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21.
Dredged material levees in coastal Louisiana are normally associated with pipeline canals or, more frequently, canals dredged
through the wetlands to allow access to drilling locations for mineral extraction. The hydrologic impact on marshes behind
the levee is of concern to coastal resource managers because of the potential impact on sediment transport and deposition,
and the effect on estuarine organism access to valuable nursery habitat. This study examined the effects of gaps in dredged
material levees, compared to continuous levees and natural channel banks, on these two aspects of marsh function. Field studies
for sediment deposition were conducted biweekly for a year, and nekton samples were collected in spring and fall. Variation
in nekton density among study arears and landscape types was great in part because of the inherent sampling gear issues and
in part because of differences in characteristics among areas. Nekton densities were generally greater in natural compared
to leveed and gapped landscapes. Differences in landscape type did not explain patterns in sediment deposition. The gaps examined
appear to be too restrictive of marsh flooding to provide efficient movements of floodwaters onto the marsh during moderate
flooding events. The “trapping” effect of the levees increases sediment deposition during extreme events. Gapping material
levees may be an effective method of partially restoring upper marsh connection to nekton, but this method may work best in
lower elevation marshes where nekton use is greater. 相似文献
22.
23.
海洋气溶胶对沿海地区降水组成的贡献 总被引:2,自引:0,他引:2
以青岛地区为对象,对沿海地区大气气溶海洋因子对降水组成的贡献,进行了研究分析。结果表明,1)夏季受海洋影响要比冬季明显得多;(2)降水中主要的碱性物质,不论是夏季或冬季,99%来自大陆气溶胶,海洋的影响可忽略;(3)海洋影响的程度和离海边的距离有关,离海愈远,受海洋影响就愈小,离海愈近,受其影响就愈大。 相似文献
24.
Dibenzothiophene (DBT) degradation mechanisms and the transformation of pathways during the incubation of three types of coastal sediments with C/N ratios ranging from 1 to 9 were investigated. The DBT degradation efficiencies were clearly improved with increasing C/N ratio in reed wetland sediments, tidal wetlands sediments and estuary wetland sediments. The quantitative response relationships between DBT degradation rates and related functional genes demonstrate that the Kodama pathway-related gene groups were dominant factors at low C/N ratios, while the 4S-related gene groups mainly determined the degradation rate when the C/N ratio was up to 5. Network analysis also shows that the pathway shifts from the Kodama pathway to the 4S pathway occurred through changes in the connections between functional genomes and rates. Furthermore, there were competition and collaboration between the Kodama and 4S pathways. The 4S pathway-related bacteria were more active in estuary wetland sediments compared with reed wetland sediments and tidal wetland sediments. The higher degradation efficiency in estuary wetland sediments may indicate the greater participation of the 4S pathway in the DBT biodegradation reaction. And the effects of ring cleavage of Kodama pathway caused more complete metabolizing of DBT. 相似文献
25.
Uncertainty plays a major role in Integrated Coastal Zone Management (ICZM). A large part of this uncertainty is connected
to our lack of knowledge of the integrated functioning of the coastal system and to the increasing need to act in a pro-active
way. Increasingly, coastal managers are forced to take decisions based on information which is surrounded by uncertainties.
Different types of uncertainty can be identified and the role of uncertainty in decision making, scientific uncertainty and
model uncertainty in ICZM is discussed. The issue of spatial variability, which is believed to be extremely important in ICZM
and represents a primary source of complexity and uncertainty, is also briefly introduced. Some principles for complex model
building are described as an approach to handle, in a balanced way, the available data, information, knowledge and experience.
The practical method of sensitivity analysis is then introduced as a method for a posterior evaluation of uncertainty in simulation
models. We conclude by emphasising the need for the definition of an analysis plan in order to handle model uncertainty in
a balanced way during the decision making process. 相似文献
26.
Development along the western beachfront of Port Alfred, which is situated along a sandy shoreline, increased markedly in
the 1960s as the coastal town became a popular holiday resort. This development included the removal of coastal vegetation,
which resulted in the destabilization of dunes and migration of sand westerly onto the road, West Beach parking lot, and lawns
of the cabanas. Sand traps were constructed to collect sand blowing across the dunes over set periods, and the net sand movement
along the mobile dune belt was calculated using Hunter's equation. The dunes show an easterly movement of sand at a rate of
3.5 m/yr, which is comparable with figures recorded along other areas of this coastline. Considering the wind regime and amount
of sand movement along this coast, it is inappropriate to clear vegetation and develop within the dune region. 相似文献
27.
An evaluation of coastal landscape of pine forest in Greece by summer visitors of various nationalities was carried out. The
visual preferences for a set of landscape, represented in photographs, expressed by these various nationality groups were
compared. The subjects used in this research came from Greece, Germany, Italy, France, Great Britain, Austria, Yugoslavia,
and Scandinavian countries. The findings show that there is an agreement over the basic preference, but, nevertheless, there
are differences of opinion between the nationality groups that might be attributed to cultural influences and the effect of
being familiar with their own environments. Since coastal landscape plays an important role in the tourist industry, these
findings could be very useful to policy-making agencies. 相似文献
28.
ABSTRACT: The relative abundance of small mammals in five forest land cover types on the upper Coastal Plain of north Mississippi was determined. Burrowing mammals accounted for one-half of the total captures; one shrew species that accounted for over one-fourth of the total captures had a strong affinity for well-stocked pine plantations. The opportunity for detention and retention of rainfall was enhanced by burrowing activity. Reductions of stormflow volumes 12 to 15 years after replacing poor quality, upland hardwoods with loblolly pine were only partially explained by increased interception of rainfall; much of the residual reductions are postulated to be due to small mammal burrows. Small mammal activity deserves further study as an important aspect of forest land hydrology. 相似文献
29.
赵玉华 《中国环境管理干部学院学报》1999,(2)
海岸带环境资源综合管理,是对海岸带资源可持续开发利用模式下的现代综合管理。本文在对区域海岸带环境资源综合管理的内涵及管理目标进行分析的基础上,以秦皇岛海岸带环境资源实施综合管理为例,提出了区域海岸带环境资源综合管理的评价过程及模式。 相似文献
30.
Chen-Tung?Arthur?ChenEmail author James?T.?Liu Ben-Jei?Tsuang 《Regional Environmental Change》2004,4(1):39-48
Rapid economic and industrial development in Taiwan over the past five decades has elevated the islands standing and earned it a place in the group known as the Four Small Dragons of Asia. Such growth, however, has been at the expense of the environment. There are currently nearly 23 million people juggling for space on the small island of 35,873 km2. Aggravating the matter further, the central mountain ranges and hills take up 73.6% of the land area with some 156 peaks surpassing 3,000 m. As a result, most people live in coastal plains which amount to only 9,490 km2. Pressure to move people inland has led to road construction and deforestation, both of which have contributed to an already high denudation rate of topsoil. As a consequence of this, thirteen rivers in Taiwan are now ranked among the top 20 worldwide in terms of sediment yield. Aside from this, the frequency of both floods and droughts increased prior to 1990, perhaps because of deforestation and global warming. Fortunately, the new conservation-orientated forest management policy of 1991 has alleviated the problem, somewhat, and the occurrence of floods and droughts has since decreased. The problem of water shortage, however, has worsened because of the warming trend in atmospheric temperature. Damming may ameliorate the water shortage problem but may affect the shoreline stability, as well as the ecology and water quality in the estuaries. Furthermore, these detrimental effects may go far beyond the estuaries, and even fisheries on the continental shelves may be affected. 相似文献