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341.
Explaining the coexistence of species that basically depend on the same resources has been a brainteaser for generations of ecologists. Different mechanisms have been proposed to facilitate coexistence in plant communities, where space is an important resource. Using a stochastic cellular automaton simulation model we analyze - separately and in combination - the influence of different species traits and processes which alter local competition on the coexistence of plant species over a fixed time horizon. We show that different species traits operate on different time scales in competition. We therefore suggest the concept of weak versus strong traits according to short- or long-term exclusion of species differing in these traits. As a consequence, highly non-linear trade-offs between weak and strong traits can result in communities. Furthermore, we found that trade-offs based on physiological species traits such as plant lifetime, dispersal range and plant growth, did not support broad and long-term coexistence—further processes such as density-dependent mortality and light-dependent colonization were necessary. This suggests that coexistence in plant communities requires (stabilizing) local processes to support the (equalizing) trade-offs in species traits. 相似文献
342.
Thomas Breuer Andrew M. Robbins Claudia Olejniczak Richard J. Parnell Emma J. Stokes Martha M. Robbins 《Behavioral ecology and sociobiology》2010,64(4):515-528
Variance in male reproductive success is expected to be high in sexually dimorphic mammals, even when it is modulated by the
costs and benefits of group living. Here, we investigate the variance in reproductive success of male western gorillas (Gorilla gorilla), a highly dimorphic primate with long-term male–female associations, using 12.5 years of data collected at Mbeli Bai in
northern Congo. Access to mates and offspring survival were both major sources of variance in male reproductive success. Males
with larger harems had lower offspring mortality with no apparent reduction in female fertility or observed tenure length,
so the size of harems did not seem to be limited by female feeding competition or by the risk of takeovers and infanticide
by outsider males. The lower mortality in larger harems may reflect improved vigilance against predators, and females may
cluster around males that enhance offspring survival. Thus, this study illustrates how a detailed analysis of the components
of male reproductive success can shed light on the interrelated social and ecological aspects that affect it. 相似文献
343.
Within this paper, we analyze the fulfillment of the Kyoto emissions reduction commitment particularly in Germany and its implication on the long-term paths of all macro-variables. Germany, like all other industrial or Annex-B countries, must reduce its emissions by 2010 according to what we call a Kyoto Forever scenario. We specifically investigate tradable permits as reduction measures in a national overlapping generations (OLG) model, where we change the discounting technique by using generation adjusted discounting (GAD) in comparison to conventional OLG discounting. We show that within our model framework Germany is able to develop along growing paths of, for example, gross domestic product (GDP) in sharp contrast to conventional results of OLG simulations. At the same time, current generations must share higher burdens in terms of lower GDP, per capita consumption and employment which can be initially interpreted as contemporary costs for reaching sustainable paths and, second, contributions for internalizing external effects. However, all costs in terms of lower macro-variables for current living generations are re-compensated through higher future values. This effect can be interpreted as an intergenerational application of full cost bearance, or, in other words, the polluter pays principle which is oriented towards sustainability of greenhouse gases abatement. 相似文献
344.
The presence of genetic damage has been investigated in two native species of the Venice lagoon: the common mussel Mytilus galloprovincialis and the grass goby Zosterisessor ophiocephalus. Two sampling campaigns were performed in summer 1998 and 1999. Aromatic-like DNA adducts were analysed in selected tissues of gobies and mussels by using the 32P-postlabelling assay. In 1999, micronuclei and other nuclear abnormalities were additionally scored on gill cells and haemocytes of individual mussels whereas inorganic (As, Cd, Cr, Hg, Ni, Pb, Sn) as well as organic contaminants (polycyclic aromatic hydrocarbons, polychlorinated biphenyls and other chlorinated compounds) were measured in the total mussel pulp. Compared to the lagoon inlet area, gobies and mussels from the industrial district (Marghera) showed significant DNA adduct levels and increased frequencies of cytogenetic alterations (evidence of genetic damage was absent or inconsistent in other sites). The substantial levels of aromatic and chlorinated contaminants detected in mussels from Marghera also support the exposure of native organisms to genotoxic agents. 相似文献
345.
