全文获取类型
收费全文 | 1790篇 |
免费 | 56篇 |
国内免费 | 21篇 |
专业分类
安全科学 | 88篇 |
废物处理 | 70篇 |
环保管理 | 406篇 |
综合类 | 175篇 |
基础理论 | 506篇 |
环境理论 | 5篇 |
污染及防治 | 417篇 |
评价与监测 | 122篇 |
社会与环境 | 53篇 |
灾害及防治 | 25篇 |
出版年
2023年 | 18篇 |
2022年 | 36篇 |
2021年 | 48篇 |
2020年 | 24篇 |
2019年 | 42篇 |
2018年 | 53篇 |
2017年 | 59篇 |
2016年 | 78篇 |
2015年 | 49篇 |
2014年 | 66篇 |
2013年 | 151篇 |
2012年 | 84篇 |
2011年 | 127篇 |
2010年 | 79篇 |
2009年 | 94篇 |
2008年 | 105篇 |
2007年 | 97篇 |
2006年 | 104篇 |
2005年 | 54篇 |
2004年 | 50篇 |
2003年 | 59篇 |
2002年 | 45篇 |
2001年 | 26篇 |
2000年 | 44篇 |
1999年 | 20篇 |
1998年 | 19篇 |
1997年 | 9篇 |
1996年 | 21篇 |
1995年 | 18篇 |
1994年 | 20篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1969年 | 4篇 |
1958年 | 2篇 |
排序方式: 共有1867条查询结果,搜索用时 437 毫秒
691.
Guo Ping Yu Shaocai Wang Liqiang Li Pengfei Li Zhen Mehmood Khalid Chen Xue Liu Weiping Zhu Yannian Yu Xing Alapaty Kiran Lichtfouse Eric Rosenfeld Daniel Seinfeld John H. 《Environmental Chemistry Letters》2019,17(3):1333-1340
Environmental Chemistry Letters - Climate change is predicted to induce more extreme events such as storms, heat waves, drought and floods. Dust storms are frequently occurring in northern China.... 相似文献
692.
Sources and major biogeochemical pathways of organic matter in the mangrove system of Rufiji estuary
Daniel Abel Shilla 《Chemistry and Ecology》2019,35(6):524-536
Fatty acids were extracted from the surface sediments (10 cm) of three sampling sites of Rufiji estuary to infer their sources and biogeochemical pathways. The fatty acids ranging from C8 to C24 were distinguished from this study, and were broadly classified into saturated (SFAs), monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs). SFAs were found to be the major fraction at station 1 and 3 where as at station 2, MUFAs dominated. A total of 19 fatty acids with a total concentration of 64.91 μg/g dry weight were characterised at station 1. C16:0 was the most abundant fatty acid contributing 21.94% of total fatty acids (TFAs). C22:2 was the second most abundant, which accounted for 9.46% of TFAs. Fatty acids ranging from C12 to C24 were identified at station 2. C20 fatty acid was the most abundant fatty acid contributing 21.94%, followed by C16:0. At station 3, fatty acids ranging from C8 to C24 were obtained. The PUFA C20:5n-3 was the most abundant fatty acid contributing 21.65%, followed by C24:0 (15.00% of TFAs). The ratio of lower molecular weight (LMW) to higher molecular weight (HMW) biomarkers was used as an indicators to distinguish higher plants organic matter from algae-derived fatty acids. 相似文献
693.
Daniel B. Fitzgerald David R. Smith David C. Culver Daniel Feller Daniel W. Fong Jeff Hajenga Matthew L. Niemiller Daniel C. Nolfi Wil D. Orndorff Barbara Douglas Kelly O. Maloney John A. Young 《Conservation biology》2021,35(5):1627-1638
Many questions relevant to conservation decision-making are characterized by extreme uncertainty due to lack of empirical data and complexity of the underlying ecologic processes, leading to a rapid increase in the use of structured protocols to elicit expert knowledge. Published ecologic applications often employ a modified Delphi method, where experts provide judgments anonymously and mathematical aggregation techniques are used to combine judgments. The Sheffield elicitation framework (SHELF) differs in its behavioral approach to synthesizing individual judgments into a fully specified probability distribution for an unknown quantity. We used the SHELF protocol remotely to assess extinction risk of three subterranean aquatic species that are being considered for listing under the U.S. Endangered Species Act. We provided experts an empirical threat assessment for each known locality over a video conference and recorded judgments on the probability of population persistence over four generations with online submission forms and R-shiny apps available through the SHELF package. Despite large uncertainty for all populations, there were key differences between species’ risk of extirpation based on spatial variation in dominant threats, local land use and management practices, and species’ microhabitat. The resulting probability distributions provided decision makers with a full picture of uncertainty that was consistent with the probabilistic nature of risk assessments. Discussion among experts during SHELF's behavioral aggregation stage clearly documented dominant threats (e.g., development, timber harvest, animal agriculture, and cave visitation) and their interactions with local cave geology and species’ habitat. Our virtual implementation of the SHELF protocol demonstrated the flexibility of the approach for conservation applications operating on budgets and time lines that can limit in-person meetings of geographically dispersed experts. 相似文献
694.
