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271.
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The treatment efficiency of wetlands depends primarily on the residence time of the polluted storm water (Walker, 1998). Because of this, increasing hydraulic residence times (HRTs) at various flow levels will increase the treatment efficiency of constructed wetlands. In this research, the effects of characteristic bottom topographic features that increase HRT were explored through the use of a two-dimensional hydrodynamic model. Based on numerical simulations of rectangular test wetlands, relationships were made between topographic features and their effects on HRT. Results from the simulations showed that creating baffled wetlands with multiple vertical-scale topography can markedly increase HRT, as is illustrated in a design example. When compared (using the hydrodynamic model) with a wetland having no bottom topography, the design example wetland increased HRT by 113% for the low-flow (142 L/sec) peak flood, and 39% for the 2-year flood event (1700 L/sec). 相似文献
274.
Andreas Stork Raphael Witte Fritz Führ 《Environmental science and pollution research international》1994,1(4):234-245
Volatilization from treated areas is a major source of pesticide residues in air, fog, and rain. This may lead to long-range
transport of pesticide residues to remote areas. Up to now most information on pesticide volatilization has come from laboratory
experiments under controlled conditions. A new system has been designed and developed to measure the volatile losses of14C-labelled chemicals after application; the method compares with agricultural practice of treating soils or plants grown in
lysimeters. Sensitive analytical methods guarantee a distinction between residues of unchanged pesticide, its metabolites
or14CO2 as a mineralization product released into the air. 相似文献
275.
Foraging strategies of the marine iguana,Amblyrhynchus cristatus 总被引:1,自引:0,他引:1
Summary Two foraging strategies were found in marine iguanas (Amblyrhynchus cristatus); (1) subtidal feeding: the animals swam out to sea and dived for algae in the subtidal zone; (2) intertidal feeding: the animals foraged around low tide in the intertidal zone on more or less exposed algae. Most marine iguanas were very consistent in their foraging strategy and so could be classified as subtidal feeders (SFs) or intertidal feeders (IFs). Feeding strategy was weight-related (Fig. 1), not sexspecific. Animals 1,200 g were IFs, animals >1,800 g SFs. Some iguanas in between followed a mixed foraging strategy. SFs foraged independently of the tides, IFs always around low tide (Figs. 2, 3). Feeding time patterns of IFs and SFs are described (Table 1). Sea motion seemed to have little effect on the foraging pattern of SFs, but strongly influenced that of IFs (Fig. 2). The smaller a marine iguana, the faster it cooled when immersed in water (Fig. 4). The difference between water temperature and core temperature of animals returning from foraging was significantly greater in IFs than SFs (Fig. 5). SFs swimming in very cold water regulated their body temperature to prevent excessive cooling. Possible costs and benefits of the two foraging strategies are discussed. Only part of a marine iguana population lives really amphibiously and only ca. 5% of a 24 h day is spent close to or in the water. All social activities, including mating, take place on land. These life history characteristics preclude those adaptations to an amphibious way of life that would at the same time reduce the iguanas' ability to be maximally active at their typical terrestrial body temperature of 35° C. 相似文献
276.
Summary Conflicts of interest within and between the sexes are important processes leading to variability in mating systems. The behavioral interactions mediating conflict are little documented. We studied pairs and harems of the snail-shell inhabiting cichlid fish Lamprologus ocellatus in the laboratory. Due to their larger size, males controlled the resource that limited breeding: snail shells. Males were able to choose among females ready to spawn. Females were only accepted if they produced a clutch within a few days of settling. When several females attempted to settle simultaneously the larger female settled first. Females were least aggressive when guarding eggs. Secondary females were more likely to settle when the primary female was guarding eggs. In established harems females continued to be aggressive against each other. The male intervened in about 80% of female aggressive interactions. Male intervention activity correlated with the frequency of aggression among the females in his harem. The male usually attacked the aggressor and chased her back to her own snail shell. When a male was removed from his harem, aggression between females increased immediately and usually the secondary female was expelled by the primary female within a few days. Time to harem break-up was shorter the more mobile the primary females' young were and did not correlate with the size difference between harem females. Male L. ocellatus interfere actively in female conflict and keep the harem together against female interests. Female conflict presumably relates to the cost of sharing male parental investment and to the potential of predation by another female's large juveniles on a female's own small juveniles.Correspondence to: F. Trillmich 相似文献
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Lactation is the most energy-intense period in the life of a female mammal. This can cause severe conflict between mother
and offspring over the duration of lactation but also between siblings over the amount of milk each pup gets from its mother.
Thus, competitive interactions between siblings are expected, and competition is likely to increase with litter size, particularly
in species where the number of offspring exceeds the number of teats. We studied sibling competition in the domestic guinea
pig (Cavia aperea f. porcellus), which has two teats, but frequently bears litters of up to five pups. By cross-fostering we created non-competition (control)
litters with two pups and competition litters with four pups and observed nursing behaviour on days 5, 10, 15 and 20 postpartum.
Pups of larger litters had lower growth rates, indicating increased competition among siblings in these litters. Pups of larger
litters had to wait longer for access to a teat and spent less time suckling than pups of smaller litters but ate more solid
food instead. Additionally, we manipulated the individual short-term need of pups by separating half of the pups of each litter
for 2 h from their mothers before observation. Within a litter, hungry pups achieved access to milk faster and spent more
time suckling than non-hungry pups. Pups competed mostly by scramble competition. Aggressive interactions occurred only in
large litters. Pups of large litters had higher cortisol levels than pups in small litters. These effects decreased with age
as pups became increasingly independent of maternal milk. Pup behaviour appears to fit better with models of scramble competition
than with those of honest signalling.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献