This study describes the deforestation impact from three settlements, 5 de Junio, El Tigre, and 30 de Agosto, near the Madidi National Park in Bolivia. First deforestation rates along the road that connects the settlements and then deforestation within each settlement are examined. Landsat Thematic Mapper (TM) imagery from 1987, 1997, and 2000 were used to measure the deforestation. Face-to-face interviews were also used to collect detailed social and land-use information. Road-building and farming have been the major causes of deforestation in this region. The TM measurements indicate a high increase in the deforestation rate along the road in the area of study. The results also show a rapidly escalating deforestation rate in 5 de Junio, a potential high future deforestation rate in El Tigre, and a gradual deforestation increase in 30 de Agosto. The information provided by the settlers about clearing was compared with the imagery analysis. Generally, the settlers estimates were lower than the deforestation as derived from the imagery. 相似文献
346.
Claudia Ringler Nguyen Vu Huy Siwa Msangi 《Journal of the American Water Resources Association》2006,42(6):1465-1482
Abstract: Recent water sector reforms and increased scarcity and vulnerability of water resources, combined with declining public funding available for large scale infrastructure investment in the sector, have led to a greater awareness by the Government of Vietnam for the need to analyze water resource allocation and use in an integrated fashion, at the basin scale, and from a perspective of economic efficiency. In this study we focus on the development, application, and selected policy analyses using an integrated economic hydrologic river basin model for the Dong Nai River Basin in southern Vietnam. The model framework depicts the sectoral structure and location of water users (agriculture, industry, hydropower, domestic, and the environment) and the institutions for water allocation in the basin. Water benefit functions are developed for the major water uses subject to physical limitations and to constraints of system control and policy. Based on this modeling framework, we will analyze policies that can affect water allocation and use at the basin level, including both basin-specific and general macroeconomic policies. 相似文献
347.
Jan Sendzimir Zsuzsana Flachner Claudia Pahl-Wostl Christian Knieper 《Environmental Science & Policy》2010,13(7):604-619
In river basins transformation from traditions of reactive flood defense to more adaptive management regimes is difficult. How regime components reinforce each other to set its development path may induce inertia and path dependency. Transformation may require profound shifts in the institutions, technologies, and personnel as well as the ecological, economic and social processes they influence in setting the basin's trajectory. Regime change has become an issue in Hungary following repeated failures of conventional management policies to handle a series of floods on the Tisza river starting in 1997. Increasing public participation pushed water policy debate toward more experimentation with alternatives, but implementation appears stalled. In this paper we review hypotheses about what factors are bridges or barriers to transformation and then use the Management Transition Framework to examine how the interactions linking action situations, operational outcomes, knowledge and institutions influenced the river management policy debate in Hungary from 1997 to 2009. Specifically we examined which factors characteristic of conventional Control vs. progressive Adaptive management regimes influenced these interactions in ways that contributed to or hindered transformation. We found that governance and social learning issues predominated, with lesser roles played by factors related to integration of sectors and different levels in the science and policy of river management. 相似文献
348.
