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111.
Corrélations simples (r) et pondérées (rp)entre S. setosa (trois stades cumulés), S. minima etS. inflata (stade 1), S. bipunctata, et les quatre paramétreshydrologiques retenus. aSeuil de signification 5%. bSeuil designification 1% 相似文献
112.
113.
Leal E Sánchez E Muriach B Cerdá-Reverter JM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(1):77-86
This study was conducted to test the sensitivity to gonadal steroids of the systems regulating food intake in sea bass. Animals
were treated with silastic implants containing 17-β-estradiol or testosterone. Self-feeding was recorded for 31 days using
computerized demand feeders and unfed-pellet recovery systems. Both steroids strongly decreased self-feeding levels, feed
efficiency and specific growth rates. The linear growth of fish treated with testosterone was higher than in 17-β-estradiol
treated fish. In the second experiment, fish were treated with lower 17-β-estradiol doses and 11-keto-androstenedione, a precursor
of the main fish androgen (11-keto-testosterone). The results demonstrated a dose–response effect of estrogen and no effect
of non-aromatizable androgens on food intake or growth performance. The inhibitory effect of testosterone on food intake seems
to be mediated by its aromatization to estradiol, while linear growth promotion is mediated by the androgen per se. Data suggest
that gonadal steroids may be involved in the seasonal feeding pattern of sea bass. The results demonstrate the sensitivity
of the mechanisms regulating food intake to estrogenic compounds and point to the risk of including feed containing estrogenic
substances in fish diets as well as the risk involved in exposure to “estrogenic environments”. 相似文献
114.
J. C. Molinero V. Vukanič D. Lučić F. Ibanez P. Nival P. Licandro A. Calbet E. D. Christou N. Daly-Yahia M. L. Fernandez de Puelles M. G. Mazzocchi I. Siokou-Frangou 《Hydrobiologia》2009,617(1):41-53
The Mediterranean Sea is located in a crossroad of mid-latitude and subtropical climatic modes that enhance contrasting environmental
conditions over both latitudinal and longitudinal ranges. Here, we show that the large-scale environmental forcing is reflected
in the basin scale trends of the adult population of the calanoid copepod Centropages typicus. The species is distributed over the whole Mediterranean basin, and maximal abundances were found in the north-western basin
associated to oceanic fronts, and in the Adriatic Sea associated to shallow and semi enclosed waters. The peak of main abundances
of C. typicus correlates with the latitudinal temperature gradient and the highest seasonal abundances occurred in spring within the 14–18°C
temperature window. Such thermal cline may define the latitudinal geographic region where C. typicus seasonally dominates the >200 μm-sized spring copepod community in the Mediterranean Sea. The approach used here is generally
applicable to investigate the large-scale spatial patterns of other planktonic organisms and to identify favourable environmental
windows for population development. 相似文献
115.
Current status of macroinvertebrate methods used for assessing the quality of European marine waters: implementing the Water Framework Directive 总被引:4,自引:1,他引:3
Ephemeral ponds are doubly insular habitats in that they are discrete in time as well as in space. Predicting species richness
based on pond size has been attempted using measures of both spatial extent and habitat duration, but habitat qualities alone
only drive community composition under the species-sorting metacommunity paradigm. We tested the hypothesis that community
composition in temporary ponds is driven by species sorting due to pond duration. In order to eliminate bias due to under-sampling,
we sampled 34 pools distributed among 3 complexes in every ponding event over a period of six years, and identified every
individual for the microcrustacean taxa. Our data were consistent with most of the predictions of the species-sorting hypothesis.
There was a clear pattern of difference between ponds in species richness as well as higher species richness in years with
higher rainfall. The set of crustacean species that we found in the pools was highly significantly nested across the region,
but not necessarily within localized groups of ponds (complexes). We also found differences in community composition among
complexes. Pond depth was the best predictor of species richness when data were summarized over the whole study, but in one
year with unusually high rainfall, pond area and hydroperiod were significant but depth was not. We did find some species
in all ponds. It is likely that given their short development time, ponds do not differ in habitat quality for these few species.
