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排序方式: 共有1075条查询结果,搜索用时 16 毫秒
41.
Joseph D. Manthey Carl H. Oliveros Michael J. Andersen Christopher E. Filardi Robert G. Moyle 《Evolution; international journal of organic evolution》2020,74(8):1788-1803
As a dispersive lineage expands its distribution across a heterogeneous landscape, it leaves behind allopatric populations with varying degrees of geographic isolation that often differentiate rapidly. In the case of oceanic islands, even narrowly separated populations often differentiate, which seems contrary to the highly dispersive nature of the founding lineage. This pattern of highly dispersive lineages differentiating across narrow sea barriers has perplexed biologists for more than a century. We used two reduced-representation genomic datasets to examine the diversification of a recent, rapid geographic radiation, the white-eyes (Aves: Zosterops) of the Solomon Islands. We incorporated methods that targeted phylogenetic structure, population structure, and explicit tests for gene flow. Both datasets showed evidence of gene flow among species, but not involving the closely spaced islands in the New Georgia Group. Instead, gene flow has occurred among the larger islands in the archipelago, including those recently connected by land bridges as well as those isolated by large expanses of deep ocean. Populations separated by shallow seas, and connected by land bridges during glacial cycles, ranged from no differentiation to both phenotypic and genomic differentiation. These complex patterns of gene flow and divergence support a model of rapid geographic radiation in which lineages differentially evolve dispersal disparity and phenotypic differences. 相似文献
42.
Interspecific pollen transfer (IPT) often leads to reproductive interference. Although character displacement of reproductive traits in plants is often considered a consequence of reproductive interference, few studies have tested whether intraspecific variation in floral morphology changes the intensity of reproductive interference among pollinator-sharing plants. We investigated whether intraspecific variation in pistil length changes the proportion of IPT (interspecific pollen transfer) in sympatric populations of Clerodendrum trichotomum and C. izuinsulare on the two islands. On Toshima Island, C. izuinsulare flowers with shorter pistils were significantly less likely to receive C. trichotomum pollen, and there was a slight tendency for longer pistiles of C. trichotomum flowers to receive less C. izuinsulare pollen, suggesting that IPT has caused character displacement in pistil length in these congeneric plants. In contrast, we did not detect any relationship between pistil length and the proportion of IPT for the two species on Niijima Island. The discrepancy between the islands may reflect differences in pollinator assemblages. 相似文献
43.
为了给黄河三角洲贝壳堤岛自然保护区维管植物资源的开发和利用提供理论依据,对黄河三角洲贝壳堤岛自然保护区植物资源进行了调查和研究,初步统计本地区维管植物共有58科、149属、228种。其中,蕨类植物3科、5属、9种;裸子植物1科、1属、1种;被子植物54科、143属、218种。从科、属、种三个层次对其植物区系进行了统计分析后得出结论:该区植物多样性贫乏;区系属的分化程度高;地理成分复杂,分布类型多样;无特有现象。 相似文献
44.
Nicolás M. Suárez Ana González Eva Betancor José J. Pestano 《Conservation Genetics》2009,10(3):581-583
The blue chaffinch, Fringilla teydea, is an endemic species of the Canary Islands. This species is formed by two subspecies: The Teneriffean blue chaffinch (F. t. teydea), and the endangered Gran Canarian blue chaffinch, (F. t. polatzeki). Here we report the isolation and characterization of nine tetranucleotide microsatellites (AAAG and AAAT) from the Gran
Canarian subspecies, using an enrichment protocol. An average of 7.8 alleles per locus and an average observed heterozygosity
of 0.773 were found (n = 28). The loci were tested for their ability to cross amplify in the Teneriffean subspecies and in the common chaffinch
(Fringilla coelebs). These microsatellites will be used to manage a captive breeding programme for the endangered Gran Canarian subspecies. 相似文献
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47.
Kevin D. Lafferty Ana E. Garcia-Vedrenne John P. McLaughlin Jasmine N. Childress Marisa F. Morse Christopher L. Jerde 《Journal of fish biology》2021,98(2):415-425
At Palmyra Atoll, the environmental DNA (eDNA) signal on tidal sand flats was associated with fish biomass density and captured 98%–100% of the expected species diversity there. Although eDNA spilled over across habitats, species associated with reef habitat contributed more eDNA to reef sites than to sand-flat sites, and species associated with sand-flat habitat contributed more eDNA to sand-flat sites than to reef sites. Tides did not disrupt the sand-flat habitat signal. At least 25 samples give a coverage >97.5% at this diverse, tropical, marine system. 相似文献
48.
