotope ratios within the uncertainty of the method (0.1‰ for the 26Mg/24Mg ratio, 2SD). Although isotopic variations of less than about 0.1‰ could still be present, the data demonstrate that, at this level of uncertainty, the bulk silicate Earth and chondritic Mg reservoir have a homogeneous δ26Mg = −0.23‰ (26Mg/24Mg ratio of the sample relative to the DSM3 standard set to zero by definition). This implies that neither planetary accretion processes nor partial mantle melting and subsequent shallow-level differentiation have fractionated Mg isotope ratios. These observations imply in particular that the formation of the Earth cannot stem from preferential sorting of chondrite constituents that would have been fractionated in their Mg isotope composition. It also implies that unlike oxygen isotopes, there was no zonation in Mg isotopes in the inner solar system. 相似文献
129.
Andreas Pack Katrina Kremer Nina Albrecht Klaus Simon Andreas Kronz 《Geochemical transactions》2010,11(1):4
Background
In aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination with CO2-laser heating, containerless melting at high temperature of oxides and silicates is possible. We apply aerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reduction experiments. 相似文献130.
Large parts of the tidal estuary of river Elbe (Germany) are characterized by regular patterns of sand dunes. They evolve
due to complex sand transport mechanisms and show multi-faceted migration patterns, which are influenced by hydrodynamic boundary
conditions such as runoff and tidal forces. This study aims at increasing the understanding of the way hydrodynamic boundary
conditions influence dune behavior. This is the basis of an effective sediment management as well as an important requirement
for planning offshore structures. From a unique data set of up to six annual bathymetrical multibeam soundings between 1995
and 2010, bedform characteristics and migration rates were processed and analyzed with a set of automated methods. The influence
of river runoff, water levels, current velocities, tidal range, and river depth on characteristics and migration were tested
statistically. The results show that migration is mainly dominated by the incoming flood tide while rates and directions depend
on the amount of runoff originating from the inland catchment. 相似文献