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31.
Begging and provisioning in broods of asynchronously-hatched yellow-headed blackbird nestlings 总被引:13,自引:0,他引:13
Studies of begging have found a positive relationship between begging level and provisioning level. Studies of unequal nestlings, however, have found that small nestlings generally beg more but are fed less than their larger siblings. We manipulated the begging levels of yellow-headed blackbird (Xanthocephalus xanthocephalus) chicks to investigate how begging benefits individuals in broods of unequal siblings. Food-deprived chicks begged more and were fed more; satiated chicks begged less and were fed less. When we deprived each chick of a brood in turn, large and small chicks generally increased begging and received more provisioning. Small chicks, however, rarely received more food than their larger siblings even when they behged relatively more. Parent yellow-headed blackbirds increase provisioning to hungry begging chicks, but also allocate food based on relative offspring size. 相似文献
32.
低磷胁迫下不同水稻品种根系吸收能力差异的生理与遗传本质 总被引:13,自引:0,他引:13
在低磷(1mg L-1)和适磷水平(10mg L^-1)下,分别以混合培养方式研究了粳稻京系17(Oryza sativa ssp.japonica)(JX17)和粘稻窄叶青8号(Oryza sativa ssp.indica)(ZYQ8)对磷营养的反应。结果表明,低磷胁迫下,JX17较ZYQ8吸收更多磷素,干物重也显著增加。相反,ZYQ8则受到更强的磷胁迫,吸磷量和干物重降低,主要是因为JX17具有较高的吸磷速度,单位根长吸磷量大,即根系高亲和力磷酸盐转运蛋白表达强,最大限度地吸收可能利用的磷素,从而改善植株营养状况,同时又有较多的磷被分配到根系,使根第,根表面积和根干重相应提高,进一步增加了其在低磷胁迫条件下的竞争磷营养的优势。图3表2参17 相似文献
33.
Matthew?A.?CooperEmail author Filippo?Aureli Mewa?Singh 《Behavioral ecology and sociobiology》2004,56(3):217-227
Socioecological theory suggests that between-group competition is an important factor affecting the nature of primate social relationships. Between-group encounters in macaques may involve female resource defense, male mate defense, and male resource defense. We observed between-group encounters in two groups (a forest group and a temple group) of bonnet macaques (Macaca radiata). We observed 102 encounters in 875 h of observation of the forest group (1.40 per 12-h day) and 58 encounters in 907 h of observation of the temple group (0.77 per 12-h day). Aggressive interactions between groups occurred in 32.4% and 29.3% of encounters in the forest and temple groups, respectively. Overall, we found little support for the female resource defense hypothesis. Females in both groups rarely participated aggressively in between-group encounters. We found support for the male mate defense hypothesis. For example, males of the forest group were more aggressive during encounters in the mating season than in the non-mating season. Males were also aggressive to females from their own group immediately following encounters. We also found partial support for the male resource defense hypothesis. Encounters in the forest group occurred in a feeding context more often than expected based on time budgets. Also, males in the temple group were more often aggressive in food-related encounters than in other encounters. The findings of this study suggest that socioecological models of primate social relationships need to distinguish male and female strategies during between-group encounters and integrate the resulting functional outcomes.Communicated by T. Czeschlik 相似文献
34.
