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   51篇
  免费   3篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2015年   4篇
  2014年   4篇
  2013年   3篇
  2012年   2篇
  2011年   5篇
  2010年   2篇
  2009年   1篇
  2008年   2篇
  2007年   1篇
  2006年   2篇
  2002年   1篇
  2000年   2篇
  1997年   1篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1987年   1篇
  1979年   1篇
  1978年   1篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1971年   2篇
  1970年   1篇
  1969年   3篇
  1966年   1篇
排序方式: 共有54条查询结果,搜索用时 15 毫秒
1.
2.
Da Silva Cortinhas, M. C., Glienke, C., Prioli, A. J., Noleto, R. B., Matoso, D. A. and Cestari, M. M. 2010. A prime inference on genetic diversity (RAPDs) in the marine fish Atherinella brasiliensis (Teleostei, Atherinopsidae) from Southern Brazil. —Acta Zoologica (Stockholm) 91 : 242–248 As a result of the importance of Atherinella brasiliensis in estuarine environments, random amplified polymorphic DNA (RAPD) markers were used to verify the genetic diversity in A. brasiliensis from two different places in Paranaguá Bay (Paraná State) and one from the Conceição Lagoon (Santa Catarina State). Cytogenetic data have shown a high karyotypic diversity in some populations, although in others this peculiarity demonstrates rearrangements such as heterochromatinization. In the present study, a low level of genetic structuring between the samples from Conceição Lagoon compared with the others was observed through principal coordinate analysis (PCO), analysis of molecular variance and Mantel test according to 79 RAPD markers. As this specie does not perform horizontal migration and the individuals of Conceição Lagoon are isolated, three hypotheses are proposed to explain the results: (i) similar environments may show homogeneous populations not depending on the geographical distance, (ii) because vicariant events that formed the bays occurred in a recent period, the fragmentation effects over the structuring of the genetic diversity may still be low and not totally detectable by the RAPD technique and (iii) the isolation time or the number of generations may not be enough to promote a possible differentiation and genetic structuring between the specimens of these three places. The specimens of these places present a low level of differentiation and genetic structuring so we can consider them as a unique homogeneous population.  相似文献   
3.
During their lifetime, plants need to adapt to a changing environment, including light and temperature. To understand how these factors influence plant growth, we investigated the physiological and antioxidant responses of two Arabidopsis accessions, Shahdara (Sha) from the Shahdara valley (Tajikistan, Central Asia) in a mountainous area and Lovvik‐5 (Lov‐5) from northern Sweden to different light and temperature conditions. These accessions originate from different latitudes and have different life strategies, both of which are known to be influenced by light and temperature. We showed that both accessions grew better in high‐light and at a lower temperature (16°C) than in low light and at 23°C. Interestingly, Sha had a lower chlorophyll content but more efficient non‐photochemical quenching than Lov‐5. Sha, also showed a higher expression of vitamin E biosynthetic genes. We did not observe any difference in the antioxidant prenyllipid level under these conditions. Our results suggest that the mechanisms that keep the plastoquinone (PQ)‐pool in more oxidized state could play a role in the adaptation of these accessions to their local climatic conditions.  相似文献   
4.
5.
AimTo report the long-term follow-up of a cohort of adult patients with LGG post-operatively irradiated in one institution, and to identify prognostic factors for progression free survival.BackgroundThere is little consensus about the optimal treatment for low-grade glioma (LGG), and the clinical management of LGG is one of the most controversial areas in neurooncology. Radiation therapy is one option for treatment of patients with LGG, whereas other options include postoperative observation.Materials and methodsBetween 1975 and 2005, 180 patients with LGG (WHO II) received postoperative irradiation after non radical (subtotal or partial) excision. Patients had to be 18 years of age or older, and have histologic proof of supratentorial fibrillary (FA), protoplasmic (PA) or gemistocytic astrocytoma (GA). Radiotherapy was given within 3–10 weeks after surgery. Treatment fields were localized and included the preoperative tumor volume, with a 1–2 cm margin, treated to a total dose of 50–60 Gy in 25–30 fractions over 5–6 weeks.ResultsActuarial ten-year progression free survival (APFS) in the whole group was 19%. The worse prognosis was observed in patients with GA. Ten-year APFS rates for GA, PA and FA were 10%, 18% and 22%, respectively.ConclusionThe findings from our long-term cohort of 180 patients with LGG confirmed by uni- and multivariate analysis demonstrated that only astrocytoma histology significantly determined the prognosis. The best survival was observed in patients with the fibrillary variant, and the worst for the gemistocytic one.  相似文献   
6.
