全文获取类型
收费全文 | 177篇 |
免费 | 10篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 5篇 |
地球物理 | 43篇 |
地质学 | 89篇 |
海洋学 | 12篇 |
天文学 | 21篇 |
综合类 | 5篇 |
自然地理 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 11篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 7篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1976年 | 3篇 |
排序方式: 共有198条查询结果,搜索用时 203 毫秒
61.
Carbon dioxide (CO2) has been injected in the subsurface permeable formations as a means to cut atmospheric CO2 emissions and/or enhance oil recovery (EOR). It is important to constrain the boundaries of the CO2 plume in the target formation and/or other formations hosting the CO2 migrated from the target formation. Monitoring methods and technologies to assess the CO2 plume boundaries over time within a reservoir of interest are required. Previously introduced methods and technologies on pressure monitoring to detect the extent of the CO2 plume require at least two wells, i.e. pulser and observation wells. We introduce pressure transient technique requiring single well only. Single well pressure transient testing (drawdown/buildup/injection/falloff) is widely used to determine reservoir properties and wellbore conditions. Pressure diagnostic plots are used to identify different flow regimes and determine the reservoir/well characteristics. We propose a method to determine the plume extent for a constant rate pressure transient test at a single well outside the CO2 plume. Due to the significant contrast between mobility and storativity of the CO2 and native fluids (oil or brine), the CO2 boundary causes deviation in the pressure diagnostic response from that corresponding to previously identified heterogeneities. Using the superposition principle, we develop a relationship between the deviation time and the plume boundary. We demonstrate the applicability of the proposed method using numerically generated synthetic data corresponding to homogeneous, heterogeneous, and anisotropic cases to evaluate its potential and limitations. We discuss ways to identify and overcome the potential limitations for application of the method in the field. 相似文献
62.
Vinh T. Tran Nagaraj C. Shivaramaiah Thuan D. Nguyen Eamonn P. Glennon Andrew G. Dempster 《GPS Solutions》2018,22(1):24
The sampling frequency of a digitized intermediate frequency signal has a strong effect on the measurement accuracy of Global Navigation Satellite System (GNSS) receivers. The delay-locked loop tracking error is significant when the sampling frequency is an integer multiple of the code chipping rate, the so-called commensurate sampling frequency, and the number of distinct instantaneous residual code phases is low. This results in distortions of the correlation shape and discriminator functions that lead to a significant accuracy degradation. These effects are most pronounced when the sampling frequency is low. Notwithstanding, it is generally good for receivers to keep the sampling frequency to a minimum owing to the processing load and power consumption. It creates a challenge for existing GNSS signal processing techniques. Random, sine and sawtooth jitters have been found to mitigate these distortions considerably. A software algorithm and two hardware receiver implementations of these solutions are proposed. A register-based architecture can be directly applied to the conventional receiver architecture, while the increase in resource and power consumption is insignificant. A RAM-based design cannot only considerably minimize utilized resources but also slightly reduce the power consumption compared to the conventional architecture. 相似文献
63.
The Song Ma region, which is located in the northwestern Vietnam represents the zone of amalgamation between Indochina and South China blocks. Numerous scattered ultramafic rocks occur in this region in association with Early to Middle Palaeozoic greenschists and paragneisses, and all these rocks were subjected to hydrous metamorphism and deformation. Here, we present new field data, mineral chemistry and geochemistry from a suite of hydrated peridotites within the Song Ma region and discuss the tectonic significances of the region. We also combine the available data within the Song Ma region and Indochina–South China blocks to discuss the tectonic evolution of the subduction zone. Based on the results, we suggest that the peridotites from the Song Ma are mantle residues that suffered a high degree of partial melting in a forearc tectonic setting. The present data together with the available data within the Song Ma region and the Indochina and South China blocks clearly represent a southward directed Middle Palaeozoic subduction system. The Middle Palaeozoic subduction and accretion events mark the evolutionary history along an active convergent margin between the Indochina and South China blocks, possibly related to the amalgamation of the Pangaea supercontinent. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
64.
Tran Van Phong Binh Thai Pham Phan Trong Trinh Hai-Bang Ly Quoc Hung Vu Lanh Si Ho Hiep Van Le Lai Hop Phong Mohammadtaghi Avand Indra Prakash 《Ground water》2021,59(5):745-760
Groundwater is one of the major valuable water resources for the use of communities, agriculture, and industries. In the present study, we have developed three novel hybrid artificial intelligence (AI) models which is a combination of modified RealAdaBoost (MRAB), bagging (BA), and rotation forest (RF) ensembles with functional tree (FT) base classifier for the groundwater potential mapping (GPM) in the basaltic terrain at DakLak province, Highland Centre, Vietnam. Based on the literature survey, these proposed hybrid AI models are new and have not been used in the GPM of an area. Geospatial techniques were used and geo-hydrological data of 130 groundwater wells and 12 topographical and geo-environmental factors were used in the model studies. One-R Attribute Evaluation feature selection method was used for the selection of relevant input parameters for the development of AI models. The performance of these models was evaluated using various statistical measures including area under the receiver operation curve (AUC). Results indicated that though all the hybrid models developed in this study enhanced the goodness-of-fit and prediction accuracy, but MRAB-FT (AUC = 0.742) model outperformed RF-FT (AUC = 0.736), BA-FT (AUC = 0.714), and single FT (AUC = 0.674) models. Therefore, the MRAB-FT model can be considered as a promising AI hybrid technique for the accurate GPM. Accurate mapping of the groundwater potential zones will help in adequately recharging the aquifer for optimum use of groundwater resources by maintaining the balance between consumption and exploitation. 相似文献
65.
