首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1107篇
  免费   42篇
  国内免费   24篇
安全科学   56篇
废物处理   63篇
环保管理   299篇
综合类   101篇
基础理论   296篇
环境理论   4篇
污染及防治   221篇
评价与监测   76篇
社会与环境   48篇
灾害及防治   9篇
  2023年   14篇
  2022年   14篇
  2021年   17篇
  2020年   24篇
  2019年   16篇
  2018年   44篇
  2017年   44篇
  2016年   64篇
  2015年   46篇
  2014年   44篇
  2013年   85篇
  2012年   65篇
  2011年   88篇
  2010年   52篇
  2009年   57篇
  2008年   59篇
  2007年   63篇
  2006年   49篇
  2005年   31篇
  2004年   44篇
  2003年   34篇
  2002年   30篇
  2001年   14篇
  2000年   18篇
  1999年   17篇
  1998年   18篇
  1997年   19篇
  1996年   15篇
  1995年   8篇
  1994年   3篇
  1993年   12篇
  1992年   9篇
  1991年   8篇
  1990年   3篇
  1989年   3篇
  1988年   4篇
  1987年   8篇
  1986年   6篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1980年   6篇
  1978年   2篇
  1976年   1篇
排序方式: 共有1173条查询结果,搜索用时 781 毫秒
521.
Approaches to assess the impacts of landscape disturbance scenarios on species range from metrics based on patterns of occurrence or habitat to comprehensive models that explicitly include ecological processes. The choice of metrics and models affects how impacts are interpreted and conservation decisions. We explored the impacts of 3 realistic disturbance scenarios on 4 species with different ecological and taxonomic traits. We used progressively more complex models and metrics to evaluate relative impact and rank of scenarios on the species. Models ranged from species distribution models that relied on implicit assumptions about environmental factors and species presence to highly parameterized spatially explicit population models that explicitly included ecological processes and stochasticity. Metrics performed consistently in ranking different scenarios in order of severity primarily when variation in impact was driven by habitat amount. However, they differed in rank for cases where dispersal dynamics were critical in influencing metapopulation persistence. Impacts of scenarios on species with low dispersal ability were better characterized using models that explicitly captured these processes. Metapopulation capacity provided rank orders that most consistently correlated with those from highly parameterized and data-rich models and incorporated information about dispersal with little additional computational and data cost. Our results highlight the importance of explicitly considering species’ ecology, spatial configuration of habitat, and disturbance when choosing indicators of species persistence. We suggest using hybrid approaches that are a mixture of simple and complex models to improve multispecies assessments.  相似文献   
522.
The loss of forest is a leading cause of species extinction, and reforestation is 1 of 2 established interventions for reversing this loss. However, the role of reforestation for biodiversity conservation remains debated, and lacking is an assessment of the potential contribution that reforestation could make to biodiversity conservation globally. We conducted a spatial analysis of overlap between 1,550 forest-obligate threatened species’ ranges and land that could be reforested after accounting for socioeconomic and ecological constraints. Reforestation on at least 43% (∼369 million ha) of reforestable area was predicted to potentially benefit threatened vertebrates. This is approximately 15% of the total area where threatened vertebrates occur. The greatest opportunities for conserving threatened vertebrate species are in the tropics, particularly Brazil and Indonesia. Although reforestation is not a substitute for forest conservation, and most of the area containing threatened vertebrates remains forested, our results highlight the need for global conservation strategies to recognize the potentially significant contribution that reforestation could make to biodiversity conservation. If implemented, reforestation of ∼369 million ha would also contribute substantially to climate-change mitigation, offering a way to achieve multiple sustainability commitments at once. Countries must now work to overcome key barriers (e.g., unclear revenue streams, high transaction costs) to investment in reforestation.  相似文献   
523.
