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101.
在热带海洋环境中,红树林是具有较高生产力的生态系[1,2].通常认为,红树林湿地区域可为毗连的沿岸水域和相关的生物群落生境提供有机物和无机物[3~5].尽管在红树林区域中具有很高的生产率,但红树林的树木一般是生长在营养比较贫瘠的热带地区. 相似文献
102.
Jakobsen L Sandvang D Hansen LH Bagger-Skjøt L Westh H Jørgensen C Hansen DS Pedersen BM Monnet DL Frimodt-Møller N Sørensen SJ Hammerum AM 《Environment international》2008,34(1):108-115
The aim of the study was to investigate the potential spread of gentamicin resistant (GEN(R)) Escherichia coli isolates or GEN(R) determinants from a Danish university hospital to the waste water environment. Waste water samples were collected monthly from the outlets of the hospital bed wards and the inlet of the related waste water treatment plant (WWTP) from October 2002 to August 2003. Waste water samples were also collected monthly from a residential area in the same period to be able to compare the prevalence of GEN(R)E. coli isolates from hospital related and residential waste water. The waste water isolates were compared to GEN(R)E. coli isolates obtained consecutively from September 2002 to September 2003 from patients mainly with urinary tract infections at the hospital with respect to Pulsed Field Gel Electrophoresis (PFGE) profiles. All isolates were investigated for GEN(R) mechanisms (aac(3)-II, aac(3)-IV, ant(2')-I, armA), phenotypic resistance pattern, and virulence genes (hlyA, chuA, sfaS, fogG, malX, traT, iutA, fyuA, iroN, cnf1) to investigate if the hospital and waste water could be reservoirs of antimicrobial resistance and virulence. The ability for GEN(R) determinants to transfer horizontally was investigated by mating experiments. A total of 38, 15, 21, and two GEN(R)E. coli were isolated from patients, the hospital outlets, the inlet of the WWTP, and the residential area, respectively. GEN(R)E. coli were more prevalent in waste water from the hospital and the WWTP than in waste water from the residential area. PFGE profiling revealed no spread of specific patient isolates to the waste water. The aac(3)-II gene was detected both in patient and waste water isolates. Furthermore horizontal transfer of the aac(3)-II gene of patient origin to a recipient was shown in vitro, indicating a potential spread of the gene from patient isolates to waste water isolates. Regardless of origin, most isolates exhibited multi-resistance and contained several virulence genes. In conclusion, our study showed a possible spread of aac(3)-II from the hospital to the waste water. Most of the GEN(R)E. coli isolates from both patients and waste water had a multi-resistant phenotype and contained virulence genes and should therefore be considered reservoirs of antimicrobial resistance and virulence genes. 相似文献
103.
Gravity orientation in social wasp comb cells (Vespinae) and the possible role of embedded minerals 总被引:1,自引:0,他引:1
Ishay JS Barkay Z Eliaz N Plotkin M Volynchik S Bergman DJ 《Die Naturwissenschaften》2008,95(4):333-342
Social wasps and hornets maintain their nest in the dark. The building of the combs by all Vespinae is always in the direction of the gravitational force of Earth, and in each cell's ceiling, at least one 'keystone' is embedded and fastened by saliva. The sensory mechanisms that enable both building of sizeable symmetrical combs and nursing of the brood in the darkness merit investigation, and the aim of the present study was to identify and characterize the 'keystones' that exist in the ceiling and in the walls of the social wasp comb cells. Bio-ferrography was used to isolate magnetic particles on slides. These slides, as well as original cells, were analyzed in an environmental scanning electron microscope by a variety of analytical tools. It was found that both the roof and the walls of each comb cell bear minerals, like ferrites, as well as Ti and Zr. The latter two elements are less abundant in the soil around the nest. Ti and Zr are known to reflect infrared (IR) light. IR imaging showed a thermoregulatory center in the dorsal thorax of the adult Oriental hornet. It is not known yet whether these insects can sense IR light. 相似文献
104.