These results taken together emphasize the variability inherent in ephemeral pond ecology, with detectable differences in
crustacean communities and the factors influencing them between years as well as between ponds, and at scales of meters as
well as kilometers. Although our data provide further evidence that species sorting on pond permanence is an important factor
structuring temporary pond crustacean communities, our assumption that dispersal is not limiting still needs to be tested.
相似文献
Bonnie J. RipleyEmail: |
116.
The influence of the hydraulic retention time (HRT) and organic loading rate (OLR) on the performance of the hydrolytic–acidogenic step of a two-stage anaerobic digestion process of sunflower oil cake (SuOC) were assessed. The experiments were performed in laboratory-scale completely stirred tank reactors at mesophilic (35 °C) temperature. Six OLR (ranging from 4 to 9 g VS L−1 d−1) for four HRTs (8, 10, 12 and 15 days) were tested to check the effect of each operational variable. Based on the results obtained, it can be concluded that the hydrolysis yields obtained for all HRTs and OLRs assayed were in the range of 20.5–30.1%. In addition, the acidification degree of the substrate was mainly influenced by the OLR but not by the HRTs, the highest value (83.8%) being achieved for an HRT of 10 days and an OLR of 6 g VS L−1 d−1. 相似文献
117.
118.
Borja Jiménez-Alfaro Ana Colubi Gil González-Rodríguez 《Biodiversity and Conservation》2010,19(13):3667-3684
Setting species priorities is commonly based on the assessment of multiple conservation criteria, and point-scoring methods
are broadly used for obtaining ranked species lists. However, the implications of different procedures in the performance
and application of resulting lists have been scarcely investigated. In this study, we test the effect of using distinct transformation
and summarization of criteria for computing ranked lists for species prioritization and allocation of seed collection resources.
The study is focused on the Cantabrian Range (Spain), where 127 vascular plants of conservation concern were scored according
to four criteria (threat, protection, endemicity and rarity) related to different geographical scales. Four conservation priority
indices (CPI) were computed using a combination of (a) ordinal- versus quantile-weighted transformation and (b) mean versus
factorial summarization. Quantile transformation and factorial summarization provided a more quantitative CPI. Although the
contribution of criteria to the final indices was different under quantile and ordinal transformations, the four CPI were
strongly correlated. However, slight differences between indices reflected divergences in the selection of species priorities
when low conservation funds are available, and 14 to 32% of the species composition in priority groups changed. Our results
suggest that different point-scoring procedures might have high impact on the application of priority lists for selecting
conservation targets, especially when different funding scenarios are compared. We also recommend to (1) avoid ordinal scoring
methods, (2) use unequally weighted transformations and (3) apply point-scoring methods based on multi-scale criteria for
integrating existing lists in biogeographical areas 相似文献
119.
The polar bear is the only living ursid with a fully carnivorous diet. Despite a number of well-documented craniodental adaptations for a diet of seal flesh and blubber, molecular and paleontological data indicate that this morphologically distinct species evolved less than a million years ago from the omnivorous brown bear. To better understand the evolution of this dietary specialization, we used phylogenetic tests to estimate the rate of morphological specialization in polar bears. We then used finite element analysis (FEA) to compare the limits of feeding performance in the polar bear skull to that of the phylogenetically and geographically close brown bear. Results indicate that extremely rapid evolution of semi-aquatic adaptations and dietary specialization in the polar bear lineage produced a cranial morphology that is weaker than that of brown bears and less suited to processing tough omnivorous or herbivorous diets. Our results suggest that continuation of current climate trends could affect polar bears by not only eliminating their primary food source, but also through competition with northward advancing, generalized brown populations for resources that they are ill-equipped to utilize. 相似文献
120.