We report the first study on the occurrence of antibiotic-resistant enterococci in coastal bathing waters in Malaysia. One hundred and sixty-five enterococci isolates recovered from two popular recreational beaches in Malaysia were speciated and screened for antibiotic resistance to a total of eight antibiotics. Prevalence of Enterococcus faecalis and Enterococcus faecium was highest in both beaches. E. faecalis/E. faecium ratio was 0.384:1 and 0.375:1, respectively, for isolates from Port Dickson (PD) and Bagan Lalang (BL). Analysis of Fisher’s exact test showed that association of prevalence of E. faecalis and E. faecium with considered locations was not statistically significant (p?<?0.05). Chi-square test revealed significant differences (χ 2?=?82.630, df?=?20, p?<?0.001) in the frequency of occurrence of enterococci isolates from the considered sites. Resistance was highest to nalidixic acid (94.84 %) and least for chloramphenicol (8.38 %). One-way ANOVA using Tukey–Kramer multiple comparison test showed that resistance to ampicillin was higher in PD beach isolates than BL isolates and the difference was extremely statistically significant (p?<?0.0001). Frequency of occurrence of multiple antibiotic resistance (MAR) isolates were higher for PD beach water (64.29 %) as compared to BL beach water (13.51 %), while MAR indices ranged between 0.198 and 0.48. The results suggest that samples from Port Dickson may contain MAR bacteria and that this could be due to high-risk faecal contamination from sewage discharge pipes that drain into the sea water.  相似文献   
524.
Stormwater utility fees (SUFs) are one way to fill the growing gap between stormwater management needs and available funding. However, there is a lack of data on the overall role they play in stormwater program budgets. This paper presents an evaluation of SUFs across multiple jurisdictions to understand their contributions to overall revenue, the uses of revenue, and the extent to which ratemaking is equitable within and between jurisdictions. We compiled data on SUFs for 124 jurisdictions and program budgets for 80 jurisdictions to describe the composition of revenues and influence of municipal stormwater permit status. We also calculated SUFs applied to individual parcels in 11 jurisdictions to assess two equity outcomes: proportionality and affordability. Results indicate that SUF revenue contributed 91% of the $537.7 million in total 2019 stormwater program operational revenue. There was enormous variation among jurisdictions in annual SUF revenue per capita ($17–328), per housing unit ($42–1007), and on an area-normalized basis (<$0.01–2.70 per ft2 impervious surface). SUFs in some cities were large enough to burden low-income households, and the way they are billed may preclude assistance for renters. In the context of escalating costs driven in part by new regulatory requirements, these results illustrate the tension between achieving full cost recovery for stormwater services and ensuring prices are affordable for ratepayers.  相似文献   
525.
Ecological distance-based spatial capture–recapture models (SCR) are a promising approach for simultaneously estimating animal density and connectivity, both of which affect spatial population processes and ultimately species persistence. We explored how SCR models can be integrated into reserve-design frameworks that explicitly acknowledge both the spatial distribution of individuals and their space use resulting from landscape structure. We formulated the design of wildlife reserves as a budget-constrained optimization problem and conducted a simulation to explore 3 different SCR-informed optimization objectives that prioritized different conservation goals by maximizing the number of protected individuals, reserve connectivity, and density-weighted connectivity. We also studied the effect on our 3 objectives of enforcing that the space-use requirements of individuals be met by the reserve for individuals to be considered conserved (referred to as home-range constraints). Maximizing local population density resulted in fragmented reserves that would likely not aid long-term population persistence, and maximizing the connectivity objective yielded reserves that protected the fewest individuals. However, maximizing density-weighted connectivity or preemptively imposing home-range constraints on reserve design yielded reserves of largely spatially compact sets of parcels covering high-density areas in the landscape with high functional connectivity between them. Our results quantify the extent to which reserve design is constrained by individual home-range requirements and highlight that accounting for individual space use in the objective and constraints can help in the design of reserves that balance abundance and connectivity in a biologically relevant manner.  相似文献   
526.
Sudden Oak Death has been impacting California’s coastal forests for more than a decade. In that time, and in the absence of a centrally organized and coordinated set of mandatory management actions for this disease in California’s wildlands and open spaces, many local communities have initiated their own management programs. We present five case studies to explore how local-level management has attempted to control this disease. From these case studies, we glean three lessons: connections count, scale matters, and building capacity is crucial. These lessons may help management, research, and education planning for future pest and disease outbreaks.  相似文献   
527.