Plotkin M Hod I Zaban A Boden SA Bagnall DM Galushko D Bergman DJ 《Die Naturwissenschaften》2010,97(12):1067-1076
The Oriental hornet worker correlates its digging activity with solar insolation. Solar radiation passes through the epicuticle,
which exhibits a grating-like structure, and continues to pass through layers of the exo-endocuticle until it is absorbed by the pigment melanin in the brown-colored cuticle or xanthopterin in the yellow-colored
cuticle. The correlation between digging activity and the ability of the cuticle to absorb part of the solar radiation implies
that the Oriental hornet may harvest parts of the solar radiation. In this study, we explore this intriguing possibility by
analyzing the biophysical properties of the cuticle. We use rigorous coupled wave analysis simulations to show that the cuticle
surfaces are structured to reduced reflectance and act as diffraction gratings to trap light and increase the amount absorbed
in the cuticle. A dye-sensitized solar cell (DSSC) was constructed in order to show the ability of xanthopterin to serve as
a light-harvesting molecule. 相似文献
105.
Global assessment of the non-equilibrium concept in rangelands 总被引:2,自引:0,他引:2
The non-equilibrium concept of rangeland dynamics predicts that the potential for grazing-induced degradation is low in rangelands with relatively variable precipitation. To date, evidence in support of the non-equilibrium concept has been inconsistent. Using a standardized protocol, including a newly developed global map of rainfall variability, we reviewed the incidence of degradation in relation to rainfall variability across 58 published studies. We distinguished between (1) zonal degradation (i.e., degradation independent of water and key resources), (2) degradation in the presence of key resources, and (3) degradation in the presence of water. For studies not affected by proximity to permanent water or key resources, we found strong support for the non-equilibrium concept for rangelands. Zonal degradation was absent at CV (coefficient of variation) values above 33%, which has been proposed as a critical threshold. Grazing degradation was almost entirely restricted to areas with relatively stable annual precipitation as expressed by a low CV, or to rangelands with key resources or water points nearby. To better understand rangeland dynamics, we recommend that future studies use globally comparable measures of degradation and rainfall variability. Our work underlines that rangelands with relatively stable rainfall patterns, and those with access to water or key resources, are potentially vulnerable to degradation. Grazing management in such areas should incorporate strategic rest periods. Such rest periods effectively mimic natural fluctuations in herbivore populations, which are a defining characteristic of non-degraded rangelands occurring under highly variable precipitation regimes. 相似文献
106.
Contemporary efforts to protect biological diversity recognize the importance of sustaining traditional human livelihoods, particularly uses of the land that are compatible with intact landscapes and ecologically complete food webs. However, these efforts often confront conflicting goals. For example, conserving native predators may harm pastoralist economies because predators consume domestic livestock that sustain people. This potential conflict must be reconciled by policy, but such reconciliation requires a firm understanding of the effects of predators on the prey used by people. We used a long-term, large-scale database and Bayesian models to estimate the impacts of lynx (Lynx lynx), wolverine (Gulo gulo), and brown bear (Ursus arctos) on harvest of semi-domesticated reindeer (Rangifer tarandus) by Sami pastoralists in Sweden. The average annual harvest of reindeer averaged 25% of the population (95% credible interval = 19, 31). Annual harvest declined by 96.6 (31, 155) reindeer for each lynx family group (the surveyed segment of the lynx population) in a management unit and by 94.3 (20, 160) for each wolverine reproduction (the surveyed segment of the wolverine population). We failed to detect effects of predation by brown bear. The mechanism for effects of predation on harvest was reduced population growth rate. The rate of increase of reindeer populations declined with increasing abundance of lynx and wolverine. The density of reindeer, latitude, and weather indexed by the North Atlantic Oscillation also influenced reindeer population growth rate. We conclude that there is a biological basis for compensating the Sámi reindeer herders for predation on reindeer. 相似文献
107.
