全文获取类型
收费全文 | 175篇 |
免费 | 15篇 |
国内免费 | 1篇 |
出版年
2022年 | 4篇 |
2021年 | 5篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2009年 | 12篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有191条查询结果,搜索用时 546 毫秒
121.
Yue-Ping Ma Liang Zhao Wen-Jie Zhang Ying-Hua Zhang Xia Xing Xia-Xia Duan Jing Hu AJ Harris Pei-Liang Liu Si-Lan Dai Jun Wen 《植物分类学报:英文版》2020,58(6):925-944
The origins of cultivated chrysanthemums have attracted considerable attention, but they remain poorly known. Here, we reconstructed the phylogeny of representative well‐known cultivars and wild species of the genus Chrysanthemum using chloroplast genomes and the nuclear LEAFY gene. Our results suggest that geographic and ecological factors may determine the opportunities for wild species to be involved in the origin of the cultivars. The wild species C. indicum, C. zawadskii, C. dichrum, C. nankingense, C. argyrophyllum, and C. vestitum were likely directly or indirectly involved as paternal species of most of the chrysanthemum cultivars examined in this study. Yet, the maternal species is supported to be a lineage of an extinct wild Chrysanthemum species and its subsequent cultivars, as all accessions of chrysanthemum cultivars sampled formed a strongly supported clade, distinct from all other species of Chrysanthemum in the plastome tree. Thus, the cultivated chrysanthemums originated from multiple hybridizations involving several paternal species rather than only two or a few wild species, with an extinct species and its subsequent cultivars serving as the maternal parents. This finding is consistent with Chrysanthemum having high rates of hybridization and gene flow, which has been demonstrated within previous studies; nevertheless, it is important to unravel the role of an extinct wild Chrysanthemum species as the ultimate maternal parent species for all the chrysanthemum cultivars. Our results also suggest that C. vestitum from Tianzhu and Funiu Mountains in Anhui and Henan Provinces of China represent two distinct cryptic species. 相似文献
122.
James M Duckers Bronwen AJ Evans William D Fraser Michael D Stone Charlotte E Bolton Dennis J Shale 《Respiratory research》2011,12(1):101
Background
Osteoporosis is common in patients with COPD but the likely multi-factorial causes contributing to this condition (e.g. sex, age, smoking, therapy) mask the potential contribution from elements related to COPD. In order to study osteoporosis and bone mineral density (BMD) related to COPD, we studied a well-defined group of patients and controls.Methods
BMD, forced expiratory volume in one second (FEV1), circulating bone biomarkers and biochemistry were determined in 30 clinically stable male ex-smokers with confirmed COPD and 15 age matched "ex-smoker" male controls. None of the patients were on inhaled corticosteroids or received more than one short course of steroids.Results
Mean (SD) FEV1% predicted of patients was 64(6)%, the majority having Global Initiative for Chronic Obstructive Lung Disease (GOLD) II airflow obstruction. There were 5/30 patients and 1/15 controls who were osteoporotic, while a further 17 patients and 5 controls were osteopenic. The BMD at the hip was lower in patients than controls, but not at the lumbar spine. Mean values of procollagen type 1 amino-terminal propeptide and osteocalcin, both markers of bone formation, and Type 1 collagen β C-telopeptide, a marker of bone resorption, were similar between patients and controls. However, all bone biomarkers were inversely related to hip BMD in patients (r = -0.51, r = -0.67, r = -0.57, p < 0.05) but did not relate to lumbar spine BMD. 25-OH Vitamin D was lower in patients.Conclusions
Men with COPD had a greater prevalence of osteoporosis and osteopenia than age matched male controls, with a marked difference in BMD at the hip. Bone biomarkers suggest increased bone turnover. 相似文献123.
124.
125.
