全文获取类型
收费全文 | 277篇 |
免费 | 11篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 11篇 |
废物处理 | 10篇 |
环保管理 | 82篇 |
综合类 | 35篇 |
基础理论 | 71篇 |
环境理论 | 3篇 |
污染及防治 | 47篇 |
评价与监测 | 11篇 |
社会与环境 | 12篇 |
灾害及防治 | 9篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 27篇 |
2012年 | 11篇 |
2011年 | 26篇 |
2010年 | 15篇 |
2009年 | 5篇 |
2008年 | 21篇 |
2007年 | 23篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 17篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有291条查询结果,搜索用时 31 毫秒
51.
The Arctic experiences a high-radiation environment in the summer with 24-hour daylight for more than two months. Damage to plants and ecosystem metabolism can be muted by overcast conditions common in much of the Arctic. However, with climate change, extreme dry years and clearer skies could lead to the risk of increased photoxidation and photoinhibition in Arctic primary producers. Mosses, which often exceed the NPP of vascular plants in Arctic areas, are often understudied. As a result, the effect of specific environmental factors, including light, on these growth forms is poorly understood. Here, we investigated net ecosystem exchange (NEE) at the ecosystem scale, net Sphagnum CO2 exchange (NSE), and photoinhibition to better understand the impact of light on carbon exchange from a moss-dominated coastal tundra ecosystem during the summer season 2006. Sphagnum photosynthesis showed photoinhibition early in the season coupled with low ecosystem NEE. However, later in the season, Sphagnum maintained a significant CO2 uptake, probably for the development of subsurface moss layers protected from strong radiation. We suggest that the compact canopy structure of Sphagnum reduces light penetration to the subsurface layers of the moss mat and thereby protects the active photosynthetic tissues from damage. This stress avoidance mechanism allowed Sphagnum to constitute a significant percentage (up to 60%) of the ecosystem net daytime CO2 uptake at the end of the growing season despite the high levels of radiation experienced. 相似文献
52.
Shane A. Richards Mark J. Whittingham Philip A. Stephens 《Behavioral ecology and sociobiology》2011,65(1):77-89
Behavioural ecologists often study complex systems in which multiple hypotheses could be proposed to explain observed phenomena.
For some systems, simple controlled experiments can be employed to reveal part of the complexity; often, however, observational
studies that incorporate a multitude of causal factors may be the only (or preferred) avenue of study. We assess the value
of recently advocated approaches to inference in both contexts. Specifically, we examine the use of information theoretic
(IT) model selection using Akaike’s information criterion (AIC). We find that, for simple analyses, the advantages of switching
to an IT-AIC approach are likely to be slight, especially given recent emphasis on biological rather than statistical significance.
By contrast, the model selection approach embodied by IT approaches offers significant advantages when applied to problems
of more complex causality. Model averaging is an intuitively appealing extension to model selection. However, we were unable
to demonstrate consistent improvements in prediction accuracy when using model averaging with IT-AIC; our equivocal results
suggest that more research is needed on its utility. We illustrate our arguments with worked examples from behavioural experiments. 相似文献
53.
54.
Joel Elliott Kathleen Holmes Rachel Chambers Kate Leon Peter Wimberger 《Marine Biology》2008,156(1):39-53
Mytilus galloprovincialis (Mg), the Mediterranean blue mussel, is sympatric with the native M. trossulus (Mt) throughout much of the north Pacific, likely as the result of human introduction. We investigated the distribution of the
two species and their hybrids (Mgt) in Puget Sound, Washington, to determine whether differences occur in habitat preference between the two species and hybrids.
