全文获取类型
收费全文 | 17579篇 |
免费 | 283篇 |
国内免费 | 381篇 |
专业分类
安全科学 | 617篇 |
废物处理 | 752篇 |
环保管理 | 2647篇 |
综合类 | 2976篇 |
基础理论 | 4492篇 |
环境理论 | 7篇 |
污染及防治 | 4616篇 |
评价与监测 | 993篇 |
社会与环境 | 1018篇 |
灾害及防治 | 125篇 |
出版年
2023年 | 95篇 |
2022年 | 171篇 |
2021年 | 168篇 |
2020年 | 189篇 |
2019年 | 151篇 |
2018年 | 284篇 |
2017年 | 269篇 |
2016年 | 412篇 |
2015年 | 334篇 |
2014年 | 445篇 |
2013年 | 1413篇 |
2012年 | 615篇 |
2011年 | 888篇 |
2010年 | 669篇 |
2009年 | 762篇 |
2008年 | 833篇 |
2007年 | 872篇 |
2006年 | 719篇 |
2005年 | 608篇 |
2004年 | 625篇 |
2003年 | 569篇 |
2002年 | 542篇 |
2001年 | 643篇 |
2000年 | 522篇 |
1999年 | 317篇 |
1998年 | 212篇 |
1997年 | 231篇 |
1996年 | 223篇 |
1995年 | 268篇 |
1994年 | 211篇 |
1993年 | 213篇 |
1992年 | 180篇 |
1991年 | 186篇 |
1990年 | 179篇 |
1989年 | 183篇 |
1988年 | 156篇 |
1987年 | 135篇 |
1986年 | 156篇 |
1985年 | 145篇 |
1984年 | 193篇 |
1983年 | 147篇 |
1982年 | 173篇 |
1981年 | 158篇 |
1980年 | 130篇 |
1979年 | 149篇 |
1978年 | 94篇 |
1977年 | 98篇 |
1975年 | 88篇 |
1974年 | 93篇 |
1972年 | 96篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
The extent to which genetic divergence can occur in the absence of physical barriers to gene flow is currently one of the most controversial topics in evolutionary biology, with implications for our understanding of speciation, phenotypic plasticity and adaptive potential. This is illustrated by a recent study reporting a surprising pattern of genetic differentiation between intertidal and subtidal morphotypes of the broadcast-spawning Antarctic limpet Nacella concinna. To explore this further, we collected almost 400 Antarctic limpets from four depths (intertidal, 6, 15 and 25 m) at Adelaide island, Antarctica, and conducted a combined morphometric and genetic analysis using 168 polymorphic amplified fragment length polymorphism (AFLP) loci. Morphological analysis revealed not only pronounced differences between the two morphotypes, but also a continuous cline in shell shape from the intertidal zone down to 25 m depth, suggesting that the distinction between the morphotypes may be artificial. Moreover, genetic analysis using both F st and a Bayesian analogue found no evidence for differentiation either between the two morphotypes or by depth, and a Bayesian cluster analysis did not detect any cryptic genetic structure. Our findings lend support to the notion that limpets can be phenotypically highly plastic, although further studies are required to determine unequivocally whether there is any genetic basis to the observed variation in shell morphology. 相似文献
892.
Most woody plants contain a diverse array of plant secondary metabolites (PSMs) that deter vertebrate herbivores. However,
mammalian folivores have evolved a complex of physiological and behavioural strategies to counter these compounds, leading
to the development of an “evolutionary arms race”. Marsupial folivores are ideal models to investigate the role of PSMs in
the interaction between the external foraging environment and the digestive physiology of mammalian herbivores, as we have
a very strong understanding of the diversity and modes of action of PSMs in Eucalyptus, as well as the mechanisms by which animals overcome the effects of these compounds. Studies of marsupial folivores have
benefited from the facts that: these herbivores subsist on relatively poor quality diets; they include feeding types from
specialist species such as the koala, to generalists; and life history factors such as maternal investment in reproduction
can be measured more easily than in eutherians. Here, we describe patterns of spatial variation in the types and distributions
of plant secondary metabolites in Australian forests and discuss how this variation influences foraging behaviour, habitat
selection and life history strategies in arboreal, folivorous marsupials. We also provide a summary of our understanding of
the mechanisms by which marsupials detect and regulate their intake of toxic compounds. While our examples are drawn largely
from studies of the interaction between marsupials and Eucalyptus, this knowledge is applicable to advancing our understanding of interactions in plant–mammal systems more broadly. We also
identify and discuss key areas that should be the focus of future research. 相似文献
893.