Daniel Barrios-O'Neill 《Conservation biology》2021,35(1):307-315
Agriculture, overexploitation, and urbanization remain the major threats to biodiversity in the Anthropocene. The attention these threats garner among leading environmental nongovernmental organizations (eNGOs) and the wider public is critical in fostering the political will necessary to reverse biodiversity declines worldwide. I analyzed the advocacy of leading eNGOs on Twitter by scraping account timelines, screening content for advocacy relating to biodiversity threats and, for prevalent threats, further screening content for positive and negative emotional language with a sentiment lexicon. Twitter advocacy was dominated by the major threats of climate change and overexploitation and the minor threat of plastic pollution. The major threats of agriculture, urbanization, invasions, and pollution were rarely addressed. Content relating to overexploitation and plastic pollution was more socially contagious than other content. Increasing emotional negativity further increased social contagion, whereas increasing emotional positivity did not. Scientists, policy makers, and eNGOs should consider how narrowly focused advocacy on platforms like Twitter will contribute to effective global biodiversity conservation. 相似文献
695.
Reigosa-Alonso Andrés Lorenzo Dacunha Ricardo Arenas-Lago Daniel Vega Flora A. Rodríguez-Seijo Andrés 《Environmental geochemistry and health》2021,43(10):4283-4297
Environmental Geochemistry and Health - Civilian and military shooting range facilities cause environmental issues in several countries due to the accumulation of Potentially Toxic Elements; as a... 相似文献
696.
Reed F. Noss Jennifer M. Cartwright Dwayne Estes Theo Witsell Gregg Elliott Daniel Adams Matthew Albrecht Ryan Boyles Patrick Comer Chris Doffitt Don Faber-Langendoen JoVonn Hill William C. Hunter Wesley M. Knapp Michael E. Marshall Jason Singhurst Christopher Tracey Jeffrey Walck Alan Weakley 《Conservation biology》2021,35(6):1715-1724
Despite its successes, the U.S. Endangered Species Act (ESA) has proven challenging to implement due to funding limitations, workload backlog, and other problems. As threats to species survival intensify and as more species come under threat, the need for the ESA and similar conservation laws and policies in other countries to function efficiently has grown. Attempts by the U.S. Fish and Wildlife Service (USFWS) to streamline ESA decisions include multispecies recovery plans and habitat conservation plans. We address species status assessment (SSA), a USFWS process to inform ESA decisions from listing to recovery, within the context of multispecies and ecosystem planning. Although existing SSAs have a single-species focus, ecosystem-based research can efficiently inform multiple SSAs within a region and provide a foundation for transition to multispecies SSAs in the future. We considered at-risk grassland species and ecosystems within the southeastern United States, where a disproportionate number of rare and endemic species are associated with grasslands. To initiate our ecosystem-based approach, we used a combined literature-based and structured World Café workshop format to identify science needs for SSAs. Discussions concentrated on 5 categories of threats to grassland species and ecosystems, consistent with recommendations to make shared threats a focus of planning under the ESA: (1) habitat loss, fragmentation, and disruption of functional connectivity; (2) climate change; (3) altered disturbance regimes; (4) invasive species; and (5) localized impacts. For each threat, workshop participants identified science and information needs, including database availability, research priorities, and modeling and mapping needs. Grouping species by habitat and shared threats can make the SSA process and other planning processes for conservation of at-risk species worldwide more efficient and useful. We found a combination of literature review and structured discussion effective for identifying the scientific information and analysis needed to support the development of multiple SSAs. Article impact statement: Species status assessments can be improved by an ecosystem-based approach that groups imperiled species by shared habitats and threats. 相似文献
697.
