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91.
In plants such as the garden pea (Pisum sativum L.), it is widely thought that the auxin indole-3-acetic acid (IAA) is synthesised mainly in the immature tissues of the
apical bud and then transported basipetally to other parts of the plant. Consistent with this belief are results showing that
removal of the apical bud markedly reduces the IAA content in the stem. However, it has also been suggested that the mature
leaves may synthesise substantial amounts of IAA, which enters the basipetal transport stream after being transported to the
shoot apex in the phloem (Cambridge and Morris in Planta 99:583–588, 1996). To examine this theory, we defoliated pea plants and measured the effect on IAA content in the remaining shoot tissues.
IAA levels were reduced in the internodes, and to a lesser extent in the apical bud, after defoliation, suggesting that mature
leaves are indeed an important source of auxin for the shoot. Consistent with this idea, we have demonstrated that mature,
fully expanded leaves are capable of de novo IAA synthesis. Furthermore, we report evidence for the presence of IAA in the
phloem sap of pea. Together these results support those of Cambridge and Morris, suggesting that mature leaves are a source
of the IAA in the basipetal transport stream. 相似文献
92.
Joshua M. Shulman Lori B. Chibnik Cristin Aubin Julie A. Schneider David A. Bennett Philip L. De Jager 《PloS one》2010,5(6)
Background
Recent genetic studies have identified a growing number of loci with suggestive evidence of association with susceptibility to Alzheimer''s disease (AD). However, little is known of the role of these candidate genes in influencing intermediate phenotypes associated with a diagnosis of AD, including cognitive decline or AD neuropathologic burden.Methods/Principal Findings
Thirty-two single nucleotide polymorphisms (SNPs) previously implicated in AD susceptibility were genotyped in 414 subjects with both annual clinical evaluation and completed brain autopsies from the Religious Orders Study and the Rush Memory and Aging Project. Regression analyses evaluated the relation of SNP genotypes to continuous measures of AD neuropathology and cognitive function proximate to death. A SNP in the zinc finger protein 224 gene (ZNF224, rs3746319) was associated with both global AD neuropathology (p = 0.009) and global cognition (p = 0.002); whereas, a SNP at the phosphoenolpyruvate carboxykinase locus (PCK1, rs8192708) was selectively associated with global cognition (p = 3.57×10−4). The association of ZNF224 with cognitive impairment was mediated by neurofibrillary tangles, whereas PCK1 largely influenced cognition independent of AD pathology, as well as Lewy bodies and infarcts.Conclusions/Significance
The findings support the association of several loci with AD, and suggest how intermediate phenotypes can enhance analysis of susceptibility loci in this complex genetic disorder. 相似文献93.
IL2RA Genetic Heterogeneity in Multiple Sclerosis and Type 1 Diabetes Susceptibility and Soluble Interleukin-2 Receptor Production 下载免费PDF全文
Lisa M. Maier Christopher E. Lowe Jason Cooper Kate Downes David E. Anderson Christopher Severson Pamela M. Clark Brian Healy Neil Walker Cristin Aubin Jorge R. Oksenberg Stephen L. Hauser Alistair Compston Stephen Sawcer The International Multiple Sclerosis Genetics Consortium Philip L. De Jager Linda S. Wicker John A. Todd David A. Hafler 《PLoS genetics》2009,5(1)
Multiple sclerosis (MS) and type 1 diabetes (T1D) are organ-specific autoimmune disorders with significant heritability, part of which is conferred by shared alleles. For decades, the Human Leukocyte Antigen (HLA) complex was the only known susceptibility locus for both T1D and MS, but loci outside the HLA complex harboring risk alleles have been discovered and fully replicated. A genome-wide association scan for MS risk genes and candidate gene association studies have previously described the IL2RA gene region as a shared autoimmune locus. In order to investigate whether autoimmunity risk at IL2RA was due to distinct or shared alleles, we performed a genetic association study of three IL2RA variants in a DNA collection of up to 9,407 healthy controls, 2,420 MS, and 6,425 T1D subjects as well as 1,303 MS parent/child trios. Here, we report “allelic heterogeneity” at the IL2RA region between MS and T1D. We observe an allele associated with susceptibility to one disease and risk to the other, an allele that confers susceptibility to both diseases, and an allele that may only confer susceptibility to T1D. In addition, we tested the levels of soluble interleukin-2 receptor (sIL-2RA) in the serum from up to 69 healthy control subjects, 285 MS, and 1,317 T1D subjects. We demonstrate that multiple variants independently correlate with sIL-2RA levels. 相似文献
94.
A random peptide library fused to CCR5 for selection of mimetopes expressed on the mammalian cell surface via retroviral vectors 总被引:3,自引:0,他引:3
A random peptide library was expressed on the surface of a mammalian cell by applying retroviral vectors. The random sequence was fused to the CCR5 chemokine receptor, which served as a scaffold to present the library at the cell surface. We used this library to isolate an epitope mimetope in a proof of principle system. This approach can become a tool for rapid creation of peptidic expression domains in a eukaryotic environment. Applications include the creation of decoys for receptors in cell-cell interactions, screening for molecules that drive ligand expression on target cells in two-cell interaction screens, among other utilities. 相似文献
95.
The sequencing of the human genome and the intense study of its variation in different human populations have improved our understanding of the genome's architecture. It is now becoming clear that segments of the genome that are unbroken by reshuffling or recombination during meiosis create a mosaic of DNA 'haplotype blocks'. Here, we discuss the advantages and limitations of this block structure. Haplotype blocks hold the promise of reducing the complexity of analysing the human genome for association with disease. But can they deliver on this promise? First generation maps of these block patterns, such as the admixture and haplotype maps, are now emerging and, it is to be hoped, will accelerate the discovery of alleles that contribute to susceptibility to human inflammatory diseases. 相似文献
96.
