首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   87篇
  免费   2篇
  2023年   1篇
  2021年   1篇
  2018年   2篇
  2017年   2篇
  2016年   4篇
  2015年   4篇
  2014年   5篇
  2013年   6篇
  2012年   4篇
  2011年   3篇
  2010年   11篇
  2009年   3篇
  2008年   4篇
  2007年   3篇
  2006年   7篇
  2005年   5篇
  2004年   3篇
  2003年   1篇
  2002年   2篇
  2001年   1篇
  2000年   3篇
  1999年   1篇
  1997年   1篇
  1995年   1篇
  1990年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1981年   2篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1970年   1篇
排序方式: 共有89条查询结果,搜索用时 31 毫秒
1.
Summary

Tests on disbudding and their effects on the histogenesis of the wood ring. In this work the effects of hormonic character which appear during the histogenesis of the wood ring have been studied testing disbudding effects on the peach tree.

Some observations on the consequences due to defoliation are also included.

By removal of the buds, the annual ring shows a greater depth and a more marked uniformity of structure, due to an increased frequency of the vascular elements.

By removal of the leaves, the cambial activity is completely inhibited. These results are attributed to the fact that the leaves, according to the more recent hypotheses, produce the substance which stimulates the formation of the wood elements and the differentiation of the newly formed elements.

This inactive substance, produced by the leaf, would exert its action only when the buds, towards which it is directed, transform it into its active form. The removal of the buds would eliminate the centres of diffusion of the inactive substance and also its centres of activation and concentration for the coming rest period, in view of a new vegetative cycle.

As a conseguence the circulation of the inactive substance is more marked, as it is probably activated by the cambium, and its activity lasts longer, producing in the annual ring those characters peculiar to the spring wood, that is of a season in which the circulation of this substance is at its utmost.  相似文献   
2.
Irisin was first identified in muscle cells. We detected irisin immunoreactivity in various organs of the crested porcupine (Hystrix cristata). In the epidermis, irisin immunoreactivity was localized mainly in stratum basale, stratum spinosum and stratum granulosum layers; immunoreactivity was not observed in the stratum corneum. In the dermis, irisin was found in the external and internal root sheath, cortex and medulla of hair follicles, and in sebaceous glands. Irisin immunoreactivity was found in the neural retina and skeletal muscle fibers associated with the eye. The pineal and thyroid glands also exhibited irisin immunoreactivity.  相似文献   
3.
4.
A 3-doxylcholestane spin label was employed in addition to 5-doxylstearoyl lecithin for a more detailed study of the different effects exerted by variously oxidized lecithins on fatty acid alignment in phospholipid planar bilayers. Either spin label was enclosed in oriented PLPC planar samples also containing in turn a variety of conjugated-dienes lecithins and cleaved chain lecithins, in order to monitor EPR spectral angular dependence loss. Data obtained by use of arachidonoyl-hydroxystearoyl-PC and palmitoyl-hydroxylinoleoyl-PC confirm that the 5-DSPC nitroxide ring almost completely retains its orientation in CD-PCs-containing planar membranes, in contrast with angular dependence loss observed in the presence of the CC-PC molecular species palmitoyl-oxononanoyl-PC and palmitoyl-oxovaleroyl-PC, already seen with cleaved-chain palmitoyl-glutaroyl-PC and palmitoyl-azelaoyl-PC. However, the 3-DC nitroxide ring also loses its orientation with CD-PCs, in addition to being disoriented by cleaved chain-lecithins, similarly to 5DSPC. Joint information from the two spin labels will help to clarify whether OXPC-related disordering involved the whole bilayer structure or only the hydrophobic core. In addition, the propensity of different OXPCs to form bilayer vesicles in water suspension was also determined by Sepharose 4B gel-chromatography. The results suggest that CD-PCs might yield SPB bilayer structures with a disordered hydrophobic core, while pure CC-PC more probably forms non-bilayer disordered structures, possibly micelles or mixed micelle/bilayers.  相似文献   
5.