Xia Y Massé DI McAllister TA Beaulieu C Ungerfeld E 《Waste management (New York, N.Y.)》2012,32(3):404-409
Biogas production from anaerobic digestion of chicken feathers with swine manure or slaughterhouse sludge was assessed in two separate experiments. Ground feathers without any pre-treatment were added to 42-L digesters inoculated with swine manure or slaughterhouse sludge, representing 37% and 23% of total solids, respectively and incubated at 25 °C in batch mode. Compared to the control without feather addition, total CH4 production increased by 130% (P < 0.001) and 110% (P = 0.09) in the swine manure and the slaughterhouse sludge digesters, respectively. Mixed liquor NH4N concentration increased (P < 0.001) from 4.8 and 3.1 g/L at the beginning of the digestion to 6.9 and 3.5 g/L at the end of digestion in the swine manure and the slaughterhouse sludge digesters, respectively. The fraction of proteolytic microorganisms increased (P < 0.001) during the digestion from 12.5% to 14.5% and 11.3% to 13.0% in the swine manure and the slaughterhouse sludge digesters with feather addition, respectively, but decreased in the controls. These results are reflective of feather digestion. Feather addition did not affect CH4 yields of the swine manure digesters (P = 0.082) and the slaughterhouse sludge digesters (P = 0.21), indicating that feathers can be digested together with swine manure or slaughterhouse sludge without negatively affecting the digestion of swine manure and slaughterhouse sludge. 相似文献
698.
Allocating chemical defenses to regions or tissues most at risk for predatory attack may provide protection while simultaneously
minimizing associated metabolic costs. Chemical defense allocation patterns were investigated in the aspiculate sponges Ircinia felix, I. campana, and Aplysina fulva collected between July 2005 and April 2006 from J Reef off the coast of Georgia, U.S.A. It was predicted that chemical defenses
would be (1) higher in the outermost 2 mm layer of the sponge; (2) positively correlated with tissue nutritional quality;
and (3) correlated with structural components such as spongin fibers. Whereas defensive chemicals were concentrated in the
outer 2 mm of A. fulva, the Ircinia species had higher concentrations in deeper tissue layers. Furthermore, no significant positive or negative correlation between
chemical defenses and nutritional quality or levels of structural components was observed in these sponges. Overall, these
results do not support the prediction that predation pressure by fish and large mobile invertebrates significantly impacts
chemical defense allocation in these sponges. 相似文献
699.
Transformity is one of the core concepts in Energy Systems Theory and it is fundamental to the calculation of emergy. Accurate evaluation of transformities and other emergy per unit values is essential for the broad acceptance, application and further development of emergy methods. Since the rules for the calculation of emergy are different from those for energy, particular calculation methods and models have been developed for use in the emergy analysis of networks, but double counting errors still occur because of errors in applying these rules when estimating the emergies of feedbacks and co-products. In this paper, configurations of network energy flows were classified into seven types based on commonly occurring combinations of feedbacks, splits, and co-products. A method of structuring the network equations for each type using the rules of emergy algebra, which we called “preconditioning” prior to calculating transformities, was developed to avoid double counting errors in determining the emergy basis for energy flows in the network. The results obtained from previous approaches, the Track Summing Method, the Minimum Eigenvalue Model and the Linear Optimization Model, were reviewed in detail by evaluating a hypothetical system, which included several types of interactions and two inputs. A Matrix Model was introduced to simplify the calculation of transformities and it was also tested using the same hypothetical system. In addition, the Matrix Model was applied to two real case studies, which previously had been analyzed using the existing method and models. Comparison of the three case studies showed that if the preconditioning step to structure the equations was missing, double counting would lead to large errors in the transformity estimates, up to 275 percent for complex flows with feedback and co-product interactions. After preconditioning, the same results were obtained from all methods and models. The Matrix Model reduces the complexity of the Track Summing Method for the analysis of complex systems, and offers a more direct and understandable link between the network diagram and the matrix algebra, compared with the Minimum Eigenvalue Model or the Linear Optimization Model. 相似文献
700.
Abstract: Matrix population models have entered the mainstream of conservation biology, with analysis of proportional sensitivities (elasticity analysis) of demographic rates becoming important components of conservation decision making. We identify areas where management applications using elasticity analysis potentially conflict with the mathematical basis of the technique, and we use a hypothetical example and three real data sets (Prairie Chicken [ Tympanuchus cupido ], desert tortoise [ Gopherus agassizii ], and killer whale [ Orcinus orca ]) to evaluate the extent to which conservation recommendations based on elasticities might be misleading. First, changes in one demographic rate can change the qualitative ranking of the elasticity values calculated from a population matrix, a result that dampens enthusiasm for ranking conservation actions based solely on which rates have the highest elasticity values. Second, although elasticities often provide accurate predictions of future changes in population growth rate under management perturbations that are large or that affect more than one rate concurrently, concordance frequently fails when different rates vary by different amounts. In particular, when vital rates change to their high or low values observed in nature, predictions of future growth rate based on elasticities of a mean matrix can be misleading, even predicting population increase when the population growth rate actually declines following a perturbation. Elasticity measures will continue to be useful tools for applied ecologists, but they should be interpreted with considerable care. We suggest that studies using analytical elasticity analysis explicitly consider the range of variation possible for different rates and that simulation methods are a useful tool to this end. 相似文献