全文获取类型
收费全文 | 661篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
安全科学 | 31篇 |
废物处理 | 15篇 |
环保管理 | 156篇 |
综合类 | 71篇 |
基础理论 | 175篇 |
污染及防治 | 137篇 |
评价与监测 | 64篇 |
社会与环境 | 13篇 |
灾害及防治 | 12篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 18篇 |
2016年 | 28篇 |
2015年 | 11篇 |
2014年 | 21篇 |
2013年 | 75篇 |
2012年 | 31篇 |
2011年 | 42篇 |
2010年 | 27篇 |
2009年 | 30篇 |
2008年 | 30篇 |
2007年 | 26篇 |
2006年 | 32篇 |
2005年 | 21篇 |
2004年 | 27篇 |
2003年 | 22篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1954年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有674条查询结果,搜索用时 343 毫秒
71.
Melissa Emery Thompson Martin N. Muller Richard W. Wrangham 《Behavioral ecology and sociobiology》2014,68(12):1973-1983
Sexual conflict develops when the optimal reproductive strategy for one sex inflicts fitness costs upon the other sex. Among species with intense within-group feeding competition and high costs of reproduction, females are expected to experience reduced foraging efficiency by associating with males, and this may compromise their reproductive ability. Here, we test this hypothesis in chimpanzees, a species with flexible grouping patterns in which female avoidance of large subgroups has been attributed to their relatively high costs of grouping. In an >11-year study of the Kanyawara community of East African chimpanzees (Pan troglodytes schweinfurthii) in the Kibale National Park, Uganda, the availability of sexually receptive females was a key determinant of the number of males in parties. In turn, females experienced significantly lower C-peptide of insulin levels, indicative of reduced energy balance, during periods when they associated with more males. Female associates did not produce the same negative effect. C-peptide levels positively and significantly predicted female ovarian steroid production, indicating that the costs of associating with males can lead to downstream reproductive costs. Therefore, we conclude that Kanyawara chimpanzees exhibit sexual conflict over subgroup formation, with the large groupings that allow males to compete for mating opportunities inflicting energetic and reproductive costs on females. Because association with males is central to female chimpanzees’ anti-infanticide strategy, and males may confer other benefits, we propose that reproductive success in female chimpanzees hinges on a delicate balance between the costs and benefits of associating with male conspecifics. 相似文献
72.
Many cooperative bird species have an extended period of post-fledging care. Despite the fact that this period of care can last up to several months, it remains a relatively understudied stage of chick development. This period, when young are actively begging but highly mobile, provides an opportunity for young to maximise the amount of care they receive by selectively choosing particular adults to beg from. In pied babblers Turdoides bicolor (a cooperatively breeding passerine), fledglings closely follow foraging adults and beg for food regularly (a behavioural interaction termed social foraging). Using a combination of natural observations and experimental manipulations, we found that fledgling pied babblers preferentially socially forage with adult care-givers who have high foraging success, since this results in young receiving more food. By supplementally feeding adults to artificially increase their foraging success, we increased the proportion of time that fledglings chose to socially forage with them, confirming that fledglings are selectively choosing dyadic interactions with the best adult foragers. These results indicate that pied babbler fledglings are sensitive to and can respond to short-term changes in adult foraging success, enabling them to maximize their nutritional intake, a behavioural adjustment that has long-term benefits in this system. 相似文献
73.
Ellie Owen Francis Daunt Colin Moffat David A. Elston Sarah Wanless Paul Thompson 《Marine Biology》2013,160(4):987-999
A key challenge in ecology is to find ways to obtain complete and accurate information about the diets of animals. To respond to this challenge in seabirds, traditional methods (usually stomach content analysis or observations of prey at nests) have been supplemented with indirect methods or molecular trophic markers. These techniques have the potential to extend the period of investigation outside the few short months of breeding and avoid biases. Here, we use an analysis of fatty acids (FAs) and fatty alcohols (FALs) from blood, adipose tissue and stomach oil to investigate how the diets of male and female common guillemots (Uria aalge), black-legged kittiwakes (Rissa tridactyla) and northern fulmars (Fulmarus glacialis) differed through the sampling period (prelaying and breeding season) and by sex. Diets of both sexes of all three species generally varied across the season, but sex differences were apparent only in fulmars during prelaying. Our study shows that FA/FAL analysis can provide significant insights into diets of seabirds, in particular periods of the annual cycle which are not readily studied using traditional methods. 相似文献
74.
