全文获取类型
收费全文 | 4262篇 |
免费 | 416篇 |
专业分类
4678篇 |
出版年
2022年 | 41篇 |
2021年 | 91篇 |
2020年 | 39篇 |
2019年 | 45篇 |
2018年 | 65篇 |
2017年 | 46篇 |
2016年 | 97篇 |
2015年 | 170篇 |
2014年 | 203篇 |
2013年 | 237篇 |
2012年 | 303篇 |
2011年 | 342篇 |
2010年 | 211篇 |
2009年 | 191篇 |
2008年 | 263篇 |
2007年 | 270篇 |
2006年 | 208篇 |
2005年 | 249篇 |
2004年 | 244篇 |
2003年 | 229篇 |
2002年 | 238篇 |
2001年 | 41篇 |
2000年 | 24篇 |
1999年 | 57篇 |
1998年 | 74篇 |
1997年 | 44篇 |
1996年 | 37篇 |
1995年 | 31篇 |
1994年 | 42篇 |
1993年 | 43篇 |
1992年 | 29篇 |
1991年 | 23篇 |
1990年 | 41篇 |
1989年 | 19篇 |
1988年 | 23篇 |
1987年 | 14篇 |
1986年 | 28篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1975年 | 14篇 |
1973年 | 21篇 |
1972年 | 13篇 |
1970年 | 13篇 |
排序方式: 共有4678条查询结果,搜索用时 15 毫秒
61.
62.
Bruce R. Mate Kelly A. Rossbach Sharon L. Nieukirk Randall S. Wells A. Blair Irvine Michael D. Scott Andrew J. Read 《Marine Mammal Science》1995,11(4):452-463
An adult, female bottlenose dolphin ( Tursiops trucncatus ) was radio tagged and monitored via satellite-based Argos receivers for 25 d from 28 June to 23 July 1990, in Tampa Bay, Florida. A total of 794 transmissions were obtained during 106 satellite passes. A mean of 3.9 (SE = 0.24) locations/day were determined by Service Argos and showed the animal remained in the bay, usually close to the southeastern shore. The dolphin moved at least 581 km at a minimum mean speed of 1.2 (SE = 0.1) km/h. Data from 63, 922 dives were recorded. The animal spent an average of 87.1 (SE = 0.6)% of the time submerged, with a mean dive duration of 25.8 (SE = 0.5) sec. Mean dive duration differed significantly between four periods of the day, as did the mean percent of time spent submerged. During the early morning the animal spent more time at the surface, averaged shorter dives, and was submerged less than other times of day. This is the first study to demonstrate die1 dive cycles in a bottlenose dolphin. Four months after tag loss, the dolphin was photographed with no evidence of necrosis or disfigurement of the dorsal fin. Satellite telemetry was demonstrated as an effective means of documenting the movements and dive behavior of a small inshore cetacean. 相似文献
63.
Ruben Attali Sharon Aharoni Susan Treves Ori Rokach Michal Becker Cohen Yakov Fellig Rachel Straussberg Talya Dor Muhannad Daana Stella Mitrani-Rosenbaum Yoram Nevo 《PloS one》2013,8(7)
We describe an autosomal recessive heterogeneous congenital myopathy in a large consanguineous family. The disease is characterized by variable severity, progressive course in 3 of 4 patients, myopathic face without ophthalmoplegia and proximal muscle weakness. Absence of cores was noted in all patients. Genome wide linkage analysis revealed a single locus on chromosome 19q13 with Zmax = 3.86 at θ = 0.0 and homozygosity of the polymorphic markers at this locus in patients. Direct sequencing of the main candidate gene within the candidate region, RYR1, was performed. A novel homozygous A to G nucleotide substitution (p.Y3016C) within exon 60 of the RYR1 gene was found in patients. ARMS PCR was used to screen for the mutation in all available family members and in an additional 150 healthy individuals. This procedure confirmed sequence analysis and did not reveal the A to G mutation (p.Y3016C) in 300 chromosomes from healthy individuals. Functional analysis on EBV immortalized cell lines showed no effect of the mutation on RyR1 pharmacological activation or the content of intracellular Ca2+ stores. Western blot analysis demonstrated a significant reduction of the RyR1 protein in the patient’s muscle concomitant with a reduction of the DHPRα1.1 protein. This novel mutation resulting in RyR1 protein decrease causes heterogeneous clinical presentation, including slow progression course and absence of centrally localized cores on muscle biopsy. We suggest that RYR1 related myopathy should be considered in a wide variety of clinical and pathological presentation in childhood myopathies. 相似文献
64.
