全文获取类型
收费全文 | 326篇 |
免费 | 1篇 |
国内免费 | 5篇 |
专业分类
安全科学 | 13篇 |
废物处理 | 28篇 |
环保管理 | 42篇 |
综合类 | 40篇 |
基础理论 | 80篇 |
环境理论 | 2篇 |
污染及防治 | 86篇 |
评价与监测 | 21篇 |
社会与环境 | 18篇 |
灾害及防治 | 2篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 13篇 |
2015年 | 3篇 |
2014年 | 13篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 19篇 |
2010年 | 13篇 |
2009年 | 24篇 |
2008年 | 22篇 |
2007年 | 26篇 |
2006年 | 27篇 |
2005年 | 16篇 |
2004年 | 8篇 |
2003年 | 21篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有332条查询结果,搜索用时 343 毫秒
311.
Jens Havskov Sørensen Alix Rasmussen Thomas Ellermann Erik Lyck 《Atmospheric environment (Oxford, England : 1994)》1998,32(24):101
During the first European Tracer Experiment (ETEX) tracer gas was released from a site in Brittany, France, and subsequently observed over a range of 2000 km. Hourly measurements were taken at the National Environmental Research Institute (NERI) located at Risø, Denmark, using two measurement techniques. At this location, the observed concentration time series shows a double-peak structure occurring between two and three days after the release. By using the Danish Emergency Response Model of the Atmosphere (DERMA), which is developed at the Danish Meteorological Institute (DMI), simulations of the dispersion of the tracer gas have been performed. Using numerical weather-prediction data from the European Centre for Medium-Range Weather Forecast (ECMWF) by DERMA, the arrival time of the tracer is quite well predicted, so also is the duration of the passage of the plume, but the double-peak structure is not reproduced. However, using higher-resolution data from the DMI version of the HIgh Resolution Limited Area Model (DMI-HIRLAM), DERMA reproduces the observed structure very well. The double-peak structure is caused by the influence of a mesoscale anti-cyclonic eddy on the tracer gas plume about one day earlier. 相似文献
312.
313.
Industrial-scale injection of CO2 into saline formations in sedimentary basins will cause large-scale fluid pressurization and migration of native brines, which may affect valuable groundwater resources overlying the deep sequestration aquifers. In this paper, we discuss how such basin-scale hydrogeologic impacts (1) may reduce current storage capacity estimates, and (2) can affect regulation of CO2 storage projects. Our assessment arises from a hypothetical future carbon sequestration scenario in the Illinois Basin, which involves twenty individual CO2 storage projects (sites) in a core injection area most suitable for long-term storage. Each project is assumed to inject five million tonnes of CO2 per year for 50 years. A regional-scale three-dimensional simulation model was developed for the Illinois Basin that captures both the local-scale CO2–brine flow processes and the large-scale groundwater flow patterns in response to CO2 storage. The far-field pressure buildup predicted for this selected sequestration scenario support recent studies in that environmental concerns related to near- and far-field pressure buildup may be a limiting factor on CO2 storage capacity. In other words, estimates of storage capacity, if solely based on the effective pore volume available for safe trapping of CO2, may have to be revised based on assessments of pressure perturbations and their potential impacts on caprock integrity and groundwater resources. Our results suggest that (1) the area that needs to be characterized in a permitting process may comprise a very large region within the basin if reservoir pressurization is considered, and (2) permits cannot be granted on a single-site basis alone because the near- and far-field hydrogeologic response may be affected by interference between individual storage sites. We also discuss some of the challenges in making reliable predictions of large-scale hydrogeologic impacts related to CO2 sequestration projects. 相似文献
314.