Persistence models for mark-recapture 总被引:1,自引:0,他引:1
The stable of models available for analyzing mark-recapture data (Otis et al. Wild Momogr 66:135, 1978) includes those having
behavioral characteristics, time variation, heterogeneity, along with combinations of those characteristics. This paper proposes
use of a series of models based on the persistence model of Ramsey and Usner (Biometrics 59:331–339, 2003). We show that persistence
can be modeled in combination with behavior and with time variation. We apply the persistence model to situations in which
capture occasions are not equally-spaced in time. Two case studies illustrate the use of these extended persistence models. 相似文献
894.
Emma Nelson Christy L. Hoffman Melissa S. Gerald Susanne Shultz 《Behavioral ecology and sociobiology》2010,64(6):1001-1009
Female rhesus macaques exhibit matrilineal dominance structures, and high dominance rank confers fitness benefits across a
lifetime and across generations. Rank effects are “inherited” through social processes that are well understood; however,
biological mechanisms that might impact these processes are not well known. Recently, it has been shown that prenatal androgens
appear to be implicated in supporting dominance rank hierarchies in some mammals. In humans, interindividual differences in
the second (index) to fourth (ring) digit ratio (2D:4D) have been linked indirectly to variation in prenatal androgens, with
low 2D:4D in both sexes associated with higher inferred prenatal androgen effects. 2D:4D has also been related to dominant
social behavior and has been shown to co-vary with social systems across nonhuman primate species. Here, we investigate how
2D:4D co-varies with socially inherited dominance rank in female rhesus macaques. Low 2D:4D was associated with higher-ranking
females, while higher 2D:4D was associated with lower-ranking females. Similar relationships were also shown between ranked
families within matrilines. This is the first study to show such a relationship between 2D:4D and dominance rank in a nonhuman
primate and suggests that prenatal androgen effects could be involved in the maintenance of dominance rank in female cercopithecine
primates. 相似文献
895.
Lisa R. Goshe Larisa Avens Frederick S. Scharf Amanda L. Southwood 《Marine Biology》2010,157(8):1725-1740
Despite the vast amount of research on threatened and endangered green turtle populations, some uncertainty regarding stage
durations, growth rates, and age at maturation remains. We used skeletochronology to address this gap in knowledge for green
turtle populations in the North Atlantic Ocean that use coastal waters along the southeastern U.S. as developmental habitat.
Oceanic stage duration was estimated at 1–7 years (
[`(\textX)] \overline{\text{X}} = 3 years). Several growth models, including von Bertalanffy, logistic, Gompertz, and power functions were evaluated for
describing sex-specific length-at-age data. Ages at maturation estimated using mean size at nesting for females from each
genetic sub-population contributing juveniles to this neritic foraging area were 44 years (Florida), 42.5 years (Costa Rica),
and 42 years (Mexico), which were higher than previously reported ages. This implies that nesting populations comprising primarily
individuals utilizing foraging grounds in the southeastern U.S. may take longer to recover than previously estimated. 相似文献
896.
This study has demonstrated an interaction between the effect of increased ocean acidity and temperature (40 days exposure) on a number of key physiological parameters in the ophiuroid brittlestar, Ophiura ophiura. Metabolic upregulation is seen in the low pH treatments when combined with low temperature. However, this is far outweighed by the response to elevated temperature (+4.5°C). In the high temperature/low pH treatments treatments (where calcite is undersaturated) there appears to be an energetic trade-off likely in order to maintain net calcification where dissolution of calcium carbonate may occur. This energy deficit results in a ~30% reduction in the rate of arm regeneration at pH 7.3 which is predicted to be reached by the year 2300. This understanding of how O. ophiura responds to ocean acidification, taking into account an interactive effect of temperature, suggests that fitness and survival may indirectly be reduced through slower recovery from arm damage. 相似文献
897.
