全文获取类型
收费全文 | 798篇 |
免费 | 70篇 |
国内免费 | 85篇 |
专业分类
安全科学 | 213篇 |
废物处理 | 16篇 |
环保管理 | 87篇 |
综合类 | 334篇 |
基础理论 | 94篇 |
污染及防治 | 65篇 |
评价与监测 | 68篇 |
社会与环境 | 48篇 |
灾害及防治 | 28篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 33篇 |
2021年 | 38篇 |
2020年 | 39篇 |
2019年 | 31篇 |
2018年 | 23篇 |
2017年 | 38篇 |
2016年 | 36篇 |
2015年 | 42篇 |
2014年 | 32篇 |
2013年 | 41篇 |
2012年 | 67篇 |
2011年 | 64篇 |
2010年 | 50篇 |
2009年 | 40篇 |
2008年 | 32篇 |
2007年 | 53篇 |
2006年 | 48篇 |
2005年 | 33篇 |
2004年 | 17篇 |
2003年 | 28篇 |
2002年 | 22篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有953条查询结果,搜索用时 15 毫秒
321.
322.
突发性大气环境污染事故应急监测布点研究 总被引:5,自引:1,他引:5
采样点的布设在应急监测过程中起着至关重要的作用,科学、合理地布置采样点是应急监测的关键技术之一,采样点必须分布在整个事故影响区域。引入气体扩散模式预测事故影响范围,根据毒负荷标准在事故影响区内划分危险区。阐述了应急监测采样点布设原则及事故初期、中期、后期的特点,并对三个时期采样点布设方法进行研究。 相似文献
323.
DAVID A. FEARY JOSHUA E. CINNER NICHOLAS A. J. GRAHAM FRASER A. JANUCHOWSKI‐HARTLEY 《Conservation biology》2011,25(2):341-349
Abstract: Customary management systems (i.e., management systems that limit the use of marine resources), such as rotational fisheries closures, can limit harvest of resources. Nevertheless, the explicit goals of customary management are often to influence fish behavior (in particular flight distance, i.e., distance at which an organism begins to flee an approaching threat), rather than fish abundance. We explored whether the flight distance of reef fishes targeted by local artisanal fishers differed between a customary closure and fished reefs. We also examined whether flight distance of these species affected fishing success and accuracy of underwater visual census (UVC) between customary closed areas and areas open to fishing. Several species demonstrated significant differences in flight distance between areas, indicating that fishing activity may increase flight distance. These relatively long flight distances mean that in fished areas most target species may stay out of the range of spear fishers. In addition, mean flight distances for all species both inside and outside the customary‐closure area were substantially smaller than the observation distance of an observer conducting a belt‐transect UVC (mean [SE]= 8.8 m [0.48]). For targeted species that showed little ability to evade spear fishers, customary closures may be a vital management technique. Our results show that customary closures can have a substantial, positive effect on resource availability and that conventional UVC techniques may be insensitive to changes in flight behavior of fishes associated with fishing. We argue that short, periodic openings of customary closures may allow the health of the fish community to be maintained and local fishers to effectively harvest fishes. 相似文献
324.
