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101.
Laboratory experiments on scaled mountain wakes have provided the first demonstration that indicates the existence of two distinct mechanisms for the formation of the long-lived vortex structures that have been frequently observed in satellite imagery. In a series of laboratory experiments the well-known von Kármán vortex shedding mechanism has been observed at low values of Froude number (corresponding to low speed flow and strong stratification). At high Froude numbers the initial highly turbulent wake evolves into a vortex pattern similar to the far-wake dipole eddies previously observed in laboratory studies of submerged stratified wakes. In satellite imagery vortex structures have been observed to persist for hundreds of kilometers. In the present laboratory experiments far-wake dipole eddies were observed to persist for at least 200 diameters downstream, which corresponds to ~4,000?km when scaled to actual mountains. When generated at multiple sites along a continental mountain chain, these eddy structures could play a significant role in the development and variability of multi-scale weather and climate patterns.  相似文献   
102.
Until around 1995 it was challenging to make the scientific results of research projects publicly available except through presentations at meetings or conferences, or as papers in academic journals. Then it began to be clear that the Internet could become the main medium to publish and share new information with a much wider audience. The DESIRE Project (desertification mitigation and remediation of land—a global approach for local solutions) has built on expertise gained in previous projects to develop an innovative online ‘Harmonized Information System’ (HIS). This documents the context, delivery and evaluation of all tasks in the DESIRE Project using non-scientific terminology, with much of it also available in the local languages of the study sites. The DESIRE-HIS makes use of new possibilities for communication, including video clips, interactive tools, and links to social media networks such as Twitter. Dissemination of research results using this approach has required careful planning and design. This paper sets out the steps that have culminated in a complete online Information System about local solutions to global land management problems in desertification-affected areas, including many practical guidelines for responsible land management. As many of those who are affected by desertification do not have Internet access, printable dissemination materials are also available on the DESIRE-HIS.  相似文献   
103.
A project-based system for including farmers in the EU ETS   总被引:1,自引:0,他引:1  
Farmers in the EU do not trade greenhouse gases under the Kyoto agreement. This is an empirical puzzle because agriculture is a significant contributor of greenhouse gases (GHG) in the EU and may harvest private net gains from trade. Furthermore, the US has strongly advocated land-use practices as 'the missing link' in past climate negotiations. We argue that farmers have relatively low marginal reduction costs and that consequences in terms of the effect on permit price and technology are overall positive in the EU Emission Trading System (ETS). Thus, we propose a project-based system for including the farming practices in the EU ETS that reduces the uncertainty from measuring emission reduction in this sector. The system encourages GHG reduction either by introducing a new and less polluting practice or by reducing the polluting activity. When doing so, farmers will receive GHG permits corresponding to the amount of reduction which can be stored for later use or sold in the EU ETS.  相似文献   
104.
Estimating contaminant distributions in environmental media is necesary to evaluate human and ecological hazards. Because of uncertainties in release histories and transport, traditional sampling and statistical techniques applicable to the experimental sciences may not be suitable for exploratory studies at hazardous waste sites. An approach that relies on cluster analysis of principal components (PCA) was used to identify contaminated wild asparagus (Asparagus officinalis) growing in the vicinity of waste disposal sites along the Columbia River at the U.S. Department of Energy's Hanford Site in southeast Washington state. Metals in soil samples taken from the sites contained elevated levels of Ag, Al, Ba, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn, and V. Samples of asparagus tissue were collected from the river near the waste site, from Hanford old fields abandoned 52 years ago, and from commercial fields in the neighboring communities. Dried tissues were analyzed for metals content by ICP-mass spectrometry, furnace AA, and cold vapor AA. Tissue concentrations of elements varied over 5 orders of magnitude, from K at 46 900 ppm to As and Ag at maximum concentrations below 1 ppm. PCA produced four components that accounted for 66.2% of the metals variance. Subsequent cluster analysis using Ward's minimum variance separated the data into Columbia River and old-field groups, with the River group further divided into three clusters: plants primarily upriver from the waste sites, plants primarily downriver, and plants growing in or near the waste sites. The clustering showed that the more soluble components of the discharges (Ba and Ca) showed a pattern of distribution in the asparagus plants consistent with the ground water flow pattern, in that these elements were found far downriver of the disposal sites themselves. In contrast, the less mobile elements Al, Cd, Cr, Fe, Mn, Tl, and Zn were elevated only near the most-recently used waste disposal area. Asparagus from agricultural fields, including fields abandoned 50 years ago, contained higher concentrations of Fe, Cu, Pb, K, and Ni than did the wild riverine plants.The U.S. Governments right to retain a non-exclusive royalty free licence in and to any copyright is acknowledged.  相似文献   
105.
