全文获取类型
收费全文 | 430篇 |
免费 | 10篇 |
国内免费 | 5篇 |
专业分类
安全科学 | 16篇 |
废物处理 | 20篇 |
环保管理 | 54篇 |
综合类 | 60篇 |
基础理论 | 143篇 |
环境理论 | 1篇 |
污染及防治 | 118篇 |
评价与监测 | 19篇 |
社会与环境 | 11篇 |
灾害及防治 | 3篇 |
出版年
2023年 | 11篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 16篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 41篇 |
2010年 | 22篇 |
2009年 | 24篇 |
2008年 | 16篇 |
2007年 | 30篇 |
2006年 | 16篇 |
2005年 | 16篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1992年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1962年 | 1篇 |
1957年 | 1篇 |
1941年 | 1篇 |
1937年 | 3篇 |
1918年 | 1篇 |
排序方式: 共有445条查询结果,搜索用时 15 毫秒
71.
Benthic-planktonic coupling, regime shifts, and whole-lake primary production in shallow lakes 总被引:2,自引:0,他引:2
Alternative stable states in shallow lakes are typically characterized by submerged macrophyte (clear-water state) or phytoplankton (turbid state) dominance. However, a clear-water state may occur in eutrophic lakes even when macrophytes are absent. To test whether sediment algae could cause a regime shift in the absence of macrophytes, we developed a model of benthic (periphyton) and planktonic (phytoplankton) primary production using parameters derived from a shallow macrophyte-free lake that shifted from a turbid to a clear-water state following fish removal (biomanipulation). The model includes a negative feedback effect of periphyton on phosphorus (P) release from sediments. This in turn induces a positive feedback between phytoplankton production and P release. Scenarios incorporating a gradient of external P loading rates revealed that (1) periphyton and phytoplankton both contributed substantially to whole-lake production over a broad range of external P loading in a clear-water state; (2) during the clear-water state, the loss of benthic production was gradually replaced by phytoplankton production, leaving whole-lake production largely unchanged; (3) the responses of lakes to biomanipulation and increased external P loading were both dependent on lake morphometry; and (4) the capacity of periphyton to buffer the effects of increased external P loading and maintain a clear-water state was highly sensitive to relationships between light availability at the sediment surface and the of P release. Our model suggests a mechanism for the persistence of alternative states in shallow macrophyte-free lakes and demonstrates that regime shifts may trigger profound changes in ecosystem structure and function. 相似文献
72.
Patrik Kraufvelin Ann Lindholm Morten Foldager Pedersen Lars Andreas Kirkerud Erik Bonsdorff 《Marine Biology》2010,157(1):29-47
The littoral zone of temperate rocky shores is normally dominated by perennial macroalgae (e.g. Fucus, Ascophyllum, Laminaria), but nutrient enrichment and/or permanently decreased wave action may lead to structural community changes from dominance
of perennials to increased amounts of annual opportunistic species (mainly green algae). Macroalgal biomass, diversity and
production as well as relationships between the two latter were studied using Solbergstrand’s rocky shore mesocosms in SE
Norway in connection with a long-term experimental manipulation of nutrient addition and wave action (high and low levels
of both factors applied in a crossed way to eight outdoor basins). After more than 2 years of experimental treatment, the
total standing stock of macroalgae was larger in low nutrient than in high nutrient treatments as well as in high wave compared
to low wave treatments (in autumn only). For macroalgal functional groups, bushy and filamentous brown and filamentous red
algae were generally favoured by low nutrient concentrations, while annual filamentous and sheet-like green algae were stimulated
by the nutrient enrichment. There was only one significant interaction between nutrient enrichment and wave action (for brown
filamentous algae in autumn) and also only one significant main effect of the wave treatment (for bushy brown algae in autumn).
Surprisingly, the high nutrient treatments supported a higher diversity of macroalgae, whereas the low nutrient treatments
generally showed higher production rates. Moreover, significantly negative correlations were found between macroalgal diversity
and primary productivity in both summer and autumn. This study shows that it is the biological components of the communities
subjected to external forcing (nutrient addition or decreased wave action) that regulate production and this contradicts the
common misperception that resource production in natural systems simply can be fast-forwarded by fertilization. The negative
relationships between diversity and productivity, although a consequence of unexpected results for diversity and production,
are also novel and hint towards species identities having more important functional consequences than general species dominance
patterns and the amount of species per se. These results also emphasise the context dependency of findings within the field
of biodiversity and ecosystem functioning. 相似文献
73.