The Revised Classification of Eukaryotes 总被引:1,自引:0,他引:1
Sina M. Adl Alastair G. B. Simpson Christopher E. Lane Julius Lukeš David Bass Samuel S. Bowser Matthew W. Brown Fabien Burki Micah Dunthorn Vladimir Hampl Aaron Heiss Mona Hoppenrath Enrique Lara Line le Gall Denis H. Lynn Hilary McManus Edward A. D. Mitchell Sharon E. Mozley‐Stanridge Laura W. Parfrey Jan Pawlowski Sonja Rueckert Laura Shadwick Conrad L. Schoch Alexey Smirnov Frederick W. Spiegel 《The Journal of eukaryotic microbiology》2012,59(5):429-514
This revision of the classification of eukaryotes, which updates that of Adl et al. [J. Eukaryot. Microbiol. 52 (2005) 399], retains an emphasis on the protists and incorporates changes since 2005 that have resolved nodes and branches in phylogenetic trees. Whereas the previous revision was successful in re‐introducing name stability to the classification, this revision provides a classification for lineages that were then still unresolved. The supergroups have withstood phylogenetic hypothesis testing with some modifications, but despite some progress, problematic nodes at the base of the eukaryotic tree still remain to be statistically resolved. Looking forward, subsequent transformations to our understanding of the diversity of life will be from the discovery of novel lineages in previously under‐sampled areas and from environmental genomic information. 相似文献
65.
66.
Claudia Geue Olivia Wu Yiqiao Xin Robert Heggie Sharon Hutchinson Natasha K. Martin Elisabeth Fenwick David Goldberg Consortium ECDC 《PloS one》2015,10(12)
Introduction
Studies evaluating the cost-effectiveness of screening for Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) are generally heterogeneous in terms of risk groups, settings, screening intervention, outcomes and the economic modelling framework. It is therefore difficult to compare cost-effectiveness results between studies. This systematic review aims to summarise and critically assess existing economic models for HBV and HCV in order to identify the main methodological differences in modelling approaches.Methods
A structured search strategy was developed and a systematic review carried out. A critical assessment of the decision-analytic models was carried out according to the guidelines and framework developed for assessment of decision-analytic models in Health Technology Assessment of health care interventions.Results
The overall approach to analysing the cost-effectiveness of screening strategies was found to be broadly consistent for HBV and HCV. However, modelling parameters and related structure differed between models, producing different results. More recent publications performed better against a performance matrix, evaluating model components and methodology.Conclusion
When assessing screening strategies for HBV and HCV infection, the focus should be on more recent studies, which applied the latest treatment regimes, test methods and had better and more complete data on which to base their models. In addition to parameter selection and associated assumptions, careful consideration of dynamic versus static modelling is recommended. Future research may want to focus on these methodological issues. In addition, the ability to evaluate screening strategies for multiple infectious diseases, (HCV and HIV at the same time) might prove important for decision makers. 相似文献67.
