全文获取类型
收费全文 | 1903篇 |
免费 | 179篇 |
国内免费 | 4篇 |
专业分类
2086篇 |
出版年
2022年 | 11篇 |
2021年 | 38篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 36篇 |
2017年 | 24篇 |
2016年 | 45篇 |
2015年 | 79篇 |
2014年 | 78篇 |
2013年 | 142篇 |
2012年 | 135篇 |
2011年 | 116篇 |
2010年 | 83篇 |
2009年 | 85篇 |
2008年 | 114篇 |
2007年 | 128篇 |
2006年 | 108篇 |
2005年 | 120篇 |
2004年 | 104篇 |
2003年 | 100篇 |
2002年 | 97篇 |
2001年 | 21篇 |
2000年 | 14篇 |
1999年 | 25篇 |
1998年 | 22篇 |
1997年 | 24篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 20篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1974年 | 8篇 |
1970年 | 5篇 |
1968年 | 7篇 |
排序方式: 共有2086条查询结果,搜索用时 15 毫秒
51.
Stable transformation of papaya via microprojectile bombardment 总被引:27,自引:0,他引:27
Maureen M. M. Fitch Richard M. Manshardt Dennis Gonsalves Jerry L. Slightom John C. Sanford 《Plant cell reports》1990,9(4):189-194
Summary Stable transformation of papaya (Carica papaya L.) has been achieved following DNA delivery via high velocity microprojectiles. Three types of embryogenic tissues, including immature zygotic embryos, freshly explanted hypocotyl sections, and somatic embryos derived from both, were bombarded with tungsten particles carrying chimeric NPTII and GUS genes. All tissue types were cultured prior to and following bombardment on half-strength MS medium supplemented with 10 mg 1–1 2,4-D, 400 mg 1–1 glutamine, and 6% sucrose. Upon transfer to 2,4-D-free medium containing 150 mg 1–1 kanamycin sulfate, ten putative transgenic isolates produced somatic embryos and five regenerated leafy shoots. Leafy shoots were produced six to nine months following bombardment. Tissues from 13 of these isolates were assayed for NPTII activity, and 10 were positive. Six out of 15 isolates assayed for GUS expression were positive. Three isolates were positive for both NPTII and GUS,Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- GUS
-glucuronidase
- X-gluc
5-Br-4-Cl-3-indolyl--D-glucuronic acid
- CaMV
cauliflower mosaic virus
- NOS
nopaline synthase
- NPTII
neomycin phosphotransferase II
Journal Series no. 3448 of the Hawaii Institute of Tropical Agriculture and Human Resources 相似文献
52.
A. Justin Nowakowski James I. Watling Michelle E. Thompson George A. Brusch IV Alessandro Catenazzi Steven M. Whitfield David J. Kurz Ángela Suárez‐Mayorga Andrés Aponte‐Gutiérrez Maureen A. Donnelly Brian D. Todd 《Ecology letters》2018,21(3):345-355
Human activities often replace native forests with warmer, modified habitats that represent novel thermal environments for biodiversity. Reducing biodiversity loss hinges upon identifying which species are most sensitive to the environmental conditions that result from habitat modification. Drawing on case studies and a meta‐analysis, we examined whether observed and modelled thermal traits, including heat tolerances, variation in body temperatures, and evaporative water loss, explained variation in sensitivity of ectotherms to habitat modification. Low heat tolerances of lizards and amphibians and high evaporative water loss of amphibians were associated with increased sensitivity to habitat modification, often explaining more variation than non‐thermal traits. Heat tolerances alone explained 24–66% (mean = 38%) of the variation in species responses, and these trends were largely consistent across geographic locations and spatial scales. As habitat modification alters local microclimates, the thermal biology of species will likely play a key role in the reassembly of terrestrial communities. 相似文献
53.
