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61.
Suikkanen Sanna; Engstrom-Ost Jonna; Jokela Jouni; Sivonen Kaarina; Viitasalo Markku 《Journal of plankton research》2006,28(6):543-550
Extracts of Aphanizomenon flos-aquae and Nodularia spumigena,the two most common cyanobacteria forming recurrent blooms inthe Baltic Sea, decrease the abundance of some phytoplanktonspecies via the release of allelopathic substances. We investigatedhow cell-free filtrates of the two cyanobacteria, as well aspurified hepatotoxin nodularin, produced by N. spumigena affectedcell numbers, chlorophyll a content and 14CO2 uptake of thecryptophyte Rhodomonas sp. Both cyanobacterial filtrates significantlyretarded the growth of Rhodomonas sp., A. flos-aquae filtrateup to 46%, whereas purified nodularin showed no significanteffect on any of the growth parameters of the cryptophyte. Theseresults suggest that the allelopathic effect of N. spumigenais most probably due to metabolite(s) other than nodularin,possibly acting via the damage of the target cells. 相似文献
62.
Peltola M Kanto Oqvist C Ekman J Kosonen M Jokela S Kolari M Korhonen P Salkinoja-Salonen M 《Journal of industrial microbiology & biotechnology》2008,35(12):1651-1657
Deinococcus geothermalis has frequently been isolated from pink colored deposits of paper industry processes. Laboratory studies have shown that D. geothermalis is capable of forming on nonliving surfaces patchy biofilms that are resistant to adverse agents such as extreme pH, desiccation,
solubilising detergents and biocides. This study was done to quantitatively assess the role of D. geothermalis as a biofouler in paper industry. Colored deposits were collected from 24 European and North American paper and board machines
and the densities of the bacterial 16S rRNA genes and those of the red slime producers D. geothermalis and Meiothermus spp. were measured by QPCR (quantitative real time PCR). D. geothermalis was found at nine machines, usually from splash area deposits, but its contribution was minor, 0.001–1%, to the total bacterial
burden of 8.3 to log 10.5 log units per gram wet-weight of the deposits. When D. geothermalis was found in a measurable quantity, Meiothermus spp. also was found, often in bulk quantity (7–100% of the total bacteria). The data are in line with the properties of D. geothermalis known from laboratory biofilm studies, indicating this species is a pioneer coloniser of machine surfaces and may help other
bacteria to adhere and grown into biofilms, rather than competing with them. 相似文献
63.
The effects of genotypic differences on soil organic carbon (SOC) cycling and their interactions with forest management systems are poorly understood. This study was undertaken to examine the effects of family and family × management interactions on SOC and to evaluate the distribution of SOC across different size–density fractions in a forested Spodosol. The study site consisted of a 6-year-old loblolly pine plantation that was managed under two intensities (high and low level of fertilization and chemical understory control) and included three full-sib families (fast, medium and slow growers, designated a priori based on above ground growth). The fast growing family exhibited 59% higher C (p?=?0.04) than the slow growing family in the 2,000 to 250-μm light density fraction. The medium grower exhibited 8% higher aggregate C than the fast grower in the 250 to 150-μm medium density (p?=?0.05) and 2,000 to 250-μm heavy density (p?=?0.06) fractions. Family and management effects were detected among all three density fractions. The 2,000 to 250-μm medium density fraction contained the most C. A modified size–density fractionation and sonication procedure proved sensitive for detecting significant family and management effects in as few as 6 years. These results highlight the potential of genotypic deployment as a factor influencing C sequestration and the need to fully understand the long-term effects of genotypic differences and forest management activities on SOC pools. 相似文献
64.
Temperature-related birth sex ratio bias in historical Sami: warm years bring more sons 总被引:1,自引:0,他引:1
The birth sex ratio of vertebrates with chromosomal sex determination has been shown to respond to environmental variability, such as temperature. However, in humans the few previous studies on environmental temperature and birth sex ratios have produced mixed results. We examined whether reconstructed annual mean temperatures were associated with annual offspring sex ratio at birth in the eighteenth to nineteenth century Sami from northern Finland. We found that warm years correlated with a male-biased sex ratio, whereas a warm previous year skewed sex ratio towards females. The net effect of one degree Celsius increase in mean temperature during these 2 years corresponded to approximately 1% more sons born annually. Although the physiological and ecological mechanisms mediating these effects and their evolutionary consequences on parental fitness remain unknown, our results show that environmental temperature may affect human birth sex ratio. 相似文献
65.
