全文获取类型
收费全文 | 242篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
安全科学 | 5篇 |
废物处理 | 13篇 |
环保管理 | 14篇 |
综合类 | 128篇 |
基础理论 | 33篇 |
环境理论 | 2篇 |
污染及防治 | 34篇 |
评价与监测 | 4篇 |
社会与环境 | 12篇 |
出版年
2021年 | 3篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 6篇 |
2011年 | 9篇 |
2010年 | 4篇 |
2009年 | 9篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2003年 | 3篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1974年 | 3篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 4篇 |
1966年 | 5篇 |
1965年 | 3篇 |
1964年 | 8篇 |
1963年 | 2篇 |
1962年 | 5篇 |
1961年 | 4篇 |
1960年 | 3篇 |
1959年 | 5篇 |
1958年 | 2篇 |
1957年 | 4篇 |
1956年 | 5篇 |
1955年 | 5篇 |
1954年 | 7篇 |
1953年 | 2篇 |
1952年 | 4篇 |
1948年 | 2篇 |
1943年 | 2篇 |
1941年 | 3篇 |
1936年 | 3篇 |
1930年 | 2篇 |
1928年 | 3篇 |
排序方式: 共有245条查询结果,搜索用时 62 毫秒
51.
The compilation of ozone data for the federal states of Hesse and Northrhine-Westphalia (NRW) in Germany indicated that the concentration of ozone level slightly decreased during the years 1990–1998. The average concentration of ozone over forest areas is significantly higher than over cities. Only the maximum figures in the years approached one another. However, values passing the legal thresholds (180 μg ozone/m3) were two to three-fold higher over forests than over cities. The ozone concentration in air is inversely proportional to the traffic density. It is suggested that the lower NOx concentration over the forest than over cities is involved in the maintenance of the higher ozone-concentration over forest areas. In the cities, the ozone is reduced by NO to almost zero at night, whereas it is reduced by only about 50% over forests with lower NO concentrations. This reduction is only partially compensated in connection with the photolysis of NO2 and the subsequent oxidation of O2 to O3 during the day. The ozone situation is principally the same in the federal states of Hesse and Northrhine-Westphalia. 相似文献
52.
Tarik Hadzibeganovic Francisco W. S. Lima Dietrich Stauffer 《Behavioral ecology and sociobiology》2014,68(7):1059-1072
We study the effects of working memory capacity and network rewiring probability on the evolution of cooperation in the standard and modified versions of an agent-based model of tag-mediated altruism. In our evolutionary model, computational agents populate a large complex network, engage into multiplayer Prisoner’s Dilemma-like interactions, and reproduce sexually. Agents carry discernible phenotypic traits subject to mutation, memorize their own experiences, and employ different strategies when interacting with different types of co-players. Choices made are selected from a pool of two conditional and two unconditional strategies, depending on the available memory contents and phenotypic similarity among interactors. For the dominating strategy in our standard model version, we found a strong dependence of cooperation on network structure and a weak one on memory, whereas in the modified version, the structural effect was weaker than that of memory. Most importantly, we found that the previously reported decline of cooperation in memory-based models, typically observed at a high memory capacity, is now prevented with the help of tags. This suggests that the evolutionary advantages of memory capacity limits may be far more complex than previously assumed. For much smaller systems, we observed a quasi-symmetric alternation of the two winning groups of strategists. This result provides an example of ingroup biased interactions that are characterized by bursts of intra-tag cooperation interspersed with periods of unconditional transient altruism. Such switches of strategies may represent a boosting mechanism necessary for the emergence and stability of global altruism in its early evolutionary stages. 相似文献
53.
Dietrich Mebs Georg Petschenka Werner Pogoda Stefan W. Toennes Jens Amendt Barbara K. Zajac Susanne Dobler 《Chemoecology》2014,24(4):159-164
The blowfly Lucilia bufonivora shows high host specificity for toads despite the host’s toxic skin secretion, which consists mainly of bufadienolides. These toxins are effective blockers of the Na+, K+-ATPase, an enzyme that is essential for many physiological processes in animals. Whereas common toad (Bufo bufo) toxins were identified in the larvae of the fly, few toxins were found in the pupae and empty puparia as trace amounts, while adult flies were entirely free of these toxic compounds. Similar results were obtained when larvae of generalist necrophagous blowflies (L. sericata, Calliphora vicina) fed on toad carcasses. Analysis of the Na+, K+-ATPase gene revealed no amino acid substitution at positions known to mediate resistance to bufadienolides in other systems. Alternative mechanisms of resistance such as efficient excretion of the compounds may enable the flies to use this poisonous food source. 相似文献
54.
