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   179篇
  免费   8篇
  国内免费   1篇
  2022年   3篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   3篇
  2016年   5篇
  2015年   13篇
  2014年   8篇
  2013年   14篇
  2012年   11篇
  2011年   7篇
  2010年   12篇
  2009年   7篇
  2008年   15篇
  2007年   6篇
  2006年   10篇
  2005年   16篇
  2004年   5篇
  2003年   8篇
  2002年   7篇
  2001年   1篇
  2000年   1篇
  1998年   3篇
  1997年   5篇
  1996年   4篇
  1995年   4篇
  1994年   2篇
  1992年   1篇
  1991年   4篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
排序方式: 共有188条查询结果,搜索用时 365 毫秒
31.
In this study, the effect of sequential inoculation with non-Saccharomyces (Hanseniaspora guilliermondii) and Saccharomyces cerevisiae yeast on the distinctive characteristics of the Campanino white wine was investigated. For this purpose, three independent winemaking experiments were carried out on an industrial scale (batches A, B and C). In detail, the first one was carried out using the sequential inoculation technique while the other two, using a S. cerevisiae single-strain starter or no inoculation representing the control batches. Microbiological and chemical parameters and sensorial profiles of the wines were defined. Interestingly, the results showed that when sequential cultures (H. guilliermondii in a sequential mixture with S. cerevisiae) were used, a better wine aroma and quality was observed. More specifically, the wine obtained by sequential inoculation showed lower acetic acid values and enhanced volatile profiles than the wine from the control batches. Finally, sensorial analysis confirmed that the sequential cultures led to an improvement in wine flavour. Therefore, results suggest that the sequential inoculation using non-Saccharomyces and Saccharomyces yeast represents a biotechnological practice that can improve the quality features of traditional white wine. It has been shown for the first time that on an industrial scale H. guilliermondii could be used in sequential inoculum with S. cerevisiae in making white Campanino wine.

Graphical abstract

  相似文献   
32.
33.
The organization of chromosomes into euchromatin and heterochromatin is amongst the most important and enigmatic aspects of genome evolution. Constitutive heterochromatin is a basic yet still poorly understood component of eukaryotic chromosomes, and its molecular characterization by means of standard genomic approaches is intrinsically difficult. Although recent evidence indicates that the presence of transcribed genes in constitutive heterochromatin is a conserved trait that accompanies the evolution of eukaryotic genomes, the term heterochromatin is still considered by many as synonymous of gene silencing. In this paper, we comprehensively review data that provide a clearer picture of transcribed sequences within constitutive heterochromatin, with a special emphasis on Drosophila and humans.  相似文献   
34.
Autoimmune hypophysitis can be reproduced experimentally by the injection of pituitary proteins mixed with an adjuvant into susceptible mice1. Mouse models allow us to study how diseases unfold, often providing a good replica of the same processes occurring in humans. For some autoimmune diseases, like type 1A diabetes, there are models (the NOD mouse) that spontaneously develop a disease similar to the human counterpart. For many other autoimmune diseases, however, the model needs to be induced experimentally. A common approach in this regard is to inject the mouse with a dominant antigen derived from the organ being studied. For example, investigators interested in autoimmune thyroiditis inject mice with thyroglobulin2, and those interested in myasthenia gravis inject them with the acetylcholine receptor3. If the autoantigen for a particular autoimmune disease is not known, investigators inject a crude protein extract from the organ targeted by the autoimmune reaction. For autoimmune hypophysitis, the pathogenic autoantigen(s) remain to be identified4, and thus a crude pituitary protein preparation is used. In this video article we demonstrate how to induce experimental autoimmune hypophysitis in SJL mice.Download video file.(63M, mov)  相似文献   
35.
Anthocyanins are a group of naturally occurring phenolic compounds as colorants in several plants, flowers and fruits. These pigments have a great importance as quality indicators, as chemotaxonomic markers and antioxidants.The content of blackberry (Rubus species) juice was investigated by HPLC/ESI/MS using narrow bore HPLC columns. Using this method we demonstrated that cyanidin-3-O-glucoside represents about 80% of the total anthocyanin contents in blackberry extract. Here we investigated antioxidant activity of the blackberry juice and cyanidin-3-O-glucoside on the endothelial dysfunction in cells and in vascular rings exposed to peroxynitrite. In human umbilical vein endothelial cells (HUVEC) in vitro, peroxynitrite caused a significant suppression of mitochondrial respiration (38 +/- 2.1% of control cells), as measured by the mitochondrial-dependent conversion of the dye MTT to formazan. Peroxynitrite caused DNA strand breakage (63 +/- 1.9% single strand vs 3 +/- 0.9% single strand in control cells), as measured by the alkaline unwinding assay, and caused an activation of PARS, as measured by the incorporation of radiolabeled NAD(+) to nuclear proteins. Blackberry juice (different dilutions that contained 80 ppm;40 ppm;14.5 ppm of cyanidin-3-O-glucoside) and cyanidin-3-O-glucoside (as chloride) (0.085 microM; 0.028 microM; 0.0085 microM) reduced the peroxynitrite-induced suppression of mitochondrial respiration, DNA damage and PARS activation in HUVECs. Vascular rings exposed to peroxynitrite exhibited reduced endothelium-dependent relaxant responses in response to acetylcholine as well as a vascular contractility dysfunction in response to norepinephrine. The development of this peroxynitrite-induced vascular dysfunction was ameliorated by the blackberry juice (different dilutions that contained 80 ppm;40 ppm;14.5 ppm of cyanidin-3-O-glucoside) and cyanidin-3-O-glucoside (as chloride) (0.085 microM;0.028 microM;0.0085 microM).In conclusion our findings clearly demonstrate that blackberry juice containing cyanidin-3-O-glucoside is a scavenger of peroxynitrite and that exert a protective effect against endothelial dysfunction and vascular failure induced by peroxynitrite.  相似文献   
36.

