全文获取类型
收费全文 | 179篇 |
免费 | 8篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 16篇 |
地球物理 | 42篇 |
地质学 | 85篇 |
海洋学 | 17篇 |
天文学 | 3篇 |
综合类 | 2篇 |
自然地理 | 10篇 |
出版年
2024年 | 1篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 18篇 |
2013年 | 25篇 |
2012年 | 12篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 5篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有194条查询结果,搜索用时 125 毫秒
91.
Keivan Kabiri Biswajeet Pradhan Helmi Zulhaidi Mohd Shafri Shattri Bin Mansor Kaveh Samimi-Namin 《Journal of the Indian Society of Remote Sensing》2013,41(4):797-806
Diffuse attenuation coefficient (k d ) is a critical parameter for benthic habitat mapping using remotely sensed data. This research attempted to develop a new approach to estimate k d in blue and green bands of QuickBird satellite image based on the integration of Lyzenga’s method and updated NASA-k d 490 algorithm. To do this, the Lyzenga’s method was utilized to determine the ratio of k d in different bands of QuickBird satellite image. Additionally, NASA-k d 490 algorithm was applied to determine k d 490 by using remotely sensed reflectance values of blue (R rs Blue ) and green (R rs Green ) bands in each pixel of QuickBird satellite image. Since the aforementioned algorithm has been developed for other types of sensors, an approach using weighted mean value of parameters for SeaWiFS, MERIS, VIIRS, and OCTS sensors were employed to estimate parameter values for QuickBird image. After determining the k d 490 values as k d for blue band, the k d values for green and red bands were subsequently obtained by using Lyzenga’s method. Then, Mumby and Edwards’ method was employed as evidence to evaluate the accuracy of the results achieved from newly developed approach. Eventually, the maximum likelihood classifier was implemented during pre and post correction steps to examine the capability of the proposed approach. The final results proved to be consistent in the areas deeper than 2 m between estimated k d values using the proposed approach and the results obtained from Mumby and Edwards’ method. On the other hand, the values estimated for extremely shallow areas seem to be overestimated. Furthermore, results demonstrated an increment of ~16 % in the overall accuracy of the classification. 相似文献
92.
Javed Mallick Yasser Alashker Shams Al-Deen Mohammad Mohd Ahmed Mohd Abul Hasan 《国际地球制图》2013,28(8):915-940
Soil erosion is the most important factor in land degradation and influences desertification in semi-arid areas. A comprehensive methodology that integrates revised universal soil loss equation (RUSLE) model and GIS was adopted to determine the soil erosion risk (SER) in semi-arid Aseer region, Saudi Arabia. Geoenvironmental factors viz. rainfall (R), soil erodibility (K), slope (LS), cover management and practice factors were computed to determine their effects on average annual soil loss. The high potential soil erosion, resulting from high denuded slope, devoid of vegetation cover and high intensity rainfall, is located towards the north western part of the study area. The analysis is investigated that the SER over the vegetation cover including dense vegetation, sparse vegetation and bushes increases with the higher altitude and higher slope angle. The erosion maps generated with RUSLE integrated with GIS can serve as effective inputs in deriving strategies for land planning/management in the environmentally sensitive mountainous areas. 相似文献
93.
Abstract Change detection study has been made for the mangrove forest of the Sunderbans (Bangladesh) using remote sensing and other ancillary data (1933–1987). At the advent of the British rule the forest was double their present extent. Its present area is about 6000.0 Sq. Km. The productive land area has been increased from 1960. Gewa (Excoecaria agallocha)‐Sundri (Heritiera fames) cover type areas have been increased at the expense of pure Sundri type. Height classes of the forest have been changed, basal area/ha has decreased. It is observed that there is a net decrease in Sundri standing volume of the order of 40% and that of Gewa 45% over the past 25 years (1960–1985). Total timber volume for all of the species has been reduced to near about a half. Timber volume/ha and basal area/ha for Gewa have increased in the Sharankhola Island of the forest. Sundri tress are being replaced by Gewa. CIR aerial photographs have been found most suitable for cover type analysis and other change detection study. Regular monitoring of the changes of the forest using remote sensing technique has been suggested. 相似文献
94.
95.
96.
With a view to difficulties with explaining the physical mechanism of solar forcing on the Earth’s climate, we applied a new
approach of determining and quantifying an influence of solar-related events on water vapor variability by correlating the
total electron content (TEC) and precipitable water vapor (PWV), both derived from ground-based GPS observations.
