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81.
Cooper IA Gilman RT Boughman JW 《Evolution; international journal of organic evolution》2011,65(9):2553-2571
Adaptive divergence of phenotypes, such as sexual dimorphism or adaptive speciation, can result from disruptive selection via competition for limited resources. Theory indicates that speciation and sexual dimorphism can result from identical ecological conditions, but co-occurrence is unlikely because whichever evolves first should dissipate the disruptive selection necessary to drive evolution of the other. Here, we consider ecological conditions in which disruptive selection can act along multiple ecological axes. Speciation in lake populations of threespine sticklebacks (Gasterosteus aculeatus) has been attributed to disruptive selection due to competition for resources. Head shape in sticklebacks is thought to reflect adaptation to different resource acquisition strategies. We measure sexual dimorphism and species variation in head shape and body size in stickleback populations in two lakes in British Columbia, Canada. We find that sexual dimorphism in head shape is greater than interspecific differences. Using a numerical simulation model that contains two axes of ecological variation, we show that speciation and sexual dimorphism can readily co-occur when the effects of loci underlying sexually dimorphic traits are orthogonal to those underlying sexually selected traits. 相似文献
82.
Population divergence in antipredator defence and behaviour occurs rapidly and repeatedly. Genetic differences, phenotypic plasticity or parental effects may all contribute to divergence, but the relative importance of each of these mechanisms remains unknown. We exposed juveniles to parents and predators to measure how induced changes contribute to shoaling behaviour differences between two threespine stickleback species (benthics and limnetics: Gasterosteus spp). We found that limnetics increased shoaling in response to predator attacks, whereas benthics did not alter their behaviour. Care by limnetic fathers led to increased shoaling in both limnetic and benthic offspring. Shoaling helps limnetics avoid trout and avian predation; our results suggest that this adaptive behaviour is the result of a combination of paternal effects, predator-induced plasticity and genetic differences between species. These results suggest that plasticity substantially contributes to the rapid divergence in shoaling behaviour across the post-Pleistocene radiation of sticklebacks. 相似文献
83.
84.
Chun-Chi Liu Chin-Chung Lin Ker-Chau Li Wen-Shyen E Chen Jiun-Ching Chen Ming-Te Yang Pan-Chyr Yang Pei-Chun Chang Jeremy JW Chen 《BMC bioinformatics》2007,8(1):164
Background
Genome-wide identification of specific oligonucleotides (oligos) is a computationally-intensive task and is a requirement for designing microarray probes, primers, and siRNAs. An artificial neural network (ANN) is a machine learning technique that can effectively process complex and high noise data. Here, ANNs are applied to process the unique subsequence distribution for prediction of specific oligos. 相似文献85.
Skúli Skúlason Kevin J. Parsons Richard Svanbck Katja Rsnen Moira M. Ferguson Colin E. Adams Per‐Arne Amundsen Pia Bartels Colin W. Bean Janette W. Boughman Gran Englund Jhannes Gubrandsson Oliver E. Hooker Alan G. Hudson Kimmo K. Kahilainen Rune Knudsen Bjarni K. Kristjnsson Camille A‐L. Leblanc Zophonías Jnsson Gunnar
hlund Carl Smith Sigurur S. Snorrason 《Biological reviews of the Cambridge Philosophical Society》2019,94(5):1786-1808
A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well‐suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism – emphasizing eco evo devo, and identify current gaps in knowledge. 相似文献
86.
87.
Analysis of translocations observed in three different populations. I. Reciprocal translocations 总被引:1,自引:0,他引:1
S Schwartz C G Palmer P L Yu J A Boughman M M Cohen 《Cytogenetics and cell genetics》1986,42(1-2):42-52
A sample of 437 reciprocal translocations was classified into three groups according to their method of ascertainment (Group I = couples with repeated abortions; Group II = karyotypically unbalanced carriers; Group III = balanced translocation heterozygotes). Statistical analysis showed that the distributions of chromosome breaks observed in the three groups could not be accounted for by chromosome arm length alone. In couples with repeated abortions, an excess of breaks in 7p, 17p, and 22q was found, whereas in the balanced translocation heterozygotes an excess of breaks was found only in 11q. An excess of breaks was found in arms 9p, 14p, 18p, 18q, 21q, and 22q in karyotypically unbalanced probands. A significant decrease of breaks in the medial chromosome regions was accompanied by a concomitant increase in the terminal regions in all groups. The three groups demonstrated different distributions of chromosome arm involvement in the observed translocations. Balanced translocation heterozygotes had the highest frequency of large (greater than the length of 4p) translocated segments and an excess in the frequency of large-large translocations, whereas karyotypically unbalanced probands had the highest frequency of small (shorter than 21q) translocations and an excess in the frequency of small-small translocations. For each type of chromosomal imbalance observed, the balanced translocation heterozygotes demonstrated the greatest potential imbalance and the karyotypically unbalanced probands the least. 相似文献
88.
