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41.
The rapid accumulation of genomic data has led to an explosion of studies searching for signals of past selection left within DNA sequences. Yet the majority of theoretical studies investigating the traces of selection have assumed a simple form of selection, without interactions among selectively fixed sites. Fitness interactions—‘epistasis’—are commonplace, however, and take on a myriad of forms ( Whitlock et al. 1995 ; Segrèet al. 2005 ; Phillips 2008 ). It is thus important to determine how such epistasis would influence selective sweeps. On p. 5018 of this issue, Takahasi (2009) explores the effect of epistasis on genetic variation neighbouring two sites that interact in determining fitness, finding that such epistasis has a dramatic impact on the genetic variability in regions surrounding the interacting sites. 相似文献
42.
ANDREW D. B. LEAKEY ELIZABETH A. AINSWORTH STEPHANIE M. BERNARD‡ R. J. CODY MARKELZ DONALD R. ORT SARAH A. PLACELLA§ ALISTAIR ROGERS¶ MELINDA D. SMITH ERIKA A. SUDDERTH†† DAVID J. WESTON‡‡ STAN D. WULLSCHLEGER‡‡ SHENGHUA YUAN 《Global Change Biology》2009,15(5):1201-1213
The use of genomic techniques to address ecological questions is emerging as the field of genomic ecology. Experimentation under environmentally realistic conditions to investigate the molecular response of plants to meaningful changes in growth conditions and ecological interactions is the defining feature of genomic ecology. Because the impact of global change factors on plant performance are mediated by direct effects at the molecular, biochemical, and physiological scales, gene expression analysis promises important advances in understanding factors that have previously been consigned to the 'black box' of unknown mechanism. Various tools and approaches are available for assessing gene expression in model and nonmodel species as part of global change biology studies. Each approach has its own unique advantages and constraints. A first generation of genomic ecology studies in managed ecosystems and mesocosms have provided a testbed for the approach and have begun to reveal how the experimental design and data analysis of gene expression studies can be tailored for use in an ecological context. 相似文献
43.
NICOLAS PUILLANDRE MICHEL BAYLAC MARIE-CATHERINE BOISSELIER CORINNE CRUAUD SARAH SAMADI 《Biological journal of the Linnean Society. Linnean Society of London》2009,96(3):696-708
DNA sequences are currently used to propose primary hypotheses of species delimitation, especially when morphological variability is difficult to assess. In an integrative taxonomy framework, these hypotheses are then compared with other characters, such as morphology or geography, to produce robust species delimitations. For this purpose, the cytochrome oxidase subunit I (COI) gene has been sequenced for almost 50 specimens of the genus Benthomangelia , a deep-sea marine gastropod genus, collected in the South-West Pacific. Five genetic groups, displaying low and high genetic distances respectively within and between groups, were defined. COI hypotheses were compared with both the results obtained with the independent nuclear 28S gene and with an elliptic Fourier analysis of the shape of the last whorl of the shell. 28S gene analysis confirmed the same well-supported groups as COI, and elliptic Fourier analysis identified several morphological characters that vary similarly to genetic variability. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 696–708. 相似文献
44.
STEPHEN J. THACKERAY TIMOTHY H. SPARKS MORTEN FREDERIKSEN SARAH BURTHE PHILIP J. BACON JAMES R. BELL MARC S. BOTHAM TOM M. BRERETON PAUL W. BRIGHT LAURENCE CARVALHO TIM CLUTTON‐BROCK ALISTAIR DAWSON MARTIN EDWARDS J. MALCOLM ELLIOTT RICHARD HARRINGTON DAVID JOHNS IAN D. JONES JAMES T. JONES DAVID I. LEECH DAVID B. ROY W. ANDY SCOTT MATT SMITH RICHARD J. SMITHERS IAN J. WINFIELD SARAH WANLESS 《Global Change Biology》2010,16(12):3304-3313
Recent changes in the seasonal timing (phenology) of familiar biological events have been one of the most conspicuous signs of climate change. However, the lack of a standardized approach to analysing change has hampered assessment of consistency in such changes among different taxa and trophic levels and across freshwater, terrestrial and marine environments. We present a standardized assessment of 25 532 rates of phenological change for 726 UK terrestrial, freshwater and marine taxa. The majority of spring and summer events have advanced, and more rapidly than previously documented. Such consistency is indicative of shared large scale drivers. Furthermore, average rates of change have accelerated in a way that is consistent with observed warming trends. Less coherent patterns in some groups of organisms point to the agency of more local scale processes and multiple drivers. For the first time we show a broad scale signal of differential phenological change among trophic levels; across environments advances in timing were slowest for secondary consumers, thus heightening the potential risk of temporal mismatch in key trophic interactions. If current patterns and rates of phenological change are indicative of future trends, future climate warming may exacerbate trophic mismatching, further disrupting the functioning, persistence and resilience of many ecosystems and having a major impact on ecosystem services. 相似文献
45.