Background

Atypical scrapie was first identified in Norwegian sheep in 1998 and has subsequently been identified in many countries. Retrospective studies have identified cases predating the initial identification of this form of scrapie, and epidemiological studies have indicated that it does not conform to the behaviour of an infectious disease, giving rise to the hypothesis that it represents spontaneous disease. However, atypical scrapie isolates have been shown to be infectious experimentally, through intracerebral inoculation in transgenic mice and sheep. The first successful challenge of a sheep with 'field' atypical scrapie from an homologous donor sheep was reported in 2007.

Results

This study demonstrates that atypical scrapie has distinct clinical, pathological and biochemical characteristics which are maintained on transmission and sub-passage, and which are distinct from other strains of transmissible spongiform encephalopathies in the same host genotype.

Conclusions

Atypical scrapie is consistently transmissible within AHQ homozygous sheep, and the disease phenotype is preserved on sub-passage.  相似文献   
6.
Although osteoporosis and its related fractures are common in patients with COPD, patients at high risk of fracture are poorly identified, and consequently, undertreated. Since there are no fracture prevention guidelines available that focus on COPD patients, we developed a clinical approach to improve the identification and treatment of COPD patients at high risk of fracture. We organised a round-table discussion with 8 clinical experts in the field of COPD and fracture prevention in the Netherlands in December 2013. The clinical experts presented a review of the literature on COPD, osteoporosis and fracture prevention. Based on the Dutch fracture prevention guideline, they developed a 5-step clinical approach for fracture prevention in COPD. Thereby, they took into account both classical risk factors for fracture (low body mass index, older age, personal and family history of fracture, immobility, smoking, alcohol intake, use of glucocorticoids and increased fall risk) and COPD-specific risk factors for fracture (severe airflow obstruction, pulmonary exacerbations and oxygen therapy). Severe COPD (defined as postbronchodilator FEV1 < 50% predicted) was added as COPD-specific risk factor to the list of classical risk factors for fracture. The 5-step clinical approach starts with case finding using clinical risk factors, followed by risk evaluation (dual energy X-ray absorptiometry and imaging of the spine), differential diagnosis, treatment and follow-up. This systematic clinical approach, which is evidence-based and easy-to-use in daily practice by pulmonologists, should contribute to optimise fracture prevention in COPD patients at high risk of fracture.  相似文献   
7.
IntroductionEngagement of the homotypic cell-to-cell adhesion molecule cadherin-11 on rheumatoid arthritis (RA) synovial fibroblasts with a chimeric molecule containing the cadherin-11 extracellular binding domain stimulated cytokine, chemokine, and matrix metalloproteinases (MMP) release, implicating cadherin-11 signaling in RA pathogenesis. The objective of this study was to determine if cadherin-11 extracellular domain fragments are found inside the joint and if a physiologic synovial fibroblast cleavage pathway releases those fragments.MethodsCadherin-11 cleavage fragments were detected by western blot in cell media or lysates. Cleavage was interrupted using chemical inhibitors or short-interfering RNA (siRNA) gene silencing. The amount of cadherin-11 fragments in synovial fluid was measured by western blot and ELISA.ResultsSoluble cadherin-11 extracellular fragments were detected in human synovial fluid at significantly higher levels in RA samples compared to osteoarthritis (OA) samples. A cadherin-11 N-terminal extracellular binding domain fragment was shed from synovial fibroblasts after ionomycin stimulation, followed by presenilin 1 (PSN1)-dependent regulated intramembrane proteolysis of the retained membrane-bound C-terminal fragments. In addition to ionomycin-induced calcium flux, tumor necrosis factor (TNF)-α also stimulated cleavage in both two- and three-dimensional fibroblast cultures. Although cadherin-11 extracellular domains were shed by a disintegrin and metalloproteinase (ADAM) 10 in several cell types, a novel ADAM- and metalloproteinase-independent activity mediated shedding in primary human fibroblasts.ConclusionsCadherin-11 undergoes ectodomain shedding followed by regulated intramembrane proteolysis in synovial fibroblasts, triggered by a novel sheddase that generates extracelluar cadherin-11 fragments. Cadherin-11 fragments were enriched in RA synovial fluid, suggesting they may be a marker of synovial burden and may function to modify cadherin-11 interactions between synovial fibroblasts.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0647-9) contains supplementary material, which is available to authorized users.  相似文献   