Peter D. Dijkstra Renske Hekman Rüdiger W. Schulz Ton G. G. Groothuis 《Behavioral ecology and sociobiology》2007,61(4):599-609
The nature of the costs maintaining honesty of sexual signalling in inter- and intrasexual interactions remains a contentious
issue. For carotenoid-based colour ornaments, it has been hypothesized that the honesty of the signal is enforced when carotenoid
allocation to colour expression is traded off against carotenoid availability for immunocompetence. In addition, honesty is
enforced if androgens required for colour expression are immunosuppressive. We tested whether there is a trade-off between
colour expression and immunocompetence in a lek-breeding haplochromine cichlid fish, Pundamilia nyererei, from Lake Victoria with a carotenoid-based nuptial dress. First, we showed that expression of red nuptial colouration and
social rank in a group were positively correlated. We then successfully manipulated the level of colour advertisement by socially
stimulating individually housed males with a rival male: Stimulated males developed larger areas of red nuptial colouration
and had higher levels of circulating 11-ketotestosterone (11-KT) than non-stimulated males. We subsequently tested the humoral
immune response to a novel antigen (sheep red blood cells). There was no overall significant effect of social stimulation
on antibody production, but in the stimulated males, the degree of red colouration and the antibody response were negatively
correlated. This significant interaction between colour and treatment thus shows that the negative correlation between colouration
and antibody production is dependent on the (manipulated) social environment. This study provides correlational and experimental
evidence for a trade-off between expression of a sexual trait and one component of immune function in fish. We found no evidence
for a direct effect of 11-KT on antibody production, and we discuss alternative mechanisms that could mediate the trade-off. 相似文献
35.
Akiko Matsumoto-Oda Miya Hamai Hitosige Hayaki Kazuhiko Hosaka Kevin D. Hunt Eiiti Kasuya Kenji Kawanaka John C. Mitani Hiroyuki Takasaki Yukio Takahata 《Behavioral ecology and sociobiology》2007,61(5):661-668
Although estrous synchrony has been reported in a number of mammalian species, most often among primates, methodological and
analytical problems make it difficult to interpret these results. We developed a novel estrous synchrony index and employed
a randomization procedure to analyze long-term observations of female chimpanzee (Pan troglodytes schweinfurthii) estrous cycles at the Mahale Mountains National Park, Tanzania. Our results revealed that female chimpanzees at Mahale avoid
synchronizing their estrous periods with each other. We also found that birthrates decreased as the breeding sex ratio increased.
We suggest that estrous asynchrony decreases female–female competition for mates. Asynchrony may also reduce the potential
for male sexual coercion by nonpreferred mating partners. 相似文献
36.
William Post 《Behavioral ecology and sociobiology》1994,35(6):401-407
Female boat-tailed grackles (Quiscalus major) nest in colonies, and apparently settle independently of male activities. Associations between colony females may be mutually beneficial (cooperative hypothesis) or females may be penalized by associating (competitive hypothesis). Contrary to predictions based on either cooperative or competitive behavior, (1) reproductive success was not related to colony size nor to internest distance; (2) intracolony nesting synchronies were the same as those of the whole population, and within colonies, there was no relationship between the timing and spacing of nearest-neighbor nests; and (3) already established females were only occasionally aggressive toward females attempting to settle near them, and their aggressive response was independent of their stage of nesting. The results suggest that females act independently of each other and do not affect each other's fitness (neutral female hypothesis). Colonies may be neutral aggregations in sites secure from ground predators. Although females benefit by co-occupying predator-free sites, advantages and disadvantages of colomality do not appear to be related to intrasexual association. 相似文献
37.
Dietmar Zinner Michael H. Schwibbe Werner Kaumanns 《Behavioral ecology and sociobiology》1994,35(3):175-183
We investigated the factors affecting conception in a captive population ofPapio hamadryas. We collected data on reproductive states from 16 females over 12 years. Probability of conception was related to the outcome of the immediately preceding pregnancy and the fate of the preceding offspring. After abortions or when an infant survived more than 6 months, a female needed more cycles to conceive than when an infant died within the first 6 months post partum. The degree of estrus synchrony within, but not between, one-male units influenced the probability of conception. Females experiencing conceptive estrus showed less synchrony than those experiencing nonconceptive estrus. The number of females simultaneously in estrus within a one-male unit was negatively correlated with the probability of conception. Within our captive population, group size and male and female age had no influence on the probability of conception. The results indicate that sperm may be a limited resource in the one-male reproductive units of hamadryas baboons. Female-female competition for conception may exist and should influence the demography of one-male units. 相似文献
38.
