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81.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:6,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献
82.
Thyme travels: 15N isoscapes of Thymus vulgaris L. invasion in lightly grazed pastoral communities 下载免费PDF全文
J. A. Nielsen R. D. Frew P. A. Whigham R. M. Callaway K. J. M. Dickinson 《Austral ecology》2016,41(1):28-39
Alterations to ecosystem nitrogen (N) cycling by introduced plant species may increase the invasibility of habitat providing a positive feedback for the introduced species to become invasive. Spatial patterns of foliar and soil δ15N ratios reflect variation in rates and process of N‐cycling across invaded landscapes and provide insight into N‐source uptake and utilization strategies of invasive plant species. To evaluate invasion‐associated changes in soil and foliar δ15N at different scales: regional (among different sites), local (between north‐ and south‐facing aspect at the same site), and microsite (within populations in the same community), we measured foliar and soil δ15 N, animal faeces cover (as a proxy for grazing intensity) and N2‐fixing species cover from inside to outside Thymus vulgaris L. (thyme)‐invaded lightly grazed pastoral communities in Central Otago, southern South Island, New Zealand. Mean thyme foliar δ15N were near‐zero across the invaded landscape, and did not change across the advancing edge of invasion or with aspect. There was no evidence that associations with N2‐fixing species provide a potential N source. Soil δ15N was lower inside of thyme compared to at the edge or outside of thyme and was varied between aspects at some sites. Animal faeces cover as a proxy for grazing intensity explained only 23% of this observed variation of soil δ15N. Thyme invasion may result in lowered soil δ15N reflecting alterations to N dynamics. Associated invasion‐related impacts of animal grazing may also impact soil δ15N. Further studies are required to distinguish the underlying mechanism responsible for the observed patterns of foliar and soil δ15N values across thyme‐invaded Central Otago landscapes. 相似文献
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M. S. Pollack M. I. New G. J. O'Neill L. S. Levine C. Callaway S. Pang E. Cacciari F. Mantero A. Cassio C. Scaroni G. Chiumello G. F. Rondanini L. Gargantini G. Giovannelli R. Virdis E. Bartolotta C. Migliori C. Pintor L. Tato F. Barboni B. Dupont 《Human genetics》1981,58(3):331-337
Summary HLA genotype and HLA-linked marker data for 40 unrelated patients from central Italy and 2 unrelated patients from Sardinia with congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21-OH-def) were analyzed. The results confirm that the HLA-linked 21-OH-def gene is associated with several different HLA determinants and complete HLA haplotypes, although the only determinant with significantly increased frequency was the complement C2 allele C2B. The HLA antigens B8 and DR3 were found in significantly decreased frequencies. The haplotype A3, Cw6, Bw47, BfF, DR7, which is exceptionally rare in the general population but which has been found in many other 21-OH-def patients from diverse geographical origins, was also found in one of the Italian patients. This and other HLA haplotype associations found among the Italian patients may represent mutations that have occurred on HLA haplotypes with genetic linkage disequilibrium or, alternatively, may represent mutations that have not yet had time to become randomly associated with different HLA complex determinants. The marked negative associations with B8 and DR3 could, however, result from an interaction between the gene products of the HLA complex and the 21-OH-def phenotype. 相似文献
85.
86.
Callaway R Desroy N Dubois SF Fournier J Frost M Godet L Hendrick VJ Rabaut M 《Integrative and comparative biology》2010,50(2):237-250
Dense aggregations of tube-worms can stabilize sediments and generate oases for benthic communities that are different and often more diverse and abundant than those of the surroundings. If these features are to qualify as biogenic reefs under nature-conservation legislation such as the EC Habitats Directive, a level of stability and longevity is desirable aside from physical and biological attributes. Lanice conchilega (Pallas, 1766) is widely distributed around the European coast and aggregations of this tube-dwelling polychaete are known to have a positive effect on the biodiversity of associated species in inter- and sub-tidal areas. This increases the value of L. conchilega-rich habitats for higher trophic levels such as birds and fish. However, L. conchilega is currently not recognized as a reef builder primarily due to uncertainty about the stability of their aggregations. We carried out three studies on different spatial and temporal scales to explore a number of properties relating to stability: (1) Individual aggregations of L. conchilega of ~1 m(2) were monitored for up to 1 year, (2) records of L. conchilega from a 258-ha area over a 35-year period were analyzed, (3) the recovery of a population of L. conchilega subjected to disturbances by cultivation of Manila clams (Ruditapes philippinarum) was followed over 3 years. The studies provided evidence about the longevity of L. conchilega aggregations, their resistance to disturbance, their resilience in recovering from negative impact and their large-scale persistence. The results showed that populations of L. conchilega were prone to considerable fluctuation and the stability of aggregations depended on environmental factors and on recruitment. The tube-worms proved to be susceptible to disturbance by cultivation of Manila clams but demonstrated the potential to recover from that impact. The long-term monitoring of a large L. conchilega population in the Bay of Mont Saint Michel (France) indicated that aggregations can persist over many decades with a constant, densely populated core area and an expanding and contracting more thinly populated fringe zone. The stability of aggregations of L. conchilega and the structures they form do not unequivocally fit the currently accepted definition of a reef. However, given L. conchilega's accepted reef-like potential to influence diversity and abundance in benthic communities, we suggest clarifying and expanding the definition of reefs so that species with records of significant persistence in particular areas and which otherwise meet expectations of reefs are included within the definition. 相似文献
87.