Factors driving mortality and growth at treeline: a 30-year experiment of 92 000 conifers 总被引:1,自引:0,他引:1
Understanding the interplay between environmental factors contributing to treeline formation and how these factors influence different life stages remains a major research challenge. We used an afforestation experiment including 92 000 trees to investigate the spatial and temporal dynamics of tree mortality and growth at treeline in the Swiss Alps. Seedlings of three high-elevation conifer species (Larix decidua, Pinus mugo ssp. uncinata, and Pinus cembra) were systematically planted along an altitudinal gradient at and above the current treeline (2075 to 2230 m above sea level [a.s.l.]) in 1975 and closely monitored during the following 30 years. We used decision-tree models and generalized additive models to identify patterns in mortality and growth along gradients in elevation, snow duration, wind speed, and solar radiation, and to quantify interactions between the different variables. For all three species, snowmelt date was always the most important environmental factor influencing mortality, and elevation was always the most important factor for growth over the entire period studied. Individuals of all species survived at the highest point of the afforestation for more than 30 years, although mortality was greater above 2160 m a.s.l., 50-100 m above the current treeline. Optimal conditions for height growth differed from those for survival in all three species: early snowmelt (ca. day of year 125-140 [where day 1 is 1 January]) yielded lowest mortality rates, but relatively later snowmelt (ca. day 145-150) yielded highest growth rates. Although snowmelt and elevation were important throughout all life stages of the trees, the importance of radiation decreased over time and that of wind speed increased. Our findings provide experimental evidence that tree survival and height growth require different environmental conditions and that even small changes in the duration of snow cover, in addition to changes in temperature, can strongly impact tree survival and growth patterns at treeline. Further, our results show that the relative importance of different environmental variables for tree seedlings changes during the juvenile phase as they grow taller. 相似文献
75.
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
76.
Melissa Jacobs Jacobus Pienaar 《International journal of occupational safety and ergonomics》2013,19(2):152-161
The primary objective of this study was to investigate the relationship of work stress, consisting of role stressors and job insecurity, with safety compliance at work. A secondary objective was to test for the possible moderating effect of individual employees’ coping behaviour between experienced work stress and job insecurity, and their safety compliance. A cross-sectional survey design was used (n?=?771). An electronic survey, with a biographical questionnaire and scales on role conflict, role ambiguity, role overload, job insecurity, coping and safety compliance at work, was administered. The results indicated that specific aspects of work stress, notably role conflict, role ambiguity and quantitative job insecurity, and of coping, namely an avoidance style and changing the situation, were important in understanding safety compliance. A moderating effect of avoidance coping was also found. 相似文献
77.
Evidence from cross-sectional growth regressions suggests that economies dependent on natural resource exports have had slower growth than resource scarce economies. Explanations for this “curse of resources” focus on institutional and market failures caused by resource abundance. With a simple two sector model exhaustible resource model, we demonstrate that the correlation between growth and natural resource abundance can be negative in the absence of market and institutional failures. Since there is no way to distinguish between efficient and inefficient equilibria on the basis of the negative correlation between growth and resource abundance, finding that correlation is not sufficient to conclude resources are a curse, nor is it necessary to find a positive correlation between growth and resources to overturn the resource curse interpretation. We show whether resources are a curse or a blessing for an economy can only be determined by an investigation of the correlation between resource abundance and income levels. Using panel data for U.S. states for the period 1970-2001, we show that resource abundance is negatively correlated with growth rates but positively correlated with income levels. 相似文献
78.