Introduced predators have caused some of the largest documented impacts of non-native species. Interactions among predators can have complex effects, leading to both synergistic and antagonistic outcomes. Complex interactions with native predators could play an important role in mediating the impact of non-native predators. We explore the role of the native predator context on the effect of the introduced predatory cladoceran Bythotrephes longimanus. While post-invasion impacts have been well described, studies have largely ignored the role of native predators. We used a field mesocosm experiment to determine whether Bythotrephes’ impact on prey communities is influenced by the presence of the ubiquitous native predatory insect larvae Chaoborus. The two predators exhibited niche complementarity as no change in total zooplankton prey abundance was detected across predator treatments. Rather, copepod abundances increased with decreasing abundances of Chaoborus, while cladocerans decreased with increasing abundances of Bythotrephes. Thus, the replacement of Chaoborus with Bythotrephes led to changes in the overall community structure of the zooplankton prey, but had little effect on prey total abundance. More interestingly, we found evidence of biotic resistance of impact, that is, the impact of Bythotrephes on the cladoceran community was altered when the two predators co-occurred. Specifically, the predation effect of Bythotrephes was more restricted to the shallower regions of the water column in the presence of Chaoborus, leading to a reduced impact on deeper dwelling prey taxa. Overall, our results demonstrate that the native predator context is important when trying to understand the effect of non-native predators and that variation in native predator abundances and assemblages could explain variation in impact across invaded habitats. 相似文献
66.
67.
Jouni Jokela Jukka Pellinen Mirja Salkinoja-Salonen Gösta Brunow 《Applied microbiology and biotechnology》1985,23(1):38-46
Summary The ability of a mixed bacterial culture to decompose two tetrameric lignin model com-pounds as a sole source of carbon and
energy was investigated. The mixed bacterial culture con-sisted mainly of Gram negative rods. The tetram-ers contained two
types of lignin substructures, namely the most abundant β-O-4 ether structure in lignin and also the 5-5 biphenyl structure.
The tetramer (MW 638) containing two phe-nolic hydroxyls was decomposed readily; after 13 days of incubation, all intermediate
products formed were almost totally decomposed. The non-phenolic tetramer (MW 666) was decom-posed much more slowly; after
53 days of incuba-tion, 5% of the substrate was unchanged. When both tetramers were degraded simultaneously, the non-phenolic
tetramer was decomposed similarly to the phenolic tetramer.
Determination of molecular weights of cata-bolic products showed that the degradation of the non-phenolic tetramer had proceeded
at least to dimer level.
SKF 525A, inhibitor of cytochrome P-450, caused one catabolic product to accumulate in the culture medium. This indicates
involvement of cy-tochrome P-450 in the degradation pathway of the model compounds used.
We conclude that this mixed bacterial culture was able to degrade the lignin model compounds used and that free phenolic groups
seem to in-crease the biodegradability significantly. 相似文献
68.
Abstract Understanding genetic specificity in factors determining the outcome of host-parasite interactions is especially important as it contributes to parasite epidemiology, virulence, and maintenance of genetic variation. Such specificity, however, is still generally poorly understood. We examined genetic specificity in interactions among coinfecting parasites. In natural populations, individual hosts are often simultaneously infected by multiple parasite species and genotypes that interact. Such interactions could maintain genetic variation in parasite populations if they are genetically specific so that the relative fitness of parasite genotypes varies across host individuals depending on (1) the presence/absence of coinfections and/or (2) the genetic composition of the coinfecting parasite community. We tested these predictions using clones of fish eye flukes Diplostomum pseudospathaceum and Diplostomum gasterostei. We found that interactions among parasites had a strong genetic basis and that this modified genetic variation in infection success of D. pseudospathaceum between single and multiple infections as well as across multiply infected host individuals depending on the genetic identity of the coinfecting D. gasterostei. The relative magnitude of these effects, however, depended on the exposure dose, suggesting that ecological factors can modify genetic interactions between parasites. 相似文献
69.
Sultmann H; Mayer WE; Figueroa F; Tichy H; Klein J 《Molecular biology and evolution》1995,12(6):1033-1047
The recent explosive adaptive radiation of cichlids in the great lakes of
Africa has attracted the attention of both morphologists and molecular
biologists. To decipher the phylogenetic relationships among the various
taxa within the family Cichlidae is a prerequisite for answering some
fundamental questions about the nature of the speciation process. In the
present study, we used the random amplification of polymorphic DNA (RAPD)
technique to obtain sequence differences between selected cichlid species.
We then designed specific primers based on these sequences and used them to
amplify template DNA from a large number of species by the polymerase chain
reaction (PCR). We sequenced the amplified products and searched the
sequences for indels and shared substitutions. We identified a number of
such characters at three loci-- DXTU1, DXTU2, and DXTU3--and used them for
phylogenetic and cladistic analysis of the relationships among the various
cichlid groups. Our studies assign an outgroup position to Neotropical
cichlids in relation to African cichlids, provide evidence for a
sister-group relationship of tilapiines to the haplochromines, group
Cyphotilapia frontosa with the lamprologines of Lake Tanganyika, place
Astatoreochromis alluaudi to an outgroup position with respect to other
haplochromines of Lakes Victoria and Malawi, and provide additional support
for the monophyly of the remaining Lake Victoria haplochromines and the
Lake Malawi haplochromines. The described approach holds great promise for
further resolution of cichlid phylogeny.
相似文献
70.