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151.
Restriction mapping and sequencing have shown that humans have
substantially lower levels of mitochondrial genome diversity (d) than
chimpanzees. In contrast, humans have substantially higher levels of
heterozygosity (H) at protein-coding loci, suggesting a higher level of
diversity in the nuclear genome. To investigate the discrepancy further, we
sequenced a segment of the mitochondrial genome control region (CR) from 49
chimpanzees. The majority of these were from the Pan troglodytes versus
subspecies, which was underrepresented in previous studies. We also
estimated the average heterozygosity at 60 short tandem repeat (STR) loci
in both species. For a total sample of 115 chimpanzees, d = 0.075 +/0
0.037, compared to 0.020 +/- 0.011 for a sample of 1,554 humans. The
heterozygosity of human STR loci is significantly higher than that of
chimpanzees. Thus, the higher level of nuclear genome diversity relative to
mitochondrial genome diversity in humans is not restricted to
protein-coding loci. It seems that humans, not chimpanzees, have an unusual
d/H ratio, since the ratio in chimpanzees is similar to that in other
catarrhines. This discrepancy in the relative levels of nuclear and
mitochondrial genome diversity in the two species cannot be explained by
differences in mutation rate. However, it may result from a combination of
factors such as a difference in the extent of sex ratio disparity, the
greater effect of population subdivision on mitochondrial than on nuclear
genome diversity, a difference in the relative levels of male and female
migration among subpopulations, diversifying selection acting to increase
variation in the nuclear genome, and/or directional selection acting to
reduce variation in the mitochondrial genome.
相似文献
152.
Diversity in virus populations from genital secretions and peripheral blood from women recently infected with human immunodeficiency virus type 1. 总被引:6,自引:4,他引:2
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M Poss H L Martin J K Kreiss L Granville B Chohan P Nyange K Mandaliya J Overbaugh 《Journal of virology》1995,69(12):8118-8122
In order to develop a human immunodeficiency virus type 1 vaccine with global efficacy, it is important to evaluate the virus populations that are transmitted to individuals living in high-incidence areas. To determine the nature of the human immunodeficiency virus type 1 population transmitted to women during heterosexual contact, we examined the diversity of the proviral envelope gene in infected cells in both genital secretions and peripheral blood from six recently seroconverted Kenyan women. Heterogeneous virus populations were present in cervical secretions and/or peripheral blood shortly after seroconversion for five of six infected individuals, and tissue-specific variants were identified in several cases. 相似文献
153.
154.
Charles H. Pickett Ryan Rodriguez - Present address: University of California Center for Comparative Medicine Davis CA USA Jim Brown Dominique Coutinot Kim A. Hoelmer - Present address: USDA ARS BIIR S. Chapel St. Newark DE USA Ulrich Kuhlmann Henri Goulet Michael D. Schwartz Peter B. Goodell 《Biocontrol Science and Technology》2007,17(3):261-272
Lygus hesperus Knight is native to the western United States and is a perennial pest of numerous crops in California. It is responsible for triggering the early season application of insecticides on cotton, Gossypium hirsutum L., and strawberries, Fragaria L. Despite several surveys conducted in alfalfa (Medicago sativa L.) grown in central California, nymphal parasitoids associated with L. hesperus and L. elisus have not been found. Two exotic parasitoids were released into California beginning in 1998. Peristenus relictus (Ruhte), formerly P. stygicus Loan, and P. digoneutis Loan were collected from several locations in southern Europe and released at up to six locations over a 6-year period. At the original release site in Sacramento, a 0.25-ha plot of alfalfa, parasitism by P. digoneutis and P. relictus combined increased from zero to 90%, 3 years after the last releases were made. Parasitoids have been recovered from vacant fields of weedy annuals within 2 km of this site. Recoveries at more southerly release sites in central California have been poor. 相似文献
155.
156.