ROB WILLIAMS SHARON L. HEDLEY TREVOR A. BRANCH MARK V. BRAVINGTON ALEXANDRE N. ZERBINI KEN P. FINDLAY 《Conservation biology》2011,25(3):526-535
Abstract: Often abundance of rare species cannot be estimated with conventional design‐based methods, so we illustrate with a population of blue whales (Balaenoptera musculus) a spatial model‐based method to estimate abundance. We analyzed data from line‐transect surveys of blue whales off the coast of Chile, where the population was hunted to low levels. Field protocols allowed deviation from planned track lines to collect identification photographs and tissue samples for genetic analyses, which resulted in an ad hoc sampling design with increased effort in areas of higher densities. Thus, we used spatial modeling methods to estimate abundance. Spatial models are increasingly being used to analyze data from surveys of marine, aquatic, and terrestrial species, but estimation of uncertainty from such models is often problematic. We developed a new, broadly applicable variance estimator that showed there were likely 303 whales (95% CI 176–625) in the study area. The survey did not span the whales' entire range, so this is a minimum estimate. We estimated current minimum abundance relative to pre‐exploitation abundance (i.e., status) with a population dynamics model that incorporated our minimum abundance estimate, likely population growth rates from a meta‐analysis of rates of increase in large baleen whales, and two alternative assumptions about historic catches. From this model, we estimated that the population was at a minimum of 9.5% (95% CI 4.9–18.0%) of pre‐exploitation levels in 1998 under one catch assumption and 7.2% (CI 3.7–13.7%) of pre‐exploitation levels under the other. Thus, although Chilean blue whales are probably still at a small fraction of pre‐exploitation abundance, even these minimum abundance estimates demonstrate that their status is better than that of Antarctic blue whales, which are still <1% of pre‐exploitation population size. We anticipate our methods will be broadly applicable in aquatic and terrestrial surveys for rarely encountered species, especially when the surveys are intended to maximize encounter rates and estimate abundance. 相似文献
325.
326.
327.
The Avoidance Responses of Daphnia magna to the Exposure of Organophosphorus Pesticides in an On-Line Biomonitoring System 总被引:1,自引:0,他引:1
Zong-Ming Ren Zhi-Liang Li Jin-Miao Zha Kai-feng Rao Mei Ma Zijian Wang Rong-Shu Fu 《Environmental Modeling and Assessment》2009,14(3):405-410
In this study, avoidance behavior of the freshwater cladoceran Daphnia magna Straus was used as indicator to assess the early stress of accidental organophosphorus pesticide (OP) contamination. The
movement behavior was detected by a multi-species biomonitoring system. There was obvious concentration–response relationship
between the OP stress and the behavioral response even at sublethal exposure. A rising OP stress resulted in a significant
decrease of response time to escape (RTE; p<0.05). In comparison of different OPs, it was found that there was a power regression between RTE and the toxic unit of OPs.
Therefore, the avoidance behavior of D. magna was a sensitive indicator of sublethal OP stress, and the power relationship could be used to predict the early warning thresholds
of more OPs in the on-line biomonitoring system. 相似文献
328.
329.
Patchy distribution fields: sampling distance unit of a zigzag survey and reconstruction adequacy 总被引:1,自引:0,他引:1
Kalikhman I 《Environmental monitoring and assessment》2002,80(1):1-16
A mathematical model was used to examine the effects of choosingvarious units of sampling distance of a zigzag survey on the adequacy of reconstructing patchy distribution fields. The modelsimulates fish or plankton patches (or gaps) of different shapesand spatial orientations, and an acoustic survey by zigzag or parallel transects along which a unit of sampling distance is set. Adequacy of the reconstructed fields to those originally generated is evaluated by calculating their correlations (r). A priori information on the autocorrelation radii for the field in the directions of the survey (Rs) and perpendiculardirection (Rp) allows optimisation of the survey design andthe algorithm of data analysis. A field can be reconstructed properly (r2 > 0.70) if the distance between transects D < (1.0–1.5)Rs and the unit of sampling distance d < (1.0–1.5)Rp. A posteriori determination of patchorientation allows reconstruction of the best field attainable onthe basis of the survey data. In cases of field movement, if thedimension of patches in the direction of movement exceeds that ofa surveyed area, a survey in the opposite direction gives bestresults; in contrast, if the dimension of moving patches is smaller than that of a surveyed area, it is reasonable to carryout a survey in the same direction. The criterion remains validwhen a survey is carried out by zigzag transects and a unit ofsampling distance is set along them. The results obtained indicate that, for a fixed transect spacing and a given number of sampling points on each full transect, zigzag pattern allowsless adequate reconstruction of an original distribution field (in cases of both immovable and movable fields) than corresponding parallel pattern. 相似文献
330.
通过对TSP、SO2浓度在不同高度实测研究.得出平顶山市SO2在1.5m至20m不同高度监测,高度影响无显著性差异;TSP在5m至15m不同高度监测,高度影响无显著性差异。 相似文献