全文获取类型
| 收费全文 | 113篇 |
| 免费 | 5篇 |
| 国内免费 | 2篇 |
专业分类
| 测绘学 | 15篇 |
| 大气科学 | 7篇 |
| 地球物理 | 22篇 |
| 地质学 | 52篇 |
| 海洋学 | 14篇 |
| 天文学 | 9篇 |
| 自然地理 | 1篇 |
出版年
| 2022年 | 2篇 |
| 2021年 | 4篇 |
| 2020年 | 1篇 |
| 2019年 | 2篇 |
| 2018年 | 11篇 |
| 2017年 | 11篇 |
| 2016年 | 7篇 |
| 2015年 | 1篇 |
| 2014年 | 5篇 |
| 2013年 | 18篇 |
| 2012年 | 3篇 |
| 2011年 | 1篇 |
| 2010年 | 10篇 |
| 2009年 | 11篇 |
| 2008年 | 6篇 |
| 2007年 | 4篇 |
| 2006年 | 6篇 |
| 2005年 | 2篇 |
| 2004年 | 3篇 |
| 2003年 | 1篇 |
| 2002年 | 1篇 |
| 2001年 | 1篇 |
| 2000年 | 2篇 |
| 1993年 | 1篇 |
| 1987年 | 1篇 |
| 1985年 | 1篇 |
| 1982年 | 1篇 |
| 1978年 | 1篇 |
| 1975年 | 1篇 |
| 1974年 | 1篇 |
排序方式： 共有120条查询结果，搜索用时 15 毫秒
61.
The quality factors of coda and shear waves have been estimated for the SE Sabalan Mountain, geothermal region in northwestern
Iran. We have analyzed 65 local earthquakes with magnitude of 2.8 to 6.1 and 2.8 to 5 for shear and coda wave quality factor
estimation, respectively. These events were recorded on five stations installed by Building and Housing Research Center Network.
Coda normalization and Spectral decay methods have been used to estimate the frequency dependence attenuation relation for
shear wave, and single back-scattering method for coda waves. We have observed that the coda normalization method has supplied
significantly higher Q
S
values as compared to the spectral method. The results show that, in general, Q values are significantly smaller for the entire frequency range as compared to tectonically active areas and are close to
the values for volcanic areas. 相似文献
62.
Mahmoud Fatemiaghda Habib Shahnazari Mehdi Talkhablu 《Marine Georesources & Geotechnology》2017,35(7):986-998
Aggregate crushing is a phenomenon occurring in carbonate soils under shear and compressive loads resulting in settlement of the offshore structures such as piers, bridges, waterfronts, wharfs, and oil and gas extraction platform foundations. Therefore, it is of significant importance to address the above-mentioned issue through a comprehensive study. In the present research, the texture of carbonate soil in south Iran coasts and its effect at high hydrostatic pressure (2?MPa) on aggregate crushing was studied. The physical properties of coastal soils, such as the effective grain size, shape index, and angularity were then characterized to investigate their effect on grain crushing grade. The results showed that the effective grain size, shape index, angularity, and calcium carbonate content are the main parameters affecting the crushing of grains and consequently settlement of marine soils. Based on the above parameters, a relationship is proposed to estimate grain crushing in carbonate soils. 相似文献
63.
Two marine calcareous deposits as crushable soils and a siliceous sand as a noncrushable soil were used in this study to compare their monotonic response. Undrained monotonic triaxial tests were conducted on samples, which were prepared in different relative densities and consolidated under various confining pressures. The location of phase transformation point in undrained response of the sands in different initial conditions was evaluated. The effect of important parameters including relative density, confining pressure, particle shape, and particle breakage on phase transformation point was assessed. The input energy applied per unit volume of the soils was used to interpret the shearing response of crushable and noncrushable soils. The results showed that calcareous sands have more tendencies in contraction. Particle shape and breakage play a key role in engineering behavior of crushable soils. 相似文献
64.
Lepidocybium flavobrunneum (Smith, 1849) is widespread in warmer oceanic waters and has recently been recorded in the catches of tuna longline vessels in the New Zealand region. Twenty‐five specimens were caught at 31°46′‐32°03′S, 170°49′‐171°11′ E on 23–27 June 1979, thus extending the known range of the species to northern New Zealand. 相似文献
65.
Mining induced subsidence can significantly affect mining costs where major surface facilities and natural environment need to be protected. Overburden grout injection is a technology used to control coal mine subsidence by injecting the mine waste material extracted from the coal back into the inter-burden rock during longwall mining. The flowing slurry is here categorised as a nonlinear viscous cohesive (Bingham plastic) fluid. During longwall mining the grout slurry is pumped into the separated beds of the rock mass through a central vertical borehole, which is drilled deep into the inter-burden rock strata above the coal seam. However, a blockage can occur in the injection system when the slurry velocity falls below a certain critical threshold velocity, indicating a material phase change from cohesive-viscous to cohesive-frictional. In situ field injection tests through boreholes have been simulated at a smaller scale at the CSIRO laboratory in Brisbane by pumping the slurry through a radial disk (gap = 4 mm) from its centre. Laboratory experiments indicate a general, nonlinear, cohesive, viscous, frictional model for shear behaviour of the slurry, in which the material shear parameters are functions of the disk radial distance. Complete dimensional and dimensionless analytical solutions have been developed based on an approach related to Bingham–Herschel–Bulkley fluid mechanics. The derived formulae include relations for minimum pump pressure, local pressure and pressure gradient, wall shear stress, volume rate, velocity and velocity gradient. The theoretical results match the experimental measurements. The experiments covered slurries with maximum particle sizes of 0.5 to 2 mm with about 50% being larger than 100 µm. The viscosities at the various solids concentrations were measured with a standard torsion viscometer. This study differs from the previous research in several distinct aspects, namely, consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behaviour, and implementation of a friction function to mimic behaviour of the deposited and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance. 相似文献
66.
Roya Narimani Mahdi Erfanian Habib Nazarnejad Ahmad Mahmodzadeh 《Environmental Earth Sciences》2017,76(9):353
This study was undertaken to evaluate land use change impact and management scenarios on annual average surface runoff (SR) and sediment yield (SY) using the GeoWEPP tool in the Lighvanchai watershed (located in northwestern Iran). Following a sensitivity analysis, the WEPP model was calibrated (2005–2007) and validated (2008–2010) against monthly observed SY and SR. The coefficient of determination (R 2), Nash–Sutcliffe efficiency (NSE), mean bias error (MBE), and root-mean-square error (RMSE) were applied to quantitatively evaluate the WEPP model. The results indicate a satisfactory model performance with R 2 > 0.80 and NSE > 0.60. Therefore, the model for current land use (scenario 1) was run for a 30-year time period (1982–2011). The annual average of SR and sediment load were predicted as 93,584 m3/year and 4340 ton/year, respectively. To reduce the annual average surface runoff and sediment yield at the watershed scale, the second scenario (alfalfa cultivation with suitable tillage) and the third scenario (grassland development) as two management scenarios of land use changes were defined by identifying the critical hillslopes. The rate of SR and sediment load in the second scenario were 42,096 m3/year and 429 ton/year, respectively. For the third scenario, the model predictions were 30,239 m3/year and 226 ton/year, respectively. Compared to the first scenario, the reduction rates in annual average of sediment load were about 90 and 94%, respectively. Moreover, for the second and third management scenarios, the reduction rates in annual average of SR were about 55 and 67%, respectively. 相似文献
67.
68.
69.
70.