Sperm number is often a good predictor of success in sperm competition; however, it has become increasingly clear that, for
some species, variation in probability of paternity cannot be explained by sperm number alone. Intraspecific variation in
ejaculate characteristics, such as the number of viable sperm and sperm longevity, may play an equally important role in determining
fertilization success. Here, we assess variation among ejaculates in three factors that may contribute to fertilization success
(number of sperm per ejaculate, viability, and longevity), in a population of Peron’s tree frog (Litoria peronii). We detected large variation among males in the number of sperm per ejaculate and the proportion of viable sperm within
ejaculates, which could not be explained by variation in either male size or body condition. However, the proportion of viable
sperm released by males increased over the season. Finally, we assessed sperm longevity (proportion viable sperm determined
using a dual-fluorochrome vital dye) at two different temperatures. At 23°C, on average, 75% of sperm remained viable after
2 h, but there were significant differences amongst males with the percentage of viable sperm ranging from 43% to 95%. For
sperm incubated at 4°C, ejaculates varied fivefold in sperm longevity with some males having 50% viable sperm after 5 days.
Our data suggest that ejaculate characteristics (sperm number, viability, and longevity) vary widely in Peron’s tree frog
and may therefore play an important role in determining siring success both in the presence and absence of sperm competition.
We discuss the results in relation to selection on ejaculate traits via natural and sexual selection in this and other amphibians. 相似文献
74.
75.
Using dynamic energy budget (DEB) theory, this paper explores the potential of excess and harmful radiation, notably UV, to cause changes in performance and, ultimately, bleaching in scleractinian corals for a range of ambient nitrogen and (beneficial) photosynthetically active radiation levels. Two negative impacts of radiation are considered: a reduction in the capacity of the symbiont to generate energy through photosynthesis (defined in this paper as photoinhibition); an increase in the costs for the symbiont to remain viable due to repair of damage (defined in this paper as photodamage). Model predictions indicate that although both types of impact reduce the growth potential of host and symbiont, photoinhibition predominantly affects host features, except at very low ambient nitrogen levels, under which conditions the severity of nitrogen limitation is so strong that a reduction in photosynthetic rates due to photoinhibition has minimal impact. In steady state, photoinhibition leads to a reduction in host biomass, and an increase in symbiont density, implying that photoinhibition (as defined in this paper) is unlikely to cause bleaching. In contrast, the impact of photodamage is mostly affecting symbiont features, including a decline in symbiont density. Thus, photodamage may contribute to coral bleaching. Furthermore, the model predicts that, with both photoinhibition and photodamage, an increasing ratio of harmful to beneficial radiation accelerates the suppression of growth rates of symbiont and host, implying that coral health deteriorates progressively faster with increasing harmful radiation, such as UVb. 相似文献
76.
Michela Marchi Sven Erik JørgensenEloy Bécares Ilaria CorsiNadia Marchettini Simone Bastianoni 《Ecological modelling》2011,222(16):2992-3001
Using a dynamic model of Lake Chozas developed by Marchi et al. (2011), we tested three hypotheses about recovery of the indigenous community and water quality after radical changes caused by introduction of an invasive allochthonous crayfish, Procambarus clarkii:
- 1.
- Can the lake resist the pressure of an invasive species, like P. clarkii, by adaptation?
- 2.
- Can the ecosystem recover when all the crayfish are removed and low phosphorus concentrations persist in inflow water?
- 3.
- Does the simulated recovery of submerged vegetation occur at a total phosphorus concentration below 100 mg TP m−3, as estimated by Scheffer et al. (1993), Scheffer (1997), Jeppesen et al. (1998) and Zhang et al. (2003)?
- 1.
- Lake Chozas can at least partly resist by adaptation. A combination of possible parameter changes could lead to a significant increase in eco-exergy.
- 2.
- Removal of the phosphorus represented by crayfish (by harvesting) implies complete recovery of the lake and its eco-exergy, albeit not necessarily with the same organisms having the same properties.
- 3.
- The expected hysteresis created by introduction and harvesting of crayfish is observed under the following conditions: phytoplankton dominance at total phosphorus ≥ about 200-250 mg TP m−3 and submerged vegetation returns at total phosphorus < 100 mg TP m−3.
77.