Break-induced loss of heterozygosity in fission yeast: dual roles for homologous recombination in promoting translocations and preventing de novo telomere addition 下载免费PDF全文
Cullen JK Hussey SP Walker C Prudden J Wee BY Davé A Findlay JS Savory AP Humphrey TC 《Molecular and cellular biology》2007,27(21):7745-7757
Loss of heterozygosity (LOH), a causal event in tumorigenesis, frequently encompasses multiple genetic loci and whole chromosome arms. However, the mechanisms leading to such extensive LOH are poorly understood. We investigated the mechanisms of DNA double-strand break (DSB)-induced extensive LOH by screening for auxotrophic marker loss approximately 25 kb distal to an HO endonuclease break site within a nonessential minichromosome in Schizosaccharomyces pombe. Extensive break-induced LOH was infrequent, resulting from large translocations through both allelic crossovers and break-induced replication. These events required the homologous recombination (HR) genes rad32(+), rad50(+), nbs1(+), rhp51(+), rad22(+), rhp55(+), rhp54(+), and mus81(+). Surprisingly, LOH was still observed in HR mutants, which resulted predominantly from de novo telomere addition at the break site. De novo telomere addition was most frequently observed in rad22Delta and rhp55Delta backgrounds, which disrupt HR following end resection. Further, levels of de novo telomere addition, while increased in ku70Delta rhp55Delta strains, were reduced in exo1Delta rhp55Delta and an rhp55Delta strain overexpressing rhp51. These findings support a model in which HR prevents de novo telomere addition at DSBs by competing for resected ends. Together, these results suggest that the mechanisms of break-induced LOH may be predicted from the functional status of the HR machinery. 相似文献
68.
Meredith B. Jones Julian N. Rosenberg Michael J. Betenbaugh Sharon S. Krag 《Biochimica et Biophysica Acta (BBA)/General Subjects》2009
N-linked protein glycosylation was originally thought to be specific to eukaryotes, but evidence of this post-translational modification has now been discovered across all domains of life: Eucarya, Bacteria, and Archaea. In all cases, the glycans are first assembled in a step-wise manner on a polyisoprenoid carrier lipid. At some stage of lipid-linked oligosaccharide synthesis, the glycan is flipped across a membrane. Subsequently, the completed glycan is transferred to specific asparagine residues on the protein of interest. Interestingly, though the N-glycosylation pathway seems to be conserved, the biosynthetic pathways of the polyisoprenoid carriers, the specific structures of the carriers, and the glycan residues added to the carriers vary widely. In this review we will elucidate how organisms in each basic domain of life synthesize the polyisoprenoids that they utilize for N-linked glycosylation and briefly discuss the subsequent modifications of the lipid to generate a lipid-linked oligosaccharide. 相似文献
69.
André-Denis G. Wright Andrew J. Williams Barbara Winder Claus T. Christophersen Sharon L. Rodgers Kellie D. Smith 《Applied microbiology》2004,70(3):1263-1270
The molecular diversity of rumen methanogens in sheep in Australia was investigated by using individual 16S rRNA gene libraries prepared from the rumen contents obtained from six merino sheep grazing pasture (326 clones), six sheep fed an oaten hay-based diet (275 clones), and five sheep fed a lucerne hay-based diet (132 clones). A total of 733 clones were examined, and the analysis revealed 65 phylotypes whose sequences (1,260 bp) were similar to those of cultivated methanogens belonging to the order Methanobacteriales. Pasture-grazed sheep had more methanogen diversity than sheep fed either the oaten hay or lucerne hay diet. Methanobrevibacter strains SM9, M6, and NT7 accounted for over 90% of the total number of clones identified. M6 was more prevalent in grazing sheep, and SM9, despite being found in 16 of the 17 sheep, was more prevalent in sheep fed the lucerne-based diet. Five new species were identified. Two of these species exhibited very little sequence similarity to any cultivated methanogens and were found eight times in two of the six sheep that were grazing pasture. These unique sequences appear to represent a novel group of rumen archaea that are atypical for the rumen environment. 相似文献
70.
Audsley J Seaberg EC Sasadeusz J Matthews GV Avihingsanon A Ruxrungtham K Fairley K Finlayson R Hwang HS Littlejohn M Locarnini S Dore GJ Thio CL Lewin SR 《PloS one》2011,6(11):e26482