In addition, we investigated whether there were consistent size and shape differences between the native and introduced mussels
and hybrids. Measurements of over 6,000 mussels from 30 sites, of which 1,460 were genotyped for a species-specific genetic
marker, revealed that Mg and Mgt can be found throughout Puget Sound. Mg and Mgt were larger and exhibited a greater height:length ratio than Mt. Frequencies of Mg and Mgt were higher in subtidal habitats, such as docks, than on intertidal rocks, walls or pilings. Within intertidal habitats,
Mg and Mgt were more frequent than Mt in the lower reaches of the intertidal. At slightly more than half the sites the frequency of the three genotypes accorded
with random mating expectations suggesting no consistent barriers to gene flow between species. The standardized random sampling
methods and simple morphometric identification techniques described here can be used to test whether the frequency of invasive
mussels changes over time and space in Puget Sound. 相似文献
55.
Kate S. Boersma Clifford H. Ryer Thomas P. Hurst Selina S. Heppell 《Behavioral ecology and sociobiology》2008,62(12):1959-1968
Animals balance feeding and anti-predator behaviors at various temporal scales. When risk is infrequent or brief, prey can
postpone feeding in the short term and temporally allocate feeding behavior to less risky periods. If risk is frequent or
lengthy, however, prey must eventually resume feeding to avoid fitness consequences. Species may exhibit different behavioral
strategies, depending on the fitness tradeoffs that exist in their environment or across their life histories. North Pacific
flatfishes that share juvenile rearing habitat exhibit a variety of responses to predation risk, but their response to risk
frequency has not been examined. We observed the feeding and anti-predator behaviors of young-of-the-year English sole (Parophrys vetulus), northern rock sole (Lepidopsetta polyxystra), and Pacific halibut (Hippoglossus stenolepis)—three species that exhibit divergent anti-predator strategies—following exposure to three levels of predation risk: no risk,
infrequent (two exposures/day), and frequent (five exposures/day). The English sole responded to the frequent risk treatment
with higher feeding rates than during infrequent risk, following a pattern of behavioral response that is predicted by the
risk allocation hypothesis; rock sole and halibut did not follow the predicted pattern, but this may be due to the limited
range of treatments. Our observations of unique anti-predator strategies, along with differences in foraging and species-specific
ecologies, suggest divergent trajectories of risk allocation for the three species. 相似文献
56.
Matthiopoulos J Graham K Smout S Asseburg C Redpath S Thirgood S Hudson P Harwood J 《Ecology》2007,88(10):2576-2586
Ecological theory predicts that generalist predators should damp or suppress long-term periodic fluctuations (cycles) in their prey populations and depress their average densities. However, the magnitude of these impacts is likely to vary depending on the availability of alternative prey species and the nature of ecological mechanisms driving the prey cycles. These multispecies effects can be modeled explicitly if parameterized functions relating prey consumption to prey abundance, and realistic population dynamical models for the prey, are available. These requirements are met by the interaction between the Hen Harrier (Circus cyaneus) and three of its prey species in the United Kingdom, the Meadow Pipit (Anthus pratensis), the field vole (Microtus agrestis), and the Red Grouse (Lagopus lagopus scoticus). We used this system to investigate how the availability of alternative prey and the way in which prey dynamics are modeled might affect the behavior of simple trophic networks. We generated cycles in one of the prey species (Red Grouse) in three different ways: through (1) the interaction between grouse density and macroparasites, (2) the interaction between grouse density and male grouse aggressiveness, and (3) a generic, delayed density-dependent mechanism. Our results confirm that generalist predation can damp or suppress grouse cycles, but only when the densities of alternative prey are low. They also demonstrate that diametrically opposite indirect effects between pairs of prey species can occur together in simple systems. In this case, pipits and grouse are apparent competitors, whereas voles and grouse are apparent facilitators. Finally, we found that the quantitative impacts of the predator on prey density differed among the three models of prey dynamics, and these differences were robust to uncertainty in parameter estimation and environmental stochasticity. 相似文献
57.