Illegal, unreported, and unregulated (IUU) fishing is prevalent globally and has detrimental effects on commercial fish stocks and nontarget species. Effective monitoring and enforcement aimed at reducing the level of IUU fishing in extensive, remote ocean fisheries requires international collaboration. Changes in trade and vessel activities further complicate enforcement. We used a web-based survey of governmental and nongovernmental organizations engaged in reducing IUU fishing in the Southern Ocean to collect information on interorganizational collaborations. We used social-network analyses to examine the nature of collaborations among the identified 117 organizations engaged in reducing IUU fishing. International collaboration improved the ability to control and manage harvest of commercially important toothfish (Dissostichus spp.) stocks and reduced bycatch of albatrosses (Diomedeidae) and petrels (Procellariidae) in longlines of IUU fishing vessels. The diverse group of surveyed organizations cooperated frequently, thereby making a wide range of resources available for improved detection of suspected IUU vessels and trade flows, cooperation aimed at prosecuting suspected offenders or developing new policy measures. Our results suggest the importance of a central agency for coordination and for maintaining commonly agreed-upon protocols for communication that facilities collaboration. Despite their differences, the surveyed organizations have developed common perceptions about key problems associated with IUU fishing. This has likely contributed to a sustained willingness to invest in collaborations. Our results show that successful international environmental governance can be accomplished through interorganizational collaborations. Such cooperation requires trust, continuous funding, and incentives for actors to participate. 相似文献
108.
Henrik Brumm 《Behavioral ecology and sociobiology》2009,63(8):1157-1165
Bird song is a sexually selected multidimensional signal. A fundamental question regarding the evolution of sexually selected
signals is what information they convey and how their honesty is maintained. Song amplitude is a performance-related signal
trait that varies considerably between individuals, but this signal dimension has been neglected in past studies. I found
that median song amplitude in male nightingales (Luscinia megarhynchos) and zebra finches (Taeniopygia guttata) did not vary significantly with body size or residual body mass. In contrast, I found a significant negative correlation
between body size (and also residual mass) and the maximum song amplitude during interactive singing in nightingales. However,
the function of these more subtle differences in song amplitude remains to be investigated. By and large, the results of this
study suggest that mean song amplitude is unlikely to indicate a bird’s body size or current condition (measured as residual
mass). 相似文献
109.
Henrik Brumm Sue Anne Zollinger Peter J. B. Slater 《Behavioral ecology and sociobiology》2009,63(9):1387-1395
Several recent studies have tested the hypothesis that song quality in adult birds may reflect early developmental conditions,
specifically nutritional stress during the nestling period. Whilst all of these earlier studies found apparent links between
early nutritional stress and song quality, their results disagree as to which aspects of song learning or production were
affected. In this study, we attempted to reconcile these apparently inconsistent results. Our study also provides the first
assessment of song amplitude in relation to early developmental stress and as a potential cue to male quality. We used an
experimental manipulation in which the seeds on which the birds were reared were mixed with husks, making them more difficult
for the parents to obtain. Compared with controls, such chicks were lighter at fledging; they were thereafter placed on a
normal diet and had caught up by 100 days. We show that nutritional stress during the first 30 days of life reduced the birds’
accuracy of song syntax learning, resulting in poorer copies of tutor songs. Our experimental manipulations did not lead to
significant changes in song amplitude, song duration or repertoire size. Thus, individual differences observed in song performance
features probably reflect differences in current condition or motivation rather than past condition. 相似文献
110.
Occurrence and risk assessment of trace metals and metalloids in sediments and benthic invertebrates from Dianshan Lake,China 总被引:1,自引:0,他引:1
Wu Yan Zhou Yihui Qiu Yanling Chen Da Zhu Zhiliang Zhao Jianfu Bergman Ǻke 《Environmental science and pollution research international》2017,24(17):14847-14856
Environmental Science and Pollution Research - The present study measured concentrations of Cr, Ni, Cu, Zn, As, Cd, Sb, and Pb in surface sediments and two benthic invertebrate species (Anodonta... 相似文献