全文获取类型
收费全文 | 311篇 |
免费 | 27篇 |
出版年
2024年 | 1篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 10篇 |
2013年 | 20篇 |
2012年 | 31篇 |
2011年 | 21篇 |
2010年 | 19篇 |
2009年 | 7篇 |
2008年 | 18篇 |
2007年 | 25篇 |
2006年 | 17篇 |
2005年 | 14篇 |
2004年 | 26篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 2篇 |
排序方式: 共有338条查询结果,搜索用时 781 毫秒
101.
OBJECTIVE: To perform a minimally invasive procedure for atrial fibrillation without cardiopulmonary bypass, it is necessary to create transmural lesions on the beating heart. Although bipolar radiofrequency clamps can isolate the pulmonary veins, they have difficulty in performing any other left atrial lesions, particularly those of the traditional Cox-Maze procedure. This study examined the performance of an internally cooled, bipolar radiofrequency device designed for such an application. METHODS: Eleven domestic pigs underwent median sternotomy. Five animals had eight atrial lesions created with the radiofrequency device at times of 20, 30, 40, and 50 seconds. In six other pigs, the device was compared with another technology that has been used clinically for epicardial, beating heart ablation, the Guidant Flex 4 microwave device. The tissue was stained with 2,3,5-triphenyl-tetrazoluim chloride, and the lesions were sectioned at 5-mm intervals. Lesion width, depth, and transmurality were evaluated. RESULTS: The radiofrequency device had a linear dose-response relationship. Lesions were wider and deeper with increasing ablation times. A total of 40%, 45%, 60%, and 67% of lesions were transmural at times of 20, 30, 40, and 50 seconds, respectively. Ninety-one percent of lesions in tissue up to 4-mm thick were transmural after 50 seconds. However, performance in thicker tissue was poor. Lesions created by the device were deeper and more likely to be transmural than the Flex 4. CONCLUSIONS: This internally cooled, bipolar radiofrequency device can reliably create transmural lesions on tissue up to 4-mm thick and performs better than a microwave device. 相似文献
102.
Francesco Patti Manuela De Stefano Luigi Lavorgna Silvia Messina Clara Grazia Chisari Domenico Ippolito Roberta Lanzillo Veria Vacchiano Sabrina Realmuto Paola Valentino Gabriella Coniglio Maria Buccafusca Damiano Paolicelli Alessandro D’Ambrosio Patrizia Montella Vincenzo Brescia Morra Giovanni Savettieri Bruno Alfano Antonio Gallo Isabella Simone Rosa Viterbo Mario Zappia Simona Bonavita Gioacchino Tedeschi 《PloS one》2015,10(3)
Background
Magnetic Resonance Imaging (MRI) techniques provided evidences into the understanding of cognitive impairment (CIm) in Multiple Sclerosis (MS).Objectives
To investigate the role of white matter (WM) and gray matter (GM) in predicting long-term CIm in a cohort of MS patients.Methods
303 out of 597 patients participating in a previous multicenter clinical-MRI study were enrolled (49.4% were lost at follow-up). The following MRI parameters, expressed as fraction (f) of intracranial volume, were evaluated: cerebrospinal fluid (CSF-f), WM-f, GM-f and abnormal WM (AWM-f), a measure of lesion load. Nine years later, cognitive status was assessed in 241 patients using the Symbol Digit Modalities Test (SDMT), the Semantically Related Word List Test (SRWL), the Modified Card Sorting Test (MCST), and the Paced Auditory Serial Addition Test (PASAT). In particular, being SRWL a memory test, both immediate recall and delayed recall were evaluated. MCST scoring was calculated based on the number of categories, number of perseverative and non-perseverative errors.Results
AWM-f was predictive of an impaired performance 9 years ahead in SDMT (OR 1.49, CI 1.12–1.97 p = 0.006), PASAT (OR 1.43, CI 1.14–1.80 p = 0.002), SRWL-immediate recall (OR 1.72 CI 1.35–2.20 p<0.001), SRWL-delayed recall (OR 1.61 CI 1.28–2.03 p<0.001), MCST-category (OR 1.52, CI 1.2–1.9 p<0.001), MCST-perseverative error(OR 1.51 CI 1.2–1.9 p = 0.001), MCST-non perseverative error (OR 1.26 CI 1.02–1.55 p = 0.032).Conclusion
In our large MS cohort, focal WM damage appeared to be the most relevant predictor of the long-term cognitive outcome. 相似文献103.
The Protective Effect of Apocynin on Cyclosporine A‐Induced Hypertension and Nephrotoxicity in Rats 下载免费PDF全文
104.
105.
106.
107.