Species richness and density of understory plants were investigated in eight 1 ha plots, distributed one each in undisturbed
and disturbed tropical evergreen, semi-evergreen, deciduous and littoral forests of Little Andaman island, India, which falls
under one of the eight hottest hotspots of Biodiversity in the world viz. the Indo-Burma. One hundred 1 m−2 quadrats were established in each 1 ha plot, in which all the understory plants (that include herbs, undershrubs, shrubs
and herbaceous climbers) were enumerated. The total density of understory plants was 6,812 individuals (851 ha−1) and species richness was 108 species, representing 104 genera and 50 families. Across the four forest types and eight study
plots, the species richness ranged from 10 to 39 species ha−1. All the disturbed sites harbored greater number of species than their undisturbed counterparts. Herbs dominated by species
(63%) and density (4,259 individuals). The grass Eragrostis tenella (1,860 individuals; IVI 40), the invasive climber Mikania cordata (803; IVI 20) and the shrub Anaxagorea luzonensis (481; IVI 17.5) were the most abundant species. Poaceae, Asteraceae, Acanthaceae, Orchidaceae and Euphorbiaceae constituted
the species-rich families represented by 6 species each. The species-area curves attained an asymptote at 0.8 ha level except
in sites DD and DL, indicating 1 ha plot is not sufficient to capture all the understory species in disturbed forests. The
alien weeds formed about one-fourth of the species richness (31 species; 28%) and density (1,926 individuals; 28.3%) in the
study sites, indicating the extent of weed invasion and the attention required for effective conservation of the native biodiversity
of the fragile island forest ecosystem. 相似文献
49.
Symbiotic algae (Symbiodinium sp.) in scleractinian corals are important in understanding how coral reefs will respond to global climate change. The present paper reports on the diversity of Symbiodinium sp. in 48 scleractinian coral species from 25 genera and 10 families sampled from the Xisha Islands in the South China Sea, which were identified with the use of restriction fragment length polymorphism (RFLP) of the nuclear ribosomal DNA large subunit gene (rDNA). The results showed that: (i) Symbiodinium Clade C was the dominant zooxanthellae in scleractinian corals in the Xisha Islands; (ii) Symbiodinium Clade D was found in the corals Montipora aequituberculata, Galaxea fascicularis, and Plerogyra sinuosa; and (iii) both Symbiodinium Clades C and D were found simultaneously in Montipora digitata, Psammocora contigua, and Galaxeafascicularis. A poor capacity for symbiosis polymorphism, as uncovered by RFLP, in the Xisha Islands indicates that the scleractinian corals have low adaptability to environmental changes. Further studies are needed to investigate zooxanthellae diversity using other molecular markers. 相似文献
50.
Milagros Len-Barrios María Jos Lorite Javier Donate-Correa Juan Sanjun 《Systematic and applied microbiology》2009,32(6):413-420
Eleven strains were isolated from root nodules of Lotus endemic to the Canary Islands and they belonged to the genus Ensifer, a genus never previously described as a symbiont of Lotus. According to their 16S rRNA and atpD gene sequences, two isolates represented minority genotypes that could belong to previously undescribed Ensifer species, but most of the isolates were classified within the species Ensifer meliloti. These isolates nodulated Lotus lancerottensis, Lotus corniculatus and Lotus japonicus, whereas Lotus tenuis and Lotus uliginosus were more restrictive hosts. However, effective nitrogen fixation only occurred with the endemic L. lancerottensis. The E. meliloti strains did not nodulate Medicago sativa, Medicago laciniata Glycine max or Glycine soja, but induced non-fixing nodules on Phaseolus vulgaris roots. nodC and nifH symbiotic gene phylogenies showed that the E. meliloti symbionts of Lotus markedly diverged from strains of Mesorhizobium loti, the usual symbionts of Lotus, as well as from the three biovars (bv. meliloti, bv. medicaginis, and bv. mediterranense) so far described within E. meliloti. Indeed, the nodC and nifH genes from the E. meliloti isolates from Lotus represented unique symbiotic genotypes. According to their symbiotic gene sequences and host range, the Lotus symbionts would represent a new biovar of E. meliloti for which bv. lancerottense is proposed. 相似文献