全文获取类型
收费全文 | 3227篇 |
免费 | 203篇 |
国内免费 | 526篇 |
专业分类
安全科学 | 387篇 |
废物处理 | 61篇 |
环保管理 | 1035篇 |
综合类 | 1268篇 |
基础理论 | 268篇 |
污染及防治 | 363篇 |
评价与监测 | 86篇 |
社会与环境 | 260篇 |
灾害及防治 | 228篇 |
出版年
2024年 | 9篇 |
2023年 | 38篇 |
2022年 | 95篇 |
2021年 | 134篇 |
2020年 | 113篇 |
2019年 | 72篇 |
2018年 | 81篇 |
2017年 | 113篇 |
2016年 | 155篇 |
2015年 | 133篇 |
2014年 | 173篇 |
2013年 | 204篇 |
2012年 | 256篇 |
2011年 | 259篇 |
2010年 | 199篇 |
2009年 | 184篇 |
2008年 | 145篇 |
2007年 | 253篇 |
2006年 | 193篇 |
2005年 | 181篇 |
2004年 | 147篇 |
2003年 | 138篇 |
2002年 | 95篇 |
2001年 | 73篇 |
2000年 | 100篇 |
1999年 | 63篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 26篇 |
1995年 | 38篇 |
1994年 | 19篇 |
1993年 | 28篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1973年 | 3篇 |
1972年 | 7篇 |
1971年 | 8篇 |
1970年 | 3篇 |
排序方式: 共有3956条查询结果,搜索用时 5 毫秒
121.
122.
123.
泥石流输沙对小江中下游河床演变的影响 总被引:4,自引:1,他引:4
对小江中下游近90km河床及两岸泥石流进行了调查研究。得到:泥石流输沙年际和季节变化大;泥石流高强度的输沙造成小江河床特殊的平面和剖面特征;泥石流堵塞小江河道,对纵比降有再造作用;泥沙使小江河床以年均20cm~50cm速度抬升。 相似文献
124.
黄河断流成因及人文思考 总被引:2,自引:0,他引:2
日益严峻的黄河断流现象严重地影响了黄河流域经济和社会的可持续发展,也制约了西部大开发战略的实施。在分析了黄河断流的危害、成因的基础上,提出了在工程措施之外,要从人口、法律制度、产业结构等人文因素方面入手缓解黄河断流。 相似文献
125.
西藏冰湖溃决主要特征 总被引:6,自引:1,他引:6
西藏是我国冰湖分布最多的地区。冰湖常发生溃决,其中最典型是终碛冰湖的溃决。冰湖溃决所导致的泥石流,具有突发性强、频率低、洪峰高、流量大、流量过程暴涨暴落和破坏力强及灾害波及范围广等特点。从20世纪30年代中期至今,已查明西藏15个冰川终碛湖至少发生过18次溃决。通过对这些溃决事件的分析,探讨了终碛湖溃决的时空分布特征,发现该事件的发生与气候变化,特别是与气候异常年份有显著的对应关系。结合近年冰湖分布和变化资料,讨论了未来的发展趋势。具体分析了溃决洪水过程和冰湖溃决洪水泥石流演变过程。 相似文献
126.
127.
陕西潼关金矿‘94人工泥石流灾害研究 总被引:9,自引:0,他引:9
本文研究了1994年7月11日发生在陕西潼关县西峪金矿区,因暴雨引发的人工泥石流所酿成的特大灾难。通过对形成泥石流的地质、地貌、降雨和人为等其他形成的原因进行了分析。提出了今后应加强的预防措施,这对合理开发金矿资源、预防泥石流灾害,有着十分重要的科学意义。 相似文献
128.
Centrality metrics evaluate paths between all possible pairwise combinations of sites on a landscape to rank the contribution of each site to facilitating ecological flows across the network of sites. Computational advances now allow application of centrality metrics to landscapes represented as continuous gradients of habitat quality. This avoids the binary classification of landscapes into patch and matrix required by patch-based graph analyses of connectivity. It also avoids the focus on delineating paths between individual pairs of core areas characteristic of most corridor- or linkage-mapping methods of connectivity analysis. Conservation of regional habitat connectivity has the potential to facilitate recovery of the gray wolf (Canis lupus), a species currently recolonizing portions of its historic range in the western United States. We applied 3 contrasting linkage-mapping methods (shortest path, current flow, and minimum-cost-maximum-flow) to spatial data representing wolf habitat to analyze connectivity between wolf populations in central Idaho and Yellowstone National Park (Wyoming). We then applied 3 analogous betweenness centrality metrics to analyze connectivity of wolf habitat throughout the northwestern United States and southwestern Canada to determine where it might be possible to facilitate range expansion and interpopulation dispersal. We developed software to facilitate application of centrality metrics. Shortest-path betweenness centrality identified a minimal network of linkages analogous to those identified by least-cost-path corridor mapping. Current flow and minimum-cost-maximum-flow betweenness centrality identified diffuse networks that included alternative linkages, which will allow greater flexibility in planning. Minimum-cost-maximum-flow betweenness centrality, by integrating both land cost and habitat capacity, allows connectivity to be considered within planning processes that seek to maximize species protection at minimum cost. Centrality analysis is relevant to conservation and landscape genetics at a range of spatial extents, but it may be most broadly applicable within single- and multispecies planning efforts to conserve regional habitat connectivity. 相似文献
129.
Stephan F. J. De Wekker D. G. Steyn J. D. Fast M. W. Rotach S. Zhong 《Environmental Fluid Mechanics》2005,5(1-2):35-62
Data from a comprehensive field study in the Riviera Valley of Southern Switzerland are used to investigate convective boundary layer structure in a steep valley and to evaluate wind and temperature fields, convective boundary layer height, and surface sensible heat fluxes as predicted by the mesoscale model RAMS. Current parameterizations of surface and boundary layer processes in RAMS, as well as in other mesoscale models, are based on scaling laws strictly valid only for flat topography and uniform land cover. Model evaluation is required to investigate whether this limits the applicability of RAMS in steep, inhomogeneous terrain. One clear-sky day with light synoptic winds is selected from the field study. Observed temperature structure across and along the valley is nearly homogeneous while wind structure is complex with a wind speed maximum on one side of the valley. Upvalley flows are not purely thermally driven and mechanical effects near the valley entrance also affect the wind structure. RAMS captured many of the observed boundary layer characteristics within the steep valley. The wind field, temperature structure, and convective boundary layer height in the valley are qualitatively simulated by RAMS, but the horizontal temperature structure across and along the valley is less homogeneous in the model than in the observations. The model reproduced the observed net radiation, except around sunset and sunrise when RAMS does not take into account the shadows cast by the surrounding topography. The observed sensible heat fluxes fall within the range of simulated values at grid points surrounding the measurement sites. Some of the scatter between observed and simulated turbulent sensible heat fluxes are due to sub-grid scale effects related to local topography. 相似文献
130.