Efforts are accelerating to protect and restore ecosystems globally. With trillions of dollars in ecosystem services at stake, no clear framework exists for developing or prioritizing approaches to restore coral reefs even as efforts and investment opportunities to do so grow worldwide. Restoration may buy time for climate change mitigation, but it lacks rigorous guidance to meet objectives of scalability and effectiveness. Lessons from restoration of terrestrial ecosystems can and should be rapidly adopted for coral reef restoration. We propose how the 10 golden rules of effective forest restoration can be translated to accelerate efforts to restore coral reefs based on established principles of resilience, management, and local stewardship. We summarize steps to undertake reef restoration as a management strategy in the context of the diverse ecosystem service values that coral reefs provide. Outlining a clear blueprint is timely as more stakeholders seek to undertake restoration as the UN Decade on Ecosystem Restoration begins. 相似文献
58.
Raphael D. Sagarin Richard F. Ambrose Bonnie J. Becker John M. Engle Janine Kido Steven F. Lee C. Melissa Miner Steven N. Murray Peter T. Raimondi Dan Richards Christy Roe 《Marine Biology》2007,150(3):399-413
Here long-term monitoring data taken at 33 sites in southern and central California coast and islands were used to evaluate the size structure of the large intertidal limpet, Lottia gigantea in restricted-access and in easily accessible intertidal zones that encompass a wide range of ecological variables. Using multi-dimensional analysis of population size structures, we found that sites on islands and strictly protected mainland sites have significantly larger median limpet sizes and a greater range of limpet sizes than unprotected mainland sites, while no pattern occurs in latitudinal or regional comparison of sites. Although intertidal predators such as oystercatchers were not the primary focus of the monitoring efforts, extensive natural history notes taken during sampling visits support the argument that predation was not a primary cause for the size structure differences. Finally, substratum differences were determined not to have biased the observation of larger limpets in protected sites. In regard to human interactions with limpets, we conclude that the degree of enforcement against poaching is the better predictor of limpet size structure than proximity to population centers or visitation to intertidal sites. 相似文献
59.
Two novel behaviours, both adaptations of small hive beetles (Aethina tumida Murray) and Cape honeybees (Apis mellifera capensis Esch.), are described. Beetles puncture the sides of empty cells and oviposit under the pupae in adjoining cells. However, bees detect this ruse and remove infested brood (hygienic behaviour), even under such well-disguised conditions. Indeed, bees removed 91% of treatment brood (brood cells with punctured walls caused by beetles) but only 2% of control brood (brood not exposed to beetles). Only 91% of treatment brood actually contained beetle eggs; the data therefore suggest that bees remove only that brood containing beetle eggs and leave uninfected brood alone, even if beetles have accessed (but not oviposited on) the brood. Although this unique oviposition strategy by beetles appears both elusive and adaptive, Cape honeybees are able to detect and remove virtually all of the infested brood. 相似文献
60.
David M. Mushet Laurie C. Alexander Micah Bennett Kate Schofield Jay R. Christensen Genevieve Ali Amina Pollard Ken Fritz Megan W. Lang 《Journal of the American Water Resources Association》2019,55(2):307-317
We describe a collection of aquatic and wetland habitats in an inland landscape, and their occurrence within a terrestrial matrix, as a “freshwater ecosystem mosaic” (FEM). Aquatic and wetland habitats in any FEM can vary widely, from permanently ponded lakes, to ephemerally ponded wetlands, to groundwater‐fed springs, to flowing rivers and streams. The terrestrial matrix can also vary, including in its influence on flows of energy, materials, and organisms among ecosystems. Biota occurring in a specific region are adapted to the unique opportunities and challenges presented by spatial and temporal patterns of habitat types inherent to each FEM. To persist in any given landscape, most species move to recolonize habitats and maintain mixtures of genetic materials. Species also connect habitats through time if they possess needed morphological, physiological, or behavioral traits to persist in a habitat through periods of unfavorable environmental conditions. By examining key spatial and temporal patterns underlying FEMs, and species‐specific adaptations to these patterns, a better understanding of the structural and functional connectivity of a landscape can be obtained. Fully including aquatic, wetland, and terrestrial habitats in FEMs facilitates adoption of the next generation of individual‐based models that integrate the principles of population, community, and ecosystem ecology. 相似文献