Objectives

We sought to evaluate the prescribing pattern of statins according to national and regional health policy interventions and to assess specifically the adherence to the therapy in outpatient setting in Southern Italy.

Methods

A population-based study was performed on persons ≥15 years old, living in the catchment area of Caserta (Southern Italy), and registered in Arianna database between 2004 and 2010. Prevalence and incidence of new treatments with statins were calculated for each year and stratified by drug. Adherence to therapy was measured by Medication Possession Ratio. Sub-analyses by individual compound and type of cardiovascular prevention were performed.

Results

From 2004 to 2010, the one-year prevalence of statin use increased from 44.9/1,000 inhabitants to 79.8/1,000, respectively, consistently with the incidence of new use from 16.2/1,000 to 19.5/1,000, except a slight decrease after criteria reimbursement revision on 2005 (13.3/1,000). The incidence of new treatments decreased for atorvastatin, and increased for simvastatin over the study years. Overall, 43% of new users were still highly adherent to the treatment (MPR≥80%) after six months, while 26% after 4-years of follow-up. As compared with highly adherent patients, the probability to be non-adherent (MPR≤25%) at 4-years of follow-up was 26% higher for women than for men (full adj. odds ratio: 1.26; 95% CI: 1.10–1.45), and 64% higher in patients who started on primary rather than on secondary prevention (1.64; 1.29–2.07).

