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71.
72.
The Effects of Annual Harvesting on the Subsequent Phytomass and Species Composition of Grassland and Fernland: A Hong Kong Case 总被引:1,自引:0,他引:1
Anthropogenic grasslands mixed with fern and shrubland, on scales from metres to kilometres, are widespread in tropical Southeast Asia, and especially in southern China and adjoining regions where harvesting for domestic fuel is a major factor in their maintenance. Baseline surveys in grassland and fernland in 1989–90 and resurveys in 2001 of three 6 × 20 m plots in Wong Chuk Yuen, Hong Kong, showed substantial change in species composition and total aboveground phytomass as a result of annual harvesting, with more pronounced change in the fernland. Under harvesting pressure, the species composition of the grassland changed considerably, though the proportions of the various life‐forms did not. Ischaemum spp. and Miscanthus floridulus increased whereas Themeda gigantea died out while the proportion of other grass species remained much the same. Under the same regime the species composition and life‐forms of the fernland changed markedly. The proportion of Dicranopteris fern dropped substantially, though still comprising a third of the phytomass by 2001. The shrub Melastoma survived harvesting. A firebreak cut in the fernland became grassy under annual harvesting and remained grassy six years after cutting ceased. The annual harvests from the growth‐years 1991–2000 showed a substantial though variable increase in total phytomass. Analyses relating harvested phytomass with various climatic parameters showed no significant correlations. Some possible reasons for this are suggested. Although annual harvesting was clearly sustainable over the ten years of observation, the question of continued sustainability on sites harvested for centuries, the situation in much of southern China and parts of upland mainland Southeast Asia, remains unresolved. 相似文献
73.
Regional bias of landslide data in generating susceptibility maps using logistic regression: Case of Hong Kong Island 总被引:4,自引:0,他引:4
On the basis of 1,834 landslide data for Hong Kong Island (HKI), landslide susceptibility maps were generated using logistic
regression and GIS. Regional bias of the landslide inventory is examined by dividing the whole HKI into a southern and a northern
region, separated by an east-west trending water divide. It was found that the susceptibility map of southern HKI generated
by using the southern data differs significantly from that generated by using northern data, and similar conclusion can be
drawn for the northern HKI. Therefore, a susceptibility map of HKI was established based on regional data analysis, and it
was found to reflect closely the spatial distributions of historical landslides. Elevation appears to be the most dominant
factor in controlling landslide occurrence, and this probably reflects that human developments are concentrated at certain
elevations on the island. Classification plot, goodness of fit, and occurrence ratio were used to examine the reliability
of the proposed susceptibility map. The size of landslide susceptible zones varies depending on the data sets used, thus this
demonstrates that the historical landslide data may be biased and affected by human activities and geological settings on
a regional basis. Therefore, indiscriminate use of regional-biased data should be avoided. 相似文献
74.
Change of groundwater chemistry from 1896 to present in the Mid-Levels area, Hong Kong 总被引:1,自引:0,他引:1
In this study, groundwater quality information collected in 1896 (well waters), 1980/1981 (piezometric and seepage samples)
and 2002/2003 (seepage samples) in the regions centered by the Mid-Levels area, Hong Kong Island, was compared to illustrate
how groundwater quality has changed over a century and the processes controlling it. As shown by saline ammonia and nitrate
levels in the late nineteenth century, groundwater was severely polluted by widespread and obvious leakage from poorly designed
wastewater collection systems, although groundwater was still a drinking water source for local residents. The extremely high
residual chlorines in groundwater demonstrated that large doses of disinfection agents were added to wells at that time. In
view of the decline in saline ammonia and nitrate levels, groundwater became less organically polluted in the 1980s probably
due to significant improvement of the design of underground sewers. However, more leakage from sources such as salty flushing
water and fresh water pipes emerged in the past few decades which added complexity to groundwater chemical systems. Some chemicals
were used to identify possible locations of leakages. The temporal variations of the distribution of these chemicals over
the area may shed light on the rate of leakage. Leakage from service pipes seems to have improved from the early 1980s to
2002/2003. However, the area is still suffering from widespread and small-scale leakage from service pipes. More efforts should
be paid to control small leakages in the future. The findings will be instructive to various government organizations such
as the Water Supplies Department and Drainage Services Department to identify possible locations of unobvious leakages in
the area. 相似文献
75.
