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181.
Sabine Wamser Jens DauberKlaus Birkhofer Volkmar Wolters 《Agriculture, ecosystems & environment》2011,144(1):235-240
The colonisation of winter barley fields by spring breeding carabids and its temporal modulation by the amount of potential hibernation sites was studied. Species richness of carabids was lower in landscapes with high length of boundaries and a high amount of non-cropped open habitats during early stages of the beetles’ colonisation of arable fields. Species number of beetles with high dispersal potential responded to this landscape features at coarse spatial scales whereas beetles with low dispersal potential responded to intermediate scales. However, the negative impact of potential hibernation sites on colonisation diminished in later sampling phases. The patterns observed may be explained by both overwintering in arable soils in less complex landscapes and delayed colonisation in more complex landscapes. The seasonal patterns of landscape control suggest a need to account for temporal dynamics in interactions between species or functional groups and landscape properties. A high temporal resolution is needed in studies that focus on ecosystem function and services in agricultural landscapes, as direction of effect (positive/negative) of management on animal communities may change across spatial scales and within short time periods. 相似文献
182.
183.
Using bomb radiocarbon to estimate age and growth of the white shark,Carcharodon carcharias,from the southwestern Indian Ocean 总被引:1,自引:0,他引:1
184.
Manuela?Krakau Sabine?Jacobsen Kurt?Thomas?Jensen Karsten?ReiseEmail author 《Marine Biology》2012,159(1):221-230
The cockle Cerastoderma (Cardium) edule (L.) ranges from NW Africa to northern Scandinavia. Abundance in shallow coastal sediment is often high, and it attracts
commercial harvest. In this study, a complex genetic pattern has been revealed by mitochondrial DNA in 383 individuals from
19 sampling sites. Parsimony network analysis of 79 haplotypes identified two dominant central haplotypes separated by low
divergence. One is characteristic for a homogenous southwestern group of populations from Africa to the British Isles. The
other is characteristic for a heterogeneous northern group with a deviant Arctic population. At the entrance of the Baltic
Sea, a mixture zone of the dominant haplotypes was found. The estimated population expansion time for the northern haplotype
group predates that of the southwestern one, suggesting northern glacial refugia and a subsequent southern expansion of C. edule populations. 相似文献
185.
The present diary study examines how employees thrive at work in response to resources (i.e., positive meaning, relational resources, and knowledge). Thriving is conceptualized as the joint experience of vitality and learning. A total of 121 employees working in the social services sector responded to three daily surveys (in the morning, at lunchtime, and at the end of the work day) for a period of five work days. Intra‐individual analyses (hierarchical linear modeling) revealed that on days when employees experience positive meaning at work in the morning, they feel more vital at the end of the work day and have a higher sense of learning. Work behaviors such as task focus and exploration mediated the relation between positive meaning and both components of thriving. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
186.
Environmental processes affecting plant root uptake of radioactive trace elements and variability of transfer factor data: a review 总被引:8,自引:0,他引:8
Soil-to-plant transfer factors are commonly used to estimate the food chain transfer of radionuclides. Their definition assumes that the concentration of a radionuclide in a plant relates linearly solely to its average concentration in the rooting zone of the soil. However, the large range of transfer factors reported in the literature shows that the concentration of a radionuclide in a soil is not the only factor influencing its uptake by a plant. With emphasis on radiocesium and -strontium, this paper reviews the effects of competition with major ions present in the soil-plant system, the effects of rhizosphere processes and soil micro-organisms on bioavailability, the factors influencing transport to and uptake by roots and the processes affecting long-term uptake rates. Attention is given to summarizing the results of recent novel electrophysiological and genetic techniques which provide a physiologically based understanding of the processes involved in the uptake and translocation of radiocesium and -strontium by plants. 相似文献
187.
Christine Vanessa Schmidt Sabine Frohschammer Alexandra Schrempf Jürgen Heinze 《Die Naturwissenschaften》2014,101(1):69-72
Mother–son mating (oedipal mating) is practically non-existent in social Hymenoptera, as queens typically avoid inbreeding, mate only early in life and do not mate again after having begun to lay eggs. In the ant genus Cardiocondyla mating occurs among sib in the natal nests. Sex ratios are extremely female-biased and young queens face the risk of remaining without mating partners. Here, we show that virgin queens of Cardiocondyla argyrotricha produce sons from their own unfertilized eggs and later mate with them to produce female offspring from fertilized eggs. Oedipal mating may allow C. argyrotricha queens to found new colonies when no mating partners are available and thus maintains their unusual life history combining monogyny, mating in the nest, and low male production. Our result indicates that a trait that sporadically occurs in solitary haplodiploid animals may evolve also in social Hymenoptera under appropriate ecological and social conditions. 相似文献
188.