Conclusions

Prevalence and incidence of statin use increased consistently with health policy interventions. Only one-fourth of patients who newly initiated a statin were adherent to the treatment after 4-year of follow-up. Since the benefits of statins in terms of cardiovascular outcome and costs are associated with their chronic use, the identification of patient-related predictors of non-adherence such as gender, primary prevention could be suitable for physicians to improve the patients'' compliance.  相似文献   
37.
The preferred conformations of N-acetyl-N′-methyl amides of some dialkylglycines have been determined by empirical conformational-energy calculations; minimum-energy conformations were located by minimizing the energy with respect to all the dihedral angles of the molecules. The conformational space of these compounds is sterically restricted, and low-energy conformations are found only in the regions of fully extended and helical structures. Increasing the bulkiness of the substituents on the Cα, the fully extended conformation becomes gradually more stable than the helical structure preferred in the cases of dimethylglycine. This trend is, however, strongly dependent on the bond angles between the substituents on the Cα atom: In particular, helical structures are favored by standard values (111°) of the N-Cα-C′ angle, while fully extended conformations are favored by smaller values of the same angle, as experimentally observed, for instance, in the case of α,α-di-n-propylglycine.  相似文献   
38.
Callus induction and plant regeneration from gladiolus   总被引:1,自引:0,他引:1  
A method for the initiation of callus capable of plant regeneration from in vivo grown cormels of gladiolus (Gladiolus x grandiflorus Hort.) is described. Sliced cormels of the large-flowering hybrid, Peter Pears were cultured in vitro on a modified Murashige and Skoog medium, supplemented with various auxins. Yellow callus, which was either friable or compact, could be induced on all media tested. Callus induced on media with naphthaleneacetic acid failed to proliferate. Callus induced on media with 9 mM 2,4-dichlorophenoxyacetic acid showed the best growth. Addition of micro-elements and vitamins increased the induction and growth of callus capable of plant regeneration. Explants taken from the middle part of the cormels had the highest competence for callus initiation. Callus was induced on several gladiolus hybrids and the South African species G. garnierii Klatt. Callus induction was genotype dependent and among the cultivars tested, Peter Pears and White Prosperity were superior with respect to callus production on the media with either 2,4-dichlorophenoxyacetic acid or picloram. Plants were regenerated from yellow compact callus of all genotypes on media containing zeatin and benzyladenine in various concentrations.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog basal salt and vitamins (1962) - CI callus induction medium - NAA -naphthaleneacetic acid - BA 6-benzyladenine - picloram 4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid - zeatin 6-[4-hydroxy-3-methylbut-2-enylamino]purine  相似文献   
39.
The mechanistic relationship between amyloid β1‐42 (Aβ1‐42) and the alteration of Tau protein are debated. We investigated the effect of Aβ1‐42 monomers and oligomers on Tau, using mice expressing wild‐type human Tau that do not spontaneously develop Tau pathology. After intraventricular injection of Aβ1‐42, mice were sacrificed after 3 h or 4 days. The short‐lasting treatment with Aβ monomers, but not oligomers, showed a conformational PHF‐like change of Tau, together with hyperphosphorylation. The same treatment induced increase in concentration of GSK3 and MAP kinases. The inhibition of the kinases rescued the Tau changes. Aβ monomers increased the levels of total Tau, through the inhibition of proteasomal degradation. Aβ oligomers reproduced all the aforementioned alterations only after 4 days of treatment. It is known that Aβ1‐42 monomers foster synaptic activity. Our results suggest that Aβ monomers physiologically favor Tau activity and dendritic sprouting, whereas their excess causes Tau pathology. Moreover, our study indicates that anti‐Aβ therapies should be targeted to Aβ1‐42 monomers too.  相似文献   
40.
Long-distance migration is a widespread process evolved independently in several animal groups in terrestrial and marine ecosystems. Many factors contribute to the migration process and of primary importance are intra-specific competition and seasonality in the resource distribution. Adaptive migration in direction of increasing fitness should lead to the ideal free distribution (IFD) which is the evolutionary stable strategy of the habitat selection game. We introduce a migration game which focuses on migrating dynamics leading to the IFD for age-structured populations and in time varying habitats, where dispersal is costly. The model predicts migration dynamics between these habitats and the corresponding population distribution. When applied to Atlantic bluefin tunas, it predicts their migration routes and their seasonal distribution. The largest biomass is located in the spawning areas which have also the largest diversity in the age-structure. Distant feeding areas are occupied on a seasonal base and often by larger individuals, in agreement with empirical observations. Moreover, we show that only a selected number of migratory routes emerge as those effectively used by tunas.  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