全文获取类型
收费全文 | 157篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 11篇 |
地球物理 | 27篇 |
地质学 | 70篇 |
海洋学 | 9篇 |
天文学 | 29篇 |
自然地理 | 5篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 19篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 6篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有166条查询结果,搜索用时 203 毫秒
91.
Petrogenesis of group A eclogites and websterites: evidence from the Obnazhennaya kimberlite,Yakutia
Lawrence?A.?TaylorEmail author Gregory?A.?Snyder Randall?Keller David?A.?Remley Mahesh?Anand Rene?Wiesli John?Valley Nikolai?V.?Sobolev 《Contributions to Mineralogy and Petrology》2003,145(4):424-443
Mantle xenoliths from the Obnazhennaya kimberlite pipe, Yakutia, possess a large range of mineralogical and chemical compositions, from both group A and B eclogites. Major-element contents of the group A eclogites exhibit transitional features between the group B eclogites and peridotite. The Mg# of clinopyroxenes is 0.86–0.94, with 0.60–0.84 for garnets. Differences in concentration of LREEs exist between the Obnazhennaya group A and the well-studied group B eclogites from the Udachnaya kimberlite pipe. In general, garnets in the group A eclogites contain lower LREEs than those from the group B eclogites; however, the trend for clinopyroxene is reversed. High d 18O (5.46–7.81) values, and the positive Eu anomalies in the garnets and clinopyroxenes (Eu/Eu* 1.2–1.4) demonstrate the involvement of an oceanic crustal component in the formation of the group A eclogites. The group A eclogites formed between 21.0 and 37.6 kbar, and 711 and 923 °C, in a time interval of 1,071–1,237 Ma. An innovative model is proposed to explain the formation of the group A eclogites and websterites. It involves the reaction of a depleted mantle peridotite with TTG and carbonatite melts closely related to the subduction of oceanic crust. 相似文献
92.
Meena Balakrishnan 《Geochimica et cosmochimica acta》2004,68(9):2007-2024
A simple flux balance model with a diffusive, evaporative boundary layer indicates that the time constant (characteristic time) for approach to oxygen isotope steady state in the body fluid of land snails is ∼19 min or less. These comparatively short times support an assumption that the snail’s aragonitic shell is commonly precipitated from a body fluid that is at, or near, isotopic steady state. The model indicates that the steady-state δ18O value of snail shell carbonate depends upon the temperature, relative humidity, δ18O of the input liquid water, and δ18O of ambient water vapor. Model shell δ18O values were calculated for the warm, wet months corresponding to times of snail activity at some European sites. Linear regression of these predicted values against published, measured values yielded the expression: δ18Ocalc = 0.93(±0.13) δ18Omeas −0.9(±0.2), with r2 = 0.65. As indicated by the value of r2, there is scatter in the relationship, but the slope and intercept are close to one and zero, respectively, which lends credence to the model. Therefore, temporal or spatial changes recorded in the δ18O values of land snail shells appear to be selectively seasonal—commonly the warm, wet months—and include the effects of relative humidity.For carbon, the time constant for approach to isotopic steady state in the bicarbonate dissolved in the body fluid of land snails is predicted to be ∼16 min or less. New and published δ13C measurements of aragonite shell and associated organic matter exhibit an overall correlation, but with considerable scatter. As noted by previous workers, 13C-rich dietary “limestone” may account for some of the scatter. Additional scatter, according to the model presented herein, could arise from changes in the proportion of total oxidized carbon that is expelled by the snail as bicarbonate dissolved in body fluid (i.e., effects of relative changes in metabolic rates). These results affirm the need for caution in the interpretation of δ13C values of land snail aragonite shells solely in terms of dietary proportions of C3 and C4 plants. 相似文献
93.
Prinya Promprated Lawrence A. Taylor Mahesh Anand Christine Floss Nikolai V. Sobolev Nikolai P. Pokhilenko 《Lithos》2004,77(1-4):69-81
Multiple inclusions of minerals in diamonds from the Snap Lake/King Lake kimberlites of the southeastern Slave craton in Canada have been analyzed for trace elements to elucidate the petrogenetic history of these inclusions, and of their host diamonds. As observed worldwide, the harzburgitic-garnet diamond inclusions (DIs) possess sinusoidal REE patterns that indicate an early depletion event, followed by metasomatism by LREE-enriched, HREE-depleted fluids. Furthermore, these fluids appear to contain appreciable concentrations of LILE and HFSE, based on the increasing abundances of these elements in the olivine inclusion that occurs at the outer portion of a diamond compared to that near the core. The compositions of these fluids are probably a mixture of hydrous-silicic melt, carbonatitic melt, and brine, similar to the compositions of micro-inclusions in diamonds reported by Navon et al. (2003). Comparison between the compositions of majoritic and normal harzburgitic garnets shows that the former are more depleted in terms of major/minor elements (higher Cr#) but significantly more enriched in the REE (up to 10×). This characteristic may indicate the higher susceptibility for metasomatic enrichment of previously more depleted garnets. Garnets of eclogitic paragenesis show strong LREE-depleted patterns, whereas the coexisting omphacite inclusion has relatively flat light- and middle-REE but depleted HREE. Whole-rock reconstruction from coexisting garnet and omphacite inclusions indicates that the protolith of these inclusions was probably the extrusive section of an oceanic crust, subducted beneath the Slave craton. 相似文献
94.
