全文获取类型
收费全文 | 1024篇 |
免费 | 38篇 |
国内免费 | 43篇 |
专业分类
测绘学 | 33篇 |
大气科学 | 19篇 |
地球物理 | 205篇 |
地质学 | 713篇 |
海洋学 | 49篇 |
天文学 | 53篇 |
综合类 | 9篇 |
自然地理 | 24篇 |
出版年
2023年 | 3篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 39篇 |
2019年 | 22篇 |
2018年 | 100篇 |
2017年 | 86篇 |
2016年 | 89篇 |
2015年 | 42篇 |
2014年 | 80篇 |
2013年 | 138篇 |
2012年 | 44篇 |
2011年 | 70篇 |
2010年 | 46篇 |
2009年 | 48篇 |
2008年 | 29篇 |
2007年 | 15篇 |
2006年 | 25篇 |
2005年 | 18篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 28篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1105条查询结果,搜索用时 0 毫秒
881.
Geotectonics - Aswan region is a very important region for Egypt where the High Dam is situated. The wellbeing of the dam and its encompassing region is of extreme worry to all the Egyptian... 相似文献
882.
Mathematical Geosciences - 相似文献
883.
Mohammed Lami Abdel Karim Nouaman Kassem Osama Mohamed Kaoud Al Bassam Abdel Aziz Mohamed 《Arabian Journal of Geosciences》2020,13(6):1-6
Arabian Journal of Geosciences - In this work, quantitative analysis of coastal zone landform morphology is carried out through the integration of landscape index, remote sensing (RS) and... 相似文献
884.
Ahmed Zaki Ahmed Hamdi Mansi Mohamed Selim Mostafa Rabah Gamal El-Fiky 《Marine Geodesy》2018,41(3):258-269
The determination of high-resolution geoid for marine regions requires the integration of gravity data provided by different sources, e.g. global geopotential models, satellite altimetry, and shipborne gravimetric observations. Shipborne gravity data, acquired over a long time, comprises the short-wavelengths gravitation signal. This paper aims to produce a consistent gravity field over the Red Sea region to be used for geoid modelling. Both, the leave-one-out cross-validation and Kriging prediction techniques were chosen to ensure that the observed shipborne gravity data are consistent as well as free of gross-errors. A confidence level equivalent to 95.4% was decided to filter the observed shipborne data, while the cross-validation algorithm was repeatedly applied until the standard deviation of the residuals between the observed and estimated values are less than 1.5 mGal, which led to the elimination of about 17.7% of the shipborne gravity dataset. A comparison between the shipborne gravity data with DTU13 and SSv23.1 satellite altimetry-derived gravity models is done and reported. The corresponding results revealed that altimetry models almost have identical data content when compared one another, where the DTU13 gave better results with a mean and standard deviation of ?2.40 and 8.71 mGal, respectively. A statistical comparison has been made between different global geopotential models (GGMs) and shipborne gravity data. The Spectral Enhancement Method was applied to overcome the existing spectral gap between the GGMs and shipborne gravity data. EGM2008 manifested the best results with differences characterised with a mean of 1.35 mGal and a standard deviation of 11.11 mGal. Finally, the least-squares collocation (LSC) was implemented to combine the shipborne gravity data with DTU13 in order to create a unique and consistent gravity field over the Red Sea with no data voids. The combined data were independently tested using a total number of 95 randomly chosen shipborne gravity stations. The comparison between the extracted shipborne gravity data and DTU13 altimetry anomalies before and after applying the LSC revealed that a significant improvement is procurable from the combined dataset, in which the mean and standard deviation of the differences dropped from ?3.60 and 9.31 mGal to ?0.39 and 2.04 mGal, respectively. 相似文献
885.
886.
