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101.
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Gilbert Decat Leo Deckx Guy Meynen Emmy De Graef Florence Jonlet 《International journal of occupational safety and ergonomics》2006,12(2):169-176
The spectrum and the polarization of the magnetic flux density (B-field) of 6 induction heaters and 1 arc oven were measured by means of a PMM (Italy) spectrum analyser. The spectrum analysis showed that no substantial harmonics were observed while the polarization analysis revealed that the operator's exposure was non-homogeneous within a distance of 1.5 m from the heater. When the distance was larger, the body was homogeneously exposed. In general we can state that the B-field strongly varied between heaters and that exposure exceeded the occupational reference levels recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) (1998) and European Directive 2004/40/EC in 5 of the 7 heaters. Within the framework of the Directive some protection actions should be taken. Whereas mitigation of existing/old induction ovens is difficult, the design of new induction heaters and their housing should be based, among others, on electromagnetic reducing engineering concepts. 相似文献
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Elise Huchard Alexandra Alvergne Delphine Féjan Leslie A. Knapp Guy Cowlishaw Michel Raymond 《Behavioral ecology and sociobiology》2010,64(5):769-781
In mammals, fathers are facultative caretakers, and male care is expected to evolve only if it is directed towards related
young. Yet, in several promiscuous primate societies, males seem to care for infants despite a presumably low paternity confidence.
In cercopithecines, cohesive associations (‘friendships’) between a lactating female and an adult male are frequent and provide
the female and her infant with protection against various sources of aggression, including infanticide. However, the benefits
gained by males through such relationships remain unclear, in part, because the relatedness between males and their protected
infants has rarely been examined. Moreover, little is known about the nature of the cues underlying kin discrimination by
males in societies where females mate polyandrously. In this study, we combine behavioural and genetic data from wild chacma
baboons (Papio ursinus) in Namibia to investigate (1) whether males are related to their friend’s infant and (2) whether similarity between the
major histocompatibility complex (MHC) genotype of males and infants (potentially perceived through odour phenotype) favours
the establishment of friendships. We first show that males share close genetic ties with their friend’s infants, most often
by having sired the infant. Secondly, we find that male–infant MHC (Class II–DRB) similarity, in contrast to paternity, does not predict male–infant associations. Overall, our results clarify the nature
of the evolutionary benefits gained by males in these heterosexual associations, which can be considered as true paternal
care. However, the proximate mechanisms underlying paternity recognition remain to be identified. 相似文献
108.
Social influences on body size and developmental time in the bumblebee Bombus terrestris 总被引:1,自引:0,他引:1
Hagai Shpigler Matan Tamarkin Yael Gruber Maayan Poleg Adam J. Siegel Guy Bloch 《Behavioral ecology and sociobiology》2013,67(10):1601-1612
In many social insects, including bumblebees, the division of labor between workers relates to body size, but little is known about the factors influencing larval development and final size. We confirmed and extend the evidence that in the bumblebee Bombus terrestris the adult bee body size is positively correlated with colony age. We next performed cross-fostering experiments in which eggs were switched between incipient (before worker emergence) and later stage colonies with workers. The introduced eggs developed into adults similar in size to their unrelated nestmates and not to their same-age full sisters developing in their mother colony. Detailed observations revealed that brood tending by the queen decreases, but does not cease, in young colonies with workers. We next showed that both worker number and the queen presence influenced the final size of the developing brood, but only the queen influence was mediated by shortening developmental time. In colonies separated by a queen excluder, brood developmental time was shorter in the queenright compartment. These findings suggest that differences in body size are regulated by the brood interactions with the queen and workers, and not by factors inside the eggs that could vary along with colony development. Finally, we developed a model showing that the typical increase in worker number and the decrease in brood contact with the queen can account for the typical increase in body size. Similar self-organized social regulation of brood development may contribute to the optimization of growth and reproduction in additional social insects. 相似文献
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The expansion of protected areas is a critical component of strategies to promote the continued existence of biodiversity (i.e., life at all levels of biological organization) as climate changes, but scientific, social, and economic uncertainties associated with climate change are some of the major obstacles preventing such expansion. New models of climate change and species distribution and new methods of conservation planning now make it possible to explore the uncertainties associated with climate changes and species responses. Yet few reliable estimates of the costs of expanding protected areas and methods for determining these costs exist, largely because of the many (and uncertain) determinants of these costs. We developed a cost-accounting model to estimate the range in costs of various options for expanding protected areas and to explore the variables that drive these costs. Model development was informed by an existing plan to expand protected areas in the Cape Floristic Region of South Africa to address species conservation under a scenario of climate change. The 50-year present value of total costs varied from US$260 million ($1077/ha) for an off-reserve option that involves agreements with landowners and no compensation of forgone production and associated revenue to $1020 million ($4228/ha) for an on-reserve option that involves land acquisition and protection. The costs of acquiring land or compensating landowners for forgone production and development opportunities were the major drivers of the total costs across all options because most of the area identified in the protected-area expansion plan consisted of urban and high-quality agricultural lands. Total costs were also affected by changes in protected area extent and discount rate. Model-generated outputs such as these may be useful for informing implementation strategies and the allocation of future efforts in monitoring, data collection, and model development. 相似文献
110.
Guy Beauchamp 《Behavioral ecology and sociobiology》2014,68(9):1473-1479
Animals that forage in groups can produce their own food patches or scrounge the food discoveries of their companions. Mean tactic payoffs are expected to be the same at equilibrium for phenotypically equal foragers. Scrounging is also typically viewed as a risk-averse foraging strategy that provides a more even food intake rate over time. The occurrence of scrounging and the payoffs from different foraging modes have rarely been investigated in the field. Over two field seasons, I examined patch sharing in semipalmated sandpipers (Calidris pusilla) foraging on minute food items at the surface of the substrate. Birds could find patches on their own, a producing event, or join the food patches discovered by others, a scrounging event. I found that the average search time per patch did not differ between producing and scrounging but that the average time spent exploiting a patch was reduced nearly by half when scrounging. As a result, the proportion of time spent exploiting a patch, a measure of foraging payoffs, was significantly lower when scrounging. The variance in payoffs was similar for producing and scrounging. When producing their own patches, individuals that scrounged spent the same proportion of time exploiting a patch as those that only produced. However, within the same individuals, the search time for a scrounged patch was longer than the search time for a produced patch. The results show unequal payoffs for producing and scrounging in this system and suggest that low success in finding patches elicited scrounging. 相似文献