The long-term Biological Monitoring and Abatement Program (BMAP) has always needed to collect and retain high-quality data on which to base its assessments of ecological status of streams and their recovery after remediation. Its formal quality assurance, data processing, and data management components all contribute to meeting this need. The Quality Assurance Program comprehensively addresses requirements from various institutions, funders, and regulators, and includes a data management component. Centralized data management began a few years into the program when an existing relational database was adapted and extended to handle biological data. The database??s main data tables and several key reference tables are described. One of the most important related activities supporting long-term analyses was the establishing of standards for sampling site names, taxonomic identification, flagging, and other components. The implemented relational database supports the transmittal of data to the Oak Ridge Environmental Information System (OREIS) as the permanent repository. We also discuss some limitations to our implementation. Some types of program data were not easily accommodated in the central systems, and many possible data-sharing and integration options are not easily accessible to investigators. From our experience we offer data management advice to other biologically oriented long-term environmental sampling and analysis programs.  相似文献   
106.
The fundamental niche of a species is rarely if ever realized because the presence of other species restricts it to a narrower range of ecological conditions. The effects of this narrower range of conditions define how resources are partitioned. Resource partitioning has been inferred but not demonstrated previously for sympatric ursids. We estimated assimilated diet in relation to body condition (body fat and lean and total body mass) and reproduction for sympatric brown bears (Ursus arctos) and American black bears (U. americanus) in south-central Alaska, 1998-2000. Based on isotopic analysis of blood and keratin in claws, salmon (Oncorhynchus spp.) predominated in brown bear diets (> 53% annually) whereas black bears assimilated 0-25% salmon annually. Black bears did not exploit salmon during a year with below average spawning numbers, probably because brown bears deterred black bear access to salmon. Proportion of salmon in assimilated diet was consistent across years for brown bears and represented the major portion of their diet. Body size of brown bears in the study area approached mean body size of several coastal brown bear populations, demonstrating the importance of salmon availability to body condition. Black bears occurred at a comparable density (mass:mass), but body condition varied and was related directly to the amount of salmon assimilated in their diet. Both species gained most lean body mass during spring and all body fat during summer when salmon were present. Improved body condition (i.e., increased percentage body fat) from salmon consumption reduced catabolism of lean body mass during hibernation, resulting in better body condition the following spring. Further, black bear reproduction was directly related to body condition; reproductive rates were reduced when body condition was lower. High body fat content across years for brown bears was reflected in consistently high reproductive levels. We suggest that the fundamental niche of black bears was constrained by brown bears through partitioning of food resources, which varied among years. Reduced exploitation of salmon caused black bears to rely more extensively on less reliable or nutritious food sources (e.g., moose [Alces alces], berries) resulting in lowered body condition and subsequent reproduction.  相似文献   
107.
An analysis of the horizontal and the vertical zonation of the Antarctic Isopoda, combined with knowledge of the geological history of Antarctica and isopod phylogeny, revealed that the isopod family Serolidae and subfamily Arcturinae are likely to have evolved from ancestors that inhabited a cold-temperate Gondwanian province. Antarctic species of other families, such as the Munnopsidae, Nannoniscidae, Desmosomatidae and Ischnomesidae, are likely to have evolved from deep-sea ancestors. It is deduced that emigration of South Patagonian species into the Southern Ocean, although possible, probably did not occur very often. Evolutionary phenomena such as continental-drift vicariance, radiation of species on the continental shelf of Antarctica, and active migration, including submergence and emergence mechanisms are discussed.  相似文献   
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110.
Many migratory animals are experiencing rapid population declines, but migration data with the geographic scope and resolution to quantify the complex network of movements between breeding and nonbreeding regions are often lacking. Determining the most frequently used migration routes and nonbreeding regions for a species is critical for understanding population dynamics and making effective conservation decisions. We tracked the migration of individual Wood Thrushes (Hylocichla mustelina) (n = 102) from across their range with light‐level geolocators and, for the first time, quantified migration routes and wintering regions for distinct breeding populations. We identified regional and species‐level migratory connectivity networks for this declining songbird by combining our tracking results with range‐wide breeding abundance estimates and forest cover data. More than 50% of the species occupied the eastern wintering range (Honduras to Costa Rica), a region that includes only one‐third of all wintering habitat and that is undergoing intensive deforestation. We estimated that half of all Wood Thrushes in North America migrate south through Florida in fall, whereas in spring approximately 73% funnel northward through a narrow span along the central U.S. Gulf Coast (88–93°W). Identifying migratory networks is a critical step for conservation of songbirds and we demonstrated with Wood Thrushes how it can highlight conservation hotspots for regional populations and species as a whole. Conectividad de Sitios de Reproducción, Invierno y Migración del Zorzal con Base en Rastreo de Cobertura Amplia  相似文献   
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