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111.
Raphaël Jeanson Jennifer H. Fewell Root Gorelick Susan M. Bertram 《Behavioral ecology and sociobiology》2007,62(2):289-298
Empirical evidence suggests that division of labor in insect societies is positively related to group size both within and
across taxa. Response threshold models (RTM) have been commonly used to analyze patterns of division of labor. However, these
models have been explored empirically and theoretically for only a limited number of tasks, and few studies have examined
predictions of the model as colony size and work availability change. We theoretically examine how group size influences division
of labor using a fixed response-threshold model. We simultaneously explore how expected by-products of increased colony size,
including demand (total work need relative to total work force available) and task number, affect this relationship. Our results
indicate that both low demand and high task number positively influence division of labor. We suggest that these changes parallel
what is observed within social groups as their size increases, and that, in part, the commonly observed increased division
of labor with increasing group size is emergent. 相似文献
112.
Simultaneous hermaphrodites are predicted to optimally divide resources between male and female function, which can result in both size-dependent mating behaviors and conflict between potential mates. Predicted strategies include size-assortative mating, conditional exchange of gametes, and mating patterns where relative size affects investment in each sexual role. This study investigated the effect of body size on the mating strategies of a hermaphroditic opisthobranch, Bulla gouldiana. Although individuals were spatially aggregated in the field with high levels of movement and size variation, there was little evidence for predictions. Laboratory experiments, however, revealed complicated effects of mass on the probability and duration of mating, as well as gender choice. Pairs were more likely to mate if they included at least one large animal, with the larger animal typically inseminating the smaller. When both individuals were large, they were more likely to each mate in both sexual roles by switching roles once. Although B. gouldiana did not usually alternate between sexual roles multiple times within mating events, paired individuals behaved similarly (neither or both mating as sperm donors) more often than expected by chance. This suggests some level of reciprocity, which is unlikely to be conditional given rates of unilateral mating. When the larger member of the mating pair inseminated the smaller, the duration of insemination increased with the size of the smaller sperm recipient. Copulations lasted longer in pairs that switched sexual roles than in those that did not switch roles. This study suggests that variation in body size can lead to size-dependent mating patterns, but only some of the patterns in B. gouldiana support theoretical predictions. We review other studies that have addressed similar issues, providing inconsistent mating patterns in sperm-storing hermaphrodites. 相似文献
113.
Oscar Vedder Arjan L. Dekker G. Henk Visser Cor Dijkstra 《Behavioral ecology and sociobiology》2005,58(4):429-436
Allocation of parental investment is predicted to be equal at the population level between both sexes of offspring, and should lead to sex ratio biases in species that exhibit a sex-difference in parental care. Sex-differences in parental care are rarely quantified. We measured daily energy expenditure in free-living nestlings of the extremely sexually size dimorphic European sparrowhawk (Accipiter nisus), using the doubly labelled water method. These data were combined with measured growth characteristics to estimate daily and total metabolised energy intake of male and female young during the nestling stage. Females reached an asymptotic body mass 1.6 times higher than males. This resulted in a total metabolised energy an estimated 1.4 times higher for the nestling stage. Furthermore, we observed a decline in daily metabolised energy with an increase in brood size, which was significantly stronger for females than for males. These results are discussed in the context of Fishers equal allocation theory. Empirical evidence of a sex ratio bias at the end of parental care, with an overall excess of males, is lacking in this species. Consequently, our data do not support the idea of equal allocation between the sexes. The observed sex difference in daily metabolised energy in response to brood size may give scope for sex ratio bias at the level of the individual brood. 相似文献
114.
A geo-referenced data set of 12 228 first-time blood lead screening values for Syracuse, NY, children was established for the 4-year period 1992–1996. Soil lead values were measured in a 600 m by 600 m tessellation grid covering the city. The two data sets were merged for evaluation of relationships between them. Strong seasonal variation in blood lead levels suggests the importance of contaminated soils as an exposure source. When the data were aggregated at a large geographic scale (3 km2), a logarithmic model showed an R2 of > 0.65 for the regression of geometric mean blood lead on median soil lead values. Results showed a striking similarity to those obtained by Mielke et al. (1999) for a study in New Orleans, LA, USA. 相似文献
115.
