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   248篇
  免费   2篇
  国内免费   1篇
安全科学   4篇
废物处理   21篇
环保管理   23篇
综合类   33篇
基础理论   42篇
环境理论   1篇
污染及防治   83篇
评价与监测   24篇
社会与环境   18篇
灾害及防治   2篇
  2023年   3篇
  2022年   8篇
  2021年   15篇
  2020年   8篇
  2019年   6篇
  2018年   11篇
  2017年   8篇
  2016年   12篇
  2015年   9篇
  2014年   23篇
  2013年   21篇
  2012年   10篇
  2011年   15篇
  2010年   11篇
  2009年   18篇
  2008年   10篇
  2007年   8篇
  2006年   4篇
  2005年   8篇
  2004年   6篇
  2003年   5篇
  2002年   7篇
  2001年   1篇
  2000年   5篇
  1999年   6篇
  1998年   1篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1993年   1篇
  1990年   1篇
  1986年   1篇
  1984年   1篇
  1980年   1篇
  1975年   1篇
排序方式: 共有251条查询结果,搜索用时 15 毫秒
181.
This paper evaluates the influence of different policy-related and scientific choices on the calculated regional contributions to global climate change (the “Brazilian Proposal”). Policy-related choices include the time period of emissions, the mix of greenhouse gases and different indicators of climate change impacts. The scientific choices include historical emissions and model representations of the climate system. We generated and compared results of several simple climate models. We find that the relative contributions of different nations to global climate change—from emissions of greenhouse gases alone—are quite robust, despite the varying model complexity and differences in calculated absolute changes. For the default calculations, the average calculated contributions to the global mean surface temperature increase in 2000 are about 40% from OECD, 14% from Eastern Europe and Former Soviet Union, 24% from Asia and 22% from Africa and Latin America. Policy-related choices, such as time period of emissions, climate change indicator and gas mix generally have larger influence on the results than scientific choices. More specifically, choosing a later attribution start date (1990 instead of 1890) for historical emissions, decreases the contributions of regions that started emitting early, such as the OECD countries by 6 percentage points, whereas it increases the contribution of late emitters such as Asia by 8 percentage points. However, only including the fossil CO2 emissions instead of the emissions of all Kyoto gases (fossil and land use change), increases the OECD contributions by 21 percentage points and decreases the contribution of Asia by 14 percentage points.  相似文献   
182.
Gamazo  P.  Victoria  M.  Schijven  J. F.  Alvareda  E.  Tort  L. F. L.  Ramos  J.  Lizasoain  L. A.  Sapriza  G.  Castells  M.  Bessone  L.  Colina  R. 《Food and environmental virology》2020,12(1):58-67
Food and Environmental Virology - We modeled Group A Rotavirus (RVA) and Norovirus genogroup II (GII NoV) transport experiments in standardized (crystal quartz sand and deionized water with...  相似文献   
183.
In Uruguay, groundwater is frequently used for agricultural activities, as well as for human consumption in urban and rural areas. As in many countries worldwide, drinking water microbiological quality is evaluated only according to bacteriological standards and virological analyses are not mentioned in the legislation. In this work, the incidence of human viral (Rotavirus A, Norovirus GII, and human Adenovirus) and bacterial (total and thermotolerant coliform and Pseudomonas aeruginosa) contamination in groundwater in the Salto district, Uruguay, as well as the possible correlation between these groups of microorganisms, was studied. From a total of 134 groundwater samples, 42 (32.1%) were positive for Rotavirus, only 1 (0.7%) for both Rotavirus and Adenovirus, and 96 (72.6%) samples were positive for bacterial indicators. Results also show that Rotavirus presence was not associated with changes in chemical composition of the aquifer water. Bacteriological indicators were not adequate to predict the presence of viruses in individual groundwater samples (well scale), but a deeper spatial–temporal analysis showed that they are promising candidates to assess the viral contamination degree at aquifer scale, since from the number of wells with bacterial contamination the number of wells with viral contamination could be estimated.  相似文献   
184.
The current study shows the process and the results of a methodology proposed to contribute with the issue of how to evaluate the adaptation to climate variability and future climate change. The proposed methodology consists of a standard to evaluate farmer’s adaptation to climate variability, mainly due to drought in watersheds in Central America; and was created with contributions from experts and professionals around this region. The phases for this process were: (1) literature review about the topic, (2) development of a preliminary standard, (3) expert interviews for the evaluation of this preliminary standard, (4) construction of a standard to evaluate the issue of adaptation to climate variability emphasizing drought through contributions from experts and their preliminary evaluations, (5) applicability test of this standard for the evaluation of climate variability under real conditions and (6) application of this standard through a case study in the Aguas Calientes river sub-watershed in Nicaragua, which permanently undergoes drought problems and climate variability. This standard has five main principles that go from the general, considering regional and national policies and institutionalism, to the specifics at the level of watersheds. In addition to those principles, the standard contains ten criteria, 26 indicators and 51 verifiers distributed among the main five principles. In the process for testing this standard in the Aguas Calientes river watershed in Nicaragua, the score for the general applicability to this standard was middle-level (score of 3 in a scale of 1 to 5), although, for the main principles of this standard, the score was four (high).  相似文献   
185.