Elham Sadeqzadeh Charles E. de Bock Maureen R. O’Donnell Anna Timofeeva Gordon F. Burns Rick F. Thorne 《FEBS letters》2014
The interaction between the Drosophila cadherins fat and dachsous is regulated by phosphorylation of their respective ectodomains, a process catalysed by the atypical kinase four-jointed. Given that many signalling functions are conserved between Drosophila and vertebrate Fat cadherins, we sought to determine whether ectodomain phosphorylation is conserved in FAT1 cadherin, and also whether FJX1, the vertebrate orthologue of four-jointed, was involved in such phosphorylation events. Potential Fj consensus phosphorylation motifs were identified in FAT1 and biochemical experiments revealed the presence of phosphoserine and phosphothreonine residues in its extracellular domain. However, silencing FJX1 did not influence the levels of FAT1 ectodomain phosphorylation, indicating that other mechanisms are likely responsible. 相似文献
54.
Otsuki T Young DB Sasaki DT Pando MP Li J Manning A Hoekstra M Hoatlin ME Mercurio F Liu JM 《Journal of cellular biochemistry》2002,86(4):613-623
Fanconi anemia (FA), a genetic disorder predisposing to aplastic anemia and cancer, is characterized by hypersensitivity to DNA-damaging agents and oxidative stress. Five of the cloned FA proteins (FANCA, FANCC, FANCE, FANCF, FANCG) appear to be involved in a common functional pathway that is required for the monoubiquitination of a sixth gene product, FANCD2. Here, we report that FANCA associates with the IkappaB kinase (IKK) signalsome via interaction with IKK2. Components of the FANCA complex undergo rapid, stimulus-dependent changes in phosphorylation, which are blocked by kinase-inactive IKK2 (IKK2 K > M). When exposed to mitomycin C, cells expressing IKK2 K > M develop a cell cycle abnormality characteristic of FA. Thus, FANCA may function to recruit IKK2, thus providing the cell a means of rapidly responding to stress. 相似文献
55.
56.
Cutting edge: susceptibility to psoriatic arthritis: influence of activating killer Ig-like receptor genes in the absence of specific HLA-C alleles 总被引:21,自引:0,他引:21
Martin MP Nelson G Lee JH Pellett F Gao X Wade J Wilson MJ Trowsdale J Gladman D Carrington M 《Journal of immunology (Baltimore, Md. : 1950)》2002,169(6):2818-2822
NK cell activity is partially controlled through interactions between killer Ig-like receptors (KIR) on NK cells and their respective HLA class I ligands. Independent segregation of HLA and KIR genes, along with KIR specificity for particular HLA allotypes, raises the possibility that any given individual may express KIR molecules for which no ligand is present. Inhibitory receptor genes KIR2DL2/3 and KIR2DL1 were present in nearly all subjects sampled in this study, whereas their respective activating homologs, KIR2DS2 and KIR2DS1, are each present in about half of the subjects. In this work we report that subjects with activating KIR2DS1 and/or KIR2DS2 genes are susceptible to developing psoriatic arthritis, but only when HLA ligands for their homologous inhibitory receptors, KIR2DL1 and KIR2DL2/3, are missing. Absence of ligands for inhibitory KIRs could potentially lower the threshold for NK (and/or T) cell activation mediated through activating receptors, thereby contributing to pathogenesis of psoriatic arthritis. 相似文献
57.