Nature of diamonds in Yakutian eclogites: views from eclogite tomography and mineral inclusions in diamonds 总被引:1,自引:0,他引:1
Mahesh Anand Lawrence A. Taylor Kula C. Misra William D. Carlson Nikolai V. Sobolev 《Lithos》2004,77(1-4):333-348
We have performed dissections of two diamondiferous eclogites (UX-1 and U33/1) from the Udachnaya kimberlite, Yakutia in order to understand the nature of diamond formation and the relationship between the diamonds, their mineral inclusions, and host eclogite minerals. Diamonds were carefully recovered from each xenolith, based upon high-resolution X-ray tomography images and three-dimensional models. The nature and physical properties of minerals, in direct contact with diamonds, were investigated at the time of diamond extraction. Polished sections of the eclogites were made, containing the mould areas of the diamonds, to further investigate the chemical compositions of the host minerals and the phases that were in contact with diamonds. Major- and minor-element compositions of silicate and sulfide mineral inclusions in diamonds show variations among each other, and from those in the host eclogites. Oxygen isotope compositions of one garnet and five clinopyroxene inclusions in diamonds from another Udachnaya eclogite (U51) span the entire range recorded for eclogite xenoliths from Udachnaya. In addition, the reported compositions of almost all clinopyroxene inclusions in U51 diamonds exhibit positive Eu anomaly. This feature, together with the oxygen isotopic characteristics, is consistent with the well-established hypothesis of subduction origin for Udachnaya eclogite xenoliths. It is intuitive to expect that all eclogite xenoliths in a particular kimberlite should have common heritage, at least with respect to their included diamonds. However, the variation in the composition of multiple inclusions within diamonds, and among diamonds, from the same eclogite indicates the involvement of complex processes in diamond genesis, at least in the eclogite xenoliths from Yakutia that we have studied. 相似文献
95.
96.
Studies on urban heat islands using envisat AATSR data 总被引:1,自引:0,他引:1
K. V. S. Badarinath T. R. Kiran Chand K. Madhavilatha V. Raghavaswamy 《Journal of the Indian Society of Remote Sensing》2005,33(4):495-501
Urbanization has significant effects on local weather and climate and among these effects one of the most familiar is the
urban heat island, for which the temperatures of the central urban locations are several degrees higher than those of nearby
rural areas of similar elevation. Satellite data provides important inputs for estimating regional surface albedo and evapotranspiration
required in the studies related to surface energy balance. Present study describes the analysis of day and night ENVISAT-AATSR
satellite data for Urban heat island and surface thermal inertia. Field campaigns have been conducted in synchronous with
the satellite data over pass for validating the surface temperature estimated from AATSR data. Satellite derived surface temperature
values are within ±1° C from ground measured values. Heat island formations in urban regions of Hyderabad and environs can
be clearly seen in the night time data with core urban regions showing high temperatures. Apparent thermal inertia derived
from AATSR day and night data sets have shown typical variations over urban regions. 相似文献
97.
Geotechnical and Geological Engineering - Lithomargic clay is found along the Eastern and Western coasts of Southern India. Presence of weak soils like lithomargic clay below the foundations, cause... 相似文献
98.
99.
100.
Megha Maheshwari C. Mahesh Kamaljit Singh Rajkumar J. Pallipad Sandip R. Oza 《Marine Geodesy》2015,38(3):487-496
An attempt has been made to derive sea ice freeboard from Ka-band Altimeter (SARAL/AltiKa) over Arctic region for 15 March–15 April 2013 (spring) and 15 September–15 October 2013 (autumn). A waveform template matching technique is employed for classification of leads and floe pixels. The estimated sea ice freeboards were found in close agreement with “Operation IceBridge quick look” freeboards (RMSD = 0.30 m). The differences between the two freeboards were largely due to snow layer over sea ice (R = 0.8). The estimated freeboards were of the order of 0.08–0.15 m during the two seasons. 相似文献