全文获取类型
收费全文 | 297篇 |
免费 | 11篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 5篇 |
地球物理 | 83篇 |
地质学 | 163篇 |
海洋学 | 13篇 |
天文学 | 17篇 |
综合类 | 2篇 |
自然地理 | 23篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 19篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 12篇 |
2014年 | 28篇 |
2013年 | 22篇 |
2012年 | 18篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 11篇 |
2008年 | 22篇 |
2007年 | 8篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有317条查询结果,搜索用时 15 毫秒
21.
S. G. Mamedov D. M. Kuli-Zade Z. F. Alieva M. M. Musaev F. R. Mustafa 《Astronomy Reports》2016,60(9):848-852
A critical review of determinations of the number of spicules is presented, and the role of both classical and Type 2 spicules in heating and mass balance in the corona is considered. The total number of Type 2 spicules is determined, together with the upward fluxes of energy and mass to which they give rise. The total number of Type 2 spicules on the solar surface is found to be ~105, close to values obtained in other studies. The associated particle flux toward the corona is 2.5 × 1014 cm?2 s?1, an order of magnitude lower than the corresponding flux for classical spicules. The associated energy flux is 104 erg cm?2 s?1, an order of magnaitude lower than estimates obtained in other studies. The results indicate that Type 2 spicules can supply the mass lost from the corona, but are not able to fully explain coronal energy losses. 相似文献
22.
There could be some discontinuities in a soil media such as layers, earth structures, cracks, and fissures so that estimation
of stresses and deformations in these types of soil masses are somewhat different from continuous masses. The discontinuities
in a soil mass could be considered as a special link between two blocks. Transmitted swelling pressures affected by the soil
properties of the backfill especially at the interface between the backfill and retaining wall. In order to estimate the transmitted
swelling pressure distribution behind a retaining wall, using with interface element, a new finite element model and a code
(SWELPRES) have been developed. To evaluate the effect of backfill characteristics and interface element from the transmitted
lateral swelling pressures, four cases of thickness of backfills with or without interface elements are investigated. 相似文献
23.
Budakoglu Murat Unluer Ali Tugcan Doner Zeynep Kocaturk Huseyin Kaya Mustafa Kumral Mustafa Kirikoglu M. Sezai 《中国地球化学学报》2021,40(6):926-944
Acta Geochimica - In the last five decades, Rare Earth Elements (REE) are mostly produced from carbonatite complexes and alkaline magmatic environments. In this respect, pyroclastic flows produced... 相似文献
24.
Hanandeh Shadi M. Al-Bodour Wassel A. Hajij Mustafa M. 《Geotechnical and Geological Engineering》2022,40(9):4721-4734
Geotechnical and Geological Engineering - Liquefaction of saturated granular soils is marked by the total loss of shear strength of soil under dynamic cyclic or transient loading conditions due to... 相似文献
25.
The study area is situated within the complex structure and karst system of the western Taurids. Basinwide interpretation of the structural features, each of which has great importance, will enlighten many complicated hydrogeologic problems encountered in the area. Thus, considering the previous views on the structural geology of the area, an interpretation of the structural and tectonic features of the study area by means of satellite images was undertaken, and based on the data gained, new approaches were suggested to solve the hydrogeological problems. In particular, determination of the recharge-discharge mechanisms of the Olukköprü and Dumanli karst springs, which are the most important karst groundwater discharge points in the region, has been attempted. Within the framework of this study, a tectonic-lineament map of a large area covering Eirdir, Beyehir, and Sula lakes at the north and the basins to the south of these lakes was prepared. 相似文献
26.
Due to the rapid expansion of the Sudanese capital city far away from its three Niles, it has become a necessity to estimate
the sustainability of the groundwater resources in this arid area. The purpose of this study – based on the stable-isotopic
composition of groundwater – is to identify the sources of recharge and their relative contribution. The results show that
groundwater infiltrated from the Niles under the present prevailing arid climate, with greater contribution from the White
Nile compared to the Blue Nile, occupies an extension of 12 km from the Niles within the two main aquifers. Paleogroundwater
of meteoric origin, infiltrated in the cooler pluvial earlier Holocene, occupies the outer zones beyond the Niles' effect.
A rational utilization policy is recommended to preserve the finite groundwater resources.
Received: 27 August 1998 · Accepted: 2 March 1999 相似文献
27.
