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Cloning of the T gene required in mesoderm formation in the mouse 总被引:46,自引:0,他引:46
The murine developmental mutation T identifies an essential gene in mesoderm formation. Embryos lacking normal gene activity fail to form the notochord, the entire posterior region and the allantois, and die at about 10 days of gestation. We have isolated the T gene using a combination of molecular and genetic techniques, thus making molecular tools available to study processes underlying mesoderm formation in the mouse. 相似文献
43.
Lung cancer is the most common cancer in men in the United Kingdom and the second most common in women, accounting for between 25 and 40% of all cancer deaths. Cigarette smoking is widely accepted as the major cause of lung cancer and linear relationships have been established between the number of cigarettes smoked and lung cancer risk. Although approximately 50 carcinogenic chemicals have been identified in cigarette smoke, a causal link between specific compounds and lung cancer has yet to be made. Studies on cigarette smokers' urine, blood and placenta have provided indications of carcinogen exposure, and although the presence of covalently-bound adducts in human DNA provides evidence of exposure to carcinogens, there have been no reports of systematic studies on the levels of DNA adducts in human lung. We report here, using the 32P-post-labelling technique, that cigarette smokers have higher adduct levels than non-smokers, that there is a linear relationship between adduct levels and daily or lifetime cigarette consumption, and that people who have given up smoking for at least five years have adduct levels similar to those of non-smokers. 相似文献
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Evolutionary nucleotide replacements in DNA. 总被引:18,自引:0,他引:18
With the increasing availability of analytical information on mRNA molecules, it is now possible to compare homologous nucleotide sequences from different organisms and to draw conclusions about their evolution. Such comparisons have shown that silent changes in codons occur more frequently than nucleotide replacements that produce changes in amino acid sequences (code-altering changes). Furthermore, there is an important difference between amino acid sequence comparisons and nucleotide sequence comparisons. The former show only differences in amino acid residues, but the latter show several types of differences when corresponding codons are compared. Single-base replacements may be degenerate (silent) or expressed as amino acid replacements. Two-base codon changes may be degenerate, single-base changes, or be visible as such. Three-base codon changes may be degenerate (involving serine), simulate either single-base or two-base changes or be visible as such. All nine types of change are found in comparisons of genes from the viruses phi X174 and G4. The relative numbers of these nine types as based on all possible interchanges between all 61 amino acid codons were listed by Holmquist et al. and are shown in Table 1. We discuss these results in the light of the significance of nucleotide changes in molecular evolution. 相似文献
46.
There has been growing interest in exploiting potential forecast gains from the nonlinear structure of self‐exciting threshold autoregressive (SETAR) models. Statistical tests have been proposed in the literature to help analysts check for the presence of SETAR‐type nonlinearities in observed time series. However, previous studies show that classical nonlinearity tests are not robust to additive outliers. In practice, time series outliers are not uncommonly encountered. It is important to develop a more robust test for SETAR‐type nonlinearity in time series analysis and forecasting. In this paper we propose a new robust nonlinearity test and the asymptotic null distribution of the test statistic is derived. A Monte Carlo experiment is carried out to compare the power of the proposed test with other existing tests under the influence of time series outliers. The effects of additive outliers on nonlinearity tests with misspecification of the autoregressive order are also studied. The results indicate that the proposed method is preferable to the classical tests when the observations are contaminated with outliers. Finally, we provide illustrative examples by applying the statistical tests to three real datasets. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
47.
This article outlines the methodology and results of the Department of the Environment, Transport and the Regions (DETR) 1996-based household projections for England, and its regions. It examines differences between this round of projections and the previous 1992-based round. The 1996-based projections indicate that between 1996 and 2021 a growth of 3.8 million households can be expected in England, if recent trends continue. Both the national and subnational methodology and results are covered. 相似文献
48.
Ruiz-Perez VL Ide SE Strom TM Lorenz B Wilson D Woods K King L Francomano C Freisinger P Spranger S Marino B Dallapiccola B Wright M Meitinger T Polymeropoulos MH Goodship J 《Nature genetics》2000,24(3):283-286
Ellis-van Creveld syndrome (EvC, MIM 225500) is an autosomal recessive skeletal dysplasia characterized by short limbs, short ribs, postaxial polydactyly and dysplastic nails and teeth. Congenital cardiac defects, most commonly a defect of primary atrial septation producing a common atrium, occur in 60% of affected individuals. The disease was mapped to chromosome 4p16 in nine Amish subpedigrees and single pedigrees from Mexico, Ecuador and Brazil. Weyers acrodental dysostosis (MIM 193530), an autosomal dominant disorder with a similar but milder phenotype, has been mapped in a single pedigree to an area including the EvC critical region. We have identified a new gene (EVC), encoding a 992-amino-acid protein, that is mutated in individuals with EvC. We identified a splice-donor change in an Amish pedigree and six truncating mutations and a single amino acid deletion in seven pedigrees. The heterozygous carriers of these mutations did not manifest features of EvC. We found two heterozygous missense mutations associated with a phenotype, one in a man with Weyers acrodental dysostosis and another in a father and his daughter, who both have the heart defect characteristic of EvC and polydactyly, but not short stature. We suggest that EvC and Weyers acrodental dysostosis are allelic conditions. 相似文献
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