Bera M Radcliffe DE Cabrera ML Vencill WK Thompson A Hassan S 《Journal of environmental quality》2011,40(6):1983-1990
17β-estradiol and testosterone are naturally occurring steroids that co-occur in poultry litter. The effects of litter on sorption of these hormones to soil are not known. Sorption isotherms were developed for C-labeled testosterone and H-labeled estradiol in a Cecil sandy clay loam with and without poultry litter addition. The effect of applying the hormones alone (single-sorbate) or together (multisorbate) was also investigated. C-testosterone sorption in soil increased from 2 to 48 h and remained relatively constant thereafter. H-estradiol sorption in soil was relatively constant from 2 to 24 h and then decreased to 72 h. These differences may reflect transformation of the parent hormones to products with different solid-phase affinity. The maximum sorption coefficient () in soil for C-testosterone (20.2 mL g) was similar to that for H-estradiol (19.6 mL g) in single-sorbate experiments. When hormones were applied together, sorption of both hormones in soil decreased, but the C-testosterone (12.5 mL g) was nearly twice as large as the H-estradiol (7.4 mL g). We propose this resulted from competition between the hormones and their transformation products for sorption sites, with C-testosterone and its expected transformation product (androstenedione) being better competitors than H-estradiol and its expected transformation product (estrone). When poultry litter was mixed with soil, sorption increased for H-estradiol but decreased for C-testosterone. This may have been because poultry litter slowed the transformation of parent hormones. Our results show that poultry litter could have important effects on the mobility of estradiol and testosterone. 相似文献
79.
Private domestic gardens contribute substantially to the biodiversity of urban areas and benefit human health and well-being.
We previously reported a study of 267 gardens across five cities in the United Kingdom in which variation in geographical
and climatic factors had little bearing on the richness, diversity and composition of plant species. We therefore hypothesise
that garden management is an important factor in determining garden characteristics. Here, from the same sample of gardens,
we investigate potential associations between the uses to which people put their gardens, the types of management activities
they undertake, and the characteristics of those gardens. Householders (n = 265) completed a questionnaire detailing various aspects of garden use and management activities. The majority of respondents
used their gardens chiefly for relaxation, recreation, and eating. Fewer than one fifth included “gardening” amongst their
garden uses even though all performed some garden management, suggesting that not all management activity resulted from an
interest in gardening. Garden-watering and lawn-mowing were the most prevalent activities and were predictors of other types
of management including weeding, vegetation-cutting, leaf-collection, and dead-heading flowers. A number of these activities
were associated with one another, the richness and composition of plant species, and the number of land uses in gardens. However,
relationships between management activities and the amount of tall vegetation were less consistent, and garden management
appeared to be independent of garden area. More species of amphibians, birds, and mammals were observed in gardens with ponds
and in which efforts were made to attract wildlife, particularly by providing drinking water. This study supports the hypothesis
that garden use and management is associated with garden characteristics. 相似文献
80.
Donald B. Thompson 《Journal of Agricultural and Environmental Ethics》2011,24(2):165-194
The term natural is effective in the marketing of a wide variety of foods. This ambiguous term carries important meaning in Western culture.
To challenge an uncritical understanding of natural with respect to food and to explore the ambiguity of the term, the development of Western ideas of nature is first discussed. Personification and hypostasization of nature are given special emphasis. Leo Marx’s idea of the pastoral
design in literature is then used to explore the meaning of natural as applied to food, emphasizing Marx’s distinction between
a sentimental and a complex pastoral. The latter is applied to natural as a means of collapsing a dichotomy of man and nature to the idea of second nature. From this perspective an understanding of the industrialization of the food system and the importance of local and organic
food are considered. The extent to which processed foods might properly be considered natural is raised and discussed for
several common foods. Although marketing of natural foods might make us think that we consume nature, I suggest that what
is consumed is more appropriately second nature. I suggest that in order to maintain a critical perspective about one’s relationship
to the natural world, everyone should make an attempt to experience the complex pastoral with respect to at least something
that is consumed as food. When nature is understood as second nature in the context of a complex pastoral, the question of
whether a food or ingredient is to be considered natural is replaced by deliberative thought based on our best knowledge and
judgment, and the result will be less constrained by ideology. 相似文献