Dispersal and migratory behaviours are often important determinants of gene flow in wild species, and we have studied their role using ringing-recapture data in the Portuguese population of Miniopterus schreibersii, a cave-dwelling bat that forms large maternity colonies. Juvenile dispersal, usually a major agent of gene flow, appears to be negligible, as young females never settled to give birth in foreign colonies. Likewise, there was virtually no dispersal of adult females to foreign maternity colonies. This strong philopatry virtually eliminated female-mediated gene flow, but we found a great potential for male-mediated gene flow among colonies, as regional migrations temporarily joined both sexes from different colonies in the same roosts, during the mating season. In fact, females from some colonies were more likely to mate with males from foreign colonies than from their own, thus potentially bringing home genes of foreign males. In spite of this abundant gene flow, we found a pattern of isolation by distance and even strong barriers to gene flow, which is explained by the fact that migrations were usually too short to allow direct flow among distant colonies. We concluded that potential gene flow is influenced by the distance between colonies and the availability of mating roosts between them. In addition, we found this flow to be asymmetrical, with a dominant direction from the largest to the smallest colonies. Our ringing-recapture estimates of potential gene flow based on dispersal and migratory behaviour are compatible with the genetic structure of the population for both nuclear and mitochondrial DNA. Our conclusions have implications for the conservation of bats with a spatial behaviour similar to that of M. schreibersii. Colonies should be managed individually because strict female philopatry not only promotes their isolation but also minimises the contribution of immigration in rescuing declining colonies. Furthermore, the results underline the importance of preserving mating roosts to maintain gene flow among colonies.  相似文献   
186.
187.
Nitrogen (δ15N) and carbon (δ13C) stable isotopes and contaminants, such as mercury, have been widely used to characterise foraging ecology of temperate and polar seabirds. In this study, for the first time, we used isotopic signatures and mercury levels of feathers and blood of eight tropical seabird species, that forage in a range-gradient between inshore and offshore areas, to describe the foraging habits of a large tropical seabird community (from two neighboring islands of the Seychelles archipelago, western Indian Ocean) during both the breeding and inter-breeding periods. Overall, we found a high overlap in both δ15N and δ13C signatures among species. The high inter-specific overlap in δ15N values was expected, given the similarities in the diet of the species from this community. However, several unexpected results, such as (1) the consistently higher δ15N signatures of white terns (Gygis alba), (2) the large variation in inter-specific differences in δ15N signatures among the sampling groups (season, age, island and tissue) and (3) the consistent low δ15N values of breeding birds during the northwest monsoon (austral summer), suggest that δ15N signatures cannot be used as indicators of seabird trophic levels in this community. The high inter-specific overlap in δ13C signatures and the absence, during the breeding season, of a δ13C gradient that follows the inshore-offshore foraging gradient within the community can be explained by the habitat homogeneity of the Seychelles continental shelf and suggest that birds forage mostly within the limits of this “plateau”. On the other hand, the similarities in δ13C values between the breeding and inter-breeding periods in species that are known to show post-breeding dispersal, strongly support the hypothesis of a lack of latitudinal variation in δ13C signatures of POM in the central Indian Ocean, and the consequent inaccuracy of δ13C values to track seabird movements within this geographic area. Inter-specific differences in mercury levels seem to be related to prey size, while consistent higher mercury concentrations in one of the studied islands suggest different island mercury-backgrounds and possible segregation in foraging areas between the seabirds of the two islands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
188.
This paper includes the proposals made in the report “Basis for a National Strategy for Coastal Zone Management” prepared for the Portuguese Ministry of Environment, Territorial Planning and Regional Development. The final version of that report was presented in June 2006. This paper describes a theme framework followed by a discussion of concepts. Nine Primary Principles, eight Principal Objectives, and 37 Strategic Options for an Integrated Coastal Zone Management are then presented. These Strategic Options are set hierarchically according to their sequential priority, identifying the dominant types of Associated Measures. The analysis of these arrives at a set of Structural Measures, which interlink and aggregate various actions and propose a new method of integrated management for the coastal zone, which includes the “Legal Basis of Coastal Zone”; the Organization System; the Action Plan and Monitoring.  相似文献   
189.
Piper regnellii (Piperaceae) contains high levels neolignans with diverse biological activities, including insecticidal. Despite the insecticidal activity of these neolignans, Naupactus bipes (Coleoptera: Curculionidae) larvae and adults were found feeding on the leaves (adults) and roots (larvae) of P. regnellii. The present study investigated the metabolic pathway of neolignans from P. regnellii leaves in the beetle N. bipes, focusing on possible biotransformation or sequestration of these compounds by the beetle. Two of the four plant neolignans could be recovered in the feces of adults feeding on P. regnellii leaves. In addition, four degradation products were detected, including the neolignan 3-[(2R,3R)-2,3-dihydro-3-(methyl)-2-(4-hydroxyphenyl)-5-benzofuranyl]-(2E)-propenal (7), an oxidation product of conocarpan, the major plant neolignan. The adult beetle sequesters the neolignan conocarpan selectively from leaves as well as accumulates neolignan 7. Neolignan 7 was also detected in the larvae of lab-reared beetles.  相似文献   
190.
Females sometimes obtain older sires for their offspring through extra-pair interactions, but how female age influences paternity is largely unexplored and interactive effects across the age span of both sexes have not been analyzed. To test whether female choice of sire age varies with female age in the blue-footed booby (Sula nebouxii), we examined associations between ages of both partners and the probability of extra-pair paternity (EPP) in 350 broods of parents up to 22 years old in a single breeding season. Extra-pair paternity enables a female to select an alternative sire for her offspring and could function to avoid or achieve particular combinations of parental ages. A male age?×?female age interaction revealed that in young females (≤4 years), EPP decreased with increasing age of the social partner, whereas in old females (≥8 years), it increased. Moreover, sires of extra-pair (EP) chicks of young females paired to young males were on average 6.33 years older than the females’ social partners. Since female boobies control copulatory access, this pattern could imply that young females choose old sires for their proven genetic quality and that old females avoid very old males because matings with them may risk infertility or genetic defects in offspring. Taking female age into account and observing across the whole age span may be necessary for understanding female age-based mate choice.  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