全文获取类型
收费全文 | 333篇 |
免费 | 99篇 |
出版年
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 11篇 |
2006年 | 10篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1992年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 16篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1972年 | 7篇 |
1969年 | 4篇 |
1968年 | 6篇 |
1967年 | 3篇 |
1961年 | 4篇 |
1957年 | 2篇 |
排序方式: 共有432条查询结果,搜索用时 31 毫秒
71.
72.
Anika I Tsuchida Michiel Beekhuizen Marieke C ‘t Hart Timothy RDJ Radstake Wouter JA Dhert Daniel BF Saris Gerjo JVM van Osch Laura B Creemers 《Arthritis research & therapy》2014,16(5)
Introduction
This study aimed to evaluate whether profiles of several soluble mediators in synovial fluid and cartilage tissue are pathology-dependent and how their production is related to in vitro tissue formation by chondrocytes from diseased and healthy tissue.Methods
Samples were obtained from donors without joint pathology (n = 39), with focal defects (n = 65) and osteoarthritis (n = 61). A multiplex bead assay (Luminex) was performed measuring up to 21 cytokines: Interleukin (IL)-1α, IL-1β, IL-1RA, IL-4, IL-6, IL-6Rα, IL-7, IL-8, IL-10, IL-13, tumor necrosis factor (TNF)α, Interferon (IFN)γ, oncostatin M (OSM), leukemia inhibitory factor (LIF), adiponectin, leptin, monocyte chemotactic factor (MCP)1, RANTES, basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), vascular growth factor (VEGF).Results
In synovial fluid of patients with cartilage pathology, IL-6, IL-13, IFNγ and OSM levels were higher than in donors without joint pathology (P ≤0.001). IL-13, IFNγ and OSM were also different between donors with cartilage defects and OA (P <0.05). In cartilage tissue from debrided defects, VEGF was higher than in non-pathological or osteoarthritic joints (P ≤0.001). IL-1α, IL-6, TNFα and OSM concentrations (in ng/ml) were markedly higher in cartilage tissue than in synovial fluid (P <0.01). Culture of chondrocytes generally led to a massive induction of most cytokines (P <0.001). Although the release of inflammatory cytokines was also here dependent on the pathological condition (P <0.001) the actual profiles were different from tissue or synovial fluid and between non-expanded and expanded chondrocytes. Cartilage formation was lower by healthy unexpanded chondrocytes than by osteoarthritic or defect chondrocytes.Conclusions
Several pro-inflammatory, pro-angiogenic and pro-repair cytokines were elevated in joints with symptomatic cartilage defects and/or osteoarthritis, although different cytokines were elevated in synovial fluid compared to tissue or cells. Hence a clear molecular profile was evident dependent on disease status of the joint, which however changed in composition depending on the biological sample analysed. These alterations did not affect in vitro tissue formation with these chondrocytes, as this was at least as effective or even better compared to healthy chondrocytes. 相似文献73.
74.
Alan Brill 《Dreaming》2000,10(1):43-54
Maimonides' conception of true dreams posits an important role for the faculty of imagination within the growth of the intellectual self. However, unlike many modern theories of the dream, Maimonides requires one to subject the imagination to intellectual processes, in order to be able to harness the imagination for the practical knowledge. The imagination found in the dream images consists of objective graded levels based on the purity of the imagination from desire and the use of the intellect. The content of the dream is new piece of knowledge, a solution, a political agenda, or a vision for the future that needs to be contextualized within one's own life. Maimonides emphasizes the image as an intellectual object, specifically a single object and not the event. For Maimonides dreams do not give supernatural content nor are true dreams a universal part of daily life. They are extraordinary and do not have presentational immediacy. 相似文献
75.
Abstract Deoxynucleoside thiophosphoramidites and methyl phosphonothioates were synthesized and used to prepare dinucleotides containing phosphorodithioates and methylphosphonothioate internucleotide linkages. 相似文献
76.
Biosynthesis of the iron-molybdenum cofactor and the molybdenum cofactor in Klebsiella pneumoniae: effect of sulfur source. 总被引:11,自引:8,他引:3
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
NifQ- and Mol- mutants of Klebsiella pneumoniae show an elevated molybdenum requirement for nitrogen fixation. Substitution of cystine for sulfate as the sulfur source in the medium reduced the molybdenum requirement of these mutants to levels required by the wild type. Cystine also increased the intracellular molybdenum accumulation of NifQ- and Mol- mutants. Cystine did not affect the molybdenum requirement or accumulation in wild-type K. pneumoniae. Sulfate transport and metabolism in K. pneumoniae were repressed by cystine. However, the effect of cystine on the molybdenum requirement could not be explained by an interaction between sulfate and molybdate at the transport level. Cystine increased the molybdenum requirement of Mol- mutants for nitrate reductase activity by at least 100-fold. Cystine had the same effect on the molybdenum requirement for nitrate reductase activity in Escherichia coli ChlD- mutants. This shows that cystine does not have a generalized effect on molybdenum metabolism. Millimolar concentrations of molybdate inhibited nitrogenase and nitrate reductase derepression with sulfate as the sulfur source, but not with cystine. The inhibition was the result of a specific antagonism of sulfate metabolism by molybdate. The effects of nifQ and mol mutations on nitrogenase could be suppressed either by the addition of cystine or by high concentrations of molybdate. This suggests that a sulfur donor and molybdenum interact at an early step in the biosynthesis of the iron-molybdenum cofactor. This interaction might occur nonenzymatically when the levels of the reactants are high. 相似文献
77.
It has previously been shown that the mitochondrial DNA (mtDNA) of Saccharomyces cerevisiae becomes thermosensitive due to the inactivation of the mitochondrial DNA helicase gene, PIF1. A suppressor of this thermosensitive phenotype was isolated from a wild-type plasmid library by transforming a pif1 null strain to growth on glycerol at the non-permissive temperature. This suppressor is a nuclear gene encoding a 135 amino acid protein that is itself essential for mtDNA replication; cells lacking this gene are totally devoid of mtDNA. We therefore named this gene RIM1 for replication in mitochondria. The primary structure of the RIM1 protein is homologous to the single-stranded DNA binding protein (SSB) from Escherichia coli and to the mitochondrial SSB from Xenopus laevis. The mature RIM1 gene product has been purified from yeast extracts using a DNA unwinding assay dependent upon the DNA helicase activity of SV40 T-antigen. Direct amino acid sequencing of the protein reveals that RIM1 is a previously uncharacterized SSB. Antibodies against this purified protein localize RIM1 to mitochondria. The SSB encoded by RIM1 is therefore an essential component of the yeast mtDNA replication apparatus. 相似文献
78.
79.
80.
When Azotobacter vinelandii was derepressed for nitrogenase synthesis in a N-free medium containing tungstate instead of molybdate, an inactive component I was synthesized. Although this inactive component I could be activated in vivo upon addition of molybdate to the medium, it could not be activated in vitro when molybdate was added to the extracts. Activation occurred, however, when an acid-treated component I was added to extracts of cells derepressed in medium containing tungstate. Acid treatment completely abolished component I activity. Mutant strains UW45 and UW10 were unable to fix N(2). Both strains synthesized normal levels of component II but produced inactive component I. Acid-treated component I activated inactive component I in extracts of mutant strain UW45 but not mutant strain UW10. This activating factor could be obtained from N(2)-fixing Klebsiella pneumoniae, Clostridium pasteurianum, and Rhodospirillum rubrum. 相似文献