8.
BACKGROUND: Extrapulmonary tuberculosis is one of the great mimickers of medicine, and often masquerades as malignancy. As a result, patients may be referred to oncologists and surgeons for further evaluation and management, delaying the institution of appropriate anti-tuberculous drug therapy. CASE PRESENTATION: We present the case of a 21 year old man with tuberculous osteomyelitis, who was referred to the Bone and Soft Tissue Sarcoma Service at our institution with a provisional diagnosis of malignancy. Further investigation revealed extensive retroperitoneal abdominal and pelvic lymphadenopathy. The recognition of certain patterns on imaging, and finally the isolation of Mycobacterium tuberculosis from tissue samples obtained under image guidance, enabled the correct diagnosis to be made. CONCLUSION: This case highlights the importance of remaining cognisant of the protean manifestations of extrapulmonary tuberculosis, and illustrates the advantage of a clinically directed multi-modality imaging approach to diagnosis.  相似文献   
9.
Megli FM  Sabatini K 《FEBS letters》2004,573(1-3):68-72
The purpose of this study was to investigate whether, after oxidative injury in vivo, liver mitochondrial phospholipids suffered from structural defects similar to those we have previously observed after either chemical oxidation or respiration state IV incubation of isolated mitochondria in vitro. Oxidative injury of the liver was simulated by endogastric administration of CCl4 to rats in variable amounts for different times, under various conditions. Measurements of the phospholipid bilayer packing order were carried out by electron paramagnetic resonance (EPR) spectrometry of oriented planar samples of phospholipids extracted from liver mitochondria, spin labeled with 5-doxylstearoyl-lecithin. Disordering of the bilayer was revealed by the anisotropy loss of EPR spectra and reached a maximum value 4.5 h after CCl4 administration, vanishing thereafter. The observed disorder also increased with the amount of CCl4 administered, showing distinct dose-dependence, while administration of resveratrol soon after carbon tetrachloride decreased bilayer disordering by 50%. On the contrary, the order parameter S of spin labeled lecithin in isolated mitochondrial membranes from intoxicated rats revealed no change in membrane fluidity after oxidative stress. It is concluded that the phospholipid damage leading to disturbed bilayer geometry after oxidative attack already observed in model membranes and in isolated mitochondria in vitro also occurs in a simulated pathological state in vivo, indicating its possible occurrence also in real oxidative stress-linked pathologies as a contribution to the onset/sustaining of related diseases.  相似文献   
10.
Fourteen microsatellite markers were used to describe genetic diversity in a sample of 128 common bean (Phaseolus vulgaris L.) accessions cultivated within the territory of Slovenia and its nearby regions between 1800 and 2000. The accessions were grouped into three periods: period I comprising accessions from the beginning of the 19th century, while the other two periods included accessions from the middle (period II) and the end of the 20th century (period III). Seven control accessions of known Mesoamerican and Andean origin were also included in the study. A total of 130 alleles were generated. Allelic richness, in terms of number of alleles per locus, was 6.07 for period I, 6.71 for period II, and 6.07 for period III. In the UPGMA dendrogram, all studied accessions were intermixed in three main clusters, indicating that the diversity in the time periods overlapped. Two clusters consisted of accessions of Andean and Mesoamerican origin, while the third represents additional variation, which existed in this area already 200 years ago. The analysis of molecular variance showed that a great part of genetic diversity has been preserved till today, confirming the results of cluster analysis. The calculation of number of alleles per locus revealed no significant quantitative change in genetic diversity over the last 200 years of common bean cultivation. However, the calculation of genetic distances indicated slight qualitative shifts in genetic diversity of common bean germplasm over time, while the calculations of allelic frequency variation and polymorphic information content revealed recent decline of some alleles’ frequencies. These findings should stress the need for establishing an appropriate strategy of genetic resources management. The text was submitted by the authors in English.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号