The supply of freshwater to estuarine ecosystems is a critical factor in maintaining the overall health and organization of coastal marshes. Specifically along the Texas Gulf coast, the coupled effects of decreased freshwater inflows to the estuary and natural processes (e.g., precipitation, wind, and tides) can exert significant salt-stress on coastal marsh vegetation. In this project we sought to quantitatively link the inflow of freshwater to the estuary (San Antonio Bay) with Aransas National Wildlife Refuge (ANWR) coastal marsh salinity and assess the influence of salinity and inundation on Carolina wolfberry (Lycium carolinianum Walt.) phenology (leaf and fruit abundance). The Carolina wolfberry is one of the more common high marsh plant species found at ANWR and has been shown to be a key food source for endangered Whooping Cranes which inhabit the coastal marshes of the ANWR each fall/winter. Results from our study show that periods of decreased freshwater inflows to the estuary correlated with increased marsh salinity at the ANWR. Wolfberry plants at ANWR marsh sites displayed increased fruit abundance during years which had lower mean summer time salinity (June, July, and August) in San Antonio Bay; conversely, during years of increased bay salinity during the same summertime months, wolfberry plants showed decreased fruit abundance. Through the continued validation of the relationship between inflows and coastal marsh salinity, we hope to provide additional insight into how wolfberry phenology varies inter-annually across both salinity and inundation regimes and how freshwater inflows may affect food availability for the endangered Whooping Crane.  相似文献   
528.
Previous experimental work suggests flexibility in women’s mate preferences that appears to reflect the advantages of choosing healthy mates under conditions of pathogen threat and of choosing prosocial mates under conditions of resource scarcity. Following this work, we used an established priming paradigm to examine the effects of priming women’s concerns about pathogen threat versus resource scarcity on their judgments of men’s facial attractiveness and dominance. We found that women reported stronger attraction to masculine men when their concerns about pathogens were activated than when their concerns about resource scarcity were activated. In contrast, we found that women were more likely to ascribe high dominance to masculine men when their concerns about resource scarcity were activated than when their concerns about pathogens were activated. This latter result may reflect the greater importance of identifying men who pose a substantial threat to women’s resources and personal safety when resources are scarce and violence towards women is particularly common. Together, these findings suggest a double dissociation between the effects of pathogen threat and resource scarcity on women’s perceptions of the attractiveness and dominance of masculine men, potentially revealing considerably greater specialization (i.e., context specificity) in the effects of environmental threats on women’s perceptions of men than was apparent in previous research.  相似文献   
529.
The use of high-frequency acoustics has recently emerged as a viable method for mapping the areal coverage of seagrasses. Since the bubbles produced by seagrass plants are partly responsible for the observed acoustic signature, it is likely that sound transmission throughout a seagrass canopy varies on circadian cycles coinciding with photosynthetic bubble production. This study examined the propagation of high-frequency (100 kHz) sound energy through the seagrass canopies of Syringodium filiforme, Halodule wrightii and Thalassia testudinum in a shallow outdoor mesocosm. Relative changes in the received acoustic energy were recorded every hour during a 24-h period and compared to independently measured rates of oxygen production. The mean acoustic intensity of energy transmitted throughout the seagrass canopy varied by 3.5 dB for S. filiforme, 4.4 dB for T. testudinum and 4.7 dB for H. wrightii over a 24-h period. These transmission characteristics are encouraging for the future development of in situ acoustic assessments of seagrass photosynthesis.  相似文献   
530.
Understanding human attitudes toward wildlife management is critical to implementing effective conservation action and policy. Understanding the factors that shape public attitudes toward different wildlife management actions is limited, however, which can result in unpredictable public responses to interventions. We drew on comparisons between residents of 2 countries on separate continents to explore differences in attitudes toward wildlife management and determine factors important in shaping these attitudes. We surveyed representative publics via market research panels in Australia (n = 881 respondents) and the United States (n = 1287). We applied a social-identity approach and demography to identify factors that explained variance between responses about wildlife management. We compared responses between countries overall and within subgroups of respondents who strongly identified as environmentalists, animal rights activists, wildlife conservation advocates, and farmers. We created aggregate scores for the management-related response items per respondent and used regression analyses to identify the relative importance of country, identity, age, and gender in explaining variance between responses. These factors accounted for 15.3% of variance among responses. Australians overall were generally more accepting of lethal wildlife management actions than U.S. respondents. Differences in national attitudes reflected differences between United States and Australian wildlife management and policy, highlighting the importance of understanding social attitudes in shaping conservation policy. Identifying as a farmer followed by identifying as an animal rights activist most shaped attitudes toward wildlife management. Identity-related conflicts could be initiated or exacerbated by conservation interventions that fail to consider identity-related processes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号