根据地球物理探测、海底取样、钻探及现场测试等实测资料详细分析,发现粤港澳跨海大桥海域具有独特的自然条件以及复杂的海洋工程地质特征。海底地形地貌较为复杂,存在含浅层气区、活动性断层、沙波、地震活动、不规则基岩、埋藏古河道、冲刷槽沟和水下浅滩等潜在灾害地质因素,尤其粤港澳跨海大桥是特大型建筑,它经过的海域分布着多种潜在的地质灾害,应引起重视。 相似文献
76.
香港地区边坡防护与治理 总被引:1,自引:0,他引:1
自开埠以来香港地区边坡事故一直不断。香港政府多年来积极进行边坡的防护治理,成效显著。讨论了香港地区岩土边坡破坏的主要原因、防治滑坡的工程措施及边坡管理系统。香港的边坡防治经验值得内地借鉴。 相似文献
77.
Roger C.K. Chan 《GeoJournal》1998,44(3):225-237
Cross-border zones have been developed rapidly in China since 1979. This was largely due to the global economic restructuring
in the post-Fordist era. The enclave of Hong Kong plays an indispensable role in the process. While China adopts the Open
Door Policy, factories in Hong Kong are quick to relocate to the Pearl River Delta region in order to benefit from the low
production costs and other preferential policies. The paper first reviews the factors leading to the economic integration
between Hong Kong and the Pearl River Delta region of southern China. It then examines the sectoral changes and the socio-economic
data of the region. Rapid urbanization and rural urbanization are reflected in the quest for infrastructural development plans
and the loss of quality farmland. They also bring along environmental hazards. The paper concludes with the call for a comprehensive
development strategy for the region into the next century.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
78.
A vegetation analysis reveals that the Lai Chi Wo mangrove swamp in Hong Kong has 10 mangrove species comprising 76.9% of
the total number of mangrove species in Hong Kong. This swamp is a mixed community dominated byAegiceras corniculatum, Heritiera littoralis, Excoecaria agallocha, Kandelia candel, Bruguiera gymnorrhiza, with importance values of 37.88, 28.19, 14.33, 11.33 and 8.27 respectively. The community’s mangrove species diversity and
evenness, as based on the Shannon-Wiener Function, were 1.44 and 62.01%, which were lower than those of the south su-tropical
evergreen broad-leaf forest community but its ecological dominance (0.26) was higher. The correlation information field (CIF)
method, a useful analytical method for complex forest community, was adopted in the present mangrove analysis. The species
correlation information was:Aegiceras corniculatum (0.268)>Heritiera littoralis (0.250)>Kandelia candel (0.220)>Excoecaria agallocha (0.169)>Bruguiera gymnorrhiza (0.101). The correlation information of the mangrove community was 1.008.
This work was financially supported by the Agriculture and Fisheries Department of The Hong Kong Government and The Hong Kong
University of Science & Technology. 相似文献
79.
香港西博寮海峡WB7孔的第四纪沉积及硅藻研究 总被引:1,自引:1,他引:1
香港西搏寮海峡WB7孔第四纪沉积物中共有硅藻54属,186个分类单位,该硅藻生物群以沿岸潮间带和近岸浅海种为主,伴有热性,暖热性浮游硅藻。依据硅藻在剖面中的分布特征,丰度及百分比含量变化,自下而上可划分出6个硅藻组合带。并明显反映该沉积时期的古气候与古环境特征,其中第5,6,带相当于全新世,其余4个带均属更新世。 相似文献
80.
北京/上海-香港客源潜力研究* 总被引:2,自引:3,他引:2
文章对内地主要城市与香港间的客源潜力进行了研究,包括居民的赴港愿望、交通方式选择,以及上述决策与收入、职业、费用、旅行时间、安全舒适性等因子的关系。分析得出:内地居民的赴港愿望和交通方式选择具有明显特征,以上海、北京为源地或中转地的居民,作为未来访港的客源,具有较大潜力,并在交通方式选择上有较强倾向性,偏好直达列车、直达飞机等便捷、快速的交通方式,且被访者的职业、收入水平等对其旅行方式选择有重要影响;对北京、上海近期与远期赴港客源潜力作了测算。 相似文献