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Andreas J. Scheib Jonathan R. Lee Neil Breward James B. Riding 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(3):432-444
High-density regional geochemical data for surface soils in central England and East Anglia reveal that much of their geochemical character is inherited from the tills that they are developed upon. Multivariate statistical analysis highlighted three significant element associations of Al–Fe–Ga–K–La–Mg–Rb, Ca–Sr and K–Fe accounting for almost 93% of the geochemical variability of soils derived from tills. Provenancing the geochemical signatures of the latter elements enabled the construction of ice flow paths associated with two different Middle Pleistocene ‘chalky’ till sheets. A lower till sheet relating to ‘Pennine’ ice flowing from west to east across the region, and an upper till sheet deposited by North Sea ice moving into northern East Anglia, and to the west of the Fen Basin, before fanning-out across central England. Overall, geochemical signatures of different till units are largely derived from local bedrock sources, with dilution and a new geochemical signature acquired as the ice flows over and incorporates new bedrock lithologies. The results show that high resolution soil geochemical data provides a further proxy with which the flow paths of former ice sheets can be delineated. 相似文献
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Selective chemical extraction of heavy metals in tailings and soils contaminated by mining activity: Environmental implications 总被引:1,自引:0,他引:1
Paulo J.C. Favas João Pratas M. Elisa P. Gomes V. Cala 《Journal of Geochemical Exploration》2011,111(3):160-171
Total concentrations of chemical elements in soils may not be enough to understand the mobility and bioavailability of the elements. It is important to characterise the degree of association of chemical elements in different physical and chemical phases of soil. Another geochemical characterisation methodology is to apply sequential selective chemical extraction techniques. A seven-step sequential extraction procedure was used to investigate the mobility and retention behaviour of Al, Fe, Mn, Cu, Zn, Pb, Cr, Co, Ni, Mo, Cd, Bi, Sn, W, Ag, As and U in specific physical–chemical and mineral phases in mine tailings and soils in the surroundings of the abandoned Ervedosa mine. The soil geochemical data show anomalies associated with mineralised veins or influenced by mining. Beyond the tailings, the highest recorded concentrations for most elements are in soils situated in mineralised areas or under the influence of tailings. The application of principal components analysis allowed recognition of (a) element associations according to their geochemical behaviour and (b) distinction between samples representing local geochemical background and samples representing contamination. Some metal cations (Mn, Cd, Cu, Zn, Co, Cr, Ni) showed important enrichment in the most mobilisable and bioavailable (i.e., water-soluble and exchangeable) fractions due likely to the acidic conditions in the area. In contrast, oxy-anions such as Mo and As showed lower mobility because of adsorption to Fe oxy-hydroxides. The residual fraction comprised largest proportions of Sn and Al and to a lesser extent Zn, Pb, Ni, Cr, Bi, W, and Ag, which are also present at low concentrations in the bioavailable fractions. The elements in secondary mineral phases (mainly Fe, Mn, Cu, Zn, Cd, Pb, W, Bi, Mo, Cr, Ni, Co, As and U) as well as in organic matter and sulphides are temporarily withheld, suggesting that they may be released to the environment by changes in physico-chemical conditions. 相似文献
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939.
Geochemical subsoil data obtained from China and European laboratories have been
compared in this study. 787 C horizon subsoil samples from FOREGS (Forum of European Geological
Surveys) geochemical baselines mapping project were sent to China’s IGGE (Institute of Geophysical
and Geochemical Exploration) laboratory and composited to 190 samples according to the
160 km 160 km GNT (Global Terrestrial Network) cells. In addition to the FOREGS elemental analysis
package, Au, Pt, Pd, B, Ge, Br, Cl, Se, N, Li and F were also analyzed by using the IGGE’s 76 element
analytical scheme. Geochemical data statistics, scatter plotting, and geochemical map compilation techniques
have been employed to investigate differences between FOREGS and IGGE analytical results.
The results of two datasets, the IGGE’s analysis data for composited samples, and the FOREGS
average data of samples in each GNT cell, agree extremely well for about 23 elements, viz: SiO2, Sr,
Al2O3, Zr, Ba, Fe2O3, Ti, Rb, Mn, Gd, CaO, Ga, MgO, P, Pb, Na2O, Y, Th, As, U Sc, Cr, and Co. There
are slight differences between-laboratory biases shown as proportional errors between the datasets for Ni,
K2O, Tb, Tl, Cu, S, Sm, La, Ce, Pr, Nd, Eu, Ho, Er, Tm, Yb, Lu, Ta, Nb, Hf, and Dy. For Cd, Cs, Be, Sb,
In, Mo, I, Sn, and Te, the correlation of the two datasets and the similarity of the geochemical maps are
fairly good, but obvious biases exist between the two datasets at values near detection limits. Sensitivities of FOREGS analytical methods for W, Bi, Sn, Te, Be, and I are insufficient to produce
reportable values in at least 80% of the samples. Although the detection limits of Ag for both FOREGS
and IGGE are sufficient to provide reportable values, a large bias was found between the two datasets.
This study demonstrates that consistent analytical data for certain elements of global geochemical
mapping samples can be achieved by different qualified laboratories, such as China’s IGGE laboratory
and some European laboratories. For some elements, such as Ag, further research on the selection of the
proper analytical methods and on the development of quality control methods should be undertakendwith
final recommendations adhered to by all participants of the global geochemical mapping program. 相似文献
940.
K.K. Abdul Azeez T. Satish Kumar Sharana Basava T. Harinarayana A.M. Dayal 《Marine and Petroleum Geology》2011,28(5):1073-1082
As the Mesozoic sediments contribute most of the oil and gas reserves of the world, we present an integrated interpretation approach using magnetotellurics (MT) and surface geochemical prospecting studies to demarcate hydrocarbon prospective Gondwana (Mesozoic) formations underneath the Deccan flood basalts of Late Cretaceous age across Narmada-Tapti rift (between Bhusawal and Barwah) in Central India. The MT interpretation shows deep (∼5 km) basement structure between southern and central part of the MT profile however, it gradually becomes shallower to either ends of the profile with a predominant basement depth reduction in the northern end compared to the southern end. The geophysical results suggest thick (2-3.5 km) Mesozoic sediments in the area characterized by deep basement structure. The geochemical analysis of the near surface soil samples indicate higher concentrations of light gaseous hydrocarbons constituents over the area marked with thick sub-basalt Mesozoic formations. Analyses of the geochemical data imply that these hydrocarbons are genetically related, generated from a thermogenic source and these samples fall in the oil-producing zone. The temperature-depth estimations in the region supports favorable temperature conditions (80-120 °C) for oil generation at basement depths. 相似文献