Ting Lv AJ Harris Yuping Liu Tao Liu Ruifang Liang Zilan Ma Xu Su 《Ecology and evolution》2021,11(15):10258
Psammochloa villosa is an ecologically important desert grass that occurs in the Inner Mongolian Plateau where it is frequently the dominant species and is involved in sand stabilization and wind breaking. We sought to generate a preliminary demographic framework for P. villosa to support the future studies of this species, its conservation, and sustainable utilization. To accomplish this, we characterized the genetic diversity and structure of 210 individuals from 43 natural populations of P. villosa using amplified fragment length polymorphism (AFLP) markers. We obtained 1,728 well‐defined amplified bands from eight pairs of primers, of which 1,654 bands (95.7%) were polymorphic. Results obtained from the AFLPs suggested effective alleles among populations of 1.32, a Nei''s standard genetic distance value of 0.206, a Shannon index of 0.332, a coefficient of gene differentiation (G ST) of 0.469, and a gene flow parameter (Nm) of 0.576. All these values indicate that there is abundant genetic diversity in P. villosa, but limited gene flow. An analysis of molecular variance (AMOVA) showed that genetic variation mainly exists within populations (64.2%), and we found that the most genetically similar populations were often not geographically adjacent. Thus, this suggests that the mechanisms of gene flow are surprisingly complex in this species and may occur over long distances. In addition, we predicted the distribution dynamics of P. villosa based on the spatial distribution modeling and found that its range has contracted continuously since the last interglacial period. We speculate that dry, cold climates have been critical in determining the geographic distribution of P. villosa during the Quaternary period. Our study provides new insights into the population genetics and evolutionary history of P. villosa in the Inner Mongolian Plateau and provides a resource that can be used to design in situ conservation actions and prioritize sustainable utilization. 相似文献
126.
127.
Kate Jolly Gregory YH Lip Josie Sandercock Sheila M Greenfield James P Raftery Jonathan Mant Rod Taylor Deirdre Lane Kaeng Wai Lee AJ Stevens 《BMC cardiovascular disorders》2003,3(1):1-11
Background
Cardiac rehabilitation following myocardial infarction reduces subsequent mortality, but uptake and adherence to rehabilitation programmes remains poor, particularly among women, the elderly and ethnic minority groups. Evidence of the effectiveness of home-based cardiac rehabilitation remains limited. This trial evaluates the effectiveness and cost-effectiveness of home-based compared to hospital-based cardiac rehabilitation.Methods/design
A pragmatic randomised controlled trial of home-based compared with hospital-based cardiac rehabilitation in four hospitals serving a multi-ethnic inner city population in the United Kingdom was designed. The home programme is nurse-facilitated, manual-based using the Heart Manual. The hospital programmes offer comprehensive cardiac rehabilitation in an out-patient setting.Patients
We will randomise 650 adult, English or Punjabi-speaking patients of low-medium risk following myocardial infarction, coronary angioplasty or coronary artery bypass graft who have been referred for cardiac rehabilitation.Main outcome measures
Serum cholesterol, smoking cessation, blood pressure, Hospital Anxiety and Depression Score, distance walked on Shuttle walk-test measured at 6, 12 and 24 months. Adherence to the programmes will be estimated using patient self-reports of activity. In-depth interviews with non-attendees and non-adherers will ascertain patient views and the acceptability of the programmes and provide insights about non-attendance and aims to generate a theory of attendance at cardiac rehabilitation. The economic analysis will measure National Health Service costs using resource inputs. Patient costs will be established from the qualitative research, in particular how they affect adherence.Discussion
More data are needed on the role of home-based versus hospital-based cardiac rehabilitation for patients following myocardial infarction and revascularisation, which would be provided by the Birmingham Rehabilitation Uptake Maximisation Study (BRUM) study and has implications for the clinical management of these patients. A novel feature of this study is the inclusion of non-English Punjabi speakers. 相似文献128.