The attenuation of seismic waves reflects the elastic nature of the media within which the waves propagate. In this study, we calculate the Coda-Q(Q_c), frequency dependence(η), Vp/Vs and Poisson's(υ) ratios by using 2621 vertical component seismograms generated by 987 earthquakes recorded by 13 seismic stations in Eastern Anatolia, and creat a 2-D seismic tomographic Q_c model for the region. The obtained model provides significant information for exploring the boundaries of adjacent tectonic units within the upper crust and interpreting their dynamic characteristics. The 2-D Q_c model and the other parameters are consistent with the seismotectonic features of Eastern Anatolia. Highly heterogeneous Q_c values are observed in the study area dividing it into north-south directed bands of low and high attenuation. The highest η values were obtained beneath the northwestern and eastern parts of the study region. Clear, high and low υ values are obtained in the western and eastern parts of the study area, respectively. The spatial variations in the measured parameters are consistent with many geophysical observations including low Pn velocities, efficient Sn blockage, high heat flow, and widespread volcanism. Different upper crustal thicknesses and inhomogeneous stress distribution along the East and North Anatolian Fault Zones may also contribute to the observed heterogeneities. 相似文献
887.
Kaolin, cordierite, and calcite are investigated as supports for TiO2. The prepared TiO2/support samples are examined for the removal of organic dyes from wastewater. The samples are preliminarily investigated to identify the optimal loaded system using synthetic wastewater containing methylene blue (MB). Data indicate that the investigated support significantly affects the photocatalytic activity of the supported TiO2. Low photocatalytic activity toward MB degradation is observed upon using TiO2/calcite when compared to the unsupported TiO2. Interaction between calcite and titania species probably occurrs to produce the less photoactive CaTiO3 amorphous species. Anatase TiO2 is obtained upon using kaolin and cordierite as supports. The low photocatalytic performance of the TiO2/kaolin sample is also observed. A high concentration of MB on TiO2/kaolin surfaces blocks the photoactive sites. TiO2/cordierite shows the highest photocatalytic activity compared to the unsupported TiO2 as well as the other TiO2/support samples. Rigid cordierite particles suppress the agglomeration of TiO2 particles during the preparation, leading to a high exposed surface of TiO2 towards light illumination. TiO2/cordierite is investigated for the removal of organic dye from real wastewater collected from a textile dyeing factory. Color removal of up to 46% is achieved upon UV irradiation. 相似文献
888.
889.
Tesfay G. Gebremicael Yasir A. Mohamed Pieter van der Zaag Khalid Hassaballah Eyasu Y. Hagos 《水文研究》2020,34(9):2101-2116
Understanding the natural low flow of a catchment is critical for effective water management policy in semi-arid and arid lands. The Geba catchment in Ethiopia, forming the headwaters of Tekeze-Atbara basin was known for its severe land degradation before the recent large scale Soil and Water conservation (SWC) programs. Such interventions can modify the hydrological processes by changing the partitioning of the incoming rainfall on the land surface. However, the literature lacks studies to quantify the hydrological impacts of these interventions in the semi-arid catchments of the Nile basin. Statistical test and Indicators of Hydrological Alteration (IHA) were used to identify the trends of streamflow in two comparatives adjacent (one treated with intensive SWC intervention and control with fewer interventions) catchments. A distributed hydrological model was developed to understand the differences in hydrological processes of the two catchments. The statistical and IHA tools showed that the low flow in the treated catchment has significantly increased while considerably decreased in the control catchment. Comparative analysis confirmed that the low flow in the catchment with intensive SWC works was greater than that of the control by >30% while the direct runoff was lower by >120%. This implies a large proportion of the rainfall in the treated catchment is infiltrated and recharge aquifers which subsequently contribute to streamflow during the dry season. The proportion of soil storage was more than double compared to the control catchment. Moreover, hydrological response comparison from pre- and post-intervention showed that a drastic reduction in direct runoff (>84%) has improved the low flow by >55%. This strongly suggests that the ongoing intensive SWC works have significantly improved the low flows while it contributed to the reduction of total streamflow in the catchment. 相似文献
890.
Al Rashdi Mouza Rashid El Tokhi Mohamed Alaabed Sulaiman El Mowafi Walid Arabi Alya A. 《Natural Resources Research》2020,29(6):4149-4160
Natural Resources Research - Rare earth element (REE) contamination has major consequences for the environment and humans. Some forms of REEs have more serious environmental impacts than others. It... 相似文献