Huu Hieu Ho Rudy Swennen Val��rie Cappuyns Elvira Vassilieva Tom Van Gerven Tan Van Tran 《Aquatic Geochemistry》2013,19(1):57-75
The speciation and mobility of some selected trace metals (As, Cu, Mn, Pb and Zn) in sediments with depth was investigated in the Cam River-mouth (Vietnam) by collecting sediment cores and analysing porewater and sediment composition, complemented with single (ammonium-EDTA) and sequential (BCR 3-step) extractions and mineralogical analysis (XRD). All trace metals show overall decreasing trends with depth in porewater as a result of anthropogenic input in upper sediment layers. High porewater concentrations of As, Mn and Pb in oxic and suboxic sediment layers may result in groundwater pollution. Sediment-bound Pb and Mn dominate in the reducible and the acid-soluble fraction, respectively, while Cu and Zn distribute rather evenly between four extracted fractions. The porewater metal speciation, as predicted by a geochemical model Visual MINTEQ version 3.0, indicates that the toxicity of Cu, Mn, Pb and Zn (presented by the proportions of free metal ions) decreases with depth, while the toxicity of As increases when As(III) becomes more abundant. The dissolved concentrations of trace metals are not only controlled by the precipitation/dissolution of discrete hydroxide/oxide, carbonate and phosphate minerals, but also by sorption processes on major sorbents (i.e. As on goethite, and Mn and Zn on calcite and dolomite). Sulphide minerals do not show any control even in the anoxic zone most likely because of the low concentration of sulphur. 相似文献
66.
67.
Ta Hoa Phuong Nguyen Huu Cu Tran Duc Thanh Bui Van Dong 《Environmental Earth Sciences》2013,70(2):543-548
Geological wonders have been generally known as natural wonderful products. Resulted from geological processes, geological wonders are diverse in size that have geoheritage values that should be protected from damaging of substance, form and natural development. In a large scale, geological wonders can be geoheritage areas, containing several geodiversity elements that are geologically important or in a smaller scale, they can be geosites of heritage values (or geoheritage sites). In the delimitation of areas, having geoheritage values and the establishment of geoparks, the first thing is to recognise them as geosites and geoheritage areas that indicate great geological values. Besides the Ha Long bay, the world natural heritage with its outstanding aesthetic and geological values, the Cat Ba islands are typical and grandeur karst landscapes formed in tropical condition. Based on the geodiversity elements with their own geoheritage values on aesthetics, uniqueness and grandeur in the Cat Ba islands, the authors have recognised three geoheritage areas: the south cape of the Cat Ba embayment, Tung Gau (shelter), and the Lan Ha bay. Sites where Brachiopods, Crinoids and Tetracorals are exposed on the way through the island are considered as palaeontological geosites. The folds of limestone layers in the northern part of Cat Co 3 beach, with typical turbidite structures in carbonate formations are considered as a lithological geosite. The Devonian-Carboniferous boundary near the Cat Co 3 beach is regarded as a stratigraphical geosite while Que Kem and Turtle islands, etc. are considered as geomorphological geosites. 相似文献
68.
Quang-Thanh Bui Quoc-Huy Nguyen Van Manh Pham Minh Hai Pham Anh Tuan Tran 《国际地球制图》2013,28(12):1300-1314
AbstractThis study examines the potentials of remotely sensed data, GIS and some machine learning classifiers and ensemble techniques in the investigation of the non-linear relationship between malaria occurrences and socio-physical conditions in the Dak Nong province of Viet Nam. Accuracy assessment was determined with Receiver Operating Characteristic (ROC) curve and pair t-test. The results showed that the area under ROC of Random Subspace ensemble model performed better than the other models based on statistical indicators. Comparing pair t-test with Area Under Curve values showed a slight difference of about 1%. Therefore ensemble techniques had significantly improved the performance of the base classifier. However, the performances might vary according to geographic locations. It is concluded that the machine learning classifiers combined with remotely sensed data and GIS is promising for malaria vulnerability mapping, and the derived maps can be used as a fundamental basis for programmes on spatial disease control. 相似文献
69.
O. A. Deshcherevskaya V. K. Avilov Ba Duy Dinh Cong Huan Tran J. A. Kurbatova 《Izvestiya Atmospheric and Oceanic Physics》2013,49(8):819-838
A method of using the standard network weather station data for local ecosystem research is considered on the example of the modern climate of the Cát Tiên National Park (Southern Vietnam) and local climate change in 1980–2010. Special attention is focused on the environmental parameters, which play a role of the limiting factors. It is shown that the climate of Southern Vietnam responds with statistical significance to global climate change. Suggestions about the possible reactions of tropical monsoon forest ecosystem to climate change are given. 相似文献
70.