Djungarian hamsters (Phodopus sungorus) are not susceptible to stimulating effects of 6-methoxy-2-benzoxazolinone on reproductive organs 总被引:1,自引:0,他引:1
Victoria Diedrich Frank Scherbarth Susanne Jähnig Sabine Kastens Stephan Steinlechner 《Die Naturwissenschaften》2014,101(2):115-121
The secondary plant metabolite 6-methoxy-2-benzoxazolinone (6-MBOA) is abundant in vegetative parts of monocotyledons emerging in spring. This grazing protective has been shown to promote gonadal growth and, thus enable precise alignment of reproductive activity with favorable environmental conditions in a variety of seasonally breeding rodent species. Feeding and breeding ecology make the Djungarian hamster (Phodopus sungorus) a potential candidate using 6-MBOA as an acute environmental cue to optimize reproductive timing when photorefractoriness induces reproductive recrudescence. Therefore, four different experiments were designed to examine whether the hamsters’ reproductive organs are responsive to oral 6-MBOA administration under different photoperiodic conditions. Only under a long photoperiod, we found a slight increase in uterine weights. In a short photoperiod, 6-MBOA-treated hamsters showed a slight body weight gain without a change in uterine weights. However, these marginal effects are likely not to be of ecophysiological significance for reproductive timing. The results are in agreement with the common view that the annual changes in photoperiod length are not only the predominant environmental cue for Djungarian hamsters, but are also sufficient to synchronize reproductive efforts with favorable breeding conditions in highly predictable climates like the continental Asian steppes. 相似文献
189.
Sabine Perch-Nielsen Ana Sesartic Matthias Stucki 《Environmental Science & Policy》2010,13(2):131-140
Greenhouse gas intensity is a ratio comparing the greenhouse gas (GHG) emissions of an activity or economic sector to the economic value it generates. In recent years, many countries have calculated the GHG intensity of their economic sectors as a basis for policy making. The GHG intensity of tourism, however, has not been determined since tourism is not measured as an economic sector in the national accounts. While for tourism-reliant countries it would be useful to know this quantity, a number of difficulties exist in its determination. In this study, we determine the GHG intensity of tourism's value added in Switzerland by means of a detailed bottom-up approach with the main methodological focus on how to achieve consistent system boundaries. For comparison, we calculate the tourism sector's GHG intensity for selected European countries using a simpler top-down approach. Our results show that the Swiss tourism sector is more than four times more GHG intensive than the Swiss economy on average. Of all tourism's sub-sectors, air transport stands out as the sector with by far largest emissions (80%) and highest GHG intensity. The results for other countries make similar, if not as pronounced, patterns apparent. We discuss the results and possible mitigation options against the background of the goal to prevent dangerous climate change. 相似文献
190.
Living in a “stethoscope”: burrow-acoustics promote auditory specializations in subterranean rodents
Subterranean mammals rely to a great extent on audition for communication and to be alerted to danger. The only hitherto published
report on burrow acoustics revealed that in tunnels of blind mole-rats (Spalax ehrenbergi), airborne sounds of 440 Hz propagated best whereas lower and higher frequencies were effectively attenuated. Morpho-functional
analyses classify the ear of subterranean mammals as a low-sensitivity and low-frequency device. Concordantly, hearing is
characterized by low sensitivity and a restricted frequency range tuned to low frequencies (0.5–4 kHz). Some authors considered
the restricted hearing in subterranean mammals vestigial and degenerate due to under-stimulation. In contrast to this view
stand a rich (mostly low-frequency) vocal repertoire and progressive structural specializations of the middle and inner ear.
Thus, other authors considered these hearing characteristics adaptive. To test the hypothesis that acoustical environment
in burrows of different species of subterranean mammals is similar, we measured sound attenuation in burrows of Fukomys mole-rats (formerly known as Cryptomys, cf. Kock et al. 2006) of two differently sized species at different locations in Zambia. We show that in these burrows, low-frequency sounds (200–800 Hz)
are not only least attenuated but also their amplitude may be amplified like in a stethoscope (up to two times over 1 m).
We suggest that hearing sensitivity has decreased during evolution of subterranean mammals to avoid over-stimulation of the
ear in their natural environment.
We dedicate this work to Mathias Kawalika, who died in March 2006. 相似文献