Maureen L. Stanton Allison A. Snow Steven N. Handel Judith Bereczky 《Evolution; international journal of organic evolution》1989,43(2):335-346
We conducted field experiments to determine how a naturally occurring petal-color polymorphism influences mating patterns in wild radish (Raphanus raphanistrum). The polymorphism is controlled at a single genetic locus, with white petal color being completely dominant to yellow. In experimental populations with equal numbers of yellow- and white-flowered homozygous individuals, insect visitors strongly discriminated against white flowers. Pieris rapae, the most frequent pollinator, was almost 50% more likely to visit yellow than white flowers. Maternal fecundity did not differ between the morphs and was not significantly influenced by a plant's compatibility with potential donors, suggesting that seed production was not limited by receipt of compatible pollen. In contrast, the yellow-flowered morph sired approximately 75% of all seeds produced during the study. This paternity proportion was consistently greater than that expected on the basis of postpollination compatibility measures and was indistinguishable from that expected on the basis of pollinator-visitation frequency. We conclude that the male-fitness advantage of the yellow morph resulted from enhanced pollen export due to the greater attractiveness of its flowers to insect pollinators. With color morphs evenly distributed in experimental arrays, insects did not move assortatively on the basis of petal color, and we found no evidence for assortative pollen flow due to the floral polymorphism. Once postpollination compatibility relationships within populations were taken into account, paternal success of yellow donors did not differ between yellow- and white-flowered maternal plants. 相似文献
58.
Maureen Trudelle Schwarz 《Visual Anthropology: Published in cooperation with the Commission on Visual Anthropology》2013,26(2):193-195
This paper attempts to delineate a research design and method for using the photograph as a research tool. An analysis of the photograph's research suitability will consider its ability to structure “articulated visual statements” of the community and to generate “explanatory models” for analysis and interpretation. A significant aspect of the study is the material it offers for a discussion on an important methodological dimension for acquiring knowledge through visual research data. The question is not whether to use photographs as research tools, but how to fit the photograph into the research design and process. 相似文献
59.
Jane Zochling Felicity Newell Jac C Charlesworth Paul Leo Jim Stankovich Adrian Cortes Yuan Zhou Wendy Stevens Joanne Sahhar Janet Roddy Peter Nash Kathleen Tymms Maureen Rischmueller Sue Lester Susanna Proudman Matthew A Brown 《Arthritis research & therapy》2014,16(5)
Introduction
The aim of the study was to interrogate the genetic architecture and autoimmune pleiotropy of scleroderma susceptibility in the Australian population.Methods
We genotyped individuals from a well-characterized cohort of Australian scleroderma patients with the Immunochip, a custom array enriched for single nucleotide polymorphisms (SNPs) at immune loci. Controls were taken from the 1958 British Birth Cohort. After data cleaning and adjusting for population stratification the final dataset consisted of 486 cases, 4,458 controls and 146,525 SNPs. Association analyses were conducted using logistic regression in PLINK. A replication study was performed using 833 cases and 1,938 controls.Results
A total of eight loci with suggestive association (P <10-4.5) were identified, of which five showed significant association in the replication cohort (HLA-DRB1, DNASE1L3, STAT4, TNP03-IRF5 and VCAM1). The most notable findings were at the DNASE1L3 locus, previously associated with systemic lupus erythematosus, and VCAM1, a locus not previously associated with human disease. This study identified a likely functional variant influencing scleroderma susceptibility at the DNASE1L3 locus; a missense polymorphism rs35677470 in DNASE1L3, with an odds ratio of 2.35 (P = 2.3 × 10−10) in anti-centromere antibody (ACA) positive cases.Conclusions
This pilot study has confirmed previously reported scleroderma associations, revealed further genetic overlap between scleroderma and systemic lupus erythematosus, and identified a putative novel scleroderma susceptibility locus.Electronic supplementary material
The online version of this article (doi:10.1186/s13075-014-0438-8) contains supplementary material, which is available to authorized users. 相似文献60.
Methods for surveillance of fetal alcohol syndrome: The fetal alcohol syndrome surveillance network II (FASSNetII) – Arizona,Colorado, New York, 2009 ‐ 2014 下载免费PDF全文
Leslie A. O'Leary Linnette Ortiz April Montgomery Deborah J. Fox Christopher Cunniff Margaret Ruttenber April Breen Sydney Pettygrove Don Klumb Charlotte Druschel Jaime L. Frías Luther K. Robinson Jacquelyn Bertrand Kelly Ferrara Maureen Kelly Suzanne M. Gilboa F. John Meaney for the FASSNetII 《Birth defects research. Part A, Clinical and molecular teratology》2015,103(3):196-202