Antibiotic-resistant bacteria have been observed with increasing frequency over the past decades, driving the search for new drugs and stimulating the interest in natural products sources. Endophytic fungi from medicinal plants represent a great source of novel bioactive compounds useful to pharmaceutical and agronomical purposes. Diaporthe terebinthifolii is an endophytic species isolated from Schinus terebinthifolius, a plant used in popular medicine for several health problems. The strain D. terebinthifolii LGMF907 was previously reported by our group to produce secondary metabolites with biological activity against phytopathogens. Based on these data, strain LGMF907 was chosen for bioprospecting against microorganisms of clinical importance and for characterization of major secondary metabolites. In this study, different culture conditions were evaluated and the biological activity of this strain was expanded. The crude extracts demonstrated high antibacterial activity against Escherichia coli, Micrococcus luteus, Saccharomyces cerevisiae, methicillin-sensitive Staphylococcus aureus, and methicillin-resistant S. aureus. The compounds diaporthin and orthosporin were characterized and also showed activity against the clinical microorganisms evaluated. This study discloses the first isolation of diaporthin and orthosporin from D. terebinthifolii, and revealed the potential of this endophytic fungus to produce secondary metabolites with antimicrobial activity.  相似文献   
7.
8.
Mate value discrepancy (MVD) between heterosexual partners is an important factor influencing relationship satisfaction which, in turn, has an effect on the quality and the stability of the relationship. Therefore, partners’ involvement in mate retention behaviours, such as controlling behaviours, can be related to MVD and our study aims to determine whether such an association exists. In order to do so, we analysed female perception of MVD and their opinion regarding the intensity of controlling behaviours performed by themselves as well as their romantic partners. Female perception of the intensity of controlling behaviours performed by both partners was the highest in couples where a woman assesses her own mate value (MV) as higher than her partner’s MV and significantly different than in relationships where male MV exceeded those of the female. Our study also indicates that MVD should be taken into account when analysing sex differences in intensities of mate retention behaviours. Finally, we provide evidence supporting the significance of the relationship length for controlling behaviour intensity. Findings are discussed within an evolutionary perspective.  相似文献   
9.
Rideability, i.e. the ease and comfort with which a horse can be ridden, is considered to be one of the most important traits in riding horses. However, at present rideability is evaluated rather subjectively in breeding horse performance tests. The aim of the present study was to evaluate the role horse behaviour as well as degree and quality of rein tension might play in judges’ evaluation of horses’ rideability. Mares (n = 33) and stallions (n = 13) from two different mare- and one stallion-testing station were observed twice during their performance test dressage training. During these rides, rein tension was measured continuously, and frequency of behaviour patterns such as head-tossing, tail swishing, and snorting was recorded. Rein tension parameters showed reasonable repeatabilities within horse-rider pairs (e.g. mean rein tension: r2 = 0.61±0.11; variance of rein tension: r2 = 0.52±0.14). Regression analysis revealed that a larger proportion of variance in rideability scores could be explained by maximum (17%), mean (16%) and variance (15%) of rein tension compared to horses’ or riders’ behavioural parameters (tail-swishing: 5% and rider’s use of hands: 5%, respectively). According to mixed model analysis, rideability scores dropped (all P<0.05) with increasing mean, maximum and variability in rein tension (e.g. −0.37±0.14 scores per additional 10 Newton in mean tension). However, mean rein tension differed between testing stations (P<0.0001) ranging between 9.1±1.6 N in one station and 21.7±1.3 N in another station. These results indicate that quantity and consistency of rein tension is either directly or indirectly an important factor for judges to derive rideability scores. Given the importance of rein tension parameters to both rider comfort and horse welfare, potentially, measurements of rein tension along with behaviour observations assessing the quality of rein contact (e.g. distinguishing a light contact from attempts to evade contact) might be used to make the assessment of rideability more impartial.  相似文献   
10.
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