This paper aims to identify the land-use factors benefiting sustainable land management in terms of environmental conservation. For evaluating the impacts of land use on the environment, the following parameters were used: chemical fertiliser and pesticide use, land-use structure and diversity. The farmers' income, land tenure and farming scale were selected for their influence on agricultural sustainability. The analysis shows a rapid increase in use of chemical fertiliser and pesticide in the past 40 years, and an observable increase in land-use diversity. The amount of chemical fertiliser used per unit area in large-scale farming was lower than that at small scales, but large-scale farming consumes more pesticide than small-scale farming. A significant negative correlation was observed between the proportions of the holdings possessing land and the holdings using the chemical fertiliser. In order to achieve sustainable agriculture, it is necessary to manage crop systems and land use towards selecting new strains and varieties of crops and fruits with a lower demand for chemical fertiliser and a higher resistance to disease and pests, balancing large- and small-scale farming, and ensuring land tenure and economic incentives. 相似文献
55.
Resi Mencacci Elisabetta De Bernardi Alessandro Sale Johann R. E. Lutjeharms Paolo Luschi 《Marine Biology》2010,157(2):339-349
The routes of five satellite-tracked loggerhead turtles (Caretta caretta), subjected to an experimental translocation away from their usual migratory routes, have been analysed in relation to the
concurrent oceanographic conditions. Remote sensing data on sea surface temperature and height anomalies, as well as trajectories
of surface drifters were used, to get simultaneous information on the currents encountered by the turtles during their long-range
oceanic movements. Turtles mostly turned out to move in the same direction as the main currents, and their routes were often
influenced by circulation features they encountered. A comparison between turtle ground speeds with that of drifters shows
that in several instances, the turtles did not drift passively with the currents but contributed actively to the overall movement.
Two turtles embarked on an oceanic crossing, probably induced by seasonal changes in surface temperatures, a crossing that
was largely determined by the main currents existing in the area. 相似文献
56.
Manuela Baumgarten Rainer Matyssek Christian Huber Hans-Peter Dietrich 《Environmental Sciences Europe》2010,22(5):579-595
Background, aim, and scope Increasing background concentrations of ground-level tropospheric ozone and more frequent and prolonged summer drought incidences due to climate change are supposed to increase the stress on Bavarian forests. For such scenarios growth reduction and yield losses are predicted. Sustainable forest management in Bavaria aims to significantly increase the proportion of beech (Fagus sylvatica L.) because of its broad ecological amplitude. In our regional study different approaches for calculating ozone impact were used to estimate the risks for Bavarian forests in the average climatic, rather moist year 2002 and the extremely dry year 2003.Materials and methods Measurements were conducted for eleven forest ecosystem sites and two forest research sites representing typical Bavarian forest stands under different climatic conditions and situated in different altitudes. For risk assessment currently used approaches were applied either based on the calculation of the cumulative ozone exposure (external dose; MPOC maximal permitted ozone concentration; critical level AOT40phen? accumulated ozone exposure over a threshold of 40 nl [O3] l–1, for the effective phenolgy of beech) or based on the calculation of the phytomedically relevant ozone flux into the stomata (internal dose, critical level AFst>1,6, accumulated stomatal flux above a flux threshold of 1.6 nmol O3?m–2 PLA; PLA = projected leaf area). For calculations continuously recorded ozone concentrations and meteorological and phenological data from nearby rural open field background measuring stations from the national air pollution control and from forested sites were used. Additionally ozone induced leaf symptoms were assessed.Results The exposure-based indices AOT40phen and MPOC as well as the flux-based index AFst>1.6suggest that Bavarian forests are at risk from O3 during a rather moist average year concerning climate conditions (2002) as well as in an extreme dry year (2003). Thus, growth reductions of 5?% are predicted when thresholds are exceeded. Threshold exceedance occurred in both years at all plots, mostly already at the beginning of the growing season and often even many times over. Ozone induced leaf symptoms could be detected only on a few plots in a very slight occurrence.Discussion The results for the applied critical level indices differed depending on climatic conditions during the growing seasons: Regarding exposure-based indices, the highest degree of threshold exceedance occurred in the dry year of 2003 at all plots; the flux-based approach indicated the highest stomatal ozone uptake and thus an increased risk at moist sites or during humid years, whereas the risk was decreasing at dry sites with prolonged water limitation. Hence, soil and accordingly plant water availability was the decisive factor for the flux-modelled internal ozone uptake via stomata. Drought and increased ozone impact can generate synergistic, but also antagonistic effects for forest trees. At water limited rather dry forest sites restricted transpiration and thus production, but concurrently lower ozone uptake and reduced risk for damage can be expected.Conclusions, recommendations, and perspectives For realistic site-specific risk assessment in forest stands the determination of the internal ozone dose via modeling flux based internal stomatal ozone uptake is more appropriate than the calculation of the external ozone dose. The predicted 5?% growth reductions are in discrepancy with the frequently observed increment increase during the last decades in forest stands. Comprehensive and significant statistical verification for ozone induced forest growth reduction as well as the systematic validation of thresholds for ozone in the field is still lacking. However, a multiplicity of different specific new and retrospective growth analysis data should allow closing the gap. Moreover, the determination of canopy transpiration with sap flow measurements is a novel approach to provide cause-effect related, site specific results for the effective internal ozone dose as well as for canopy water supply and consecutively for regional risk estimation. A further future objective is the refinement of O3 flux modelling by further consideration of soil/water budget characteristics and the above mentioned improved estimations of crown and canopy transpiration. Further, the introduction of threshold ranges for forest trees in view of their specific regional climatic conditions and their validation in real forest stands is necessary for developing meaningful ozone risk predictions for forests. 相似文献
57.
