全文获取类型
收费全文 | 959篇 |
免费 | 50篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 92篇 |
地球物理 | 236篇 |
地质学 | 449篇 |
海洋学 | 62篇 |
天文学 | 103篇 |
综合类 | 4篇 |
自然地理 | 52篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 15篇 |
2020年 | 20篇 |
2019年 | 17篇 |
2018年 | 25篇 |
2017年 | 35篇 |
2016年 | 25篇 |
2015年 | 40篇 |
2014年 | 41篇 |
2013年 | 61篇 |
2012年 | 51篇 |
2011年 | 60篇 |
2010年 | 70篇 |
2009年 | 57篇 |
2008年 | 54篇 |
2007年 | 46篇 |
2006年 | 46篇 |
2005年 | 51篇 |
2004年 | 44篇 |
2003年 | 31篇 |
2002年 | 32篇 |
2001年 | 23篇 |
2000年 | 14篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 2篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1015条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
15.
16.
This study investigates the isotopic composition (C, O, S and Sr) of carbonates, sulphates and sulphide cements in the rock
matrix and fracture fillings in geological formations of the Southeast basin of France, using core samples collected during
the Deep Geology of France programme (GPF Ardèche theme). The Southeast basin belongs to the Alpine Tethyan margin. It is
one of the thickest sedimentary basins in Europe, reaching upwards of 9 km in certain locations. The main fluid transfer from
the basin is related to the large Pb–Zn Mississippi Valley-type district along the southern margin of the Massif Central block.
A synthesis of the tectonic, mineralogical and petrographic investigations on the GPF boreholes shows that a major fluid circulation
event occurred across the Alpine margin of Tethys during the Early Jurassic (Hettangian–Bathonian). It produced a general
cementation of the rock porosity through precipitation of dolomite, sulphate and barite. Fracture fillings yield isotopic
signatures distinct from the matrix cements. Matrix cements have particular characteristics, i.e. δ34S and δ13C that agree with a marine origin. The δ34S values of Permo-Carboniferous to Triassic sulphides from fracture cements are interpreted as resulting from the thermo-chemical
reduction of sulphates. Fracture sulphates in the same geological formations yield δ34S values that define a relatively homogeneous end-member, whose composition is similar to sulphates in the Largentière Pb–Zn
ore deposit. The source of S is attributed to the Permo-Carboniferous succession. The borehole fracture fillings are attributed
to a major fluid circulation stage compatible with the Early Jurassic stage identified from the geological investigation of
the boreholes. The formation of the Largentière deposit is considered as resulting from the mixing of this Early Jurassic
fluid with continental hydrothermal fluids circulating in a basement horst, along its margin with the sedimentary basin. Other
Pb–Zn deposits may also be related to fluid migration along the basement/sedimentary cover interface in the eastern and western
parts of the Massif Central. This regional fluid circulation event may represent a geodynamic marker of the Jurassic extensional
phase. 相似文献
17.
18.
Farid Juillot Delphine Jouvin Philipe Telouk Philippe Ildefonse Steve Sutton Gordon E. Brown Jr. 《Geochimica et cosmochimica acta》2011,75(9):2295-2308
Zinc isotopes have been studied along two smelter-impacted soil profiles sampled near one of the largest Pb and Zn processing plants in Europe located in northern France, about 50 km south of Lille. Mean δ66Zn values along these two soil profiles range from +0.22 ± 0.17‰ (2σ) to +0.34 ± 0.17‰ (2σ) at the lowest horizons and from +0.38 ± 0.45‰ (2σ) to +0.76 ± 0.14‰ (2σ) near the surface. The δ66Zn values in the lowest horizons of the soils are interpreted as being representative of the local geochemical background (mean value +0.31 ± 0.38‰), whereas heavier δ66Zn values near the surface of the two soils are related to anthropogenic Zn. This anthropogenic Zn occurs in the form of franklinite (ZnFe2O4)-bearing slag grains originating from processing wastes at the smelter site and exhibiting δ66Zn values of +0.81 ± 0.20‰ (2σ). The presence of franklinite is indicated by EXAFS analysis of the topsoil samples from both soil profiles as well as by micro-XANES analysis of the surface horizon of a third smelter-impacted soil from a distant site. These results indicate that naturally occurring Zn and smelter-derived Zn exhibit significantly different δ66Zn values, which suggests that zinc isotopes can be used to distinguish between geogenic and anthropogenic sources of Zn in smelter-impacted soils. In addition to a possible influence of additional past sources of light Zn (likely Zn-sulfides and Zn-sulfates directly emitted by the smelter), the light δ66Zn values in the surface horizons compared to smelter-derived slag materials are interpreted as resulting mainly from fractionation processes associated with biotic and/or abiotic pedological processes (Zn-bearing mineral precipitation, Zn complexation by organic matter, and plant uptake of Zn). This conclusion emphasizes the need for additional Zn isotopic studies before being able to use Zn isotopes to trace sources and pathways of this element in surface environments. 相似文献
19.
The identification of groundwater parameters in heterogeneous systems is a major challenge in groundwater modeling. Flexible parameterization methods are needed to assess the complexity of the spatial distributions of these parameters in real aquifers. In this article, we introduce an adaptative parameterization to identify the distribution of hydraulic conductivity within the large‐scale (4400 km2) Upper Rhine aquifer. The method is based on adaptative multiscale triangulation (AMT) coupled with an inverse problem procedure that identifies the parameters' distributions by reducing the error between measured and simulated heads. The AMT method has the advantage of combining both zonation and interpolation approaches. The AMT method uses area‐based interpolation rather than an interpolation based on stochastic features. The method is applied to a standard 2D groundwater model that takes into account the interactions between the aquifer and surface water bodies, groundwater recharge, and pumping wells. The simulation period covers 204 months, from January 1986 to December 2002. Recordings at 109 piezometers are used for model calibration. The simulated heads are globally quite accurate and reproduce the main dynamics of the system. The local hydraulic conductivities resulting from the AMT method agree qualitatively with existing local experimental observations across the Rhine aquifer. 相似文献
20.
Laure Moulin Ana Isabel Catarino Thomas Claessens Philippe Dubois 《Marine pollution bulletin》2011,62(1):48-54
The effect of pH ranging from 8.0 to 6.8 (total scale - pHT) on fertilization, cleavage and larval development until pluteus stage was assessed in an intertidal temperate sea urchin. Gametes were obtained from adults collected in two contrasting tide pools, one showing a significant nocturnal pH decrease (lowest pHT = 7.4) and another where pH was more stable (lowest pHT = 7.8). The highest pHT at which significant effects on fertilization and cleavage were recorded was 7.6. On the contrary, larval development was only affected below pHT 7.4, a value equal or lower than that reported for several subtidal species. This suggests that sea urchins inhabiting stressful intertidal environments produce offspring that may better resist future ocean acidification. Moreover, at pHT 7.4, the fertilization rate of gametes whose progenitors came from the tide pool with higher pH decrease was significantly higher, indicating a possible acclimatization or adaptation of gametes to pH stress. 相似文献