Basolateral K channels in an insect epithelium. Channel density, conductance, and block by barium 下载免费PDF全文
K channels in the basolateral membrane of insect hindgut were studied using current fluctuation analysis and microelectrodes. Locust recta were mounted in Ussing-type chambers containing Cl-free saline and cyclic AMP (cAMP). A transepithelial K current was induced by raising serosal [K] under short-circuit conditions. Adding Ba to the mucosal (luminal) side under these conditions had no effect; however, serosal Ba reversibly inhibited the short-circuit current (Isc), increased transepithelial resistance (Rt), and added a Lorentzian component to power density spectra of the Isc. A nonlinear relationship between corner frequency and serosal [Ba] was observed, which suggests that the rate constant for Ba association with basolateral channels increased as [Ba] was elevated. Microelectrode experiments revealed that the basolateral membrane hyperpolarized when Ba was added: this change in membrane potential could explain the nonlinearity of the 2 pi fc vs. [Ba] relationship if external Ba sensed about three-quarters of the basolateral membrane field. Conventional microelectrodes were used to determine the correspondence between transepithelially measured current noise and basolateral membrane conductance fluctuations, and ion-sensitive microelectrodes were used to measure intracellular K activity (acK). From the relationship between the net electrochemical potential for K across the basolateral membrane and the single channel current calculated from noise analysis, we estimate that the conductance of basolateral K channels is approximately 60 pS, and that there are approximately 180 million channels per square centimeter of tissue area. 相似文献
89.
Restriction-map variation with the yellow-achaete-scute region in five populations of Drosophila melanogaster 总被引:9,自引:0,他引:9
It has been proposed that the degree of recombination for a genomic region
will affect the level of both nucleotide heterozygosity and the density of
transposable elements. Both features of genomic diversity have been
examined in a number of recent reports for regions undergoing relatively
normal levels of recombination in Drosophila melanogaster. In this study
the genomic variation associated with yellow-achaete- scute loci located at
the tip of the X chromosome is examined by six- cutter restriction mapping.
In this region, as usual for regions adjacent to telomeres, crossing-over
is dramatically reduced, and published studies of visible mutants indicate
extremely little restriction-map variation. Eight six-cutter restriction
endonucleases were used to locate sequence variation in 14- and 16.5-kb
regions in 109 lines sampled from North America, Africa, and Europe. The
overall level of heterozygosity is estimated as 0.29%. Nine large
insertions, all presumed to be transposable elements, were observed.
Base-pair heterozygosity appears to be reduced compared with regions having
normal levels of recombination. The estimated heterozygosity is much higher
than reported in earlier studies of restriction-map variation among visible
mutations in the complex. The incidence of large insertions is not elevated
compared with that in other regions of the genome. This suggests that
asymmetric synapsis and exchange is not an important mechanism for the
elimination of transposable elements.
相似文献
90.
A questionnaire survey characterized a sample of 670 probands with retinitis pigmentosa (RP) and allied disorders. Segregation analysis provided some evidence for a small proportion of sporadic cases and for decreased segregation ratios of the dominant and recessive genotypes, which could be attributed to delayed age of onset in some cases. The overall incidence of RP was indirectly calculated to be approximately 1 in 3,700, while the incidence of autosomal recessive RP, including at least two genocopies, was estimated to be about 1 in 4,450. Family data analysis included the calculation of the likelihood that each family represented autosomal recessive, autosomal dominant, and X-linked inheritance patterns. These likelihoods were then converted to relative probabilities and summed over the sample population to yield estimates of the proportions of the three Mendelian types. This large, heterogeneous sample indicated that approximately 84% of the cases in the United States may be autosomal recessive, while about 10% are dominant and 6% X-linked recessive. 相似文献