The present paper outlines potential shortcomings of analyzing events in high hazard systems. We argue that the efficiency of organizational learning within high hazard systems is at least partially undermined by the subjective theories of organizing held by their members. These subjective theories basically reflect an “engineering” understanding of “how a system and its components perform”, and are assumed to involve (social-) psychological blind spots when applied to the analysis of events. More specifically, we argue that they neglect individual motives and goals that critically drive work performance and social interactions in high hazard systems. First, we focus on the process of identifying the causes of failed organizing within the course of an event analysis. Our analysis reveals a mismatch between the basic functional assumptions of the event analyst on the motives of social actors involved in an event and on the other hand, the perspective held by the social actors themselves. Second, we discuss the process of correcting failed social system performance after events. Thereby we draw on blind spots that emerge from the direct application of technical safety principles (i.e., standardization and redundancy) to the organization of social systems. Finally, we propose some future research strategies for developing event analysis methods which are aimed at improving an organization’s learning potential. 相似文献
58.
Johann Baumgärtner Josef Hartmann 《Journal of Agricultural and Environmental Ethics》2001,14(1):67-83
The paper describes the design and implementation of a plant biodiversity conservation program that was developed under funding and time constraints for diverse ecological, social, and institutional environments. The biodiversity program for alpine meadows and pastures located in the Swiss Canton of the Grisons is used as an example. The design of the sustainable program relied on existing legislation, accounted for limited ecological knowledge and expertise, and considered biodiversity as a common-pool resource. The trend to intensified cultivation of restricted areas required fast action, while the sustainability of the program design had to take into account institutional diversity. Fifteen habitats and plant communities worth conserving were known, and 57 plant species were identified as indicator species for establishing an inventory and for monitoring purposes. A small subset of 16 well known plant species was presented to the farming communities. They were invited to notify the areas in which they observed the presence of these plants. In different regions of the Canton a total number of 39 paraecologists were trained to inspect the areas notified by farmers and to recommend possible incorporation into the Cantonal inventory. This was done once the farmers signed a contract in which they agreed to follow adequate management practices. The farmers received subsidies to compensate for their losses. Communal authorities controlled the fertilizer input and cutting dates, while the paraecologists were trained to monitor plant biodiversity. The program started in 1992 and the initial phase of the inventory was terminated in 1996. At the beginning of 1996, an inventory of 2617.19 ha, most of which are meadows, was taken and managed according to the rules specified in the contract. The program was considered successful because (i) of the size of the area in the inventory, (ii) about 30%of the farmers participated, and (iii) farmers started cultivating previously abandoned farmland. 相似文献
59.
Biomass partitioning of benthic microbes in a Baltic inlet: relationships between bacteria, algae, heterotrophic flagellates and ciliates 总被引:6,自引:0,他引:6
The structure of a benthic microbial food web and its seasonal changes were studied in the shallow brackish waters of the
island of Hiddensee, northeastern Germany, at two sites in close proximity by monthly or bimonthly sampling from July 1995
to June 1996. Abundance and biomass of phototrophic and non-phototrophic bacteria, heterotrophic flagellates (HF) and ciliates
as well as the biomass of microphytobenthos were determined in the upper 0.3 cm sediment layer. Abundance of organisms showed
strong positive correlation with water temperature, with the exception of the bacteria. Non-phototrophic bacterial numbers
ranged from 7 × 108 to 6.7 × 109 cells cm−3 and phototrophic bacterial abundance from 4 × 107 to 2.7 × 108. Heterotrophic protist abundance ranged from 8 × 103 to 104 × 103 ind cm−3 for HF and from 39 to 747 ind cm−3 for ciliates. The biomass partitioning demonstrated the primary importance of non-phototrophic bacteria (min. 0.83, max.
84.87 μg C cm−3), followed by the microphytobenthos (min. 1.32, max. 50.93 μg C cm−3). The heterotrophic protists contributed roughly the same fraction to the total microbial biomass, with the biomass of the
HF being slightly higher (HF 0.23 to 1.76 μg C cm−3, ciliates 0.04 to 1.17 μg C cm−3). Taxonomic classification of the benthic HF revealed the euglenids to be the most important group in terms of abundance
and biomass, followed by thaumatomastigids and kinetoplastids. Other important groups were apusomonads, cercomonads, pedinellids
and cryptomonads. The structure of the HF assemblage showed strong seasonal changes with euglenids being the most abundant
taxa in summer, while apusomonads and thaumatomastigids were predominant in winter. Similar to the pelagic microbial food
web, benthic picophototrophic bacteria were occasionally abundant, and the feeding modes of heterotrophic protists exhibited
a great variety (predominantly omnivores, bacterivores, herbivores or predators). Filter-feeding HF were of little importance.
Contrary to the pelagic environment, a top-down control on total benthic bacterial numbers by HF seemed unlikely at the studied
stations which were characterised by muddy sand.
Received: 6 January 1999 / Accepted: 21 October 1999 相似文献
60.