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Proliferation of direct repeats near the Oenothera chloroplast DNA origin of replication 总被引:1,自引:0,他引:1
The spacer between the 16S and 23S rRNA genes of the chloroplast DNA has
been implicated as an origin of replication in several species of plants.
In the evening primrose, Oenothera, this site was found to vary greatly in
size, with plastid genomes (plastomes) being readily distinguished. To
determine whether plastome "strength" in transmission could be correlated
with variation at oriB, the 16S rRNA-trnI spacer was sequenced from five
plastomes. The size variation was found to be due to differential
amplification (and deletion) of combinations of sequences belonging to
seven families of direct repeats. From these comparisons, one short series
of direct repeats and one region capable of forming a hairpin structure
were identified as candidates for the factor that could be responsible for
the differences between strong and weak plastome types. Ample sequence
variation allowed phylogenetic inferences to be made about the
relationships among the plastomes. Phylogenetic trees also could be
constructed for most of the families of direct repeats. The amplifications
and deletions of repeats that account for the size variation at oriB are
proposed to have occurred through extensive replication slippage at this
site.
相似文献
107.
Genetic tagging: contemporary molecular ecology 总被引:2,自引:0,他引:2
PER J. PALSBØLL 《Biological journal of the Linnean Society. Linnean Society of London》1999,68(1-2):3-22
Population genetic analyses have been highly successful in deciphering inter- and intra-specific evolutionary relationships, levels of gene flow, genetic divergence and effective population sizes. Parameters estimated by traditional population genetic analyses are evolutionary averages and thus not necessarily relevant for contemporary ecological or conservation issues. Molecular data can, however, also provide insight into contemporary patterns of divergence, population size and gene flow when a sufficient number of variable loci are analysed to focus subsequent data analyses on individuals rather than populations. Genetic tagging of individuals is an example of such individual-based approaches and recent studies have shown it to be a viable alternative to traditional tagging methods. Owing to the ubiquitous presence of hyper-variable DNA sequences in eukaryote genomes it is in principle possible to tag any eukaryote species and the required DNA can be obtained indirectly from substrates such as faeces, sloughed skin and hair. The purpose of this paper is to present the concept of genetic tagging and to further advocate the extension of individual-based genetic analyses beyond the identification of individuals to other kinds of relationships, such as parent-offspring relations, which more fully exploit the genetic nature of the data. 相似文献
108.
Landfills determine the distribution of an expanding breeding population of the endangered Egyptian Vulture Neophron percnopterus 下载免费PDF全文
Human activities provide food resources for animals that are predictable in space and/or time. These resources, sometimes referred to as predictable anthropogenic food subsidies (PAFS), can be either the result of human‐generated waste or provided intentionally, sometimes as a conservation measure. Some PAFS, including landfills, are used by common species. However, little information exists about the effects that these feeding points have on rarer species that feed there, some of which are of conservation concern. This study focuses on the influence of PAFS and their spatial location on the distribution of territories of the endangered Egyptian Vulture Neophron percnopterus. We analysed a population in the NE Iberian Peninsula that has in recent decades expanded its range. We used both null model and linear model analyses to ascertain the effect of PAFS and other covariates on the occupancy of territories by the study species. PAFS appeared to play an important role in territory selection by Egyptian Vultures, as occupied territories were nearer landfills than expected by chance. Furthermore, the distance from PAFS (landfills and vulture feeding stations, or ‘restaurants’) played an important role in the probability of territory occupancy by Egyptian Vultures, in addition to other environmental variables such as surface areas of rocky south‐facing slopes, human settlement and the proximity of conspecifics. However, recent EU legislation aims to phase out open‐air landfills to reduce the negative environmental effects of these facilities. This could have an undesired impact on the endangered species that use these feeding points. We recommend management measures that can control abundant pest species but, in the long term, other measures as supplementary feeding should be considered to counteract the probable negative effect of the disappearance of landfills on endangered species. 相似文献
109.
Sanne L Nijhof Gijs Bleijenberg Cuno SPM Uiterwaal Jan LL Kimpen Elise M van de Putte 《BMC neurology》2011,11(1):23
Background
Chronic Fatigue Syndrome (CFS) is increasingly recognized as a cause of disability and inactivity in adolescents in the Netherlands. CFS is characterized by unexplained fatigue lasting more than 6 months. Cognitive Behavioural Therapy (CBT) has proven to be effective. However, CBT availability for adolescents with CFS is limited and requires special therapeutic skills not always readily available. An alternative to the face-to-face CBT is FITNET, a web-based therapeutic program designed specifically for adolescents diagnosed with CFS, and their parents. This new CBT approach appeals to the modern youth, who grow up with internet as their main source of information. A web-based program offers the opportunity to lower thresholds for the acceptance and realization of healthcare. This treatment can be activated at any chosen time. The communication between patient and therapist can elapse asynchronously. If effective, this web-based program would greatly increase the therapeutic accessibility. 相似文献110.