Silk JB Beehner JC Bergman TJ Crockford C Engh AL Moscovice LR Wittig RM Seyfarth RM Cheney DL 《Behavioral ecology and sociobiology》2010,64(11):1733-1747
Analyses of the pattern of associations, social interactions, coalitions, and aggression among chacma baboons (Papio hamadryas ursinus) in the Okavango Delta of Botswana over a 16-year period indicate that adult females form close, equitable, supportive, and
enduring social relationships. They show strong and stable preferences for close kin, particularly their own mothers and daughters.
Females also form strong attachments to unrelated females who are close to their own age and who are likely to be paternal
half-sisters. Although absolute rates of aggression among kin are as high as rates of aggression among nonkin, females are
more tolerant of close relatives than they are of others with whom they have comparable amounts of contact. These findings
complement previous work which indicates that the strength of social bonds enhances the fitness of females in this population
and support findings about the structure and function of social bonds in other primate groups. 相似文献
898.
Zhaoqing Yang Kathryn L. Sobocinski Tarang Khangaonkar Roger Fuller 《Ecological modelling》2010,221(7):1043-319
Along the Pacific Northwest coast, much of the estuarine habitat has been lost over the last century to agricultural land use, residential and commercial development, and transportation corridors. As a result, many of the ecological processes and functions have been disrupted. To protect and improve these coastal habitats that are vital to aquatic species, many projects are currently underway to restore estuarine and coastal ecosystems through dike breaches, setbacks, and removals. Understanding site-specific information on physical processes is critical for improving the success of such restoration actions. In this study, a three-dimensional hydrodynamic model was developed to simulate estuarine processes in the Stillaguamish River estuary, where restoration of a 160-acre parcel through dike setback has been proposed. The model was calibrated to observed tide, current, and salinity data for existing conditions and applied to simulate the hydrodynamic responses to two restoration alternatives. Model results were then combined with biophysical data to predict habitat responses within the restoration footprint. Results showed that the proposed dike removal would result in desired tidal flushing and conditions that would support four habitat types on the restoration footprint. At the estuary scale, restoration would substantially increase the proportion of area flushed with freshwater (<5 ppt) at flood tide. Potential implications of predicted changes in salinity and flow dynamics are discussed relative to the distribution of tidal marsh habitat. 相似文献
899.
Donald L. DeAngelis Joel C. Trexler Adam Obaza Fred Jopp 《Ecological modelling》2010,221(8):1131-1137
Small fishes in seasonally flooded environments such as the Everglades are capable of spreading into newly flooded areas and building up substantial biomass. Passive drift cannot account for the rapidity of observed population expansions. To test the ‘reaction-diffusion’ mechanism for spread of the fish, we estimated their diffusion coefficient and applied a reaction-diffusion model. This mechanism was also too weak to account for the spatial dynamics. Two other hypotheses were tested through modeling. The first—the ‘refuge mechanism’—hypothesizes that small remnant populations of small fishes survive the dry season in small permanent bodies of water (refugia), sites where the water level is otherwise below the surface. The second mechanism, which we call the ‘dynamic ideal free distribution mechanism’ is that consumption by the fish creates a prey density gradient and that fish taxis along this gradient can lead to rapid population expansion in space. We examined the two alternatives and concluded that although refugia may play an important role in recolonization by the fish population during reflooding, only the second, taxis in the direction of the flooding front, seems capable of matching empirical observations. This study has important implications for management of wetlands, as fish biomass is an essential support of higher trophic levels. 相似文献
900.
J. Carneiro L. M. Cardenas D. J. Hatch H. Trindade D. Scholefield C. D. Clegg P. Hobbs 《Environmental Chemistry Letters》2010,8(3):237-246
Nitrous oxide (N2O) affects climate change as a greenhouse gas and indirectly contributes to stratospheric ozone depletion. The main source
of N2O in soils is denitrification which requires high soil moisture, carbon and nitrate. Nitrification inhibitors can be used
to mitigate emissions of N2O from soils. In Portugal, fertilisers are often applied when soils are still relatively warm and moist conditions conducive
to denitrification. A Portuguese arable soil was inhibited with dicyandiamide, a nitrification inhibitor and the effect on
soil microbiological activity and composition was determined after 46 days. Soils were then incubated and received carbon
and ammonium under high soil water conditions and mineral N and N2O fluxes were measured during 22 days. We found that dicyandiamide decreased microbial populations and activity, but did not
alter composition. Pre-conditioning of the soil with dicyandiamide was 80% more effective in reducing fluxes of N2O than simultaneous application with fertiliser. 相似文献