Mauro Tretiach Stefano Bertuzzi Fabio Candotto Carniel Damiano Virgilio 《Oecologia》2013,173(3):649-663
CO2 gas exchange, radial growth, chlorophyll (Chl) content and photobiont density of an epiphytic population of Parmelia sulcata were monitored every 2 months during 1 year in a temperate deciduous forest of Central Italy, to verify possible seasonal variations. Light response curves of south-exposed thalli, built up in the laboratory at 6 and 27°C at optimal thallus hydration, showed that CO2 gas exchange changed significantly during the year, with a maximum for gross photosynthesis in December at both temperatures. Photoinhibition phenomena occurred in early spring, immediately before tree leaves sprouted. The principal component analysis of CO2 gas exchange parameters clearly separated the months with from the months without tree canopy cover. Radial growth, measured on marginal lobes of north- and south-exposed thalli, was the highest in December, and the lowest in April. Photobiont density, measured in lobes of south- and north-exposed thalli with a sedimentation chamber, also changed during the year: the number of photobionts was highest in June and December, and lowest in April, although no significant change in cell size and Chl content per cell was evident throughout the year. South-exposed thalli had slightly, but constantly higher photobiont density both on a weight and an area basis. The acclimation of lichen photosynthesis and Chl content to seasonal temperature and light changes should partially be re-visited on the basis of the significant variation in photobiont population density. This phenomenon still awaits, however, a satisfactory explanation, although it is probably related to the seasonal change in nutrient availability. 相似文献
108.
Mirco Rodeghiero Galina Churkina Cristina Martinez Thomas Scholten Damiano Gianelle Alessandro Cescatti 《Plant and Soil》2013,364(1-2):55-68
Aims
The partitioning of the total soil CO2 efflux into its two main components: respiration from roots (and root-associated organisms) and microbial respiration (by means of soil organic matter (SOM) and litter decomposition), is a major need in soil carbon dynamics studies in order to understand if a soil is a net sink or source of carbon.Methods
The heterotrophic component of the CO2 efflux was estimated for 11 forest sites as the ratio between the carbon stocks of different SOM pools and previously published (Δ14C derived) turnover times. The autotrophic component, including root and root-associated respiration, was calculated by subtracting the heterotrophic component from total soil chamber measured CO2 efflux.Results
Results suggested that, on average, 50.4 % of total soil CO2 efflux was derived from the respiration of the living roots, 42.4 % from decomposition of the litter layers and less than 10 % from decomposition of belowground SOM.Conclusions
The Δ14C method proved to be an efficient tool by which to partition soil CO2 efflux and quantify the contribution of the different components of soil respiration. However the average calculated heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO2 efflux partitioning (one performed in the same study area; the other a meta-analysis of soil respiration partitioning). These differences were probably due to the heterogeneity of the SOM fraction and to a sub-optimal choice of the litter sampling period. 相似文献109.
Simona Bosco Claudia Di Bene Mariassunta Galli Damiano Remorini Rossano Massai Enrico Bonari 《The International Journal of Life Cycle Assessment》2013,18(5):973-989
Purpose
Concerns about global warming led to the calculation of the carbon footprint (CF) left by human activities. The agricultural sector is a significant source of greenhouse gas (GHG) emissions, though cropland soils can also act as sinks. So far, most LCA studies on agricultural products have not considered changes in soil organic matter (SOM). This paper aimed to: (1) integrate the Hénin–Dupuis SOM model into the CF study and (2) outline the impacts of different vineyard soil management scenarios on the overall CF.Methods
A representative wine chain in the Maremma Rural District, Tuscany (Italy), made up of a cooperative winery and nine of its associated farms, was selected to investigate the production of a non-aged, high-quality red wine. The system boundary was established from vineyard planting to waste management after use. The functional unit (FU) chosen for this study was a 0.75-L bottle of wine, and all data refer to the year 2009. The SOM balance, based on Hénin–Dupuis’ equation, was integrated and run using GaBi4 software. A sensitivity analysis was performed, and four scenarios were developed to assess the impact of vineyard soil management types with decreasing levels of organic matter inputs.Results and discussion
SOM accounting reduced the overall CF of one wine bottle from 0.663 to 0.531 kg CO2-eq/FU. The vineyard planting sub-phase produced a loss of SOM while, in the pre-production and production sub-phases, the loss/accumulation of SOM was related to the soil management practices. On average, soil management in the production sub-phase led to a net accumulation of SOM, and the overall vineyard phase was a sink of CO2. Residue incorporation and grassing were identified as the main factors affecting changes in SOM in vineyard soils.Conclusions
Our results showed that incorporating SOM accounting into the wine chain’s CF analysis changed the vineyard phase from a GHG source to a modest net GHG sink. These results highlighted the need to include soil C dynamics in the CF of the agricultural product. Here, the SOM balance method proposed was sensitive to changes in management practices and was site specific. Moreover, we were also able to define a minimum data set for SOM accounting. The EU recognises soil carbon sequestration as one of the major European strategies for mitigation. However, specific measures have yet to be included in the CAP 2020. It would be desirable to include soil in the new ISO 14067—Carbon Footprint of Products. 相似文献110.
M.N. Greco M.A. Connelly G.C. Leo M.W. Olson E. Powell Z. Huang M. Hawkins C. Smith C. Schalk-Hihi A.L. Darrow H. Xin W. Lang B.P. Damiano D.J. Hlasta 《Bioorganic & medicinal chemistry letters》2013,23(9):2595-2597
By screening directed libraries of serine hydrolase inhibitors using the cell surface form of endothelial lipase (EL), we identified a series of carbamate-derived (EL) inhibitors. Compound 3 raised plasma HDL-C levels in the mouse, and a correlation was found between HDL-C and plasma compound levels. Spectroscopic and kinetic studies support a covalent mechanism of inhibition. Our findings represent the first report of EL inhibition as an effective means for increasing HDL-C in an in vivo model. 相似文献