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121.
Tole L 《Environmental management》2001,28(4):455-467
Jamaica is a small island that is losing its forest cover at a rapid rate. Due to the dependency of its largely poor population
on the many services and functions its forests provide, this loss threatens to have substantial socioeconomic and ecological
consequences for the country. Despite these basic facts, the problem of Jamaican deforestation has received very little attention
from the scientific community. This article presents results of an island-wide, satellite-based study of forest change for
Jamaica for the period 1987–1992, which was supplemented by a field trip to the island in 1999 to assess the overall accuracy
of the estimate. Landsat MSS images, which are available only up until 1992, have proved to be an invaluable and cost-effective
resource for mapping forest change in the tropics, particularly in large areas. A supervised classification indicates that
Jamaica experienced an average annual deforestation rate of 3.9% for this period, a figure higher than existing estimates
based on partial ground surveys but lower than the FAO's 1990 Tropical Forest Assessment of 5.3% for 1981–1990. Deforestation
estimates for Jamaica's 14 parishes are also presented, based on the integration of satellite-derived forest classification
maps with a parish administrative boundaries map of the island in a GIS. A correlation analysis between parish deforestation
estimates and socioeconomic and land use/quality indicators derived from official sources suggests that deforestation is occurring
most rapidly in highly populated areas possessing large numbers of small farmers who live and work under resource-poor conditions.
By providing a sense of the magnitude of and main forest loss hotspots, it is hoped that these national and subnational level
forest estimates will draw scientific attention to the problem of deforestation on the island. In addition, the socioeconomic
analysis may provide policy-makers and planners with some sense of the relative contribution of underlying driving process
in this deforestation as a first step toward the creation of effective social programs to combat the problem. 相似文献
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125.
Stephen R. Kessell 《Environmental management》1979,3(1):29-40
The application of vegetation information to resource management problems is reviewed in four areas: (1) the stratification of vegetation data by classification and gradient analysis, (2) the storage and retrieval of these data, (3) the sources of vegetation information, and (4) the accuracy and resolution requirements posed by different management applications. Conclusions indicate that the successful application of inference methods to resource management problems requires an appropriate integration of these four components. 相似文献
126.
Haimanote K. Bayabil Ali Fares Hatim O. Sharif Dawit T. Ghebreyesus Hernan A. Moreno 《Journal of the American Water Resources Association》2019,55(6):1492-1504
The objectives of this study were to (1) evaluate the performance of the Multi‐Radar Multi‐Sensor (MRMS) system in capturing precipitation compared to gauge data, and (2) assess the effects of spatial (1–50 km) and temporal (15–120 min) data aggregation scales on the performance of the MRMS system. Point‐to‐grid comparisons were conducted between 215 rain gauges and the MRMS system. The MRMS system at 1 km spatial and 15 min temporal resolutions captured precipitation reasonably well with average R2, root mean square error (RMSE), and percent bias (PBIAS) values of 0.65, 0.5 mm, and 11.9 mm; whereas Threat Score, probability of detection, and false alarm ratio were 0.57, 0.92, and 0.40, respectively. Decreasing temporal resolution from 15 min to two hours resulted in an increase in R2 and a decrease in RMSE, whereas PBIAS was not affected. Reducing spatial resolution from 1 to 50 km resulted in increases in R2 and PBIAS, whereas RMSE was decreased. Increasing spatial aggregation scale from 1 to 50 km resulted in an R2 increase of only 0.08. Similarly, improvement in R2 was only modest (0.17) compared to an eightfold reduction in temporal resolution (from 15 min to two hours). While aggregating data at coarser temporal resolutions resolved some of the under/overestimation issues of the MRMS system, it was apparent even at coarser spatial and temporal resolutions the MRMS system inherently overestimated smaller precipitation events while underestimated bigger events. 相似文献
127.
大型水面舰船目标雷达波散射特征分析 总被引:3,自引:0,他引:3
针对大型水面舰船超电大尺度和复杂外形结构特点,论述了大型水面舰船的雷达波散射机制,结合电磁理论,对大型水面舰船的各类散射源进行了结构划分,并运用现代计算电磁学和计算机图形学,计算分析了典型大型水面舰船的雷达波散射特征及各主要结构对全舰RCS的影响.结果表明,大型水面舰船上层建筑的平面直反射和面与面之间的多次散射是主要散射源. 相似文献
128.
我国洪涝灾害加剧的主要因素与进一步抗洪减灾应取的对策 总被引:12,自引:2,他引:10
我国正面临着洪涝灾害加剧的严峻形势。90年代以来,已出现了4个洪涝重灾年,每年的直接经济损失都接近或超过千亿元人民币。本文分析了导致我国洪涝灾害加剧的主要原因:首先是随着人口膨胀,大规模砍伐森林,大面积垦殖坡地,导致水土流失面积扩大,大量泥沙注入江河湖库;加之过度围垦湖泊与沿河低洼地,湖面大幅度萎缩;快速发展的城市化也使出现洪涝的可能性加大,损失加重。在总结我国抗洪防灾经验的基础上,讨论了应该进一步采取的措施,并提出了建立以Radarsat为主体的多卫星抗洪减灾遥感信息系统的设想。 相似文献
129.
探地雷达—电法—化探技术在地下排污管网探测工程中的应用 总被引:1,自引:0,他引:1
介绍探地雷达-电法化探技术的基本原理及应用于齐鲁石化公司地下排污管线进行测漏的工程实例。 相似文献
130.
目的缩短可靠性鉴定时间,降低试验费用,形成工程化方法。方法以GJB 899A—2009为依据,根据雷达产品的实际特点,选择合适的定时统计试验方案,确定可靠性鉴定试验剖面。参考国内外加速试验标准,运用阿伦尼乌斯模型、Norris-Landzberg模型、疲劳累积损伤模型对可靠性鉴定试验剖面中温度、温度循环、振动应力水平进行加速,分别给出温度、温度循环、振动应力加速因子计算方法,得到加速条件下的等效试验剖面及故障时间。结果通过可靠性加速试验等效剖面计算,雷达可靠性鉴定试验时间由1100 h等效为加速条件下367h。结论地面雷达可靠性加速试验方法能够明显缩短试验时间,降低试验成本,可以在工程中推广应用。 相似文献