Martinez-Jeronimo F Ventura-Lopez C 《Journal of environmental biology / Academy of Environmental Biology, India》2011,32(4):513-521
The knowledge of population effects of food on tropical, filter-feeding cladocerans is scarce because a reduced number of species has been extensively studied. Ceriodaphnia rigaudi Richard 1894, a small-sized cladoceran distributed mainly in tropical and subtropical regions of the world, was studied. The aim of this study was to contribute to the knowledge of the reproductive biology of a poor-known Cladoceran; for this we assessed the effect of feeding and temperature on the reproduction and life cycle of this species. Three microalga species (Pseudokirchneriella subcapitata, Ankistrodesmus falcatus, and Chlorella vulgaris) were supplied as food each at a concentration of 12 mg l(-1) (dry weight, equivalent to 1.3 x 10(6), 0.4 x 10(6) and 1.35 x 10(6) cell m1(-1), respectively, and equivalent to 7.8 microg C ml(-1), at two temperatures (20 and 25 degrees C). We evaluated, among other responses, longevity, total progeny, survival, life expectancy at birth and fecundity. Organisms fed with the microalgae A. falcatus and P subcapitata presented both higher longevity (30.7 +/- 5.91, 26.6 +/- 3.59 days, respectively) and total progeny (45 +/- 13.80, 40.7 +/- 0.66 neonates female (-1) values than those organisms fed C. vulgaris (13.5 +/- 4.63 days and 17.6 +/- 6.19 neonates female (-1), respectively). On the other hand, temperature affected significantly the population parameters of C. rigaudi, recording maximal longevity values (56.1 +/- 9.41 days) at 20 degrees C in organisms fed A. falcatus; however, age at first reproduction and total progeny were negatively affected by this temperature: sexual maturation of the females was delayed until the age of 16 days and the number of neonates produced was smaller (9.8 +/- 3.45 with C. vulgaris; 24.7 +/- 6.01 with P subcapitata, and 35.5 +/- 8.59 neonates female(-1) with A. falcatus). The best reproductive responses for C. rigaudi in this study were obtained with A. falcatus at degrees 25 degrees C. 相似文献
349.
Agudelo-Vera CM Mels AR Keesman KJ Rijnaarts HH 《Journal of environmental management》2011,92(10):2295-2303
Due to fast urbanization and increasing living standards, the environmental sustainability of our global society becomes more and more questionable. In this historical review we investigate the role of resources management (RM) and urban planning (UP) and propose ways for integration in sustainable development (SD). RM follows the principle of circular causation, and we reflect on to what extent RM has been an element for urban planning. Since the existence of the first settlements, a close relationship between RM, urbanization and technological development has been present. RM followed the demand for urban resources like water, energy, and food. In history, RM has been fostered by innovation and technology developments and has driven population growth and urbanization. Recent massive resource demand, especially in relation to energy and material flows, has altered natural ecosystems and has resulted in environmental degradation. UP has developed separately in response to different questions. UP followed the demand for improved living conditions, often associated to safety, good manufacturing and trading conditions and appropriate sanitation and waste management. In history UP has been a developing research area, especially since the industrial era and the related strong urbanization at the end of the 18th century. UP responded to new emerging problems in urban areas and became increasingly complex. Nowadays, UP has to address many objectives that are often conflicting, including, the urban sustainability. Our current urban un-sustainability is rooted in massive resource consumption and waste production beyond natural limits, and the absence of flows from waste to resources. Therefore, sustainable urban development requires integration of RM into UP. We propose new ways to this integration. 相似文献
350.
David Bierbach Claudia Kronmarck Carmen Hennige-Schulz Stefan Stadler Martin Plath 《Behavioral ecology and sociobiology》2011,65(9):1699-1707
Mate choice copying was mostly described as a strategy employed by females to assess the quality of potential mates, but also
males can copy other males’ mate choice. An open question in this context is whether and how copying males evaluate sperm
competition risk, as mating with a female that has already copulated with another male obviously sets the stage for intense
sperm competition (i.e., in species with internal fertilization). Using the livebearing Atlantic molly (Poecilia mexicana) as a model, we asked (a) whether males of that species indeed copy other males’ choices, and if they do so, (b) whether
copying males strategically adjust their behavior to sperm competition risk. We used an approach where focal males could first
choose to associate with a large or a small stimulus female. Mate choice tests were then repeated after an “observation phase”
during which either no model male was present (treatment 1, control) or the previously non-preferred female could be seen
associating (treatment 2) or physically interacting (treatment 3) with a model male. We found that, after the observation
phase, males spent considerably more time with the previously non-preferred female in treatment (2), i.e., they copied the
model male’s choice. This effect was much weaker during treatment (3) where sexual interactions between the model male and
the formerly non-preferred female were allowed. Males, therefore, seem to adjust their copying behavior strategically to the
perceived risk of sperm competition. 相似文献