A Theoretical Study of River Fragmentation by Dams and its Effects on White Sturgeon Populations 总被引:3,自引:2,他引:1
Henriette I. Jager James A. Chandler Kenneth B. Lepla Webb Van Winkle 《Environmental Biology of Fishes》2001,60(4):347-361
Most of the world's large rivers are fragmented by dams. Fragmentation of the river ecosystem alters migration patterns among fish populations and converts free-flowing river to reservoir habitat. In this study, we used an individual-based genetic metapopulation model to study the effects of fragmentation on the population viability and genetic diversity of a large-river fish, the white sturgeon, Acipenser transmontanus. In the first of two simulation experiments, we fragmented a 200km river reach by building 1 to 20 virtual dams. Increased fragmentation produced an exponential decline in the likelihood of persistence, but no extinction threshold to suggest a minimum viable length of river. Compounding isolation with the loss of free-flowing habitat did not further reduce viability until free-flowing habitat was nearly eliminated, at which point extinction was certain. Genetic diversity within (among) populations decreased (increased) as we built the first several dams. Adding more dams caused the number of persisting populations to decline and eroded genetic diversity within and among populations. Our second simulation experiment evaluated the effects of different levels of upstream and downstream migration between river segments. The results of these migration experiments highlighted the importance of balanced migration rates. We found that extinction risk was high for populations linked by high downstream, and low upstream, migration rates, as is often the case in impounded rivers. Our results support the view that migration patterns will play a significant role in determining the viability of riverine fishes, such as the white sturgeon, in river ecosystems fragmented by dams.(retired) 相似文献
97.
Microbial Ecology of the Mango Phylloplane 总被引:6,自引:0,他引:6
apd: 9 February 2001 相似文献
98.
A. D. de Jager H. K. L. Hundt A. F. Hundt K. J. Swart M. Knight J. Roberts 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,740(2):247-251
Following oral administration of the prodrug nabumetone, the major metabolite 6-methoxy-2-naphthylacetic acid (6-MNA) was determined in human plasma. Minimal sample preparation was followed by reversed-phase liquid chromatography and UV detection, affording high sample throughput. The lower limit of quantification (LLOQ) was 70 ng/ml, at a signal-to-noise ratio of 8:1. The assay method displayed good correlation (r=0.997), and can be readily employed in pharmacokinetic and bioequivalence studies. 相似文献
99.
Huib de Jong Eva C. Koffeman Jennifer M. Meerding Rianne C. Scholman Lotte Wieten Wilco de Jager Mark Klein Henny Otten Femke van Wijk Ruurd van der Zee Johannes W. J. Bijlsma Femke Broere Willem van Eden Berent J. Prakken 《Cell stress & chaperones》2014,19(4):569-578
Self-reactive T cells have shown to have a potential role as regulators of the immune system preventing or even suppressing autoimmunity. One of the most abundant proteins that can be eluted from human HLA molecules is heat shock protein 70 (HSP70). The aims of the current study are to identify HSP70 epitopes based on published HLA elution studies and to investigate whether T cells from healthy individuals may respond to such self-epitopes. A literature search and subsequent in silico binding prediction based on theoretical MHC binding motifs resulted in the identification of seven HSP70 epitopes. PBMCs of healthy controls proliferated after incubation with two of the seven peptides (H167 and H290). Furthermore H161, H290, and H443 induced CD69 expression or production of cytokines IFNγ or TNFα in healthy controls. The identification of these naturally presented epitopes and the response they elicit in the normal immune system make them potential candidates to study during inflammatory conditions as well as in autoimmune diseases. 相似文献
100.
Jager M Deechongkit S Koepf EK Nguyen H Gao J Powers ET Gruebele M Kelly JW 《Biopolymers》2008,90(6):751-758
Perturbing the structure of the Pin1 WW domain, a 34-residue protein comprised of three beta-strands and two intervening loops has provided significant insight into the structural and energetic basis of beta-sheet folding. We will review our current perspective on how structure acquisition is influenced by the sequence, which determines local conformational propensities and mediates the hydrophobic effect, hydrogen bonding, and analogous intramolecular interactions. We have utilized both traditional site-directed mutagenesis and backbone mutagenesis approaches to alter the primary structure of this beta-sheet protein. Traditional site-directed mutagenesis experiments are excellent for altering side-chain structure, whereas amide-to-ester backbone mutagenesis experiments modify backbone-backbone hydrogen bonding capacity. The transition state structure associated with the folding of the Pin1 WW domain features a partially H-bonded, near-native reverse turn secondary structure in loop 1 that has little influence on thermodynamic stability. The thermodynamic stability of the Pin1 WW domain is largely determined by the formation of a small hydrophobic core and by the formation of desolvated backbone-backbone H-bonds enveloped by this hydrophobic core. Loop 1 engineering to the consensus five-residue beta-bulge-turn found in most WW domains or a four-residue beta-turn found in most beta-hairpins accelerates folding substantially relative to the six-residue turn found in the wild type Pin1 WW domain. Furthermore, the more efficient five- and four-residue reverse turns now contribute to the stability of the three-stranded beta-sheet. These insights have allowed the design of Pin1 WW domains that fold at rates that approach the theoretical speed limit of folding. 相似文献