Hybridization is a widespread phenomenon in many vertebrate groups. Prezygotic isolating mechanisms, probably caused by selection against hybrids with reduced fitness, reduce the likelihood of such events. Although hybrid-reduced fitness relatively to parental species is common, hybridization can also be beneficial, and hybrids sometimes outperform the pure species type. In this study, we examined two potential processes, Hubbs’s principle and male–male competition, which could enhance hybridization in the waterfrog complex and thus explain the proportion of heterospecific pairs collected in a natural pond. Firstly, by collecting 791 frogs in the field to study pair and chorus composition, we showed that in a mixed Rana lessonae–Rana esculenta population, the scarcity of hybrid R. esculenta males did not account for the proportion of heterospecific pairs: indeed, when examining pairing composition in six different choruses, we found that hybrid males were always under-represented and that R. esculenta females were found paired with R. lessonae males. Secondly, we investigated experimentally whether or nor male–male competition mechanism could explain pair formation in waterfrogs. Our mating speed experiment highlights mechanisms that could explain heterospecific pairs in a context of promiscuous mating where scramble competition was intense. To measure the rapidity with which a male grasps a female, we placed males in a grid cage with a female, and the dynamics of pair formation was monitored. R. esculenta males showed a lower pairing success than R. lessonae males as a smaller proportion of them amplexed females, and more time was needed for them to get amplexed. Thus, a less adaptative mechanism than female mate choice may also explain the mating pattern observed in waterfrog species. 相似文献
39.
Tara R. Harris 《Behavioral ecology and sociobiology》2006,61(2):317-329
In theory, between-group contest (BGC) competition for food can greatly influence female social relationships and reproductive success in primates, but few studies have investigated whether such effects occur and, if so, under what ecological conditions. There is evidence that adult male black and white colobus monkeys (Colobus guereza, “guerezas”) defend the food their mates need against other groups, suggesting that BGC competition is important in this species. Using data on feeding, ranging, vegetation patterns, and intergroup encounters between six neighboring guereza groups, I provide evidence that the highly folivorous guerezas at Kanyawara, Kibale National Park, Uganda, engaged in BGC competition over unevenly dispersed, relatively high-quality feeding areas or “core areas”. Intergroup aggression was common, and groups’ home ranges overlapped. Groups were more likely to initiate high-level aggression if they encountered another group within or near their core area, and groups that initiated and won encounters often fed in the same areas in which losing groups had fed. Guerezas fed selectively on species with contagious (clumped) distributions and concentrated their feeding efforts in areas of the forest that contained the most food (core areas). Groups could be ranked in a linear dominance hierarchy, and group rank number was inversely related to the quantity and quality of food in groups’ core areas. This study not only provides good evidence that BGC competition occurs in primates but it also reinforces the idea that folivore food resources may be worth defending. 相似文献
40.
Sperm competition models on the evolution of sperm size assume associations with another sperm quality trait, sperm longevity. Sperm length can also provide an indication of possible mechanisms affecting motility and thus fertilization success. Despite their importance, however, detailed mechanisms of sperm competition at the gamete level are poorly understood. In simultaneously hermaphroditic land snails, sperm traits and cryptic female choice are assumed to be crucial in determining fertilization success. We examined the variation in sperm length and number among individuals from four natural populations of the land snail Arianta arbustorum, a species with multiple mating and long-term sperm storage. We also assessed variation in velocity, motility and longevity of sperm in snails from two of the four populations. Independent of shell size, sperm length differed among populations and, to a minor extent, even among individuals within populations. Mean sperm length of a snail was not correlated with the number of sperm delivered in a spermatophore. The mean sperm velocity (=VCL) did not differ between snails from two populations. However, VCL varied among snails. Percentage motility and longevity of sperm differed between snails from the two populations. No correlations were found between length, velocity, percentage motility and longevity of sperm. To conclude, individual snails differed in sperm quality, and this variation may partly explain the differential fertilization success between A. arbustorum snails. Moreover, our findings did not support the positive association between sperm length and longevity assumed by sperm competition models for internally fertilizing species. 相似文献