Quantitative PCR to estimate copepod feeding 总被引:1,自引:0,他引:1
Jens C. Nejstgaard Marc E. Frischer Paolo Simonelli Christofer Troedsson Markus Brakel Filiz Adiyaman Andrey F. Sazhin L. Felipe Artigas 《Marine Biology》2008,153(4):565-577
Copepods play a central role in marine food webs as grazers of plankton and as key prey for many predators. Therefore, quantifying
their specific trophic interactions is critical for understanding the role of copepods in ocean processes. However, because
of methodological constraints, it remains difficult to investigate in situ copepod feeding without reliance on laborious intrusive
and potentially biased incubation approaches. Recent advances in PCR-based methodologies have demonstrated the feasibility
of directly identifying copepod diets based on prey DNA sequences. Yet, obtaining quantitative information from these approaches
remains challenging. This study presents results of systematic efforts to develop a quantitative PCR (qPCR) assay targeted
to 18S rRNA gene fragments to estimate copepod gut content of specific species of prey algae. These results were first compared
to gut content estimates based on fluorescence in the copepod Calanus finmarchicus fed monocultures of two different microalgae species in controlled laboratory studies. In subsequent field studies, we compared
feeding rates obtained by microscopy and qPCR for Temora longicornis and Acartia clausi feeding on the haptophyte Phaeocystis globosa in natural blooms. These investigations demonstrate a semi-quantitative relationship between gut content estimates derived from qPCR, gut pigment,
and direct microscopy. However, absolute estimates of gut content based on qPCR methodology were consistently lower than expected.
This did not appear to be explained by the extraction methods used, or interference by non-target (predator) DNA in the PCR
reactions, instead suggesting digestion of prey-specific nucleic acids. Furthermore, the 18S rDNA target gene copy number
of the phytoplankton varied with growth phase. Nonetheless, when prey target gene copy number in the ambient water is quantified,
the qPCR-approach can be compared to other methods, and then used to semi-quantitatively estimate relative copepod grazing
on specific prey in situ without involving further incubations. A distinct advantage of a DNA-based molecular approach compared
to gut fluorescence and direct microscopic observation, is the ability to detect non-pigmented and macerated prey. Future
studies should aim to correct for breakdown in prey DNA and perform extensive calibrations to other methods in order to achieve
a quantitative measure of feeding rates in situ. 相似文献
315.
Temporal dynamics in a pollination network 总被引:2,自引:0,他引:2
316.
The concept of animal welfare refersto the animal's quality of life. The choice ofdefinition always reflects some basicvaluation. This makes a particular conceptionof welfare value-dependent. Also, the animalhusbandry system reflects certain values oraims. The values reflected in the chosenconception of animal welfare ought tocorrespond to values aimed for in the husbandrysystem. The IFOAM Basic Standards and otherwritings dealing with organic animal husbandryshould be taken as a departure point for adiscussion of how to interpret the conceptionof welfare in organic farming systems. Theconception of welfare is related to two corevalues in the organic agriculture movement.These core values should be considered in termsof (1) aim for holistic view and (2) aim forsustainability. A third, implicit core value,based on bio- and ecocentric views: (3) respectfor nature is needed as a supplement to thesetwo core values. There are importantimplications of these core values for an``organic' conception of animal welfare and forconfronting two dilemmas due to conflictinginterests. Comparisons among the three commonlyused welfare definitions will show thesuperiority of the third approach, which canprovide an outline for a conception of animalwelfare more suitable for organic farmingsystems. This outline combines a holisticecocentric approach with respect for theindividual animal, and it can be used as thebasis for a complex definition with emphasis onnatural behavior. Such a systemic approachconsiders welfare in relation to differentsystemic levels. The systemic view also offerspossibilities for resolving the dilemmas in newways. 相似文献
317.
Correlation between the seasonal distribution of harbour porpoises and their prey in the Sound,Baltic Sea 总被引:1,自引:1,他引:0
Signe?SveegaardEmail author Heidi?Andreasen Kim?N.?Mouritsen Jens?Peder?Jeppesen Jonas?Teilmann Carl?C.?Kinze 《Marine Biology》2012,159(5):1029-1037
Low densities of harbour porpoises in winter (November–March) and high densities in summer (April–October) were found in the
Sound, connecting the Baltic Sea and Kattegat. Due to their high energy requirements, it is hypothesized that the density
of harbour porpoises is related to local prey abundance. This was tested by examining the stomach content of 53 harbour porpoises
collected between 1987 and 2010 in the Sound (high season, 34 porpoises; low season, 19 porpoises). A total of 1,442 individual
fish specimens from thirteen species were identified. Twelve of these were present in the high–porpoise density season and
seven in the low-density season. The distribution of occurrence and the distribution of number of fish species were different
between seasons, indicating a shift in prey intake between seasons. Furthermore, during the high-density season, the mean
and total prey weight per stomach as well as the prey species diversity was higher. However, no difference was found in the
number of prey species between the two seasons, indicating a higher quality of prey in the high-density season. Atlantic cod
was found to be the main prey species in terms of weight in the high-density season while Atlantic herring and Atlantic cod
were equally important during the low-density season. Prey availability and predictability are suggested as the main drivers
for harbour porpoise distribution, and this could be caused by the formation of frontal zones in spring in the northern part
of the Sound, leading to prey concentrations in predictable areas. 相似文献
318.