88.
Inhibitory effects of Eucalyptus globulus on understorey plant growth and species richness are greater in non‐native regions 下载免费PDF全文
Pablo I. Becerra Jane A. Catford Inderjit Morgan Luce McLeod Krikor Andonian Erik T. Aschehoug Daniel Montesinos Ragan M. Callaway 《Global Ecology and Biogeography》2018,27(1):68-76
Aim
We studied the novel weapons hypothesis in the context of the broadly distributed tree species Eucalyptus globulus. We evaluated the hypothesis that this Australian species would produce stronger inhibitory effects on species from its non‐native range than on species from its native range.Location
We worked in four countries where this species is exotic (U.S.A., Chile, India, Portugal) and one country where it is native (Australia).Time period
2009–2012.Major taxa studied
Plants.Methods
We compared species composition, richness and height of plant communities in 20 paired plots underneath E. globulus individuals and open areas in two sites within its native range and each non‐native region. We also compared effects of litter leachates of E. globulus on root growth of seedlings in species from Australia, Chile, the U.S.A. and India.Results
In all sites and countries, the plant community under E. globulus canopies had lower species richness than did the plant community in open areas. However, the reduction was much greater in the non‐native ranges: species richness declined by an average of 51% in the eight non‐native sites versus 8% in the two native Australian sites. The root growth of 15 out of 21 species from the non‐native range were highly suppressed by E. globulus litter leachates, whereas the effect of litter leachate varied from facilitation to suppression for six species native to Australia. The mean reduction in root growth for Australian plants was significantly lower than for plants from the U.S.A., Chile and India.Main conclusions
Our results show biogeographical differences in the impact of an exotic species on understorey plant communities. Consistent with the novel weapons hypothesis, our findings suggest that different adaptations of species from the native and non‐native ranges to biochemical compounds produced by an exotic species may play a role in these biogeographical differences. 相似文献89.
Jayant James Jayasundar Jeong Ho Ju Lilin He Dazhi Liu Flora Meilleur Jinkui Zhao David J. E. Callaway Zimei Bu 《The Journal of biological chemistry》2012,287(44):37119-37133
Ezrin is a member of the ezrin-radixin-moesin family (ERM) of adapter proteins that are localized at the interface between the cell membrane and the cortical actin cytoskeleton, and they regulate a variety of cellular functions. The structure representing a dormant and closed conformation of an ERM protein has previously been determined by x-ray crystallography. Here, using contrast variation small angle neutron scattering, we reveal the structural changes of the full-length ezrin upon binding to the signaling lipid phosphatidylinositol 4,5-bisphosphate (PIP2) and to F-actin. Ezrin binding to F-actin requires the simultaneous binding of ezrin to PIP2. Once bound to F-actin, the opened ezrin forms more extensive contacts with F-actin than generally depicted, suggesting a possible role of ezrin in regulating the interfacial structure and dynamics between the cell membrane and the underlying actin cytoskeleton. In addition, using gel filtration, we find that the conformational opening of ezrin in response to PIP2 binding is cooperative, but the cooperativity is disrupted by a phospho-mimic mutation S249D in the 4.1-ezrin/radixin/moesin (FERM) domain of ezrin. Using surface plasmon resonance, we show that the S249D mutation weakens the binding affinity and changes the kinetics of 4.1-ERM to PIP2 binding. The study provides the first structural view of the activated ezrin bound to PIP2 and to F-actin. 相似文献
90.