Amy Gartman Mustafa Y��cel Andrew S. Madison David W. Chu Shufen Ma Christopher P. Janzen Erin L. Becker Roxanne A. Beinart Peter R. Girguis George W. Luther III 《Aquatic Geochemistry》2011,17(4-5):583-601
The sulfide (H2S/HS?) that is emitted from hydrothermal vents begins to oxidize abiotically with oxygen upon contact with ambient bottom water, but the reaction kinetics are slow. Here, using in situ voltammetry, we report detection of the intermediate sulfur oxidation products polysulfides [ $ {\text{S}}_{\text{x}}^{2 - } $ ] and thiosulfate [ $ {\text{S}}_{ 2} {\text{O}}_{ 3}^{ 2- } $ ], along with contextual data on sulfide, oxygen, and temperature. At Lau Basin in 2006, thiosulfate was identified in less than one percent of approximately 10,500 scans and no polysulfides were detected. Only five percent of 11,000 voltammetric scans taken at four vent sites at Lau Basin in May 2009 show either thiosulfate or polysulfides. These in situ data indicate that abiotic sulfide oxidation does not readily occur as H2S contacts oxic bottom waters. Calculated abiotic potential sulfide oxidation rates are <10?3 ??M/min and are consistent with slow oxidation and the observed lack of sulfur oxidation intermediates. It is known that the thermodynamics for the first electron transfer step for sulfide and oxygen during sulfide oxidation in these systems are unfavorable, and that the kinetics for two electron transfers are not rapid. Here, we suggest that different metal catalyzed and/or biotic reaction pathways can readily produce sulfur oxidation intermediates. Via shipboard high-pressure incubation experiments, we show that snails with chemosynthetic endosymbionts do release polysulfides and may be responsible for our field observations of polysulfides. 相似文献
28.
Erdem Emin Maras Mustafa Caniberk Mehmet Serhat Odabas Burcu Degerli Süleyman Sirri Maras Hadi Hakan Maras 《Arabian Journal of Geosciences》2016,9(2):164
We investigated the relationships between mineral content and the physical and mechanical properties of landscape rock using a non-destructive remote sensing method applied in the laboratory. Using this technique, the spectral properties of the landscape rock could be collected at different wavelengths without harming the samples. Differences in spectral reflectance were compared with the physical and mechanical properties of the stone. Significant correlations were observed between reflectance values and the rocks’ mechanical and physical properties, with correlation coefficients of 95 to 99 %. However, establishing a correlation between two variables is not a sufficient condition to establish a causal relationship. Mineral densities and mineral content are characteristics used for the classification of landscape rock. We have concluded that although spectral signatures from landscape rock can be used for predicting which stones might have similar features when comparing two batches of stone, the high correlations we discovered cannot confirm a cause and effect relationship that would allow for the prediction of a rock’s physical and mechanical properties. Although this conclusion is disappointing, the mineral content and the significant correlations discovered by hyperspectral reflectance scanning can be used as supplementary information when comparing two samples of landscape rock. 相似文献
29.
Capturing strain localization in reinforced soils 总被引:1,自引:1,他引:1
Lade’s single hardening soil model with Cosserat rotation embodied in the finite element method is employed to investigate
the behavior of geosynthetic reinforced soils with special attention to the development of shear banding. The ability of the
finite element model to detect shear banding in a reinforced soil is examined against three high quality small-scale laboratory
plane strain tests on Toyoura sand with and without reinforcement. These three tests were chosen because of the clear failure
surfaces that developed in the soil during loading. The FEM analyses were able to reasonably simulate the plane strain laboratory
tests including both unreinforced and reinforced cases. The FEM analyses gave reasonably good agreement with the experimental
results in terms of global stress–strain relationships and shear band occurrences. Furthermore, and based on FE analyses of
a hypothetical geosynthetic reinforced soil (GRS) retaining wall, it is shown that the geosynthetic reinforcements are very
effective in hindering the formation of shear bands in GRS retaining walls when small spacing between the reinforcement layers
was used. When used properly, the geosynthetic reinforcements made the soil behave as a truly reinforced mass of considerable
stiffness and strength. 相似文献
30.
Multivariate analysis of heavy metal contents of sediments from Gumusler creek, Nigde, Turkey 总被引:2,自引:0,他引:2
In this study, heavy metal contents of samples from Gumusler creek in Turkey were studied and the metal contamination characteristics
were investigated. In this respect, considering the pollutant sites in the area, systematic sediment samples were collected
in a zone starting from the manifestation part of the water to the entrance of the Karasu creek in Gumusler town. Samples
were taken from lower section of the river bed at 30 stations along Gumusler creek, 13 km in length and their heavy metal
contents were analyzed with XRF Spectrometer. Correlation coefficients, element coefitic coefficient correlation, dendogram
hierarchical cluster, model summary and Annova analysis statistical methods were applied to data. Strong positive correlations
were determined for some elements which are believed to have possibly the same origin. In addition, mineralizations in the
area are thought to cause variation in metal contents. Results of chemical analysis show that soil limit values and clark
values were exceeded. The heavy metal accumulation in the creek is believed to be derived from non-operated Sb-Hg-W and Fe
quarries. 相似文献