Some species of the genus Amanita are economically important gourmet mushrooms, while others cause dramatic poisonings or even deaths every year in China and in many other countries. A DNA barcode is a short segment or a combination of short segments of DNA sequences that can distinguish species rapidly and accurately. To establish a standard DNA barcode for poisonous species of Amanita in China, three candidate markers, the large subunit nuclear ribosomal RNA (nLSU), the internal transcribed spacer (ITS), and the translation elongation factor 1 alpha (tef1 α) were tested using the eukaryotic general primers for their feasibility as barcodes to identify seven species of lethal fungi and two species of edible ones which can easily be confused with the lethal ones known from China. In addition, A.phalloides—a European and North American species closely related to one of the seven taxa, A.subjunquillea was also included. PCR amplification and sequencing success rate, intra and inter specific variation and rate of species identification were considered as main criteria for evaluation of the candidate DNA barcodes. Although the nLSU had high PCR and sequencing success rates (100% and 100% respectively), occasional overlapping occurred between the intra and inter specific variations. The PCR amplification and sequencing success rates of ITS were 100% and 85.7% respectively. ITS showed high sequence variation among species group and low variation within a given species. There was a relatively high PCR amplification and sequencing success rate for tef1 α (85.7% and 100% respectively), and its intra and inter specific variation was higher than that of ITS or nLSU. All three candidate markers showed hight species resolution. ITS and tef1 α had a more clearly defined barcode gap than nLSU. Our study showed that the tef1 α and nLSU can be proposed as supplementary barcodes for the genus Amanita, while ITS can be used as a primary barcode marker considering that the ITS region may become a universal barcode marker for the fungal kingdom. 相似文献
157.
YU Ya-Ying- SHAO Gao-Neng- SHENG Zhong-Hua- JIANG Han-Wei- HE Ji-Wai- SUN Yuan-Yuan- CA Yi-Cong- HU Pei-Song- TANG Shao-Qing 《Plant Diversity》2015,37(6):871-880
Genetic diversity of 434 rice accessions collected from 16 countries, including 345 fragrance rice varieties and 89 non fragrance rice varieties, have been analyzed. A total of 573 alleles were detected by using 77 simple sequence repeats (SSR) primer pairs covering all rice 12 chromosomes. The value of allelic polymorphism information content (PIC) ranged from 0090 to 0845, with an average of 0516 per locus; Gene diversity (GD) varied from 0091 to 0859, with an average of 0573; The mean value of major allele frequencies (MAF) was 0540, covering from 0251 to 0953. In addition, 434 rice accessions are divided into three sub populations by cluster and population structure analysis, and FST between sub populations showed a mean of -0116, ranging from -0623 to 0494; The score of genetic distance calculated by Nei′s method appeared from 0207 to 0355. Major allele frequencies within each sub population distributed from 0408 to 0746, and gene diversity level from 0354 to 0699, while PIC from 0320 to 0658. Sequencing 6 mitochondrion genes in 18 rice varieties exhibited no different in 5 genes, whereas Mit4 contains a 3 SNPs in the gene body, which acts as an important marker to understanding the relationship between Indica/Japonica differentiation and the evolution of fragrant gene. Finally, genetic diversity and mitochondrion gene sequencing would help to know about the origin of fragrant resource and benefit rice breeding. 相似文献
158.
Gayathri Govindaraju CA. Jabeena Devadathan Valiyamangalath Sethumadhavan Nivethika Rajaram Arumugam Rajavelu 《Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms》2017,1860(10):1047-1057
In eukaryotes, cytosine methylation regulates diverse biological processes such as gene expression, development and maintenance of genomic integrity. However, cytosine methylation and its functions in pathogenic apicomplexan protozoans remain enigmatic. To address this, here we investigated the presence of cytosine methylation in the nucleic acids of the protozoan Plasmodium falciparum. Interestingly, P. falciparum has TRDMT1, a conserved homologue of DNA methyltransferase DNMT2. However, we found that TRDMT1 did not methylate DNA, in vitro. We demonstrate that TRDMT1 methylates cytosine in the endogenous aspartic acid tRNA of P. falciparum. Through RNA bisulfite sequencing, we mapped the position of 5-methyl cytosine in aspartic acid tRNA and found methylation only at C38 position. P. falciparum proteome has significantly higher aspartic acid content and a higher proportion of proteins with poly aspartic acid repeats than other apicomplexan pathogenic protozoans. Proteins with such repeats are functionally important, with significant roles in host-pathogen interactions. Therefore, TRDMT1 mediated C38 methylation of aspartic acid tRNA might play a critical role by translational regulation of important proteins and modulate the pathogenicity of the malarial parasite. 相似文献
159.
A new species,Bactris pliniana, from the Amazon region is described and illustrated. Its relationships within the Piranga group are discussed.
Studies on the Flora of the Guianas 78. 相似文献
160.
C. L. Granville Chapman 《BMJ (Clinical research ed.)》1934,1(3834):1186-1187