全文获取类型
收费全文 | 142篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 20篇 |
地球物理 | 34篇 |
地质学 | 80篇 |
海洋学 | 9篇 |
天文学 | 2篇 |
自然地理 | 3篇 |
出版年
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 2篇 |
2018年 | 18篇 |
2017年 | 13篇 |
2016年 | 19篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 15篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 7篇 |
2003年 | 3篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1996年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有149条查询结果,搜索用时 9 毫秒
81.
Mazouz El Hadi Hamimed Messaoud Yahiaoui Abdelouahab Benzagouta Mohamed Said Khodja Mohamed Achi Nada Duplay Joëlle 《Arabian Journal of Geosciences》2020,13(9):1-11
The creep property of rock under cyclic loading is very important in civil engineering. In order to establish a novel constitutive equation for rock under cyclic loading, a fractional-order viscoplastic body under cyclic loading was constructed based on fractional-order viscous element. A fractional-order visco-elastoplastic model (FVEPM) for rock was established by connecting constructed fractional-order viscoplastic body with Burgers model. The model was a Burgers model when the maximum value of cyclic loading was less than the critical strength of rock; otherwise, it was a FVEPM which can be used to reflect the transient, steady-state, and tertiary creep phases of rock. The cyclic loading was decomposed into a static load and a cyclic loading with a zero average stress. According to rheological mechanics theory, the rheology constitutive equation of rock under the static load can be derived. According to viscoelastic mechanics theory, the constitutive equation under cyclic loading with a zero average stress was established by introducing the variation parameters of energy storage and energy dissipation compliance caused by rock damage and fracture. Finally, a new dynamic constitutive equation of rock cyclic loading can be obtained by superimposing the constitutive equation under static load and cyclic loading with a zero average stress. Compared with existing test results of rock under cyclic loading, the proposed constitutive model can be used to describe the creep characteristics of rock under cyclic loading and reflect the presented fluctuation of strain curve of rock under cyclic loading. 相似文献
82.
Imad Kadhim Abdulzahra Ayten Hadi Hossein Azizi Yoshihiro Asahara Koshi Yamamoto 《Comptes Rendus Geoscience》2017,349(2):53-62
The Sirstan granitoid (SG), comprising diorite and granodiorite, is located in the Shalair Valley area, in the northeastern part of Iraq within the Sanandaj–Sirjan Zone (SSZ) of the Zagros Orogenic Belt. The U–Pb zircon dating of the SG rocks has revealed a concordia age of 110 Ma, which is interpreted as the age of crystallization of this granitoid body during the Middle Cretaceous. The whole-rock Rb–Sr isochron data shows an age of 52.4 ± 9.4 Ma (MSWD = 1.7), which implies the reactivation of the granitoid body in the Early Eocene due to the collision between the Arabian and Iranian plates. These rocks show metaluminous affinity with low values of Nb, Ta and Ti compared to chondrite, suggesting the generation of these rocks over the subduction zone in an active continental margin regime. The SG rocks are hornblende-bearing I-type granitoids with microgranular mafic enclaves. The positive values of ?Nd (t = 110 Ma) (+0.1 to +2.7) and the low (87Sr/86Sr)i ratios (0.7044 to 0.7057) indicate that the magma source of the SG granitoids is a depleted subcontinental mantle. The chemical and isotope compositions show that the SG body originated from the metasomatic mantle without a major role for continental contamination. Our findings show that the granitoid bodies distributed in the SSZ were derived from the continuous Neo-Tethys subduction beneath the SSZ in Mesozoic times and that the SSZ was an active margin in the Middle Cretaceous. 相似文献
83.
84.
Hazardous waste landfill site selection in Khorasan Razavi Province, Northeastern Iran 总被引:2,自引:0,他引:2
The disposal is the final step of any hazardous waste management plan. An inappropriate landfill site may have negative environmental, economical, and ecological impacts. Therefore, landfills should be sited carefully by taking into account various rules, regulations, factors, and constraints. In this study, candidate sites for hazardous landfills in the northeastern Khorasan Razavi province are determined using the integration of geographic information system and landfill susceptibility zonation methods. For this, the inappropriate areas were first removed from the model, and the suitability of remaining regions were evaluated using 15 different criteria in two steps. With this done, nine candidate sites were selected as the most suitable locations. Finally, the selected landfill sites were proposed based on environmental impact assessment (Leopold matrix) and economical studies. This study shows that Maasumabad, Kheirabad, Mayamey, and Yonsi are the best locations for the constitution of landfill in Khorasan Razavi province, respectively. 相似文献
85.
<正>The Makran accretionary prism is one of the most extensive subduction accretions on Earth.It is characterized by intense folding,thrust faulting and dislocation of the Cenozoic units consisted of sedimentary,igneous and metamorphic rocks.It is located in the southeast of Iran and southwest of Pakistan.Rock 相似文献
86.
87.
88.
One of the main factors in the effective application of a tunnel boring machine (TBM) is the ability to accurately estimate the machine performance in order to determine the project costs and schedule. Predicting the TBM performance is a nonlinear and multivariable complex problem. The aim of this study is to predict the performance of TBM using the hybrid of support vector regression (SVR) and the differential evolution algorithm (DE), artificial bee colony algorithm (ABC), and gravitational search algorithm (GSA). The DE, ABC and GSA are combined with the SVR for determining the optimal value of its user defined parameters. The optimization implementation by the DE, ABC and GSA significantly improves the generalization ability of the SVR. The uniaxial compressive strength (UCS), average distance between planes of weakness (DPW), the angle between tunnel axis and the planes of weakness (α), and intact rock brittleness (BI) were considered as the input parameters, while the rate of penetration was the output parameter. The prediction models were applied to the available data given in the literature, and their performance was assessed based on statistical criteria. The results clearly show the superiority of DE when integrated with SVR for optimizing values of its parameters. In addition, the suggested model was compared with the methods previously presented for predicting the TBM penetration rate. The comparative results revealed that the hybrid of DE and SVR yields a robust model which outperforms other models in terms of the higher correlation coefficient and lower mean squared error. 相似文献
89.
Hossein Jalalifar Naj Aziz Muhammad Hadi 《Geotechnical and Geological Engineering》2006,24(5):1203-1227
Fully encapsulated rock bolting has, in recent years, become a universally accepted system of ground reinforcement in mining
and tunnel construction. The application of bolting systems extends both to rebar as well as cable bolting. The effectiveness
of the bolt application has been studied in shear, both by laboratory tests as well as by numerical modeling. A specially
constructed double shearing apparatus (DSA) was used to examine the shearing behaviour of a bolt installed perpendicularly
across two joints. The experimental study was complemented with three-dimensional numerical analysis. Parameters examined
include, the effect of reinforced material on tension/compression zones along the sheared bolt, shear resistance, shear displacement
and induced strains and stresses during bolt bending process. The study was undertaken at both free load and pretension conditions.
The conclusions drawn from the study were the level of bolt resistance to shear was influenced by bolt profile configuration,
the strength of the rock or medium influenced the level of load generated on the bolt and the increased bolt pretension contributed
to increased shearing load of the bolted medium. The numerical simulation of the bolt/medium interaction and deformational
behaviour were found to be in close agreement with the experimental test results. 相似文献
90.