Stacy K. Tanaka Jay R. Lund 《Journal of the American Water Resources Association》2003,39(6):1509-1519
ABSTRACT: Exports from the Sacramento‐San Joaquin Delta are an important source of water for Central Valley and Southern California users. The purpose of this paper is to estimate and analyze the effects increased exports to south of Delta users would have on the Sacramento Valley economy and water management if water were managed and reallocated for purely economic benefits, as if there were an ideal Sacramento Valley water market. Current Delta exports of 6,190 thousand acre‐feet per year were increased incrementally to maximum export pumping plant capacities. Initial increases in Delta exports did not increase regional water scarcity, but decreased surplus Delta flows. Further export increases raised agricultural scarcity. Urban users suffer increased scarcity only for exports exceeding 10,393 taf/yr. Expanding exports raises the economic value of expanding key facilities (such as Engle bright Lake and South Folsom Canal) and the opportunity costs of environmental requirements. The study illustrates the physical and economic capacity of the Sacramento Valley to further increase exports of water to drier parts of the state, even within significant environmental flow restrictions. More generally, the results illustrate the physical capacity for greater economic benefits and flexibility in water management within environmental constraints, given institutional capability to reoperate or reallocate water resources, as implied by water markets. 相似文献
319.
Potential banana skins in animal social network analysis 总被引:2,自引:2,他引:0
Social network analysis is an increasingly popular tool for the study of the fine-scale and global social structure of animals.
It has attracted particular attention by those attempting to unravel social structure in fission–fusion populations. It is
clear that the social network approach offers some exciting opportunities for gaining new insights into social systems. However,
some of the practices which are currently being used in the animal social networks literature are at worst questionable and
at best over-enthusiastic. We highlight some of the areas of method, analysis and interpretation in which greater care may
be needed in order to ensure that the biology we extract from our networks is robust. In particular, we suggest that more
attention should be given to whether relational data are representative, the potential effect of observational errors and
the choice and use of statistical tests. The importance of replication and manipulation must not be forgotten, and the interpretation
of results requires care.
This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau and
R. James). 相似文献
320.
Fu-Lin Evelyn Chu Eric D. Lund Paul R. Littreal Kate E. Ruck Ellen Harvey Jean-René Le Coz Yanic Marty Jeanne Moal Philippe Soudant 《Marine Biology》2009,156(2):155-169
The kinetics and efficiency of sterol production and bioconversion of phytosterols in two heterotrophic protists Oxyrrhis marina and Gyrodinium dominans were examined by feeding them two different algal species (Rhodomonas salina and Dunaliella tertiolecta) differing in sterol profiles. R. salina contains predominantly brassicasterol (≅99%) and <2% cholesterol. The major sterols in D. tertiolecta are ergosterol (45–49%), 7-dehydroporiferasterol (29–31%) and fungisterol (21–26%). O. marina fed R. salina metabolized dietary brassicasterol to produce 22-dehydrocholesterol and cholesterol. O. marina fed D. tertiolecta metabolized dietary sterols to produce cholesterol, 22-dehydrocholesterol, brassicasterol and stigmasterol. G. dominans fed either R. salina or D. tertiolecta metabolized dietary sterols to make cholesterol, brassicasterol and a series of unknown sterols. When protists were fed R. salina, which contains cholesterol, the levels of cholesterol were increased to a magnitude of nearly 5- to 30-fold at the phytoplankton-heterotrophic
protist interface, equivalent to a production of 172.5 ± 16.2 and 987.7 ± 377.7 ng cholesterol per mg R. salina carbon consumed by O. marina and G. dominans, respectively. When protists were fed D. tertiolecta, which contains no cholesterol, a net production of cholesterol by the protists ranged from 123.2 ± 30.6 to 871.8 ± 130.8 ng
per mg algal C consumed. Cholesterol is not only the dominant sterol, but a critical precursor for many physiologically functional
biochemicals in higher animal. As intermediates, these heterotrophic protists increase the amount of cholesterol at the phytoplankton–zooplankton
interface available to higher trophic levels relative to zooplankton feeding on algae directly. 相似文献