Alfonso Marzal Maribel Reviriego Florentino de Lope Anders Pape Møller 《Behavioral ecology and sociobiology》2007,61(10):1573-1580
Immune responses constitute a major way for hosts to defend themselves against parasites. Because hosts do not habitually
produce strong responses all the time, immune responses might be costly to produce or maintain. We tested experimentally if
the production of a response to a challenge with a novel antigen resulted in a cost in terms of fitness using the highly colonial
house martin Delichon urbica as a model system. We injected adult breeding birds during laying of the first clutch with either Newcastle disease virus
(NDV) or a control injection, and the clutch was subsequently removed to induce relaying. NDV stimulates the non-specific
immune system, causing production of antibodies during a period of more than 2 weeks. Accordingly, we found an increase in
leukocyte counts in experimental birds compared to controls. Experimental treatment reduced the frequency of re-laying, caused
a delay in timing of relaying and a reduction in brood size. Quality of nestlings in terms of body size, body mass and T-cell-mediated
immune response did not differ significantly between treatments. Overall, seasonal reproductive success differed significantly
between treatments, showing that the production of an immune response by adult birds is costly in terms of future fecundity. 相似文献
116.
JOSÉ A. DÍAZ§ JAVIER PÉREZ-TRIS† JOSÉ L. TELLERÍA ROBERTO CARBONELL‡ TOMÁS SANTOS 《Conservation biology》2005,19(5):1578-1585
Abstract: We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard ( Psammodromus algirus ) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (≤10 ha) and forests (≥ 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year. Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers. 相似文献
117.
Katja?BargumEmail author Jacobus?J.?Boomsma Liselotte?Sundstr?m 《Behavioral ecology and sociobiology》2004,57(1):9-16
The genetic basis of morphological traits in social insects remains largely unexplored. This is even true for individual body size, a key life-history trait. In the social insects, the size of reproductive individuals affects dispersal decisions, so that small size in queens is often associated with reduced dispersal, and large size with long-range dispersal and independent colony founding. Worker size is connected to division of labour when workers specialize in certain tasks according to their size. In many species, variation in worker size has been shown to increase colony performance. In this study, we present the first evidence of an additive genetic component to queen size in ants, using maternal half sib analysis. We also compared intra-colony size variation in colonies with high (queen doubly mated) versus low (queen singly mated) genetic variability. We found a high and significant heritability (h2=0.51) for queen size in one of the two study years, but not in the other. Size variation among queens was greater in colonies headed by a doubly mated queen in one of the study years, but not in the other. This indicates that genetic factors can influence queen size, but that environmental factors may override these under some circumstances. The heritability for worker size was low (h2=0.09) and non-significant. Increased genetic diversity did not increase worker size variation in the colonies. Worker size appeared largely environmentally determined, potentially allowing colonies to adjust worker size ratios to current conditions.Communicated by J. Heinze 相似文献
118.
Szabolcs Lengyel 《Behavioral ecology and sociobiology》2007,61(4):589-598
When reproductive success is constant in one breeding phase, different tactics that increase variation in reproductive success
among individuals may evolve in other phases. For instance, in shorebirds, which usually have a limited clutch size of four
eggs, variation in reproductive tactics among individuals is expected either before egg-laying (e.g. diverse mating systems)
or after hatching of the young (e.g. diverse parental care). In this paper, I studied the pied avocet (Recurvirostra avosetta), a shorebird with a modal clutch size of four eggs, to test whether post-hatch chick adoption as an alternative tactic can
be linked to increased variation in annual reproductive success. When predation was high, naturally adopting pairs produced
more filial fledglings than did pairs not adopting chicks and not losing chicks to adoption. The number of filial fledglings
increased with the number of adopted young, possibly through diluting the chances of predation on filial young. Experimental
chick addition did not lead to more fledged young due to low brood integrity as shown by the frequent loss of chicks from
some experimental broods. When predation was low, larger broods occupied feeding territories with higher prey abundance than
smaller broods, possibly due to their dominance over smaller ones. Pairs that lost chicks to adoption (donors) fledged as
many filial young in their broods as did non-adopters/non-donors, whereas the total number of donors’ filial fledglings, including
those raised in adopting broods, approached that of adopters. These findings show, for the first time, that post-hatch alternative
reproductive tactics can lead to variation in annual reproductive success and to higher success for some pairs even in species
where past adaptations limit variation in reproductive success in a certain phase of reproduction. 相似文献
119.
120.