van Lent PL Nabbe KC Blom AB Sloetjes A Holthuysen AE Kolls J Van De Loo FA Holland SM Van Den Berg WB 《Arthritis research & therapy》2005,7(4):R885-R895
In previous studies we have found that FcγRI determines chondrocyte death and matrix metalloproteinase (MMP)-mediated cartilage
destruction during IFN-γ-regulated immune complex arthritis (ICA). Binding of immune complexes (ICs) to FcγRI leads to the
prominent production of oxygen radicals. In the present study we investigated the contribution of NADPH-oxidase-driven oxygen
radicals to cartilage destruction by using p47phox-/- mice lacking a functional NADPH oxidase complex. Induction of a passive ICA in the knee joints of p47phox-/- mice resulted in a significant elevation of joint inflammation at day 3 when compared with wild-type (WT) controls as studied
by histology. However, when IFN-γ was overexpressed by injection of adenoviral IFN-γ in the knee joint before ICA induction,
a similar influx of inflammatory cells was found at days 3 and 7, comprising mainly macrophages in both mouse strains. Proteoglycan
depletion from the cartilage layers of the knee joints in both groups was similar at days 3 and 7. Aggrecan breakdown in cartilage
caused by MMPs was further studied by immunolocalisation of MMP-mediated neoepitopes (VDIPEN). VDIPEN expression in the cartilage
layers of arthritic knee joints was markedly lower (between 30 and 60%) in IFN-γ-stimulated arthritic p47phox-/- mice at day 7 than in WT controls, despite significant upregulation of mRNA levels of various MMPs such as MMP-3, MMP-9,
MMP-12 and MMP-13 in synovia and MMP-13 in cartilage layers as measured with quantitative RT-PCR. The latter observation suggests
that oxygen radicals are involved in the activation of latent MMPs. Chondrocyte death, determined as the percentage of empty
lacunae in articular cartilage, ranged between 20 and 60% at day 3 and between 30 and 80% at day 7 in WT mice, and was completely
blocked in p47phox-/- mice at both time points. FcγRI mRNA expression was significantly lower, and FcγRII and FcγRIII were higher, in p47phox-/- mice than in controls. NADPH-oxidase-driven oxygen radical production determines chondrocyte death and aggravates MMP-mediated
cartilage destruction during IFN-γ-stimulated IC-mediated arthritis. Upregulation of FcγRI by oxygen radicals may contribute
to cartilage destruction. 相似文献
129.
The comprehensive analysis and visualization of data extracted from cDNA microarrays can be a time-consuming and error-prone process that becomes increasingly tedious with increased number of gene elements on a particular microarray. With the increasingly large number of gene elements on today's microarrays, analysis tools must be developed to meet this challenge. Here, we present MarC-V, a Microsoft Excel spreadsheet tool with Visual Basic macros to automate much of the visualization and calculation involved in the analysis process while providing the familiarity and flexibility of Excel. Automated features of this tool include (i) lower-bound thresholding, (ii) data normalization, (iii) generation of ratio frequency distribution plots, (iv) generation of scatter plots color-coded by expression level, (v) ratio scoring based on intensity measurements, (vi) filtering of data based on expression level or specific gene interests, and (vii) exporting data for subsequent multi-array analysis. MarC-V also has an importing function included for GenePix results (GPR) raw data files. 相似文献
130.
S K Ballas N Mohandas M R Clark S H Embury E D Smith L J Marton S B Shohet 《Biochimica et biophysica acta》1985,812(1):234-242
In order to determine the capacity of sickle cells to undergo transglutaminase-catalyzed cross-linking of membrane proteins, human normal and sickle erythrocytes were incubated with [ring-2-14C]histamine in the presence of Ca2+ and ionophore A23187. The [14C]histamine incorporation into membrane components was observed in freshly prepared erythrocytes. Incorporation of radioactivity into spectrin and Band 3 membrane components was significantly (P less than 0.001) less in sickle erythrocytes than in normal cells. Transglutaminase deficiency was excluded by the finding of increased activity of this enzyme in sickle cells from patients with reticulocytosis. The incorporation of [3H]spermine into red cell membranes was also less in sickle erythrocytes than in normal cells under the same conditions of incubation used for [ring-2-14C]histamine. Sickle erythrocytes were more permeable to these amines than normal cells. It is proposed that the gamma-glutamyl sites of membrane proteins in sickle erythrocytes are less accessible for transglutaminase-catalyzed cross-linking to histamine and polyamines in vitro, perhaps due to prior in vivo activation of this enzyme by the increased calcium in sickle cells and/or shielding secondary to altered membrane organization. 相似文献