In this study, ionospheric TEC and atmospheric PWV values are employed as solar activity and terrestrial climate parameters,
respectively. Three-year GPS data at five stations in Antarctica are analyzed on a daily mean basis. Results show significant
correlation between TEC and PWV differences during storms-affected days. The high correlation between the daily mean values
of TEC and PWV, both of which follow the seasonal signals and subsisting downward trend, suggests an influence of solar activity
on climate variability in Antarctica. These quantities are determined by changes of the upper-atmosphere level, which varies
in conformity with the zenith angle of the Sun. 相似文献
97.
Aziz Ghaderpour Khairul Nazrin Mohd Nasori Li Lee Chew Ving Ching Chong Kwai Lin Thong Lay Ching Chai 《Marine pollution bulletin》2014
The deltaic estuarine system of the Matang Mangrove Forest Reserve of Malaysia is a site where several human settlements and brackish water aquaculture have been established. Here, we evaluated the level of fecal indicator bacteria (FIB) and the presence of potentially pathogenic bacteria in the surface water and sediments. Higher levels of FIB were detected at downstream sampling sites from the fishing village, indicating it as a possible source of anthropogenic pollution to the estuary. Enterococci levels in the estuarine sediments were higher than in the surface water, while total coliforms and E. coli in the estuarine sediments were not detected in all samples. Also, various types of potentially pathogenic bacteria, including Klebsiella pneumoniae, Serratia marcescens and Enterobacter cloacae were isolated. The results indicate that the Matang estuarine system is contaminated with various types of potential human bacterial pathogens which might pose a health risk to the public. 相似文献
98.
99.
The following work aims at minimizing the environmental impact of the solid wastes (ash) that is produced after the utilization
of the bituminous limestone in thermal power stations and/or retorting processes. The laboratory tests have been selected
with respect to construction needs and possible post construction conditions. Utilization of the various types of ash in the
production of lightweight concrete block has revealed optimum results. The compressive strength of various ash–glass sand
mixes has ranged between 19 and 76 kg/cm2 at 28 days. The compressive strength of ash–tuff mixes has ranged between 54 and 63 kg/cm2 at 28 days. Ultra light mixtures using ash–polyester with a density of 0.88 kg/m3 and a compressive strength of 21 kg/cm2 at 28 days are produced at normal room curing temperature without the use of ordinary Portland cement. The high alkalinity
of El-Lajjun ash is considered a disadvantage when utilized in normal concrete mixes for structural purposes. Ash only can
be mixed with aggregates to produce lean concrete for blinding purposes for use in foundations. 相似文献
100.
Surface drainage sediments were collected, between January and April in 2005, from 6 sampling sites in Peninsular Malaysia suspected to have received different anthropogenic sources. These drainages included sites near a petrochemical plant, an electronic factory, a metal factory and 2 townships in addition to a relatively unpolluted site (a reference site). Based on the aqua-regia method, the metal concentrations for all the sampling sites except for the agricultural site (reference site) at Sg. Benut were between 60.92-1 019 μg/g dry weight for copper (Cu), 65.32-1 266.6μg/g dry weight for plumbum (Pb), 1.46-15.93 μg/g dry weight for cadmium (Cd), 330.10-484.14 μg/g dry weight for zinc (Zn) and 47.03-120.90 μg/g dry weight for nickel (Ni). All of these ranges were significantly (p< 0.05) higher than those (Cu: 8.77 μg/g; Pb: 57.42 μg/g; Cd: 0.96 μg/g; Zn: 68.21 μg/g; and Ni: 17.87 μg/g) of the reference site at Sg. Benut that only received agricultural disposal. The concentrations for the 5 metals from all the sites (except for the reference site) were higher than the Sediment Quality Values for Hong Kong by Chapman et al (1999) for the 5 metals. Based on the sequential extraction technique, 3 geochemical fractions [easily, freely leachable and exchangeable (EFLE), acid-reducible and oxidisable-organic] were also useful in identifying these polluted sites. The elevated metal concentrations found in the sediments might be related to point sources of industrial effluent and urban waste. Hence, the results emphasized the necessity for the treatment of effluents into this drainage area. As part of the effort to control illegal discharges and dumping into drainages, public awareness should be enhanced. 相似文献