Schinkel J Warren N Fransman W van Tongeren M McDonnell P Voogd E Cherrie JW Tischer M Kromhout H Tielemans E 《Journal of environmental monitoring : JEM》2011,13(5):1374-1382
The mechanistic model of the Advanced Reach Tool (ART) provides a relative ranking of exposure levels from different scenarios. The objectives of the calibration described in this paper are threefold: to study whether the mechanistic model scores are accurately ranked in relation to exposure measurements; to enable the mechanistic model to estimate actual exposure levels rather than relative scores; and to provide a method of quantifying model uncertainty. Stringent data quality guidelines were applied to the collated data. Linear mixed effects models were used to evaluate the association between relative ART model scores and measurements. A random scenario and company component of variance were introduced to reflect the model uncertainty. Stratified analyses were conducted for different forms of exposure (abrasive dust, dust, vapours and mists). In total more than 2000 good quality measurements were available for the calibration of the mechanistic model. The calibration showed that after calibration the mechanistic model of ART was able to estimate geometric mean (GM) exposure levels with 90% confidence for a given scenario to lie within a factor between two and six of the measured GM depending upon the form of exposure. 相似文献
78.
79.
Spatial anatomy of species survival: effects of predation and climate-driven environmental variability 总被引:1,自引:0,他引:1
Ciannelli L Dingsør GE Bogstad B Ottersen G Chan KS Gjøsaeter H Stiansen JE Stenseth NC 《Ecology》2007,88(3):635-646
The majority of survival analyses focus on temporal scales. Consequently, there is a limited understanding of how species survival varies over space and, ultimately, how spatial variability in the environment affects the temporal dynamics of species abundance. Using data from the Barents Sea, we study the spatiotemporal variability of the juvenile Atlantic cod (Gadus morhua) survival. We develop an index of spatial survival based on changes of juvenile cod distribution through their first winter of life (from age-0 to age-1) and study its variability in relation to biotic and abiotic factors. Over the 25 years analyzed (1980-2004), we found that, once the effect of passive drift due to dominant currents is accounted for, the area where age-0 cod survival was lowest coincided with the area of highest abundance of older cod. Within this critical region, the survival of age-0 cod was negatively affected by its own abundance, by that of older cod, and by bottom depth. Furthermore, during cold years, age-0 cod survival increased in the eastern and coldest portion of the examined area, which was typically avoided by older conspecifics. Based on these results we propose that within the examined area top-down mechanisms and predation-driven density dependence can strongly affect the spatial pattern of age-0 cod survival. Climate-related variables can also influence the spatial survival of age-0 cod by affecting their distribution and that of their predators. Results from these and similar studies, focusing on the spatial variability of survival rates, can be used to characterize species habitat quality of marine renewable resources. 相似文献
80.
Regina Lindborg Marie Stenseke Sara A.O. Cousins Jan Bengtsson Åke Berg Tomas Gustafsson N. Erik Sjödin Ove Eriksson 《Journal of environmental management》2009,90(2):499-508
Agriculture is the major land use at a global scale. In addition to food production, multifunctionality of landscapes, including values and ecosystem services like biodiversity, recreation and culture, is now focus for management. This study explores how a scenario approach, involving different stakeholders, may help to improve landscape management for biodiversity conservation. Local farmers and executives at the County Administrative Board were invited to discuss rural development and conditions for farmland biodiversity in two Swedish landscapes. The potential biodiversity for three future land use scenarios for the two landscapes was discussed: nature conservation, outdoor recreation and energy production, and compared with current and historical landscapes in each region.Analyses of habitat areas, connectedness and landscape diversity suggested that the energy and recreation scenarios had a negative impact on farmland biodiversity, whereas the nature conservation scenario, the current and historically reconstructed landscapes had a higher potential for biodiversity. The farmers appreciated the nature conservation scenario, but also the energy production scenario and they highlighted the need of increased subsidies for management of biodiversity. The farmers in the high production area were less interested in nature quality per se. The executives had similar opinions as the farmers, but disagreed on the advantages with energy production, as this would be in conflict with the high biodiversity and recreational values. The local physical and socio-economical conditions differ between landscapes and potentially shaped the stakeholders emotional attachment to the local environment, their opinions and decisions on how to manage the land. We stress the importance of incorporating local knowledge, visions and regional prerequisites for different land uses in conservation, since site and landscape specific planning for biodiversity together with a flexible subsidy system are necessary to reach the conservation goals within EU. 相似文献