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排序方式: 共有47条查询结果,搜索用时 169 毫秒
1.
The bases of conflict in biological explanation 总被引:1,自引:0,他引:1
Richard C. Lewontin 《Journal of the history of biology》1969,2(1):35-45
2.
A General Method for Investigating the Equilibrium of Gene Frequency in a Population 总被引:3,自引:0,他引:3 下载免费PDF全文
Lewontin RC 《Genetics》1958,43(3):419-434
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Max Shpak John Wakeley Daniel Garrigan Richard C. Lewontin 《Evolution; international journal of organic evolution》2010,64(5):1395-1409
Many short‐lived organisms pass through several generations during favorable growing seasons, separated by inhospitable periods during which only small hibernating or estivating refugia remain. This induces pronounced seasonal fluctuations in population size and metapopulation structure. The first generations in the growing season will be characterized by small, relatively isolated demes whereas the later generations will experience larger deme sizes with more extensive gene flow. Fluctuations of this sort can induce changes in the amount of genetic variation in early season samples compared to late season samples, a classical example being the observations of seasonal variation in allelism in New England Drosophila populations by P.T. Ives. In this article, we study the properties of a structured coalescent process under seasonal fluctuations using numerical analysis of exact state equations, analytical approximations that rely on a separation of timescales between intrademic versus interdemic processes, and individual‐based simulations. We show that although an increase in genetic variation during each favorable growing season is observed, it is not as pronounced as in the empirical observations. This suggests that some of the temporal patterns of variation seen by Ives may be due to selection against deleterious lethals rather than neutral processes. 相似文献
5.
Distribution of Gene Frequency as a Test of the Theory of the Selective Neutrality of Polymorphisms 总被引:44,自引:10,他引:34 下载免费PDF全文
The variation in gene frequency among populations or between generations within a population is a result of breeding structure and selection. But breeding structure should affect all loci and alleles in the same way. If there is significant heterogeneity between loci in their apparent inbreeding coefficients F=sp2/p(1-p), this heterogeneity may be taken as evidence for selection. We have given the statistical properties of F and shown how tests of heterogeneity can be made. Using data from human populations we have shown highly significant heterogeneity in F values for human polymorphic genes over the world, thus demonstrating that a significant fraction of human polymorphisms owe their current gene frequencies to the action of natural selection. We have also applied the method to temporal variation within a population for data on Dacus oleae and have found no significant evidence of selection. 相似文献
6.
R. C. Lewontin 《Genetics》1988,120(3):849-852
Various measures have been proposed for characterizing the statistical association that arises between alleles at different loci. Hedrick has compared these measures with the standardized measure D' proposed by Lewontin on the grounds that this latter measure is independent of allele frequency. Although D' has the same range for all allelic frequencies, in fact, D' is not "independent" of allele frequency, and no measure with that general property is possible for the multilocus association problem. The insolubility of this problem arises from the ill-defined nature of general "association." 相似文献
7.
Distinguishing the Forces Controlling Genetic Variation at the Xdh Locus in Drosophila Pseudoobscura 总被引:6,自引:4,他引:2 下载免费PDF全文
Fifty-eight isochromosomal lines sampled from two natural populations of Drosophila pseudoobscura in California and one from Bogota, Colombia, were examined using four-cutter restriction mapping. A 4.6-kb region of the xanthine dehydrogenase locus was probed and 66 of 135 restriction sites scored were polymorphic. This predicts that on average every 12th bp would be polymorphic in this region for the genes surveyed if polymorphism occurred randomly along the coding region. In addition, there were 12 insertion/deletion polymorphisms. Forty-nine distinct haplotypes were recognized in the 58 lines examined. The most common haplotype obtained a frequency of only 5%. Measures of base pair heterozygosity (0.0097) and linkage disequilibrium lead to a predicted population size in the range of 1.2-2.4 X 10(6) for the species. High levels of recombination (including gene conversion) can be inferred from the presence of all four gametic types in the data set. 相似文献
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R C Lewontin 《American journal of human genetics》1967,19(5):681-685
10.
Perspective: Evolution and detection of genetic robustness 总被引:23,自引:0,他引:23
de Visser JA Hermisson J Wagner GP Ancel Meyers L Bagheri-Chaichian H Blanchard JL Chao L Cheverud JM Elena SF Fontana W Gibson G Hansen TF Krakauer D Lewontin RC Ofria C Rice SH von Dassow G Wagner A Whitlock MC 《Evolution; international journal of organic evolution》2003,57(9):1959-1972
Abstract Robustness is the invariance of phenotypes in the face of perturbation. The robustness of phenotypes appears at various levels of biological organization, including gene expression, protein folding, metabolic flux, physiological homeostasis, development, and even organismal fitness. The mechanisms underlying robustness are diverse, ranging from thermodynamic stability at the RNA and protein level to behavior at the organismal level. Phenotypes can be robust either against heritable perturbations (e.g., mutations) or nonheritable perturbations (e.g., the weather). Here we primarily focus on the first kind of robustness–genetic robustness–and survey three growing avenues of research: (1) measuring genetic robustness in nature and in the laboratory; (2) understanding the evolution of genetic robustness; and (3) exploring the implications of genetic robustness for future evolution. 相似文献