MORPHOLOGICAL STUDIES OF LYMNAEID SNAILS FROM THE HUMAN FASCIOLIASIS ENDEMIC ZONE OF BOLIVIA 总被引:1,自引:0,他引:1
SAMADI S.; ROUMEGOUX A.; BARGUES M. D.; MAS-COMA S.; YONG M.; POINTIER J. P. 《Journal of Molluscan Studies》2000,66(1):31-44
The taxonomic position of the Lymnaeidae from the BolivianAltiplano
has been unclear. On the basis of conchological characters,some
authors reported two species from this area, Lymnaea viatrix
andL. cubensis while others, considering also anatomical
characters,considered L. viatrix as a synonym of
L. cubensis. More recentstudies demonstrated genetic
identity between the Bolivian lymnaeidsand L. truncatula
from the Iberian Peninsula. Populations recognizedas
L. cubensis correspond to a distinct genetic group, but
geneticinformation was not available for L. viatrix. In the
light ofthese genetic results, a morphometric study of both the shell
(usingRaupian parameters) and male reproductive system was carried
outof L. cubensis from Cuba (type locality), Dominican
Republic,Guadeloupe and Venezuela, and of L. truncatula from
Bolivia,France, Portugal, Spain and Morocco. Syntypes of
L. viatrixfrom Argentina (var. A. ventricosa) and specimens
of L. viatrix(var. B. elongata) from the type locality,
Peru, were also studied(conchological characters only). The
conchological study showedthe presence of a large amount of
variability between populations.This variability was not congruent
with genetic results. Alarge amount of variability was also found
using anatomicalcharacters of the male reproductive system and all of
them clearlyseparate L. cubensis from L. truncatula
independently from geographicalorigin. Thus anatomical characters,
unlike conchological parameters,do differentiate taxonomic species
inferred from genetic studies. (Received 11 September 1997; accepted 5 March 1999) 相似文献
46.
SARAH E.A. LE V. DIT DURELL JOHN D. GOSS-CUSTARD RALPH T. CLARKE & SELWYN McGRORTY 《Ibis》2000,142(1):132-138
47.
Wingbeat frequency, temperature and body size in bees and flies 总被引:1,自引:0,他引:1
ABSTRACT. This paper describes the relationship between ambient temperature and wingbeat frequency in bees and flies of different sizes, and presents new data from insects in free fight. The slope of the relationship changes with the size of the insect, and was different for insects in hovering flight compared with individuals of the same species in forward flight. 相似文献
48.
Native upland species, Nardus stricta , Eriophorum vaginatum , Erica cinerea and Vaccinium vitis-idaea were given 3 or 60 kg N ha−1 yr−1 , over 2 yr, applied as a mist (NH4 NO3 ). The high N treatment increased above-ground biomass in all four species, but only significantly in E. cinerea , E. vaginatum and N. stricta . Biomass increases in E. vaginatum and N. stricta resulted from enhanced tiller production rather than shoot elongation. Root growth increased in N. stricta , so that root:shoot ratio in this species was unchanged by N. Root growth in E. vaginatum , E. cinerea and V. vitis-idaea did not respond to N and their root:shoot ratios decreased. Tissue N concentrations increased in both shoots and roots of all species in response to N. The accumulated foliar N did not increase the proportion of N allocated to Rubisco and the photosynthetic capacities of N. stricta , E. vaginatum and V. vitis-idaea were unchanged. Thus growth responses to N were due to altered allocation rather than increased rate of photosynthesis per unit leaf area. The high N treatment increased flower production significantly in E. cinerea but not in the other species. Although in this experiment dwarf shrubs were more responsive than graminoids to N, in the field at current N inputs the enhanced tillering of the graminoids may be more competitively advantageous, especially where gaps develop in the canopy. Thus increasing N deposition may lead to increased grassiness of upland heath, and in particular, a spread of N. stricta . 相似文献
49.
OLGA V. TSYUSKO MAUREEN B. PETERS TRACEY D. TUBERVILLE CRIS HAGEN SARAH M. EPPLEY TRAVIS C. GLENN 《Molecular ecology resources》2007,7(5):883-885
Twelve polymorphic microsatellite DNA loci were isolated from saltgrass (Distichlis spicata) and optimized for future studies of its breeding system. The loci were screened for variability among 24 individuals from two populations. The primers amplified loci with numbers of alleles ranging from four to 14 per locus and polymorphic information content from 0.481 to 0.951. Observed heterozygosity varied from 0.227 to 0.958. 相似文献
50.
SARAH E. STEWART ALAN W. OWEN 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2008,41(2):139-146
A deep‐water Konservat Lagerstätte from the lower Caradoc (Sandbian) at Girvan is dominated by the trilobite Diacanthaspis trippi, the carpoids Anatifopsis n. sp.? and a new genus of ctenocystoid together with the polyplacophoran Solenocaris solenoides and the brachiopod Onniella williamsi. Most of these are multi‐element organisms, with many specimens preserved in an articulated state in finely laminated rocks, indicating minimal disturbance and suggesting that the fauna is largely an in situ association. It contains few of the species known from other deep‐water sites of similar age at Girvan which contain diverse assemblages of trilobites and brachiopods absent from the Lagerstätte. The taphonomy of the site indicates preservation by rapid burial followed by early diagenesis under dysaerobic conditions. It provides a ‘taphonomic window’ on otherwise unknown faunas from distal shelf facies on the Ordovician Laurentian margin, and, moreover, is an important reminder of the hidden biodiversity that resided in thin‐shelled, multi‐element organisms. 相似文献