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排序方式: 共有329条查询结果,搜索用时 843 毫秒
81.
82.
Birds may hover over or perch on flowers when feeding on nectar, and this assists cross-pollination if they then visit other plants. Here we investigate the curious sterile inflorescence axis of the South African Cape endemic 'rat's tail' plant (Babiana ringens, Iridaceae), whose function--unlike in other bird-pollinated plants--is exclusively to provide a perch for foraging birds. We find that this structure promotes the plant's mating success by causing the malachite sunbird (Nectarinia famosa), its main pollinator, to adopt a position ideal for the cross-pollination of its unusual ground-level flowers. 相似文献
83.
An SNP map of human chromosome 22 总被引:35,自引:0,他引:35
Mullikin JC Hunt SE Cole CG Mortimore BJ Rice CM Burton J Matthews LH Pavitt R Plumb RW Sims SK Ainscough RM Attwood J Bailey JM Barlow K Bruskiewich RM Butcher PN Carter NP Chen Y Clee CM Coggill PC Davies J Davies RM Dawson E Francis MD Joy AA Lamble RG Langford CF Macarthy J Mall V Moreland A Overton-Larty EK Ross MT Smith LC Steward CA Sulston JE Tinsley EJ Turney KJ Willey DL Wilson GD McMurray AA Dunham I Rogers J Bentley DR 《Nature》2000,407(6803):516-520
The human genome sequence will provide a reference for measuring DNA sequence variation in human populations. Sequence variants are responsible for the genetic component of individuality, including complex characteristics such as disease susceptibility and drug response. Most sequence variants are single nucleotide polymorphisms (SNPs), where two alternate bases occur at one position. Comparison of any two genomes reveals around 1 SNP per kilobase. A sufficiently dense map of SNPs would allow the detection of sequence variants responsible for particular characteristics on the basis that they are associated with a specific SNP allele. Here we have evaluated large-scale sequencing approaches to obtaining SNPs, and have constructed a map of 2,730 SNPs on human chromosome 22. Most of the SNPs are within 25 kilobases of a transcribed exon, and are valuable for association studies. We have scaled up the process, detecting over 65,000 SNPs in the genome as part of The SNP Consortium programme, which is on target to build a map of 1 SNP every 5 kilobases that is integrated with the human genome sequence and that is freely available in the public domain. 相似文献
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85.
Zusammenfassung Die Wirkung des Dinatrium-EDTA auf die Kreislaufreaktionen des Prostaglandin E1 (PGE1) wurde an narkotisierten Hunden untersucht. Das Ausmass der positiv chronotropen und inotropen Einflüsse des PGE1 war während der Infusion von EDTA bedeutend geringer als das des PGE1 vor der EDTA-Gabe. Die Gegenwart oder das Einströmen von Kalziumionen scheint in der pharmakologischen Wirkung des PGE1 eine Rolle zu spielen. 相似文献
86.
A map of human genome sequence variation containing 1.42 million single nucleotide polymorphisms 总被引:69,自引:0,他引:69
Sachidanandam R Weissman D Schmidt SC Kakol JM Stein LD Marth G Sherry S Mullikin JC Mortimore BJ Willey DL Hunt SE Cole CG Coggill PC Rice CM Ning Z Rogers J Bentley DR Kwok PY Mardis ER Yeh RT Schultz B Cook L Davenport R Dante M Fulton L Hillier L Waterston RH McPherson JD Gilman B Schaffner S Van Etten WJ Reich D Higgins J Daly MJ Blumenstiel B Baldwin J Stange-Thomann N Zody MC Linton L Lander ES Altshuler D;International SNP Map Working Group 《Nature》2001,409(6822):928-933
We describe a map of 1.42 million single nucleotide polymorphisms (SNPs) distributed throughout the human genome, providing an average density on available sequence of one SNP every 1.9 kilobases. These SNPs were primarily discovered by two projects: The SNP Consortium and the analysis of clone overlaps by the International Human Genome Sequencing Consortium. The map integrates all publicly available SNPs with described genes and other genomic features. We estimate that 60,000 SNPs fall within exon (coding and untranslated regions), and 85% of exons are within 5 kb of the nearest SNP. Nucleotide diversity varies greatly across the genome, in a manner broadly consistent with a standard population genetic model of human history. This high-density SNP map provides a public resource for defining haplotype variation across the genome, and should help to identify biomedically important genes for diagnosis and therapy. 相似文献
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88.
We give an overview of the main data of a publication-citation matrix. We show how impact factors are defined, and, in particular, point out the difference between the synchronous and the diachronous impact factor. The advantages and disadvantages of using both as tools in research evaluation are discussed. 相似文献
89.
原核表达载体pHsaE1αβ的构建和人丙酮酸脱氢酶的表达与纯化 总被引:1,自引:1,他引:0
以质粒pQE9为原型载体, 将编码hPDH的α和β亚基的cDNA串联克隆到该载体上,
成功地构建了hPDH基因的表达载体pHsaE1αβ. 并在大肠杆菌中表达了hPDH, 通过
亲和层析法进行纯化, 对一些生物化学性质进行表征. 相似文献
90.
Eight species previously unreported for Wyoming are listed. A range extension is noted for Erigeron humilis, and Cymopterus bipinnatus is verified as occurring in Wyoming. 相似文献