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   52篇
  免费   3篇
  2022年   1篇
  2021年   5篇
  2020年   1篇
  2019年   2篇
  2018年   1篇
  2017年   3篇
  2016年   3篇
  2015年   6篇
  2014年   3篇
  2013年   5篇
  2012年   3篇
  2011年   2篇
  2010年   2篇
  2009年   1篇
  2008年   1篇
  2007年   2篇
  2006年   3篇
  2005年   1篇
  2004年   2篇
  2002年   2篇
  2000年   2篇
  1996年   1篇
  1995年   2篇
  1978年   1篇
排序方式: 共有55条查询结果,搜索用时 31 毫秒
41.
We conducted a quantitative assessment of forage biomass in Harshin district to determine its annual productive potential, carrying capacity, and stocking rates. The dominant Land Use and Land Cover include woodland (35.5%), shrubs (28.3%), grassland (10.6%), and bare land (25.5%). The region has browse‐rich shrubland that is edible to dromedary and goats, as well as massive grassland plains for sheep and cattle. The interannual rainfall variation is 16.5% which implies that the rangeland is a subsistence equilibrium system. The range of forage production is between 105 and 2,310 kg/ha, whereas the average productivity of the district is 742.6 kg/ha. The result indicates that the average carrying capacity of the district is 0.3 TLU ha?1 year?1 (4.9 ha TLU?1 year?1) while the existing stocking rate is 5.4 TLU ha?1 year?1 (0.18 ha TLU?1 year?1). This implies that the grazing intensity in the district is much higher than its carrying capacity (recommended rate), which has seen overstocking or grazing pressure excesses of 5.1 TLU/ha (7.2 cattle/ha). Thus, it clearly signals the risk of overgrazing in the district. If this trend continues, the grazing will not be sustainable and there will be shortage of forage as well as expansion of land degradation (due to overgrazing) in the near future.  相似文献   
42.
43.
44.
Maraviroc (MVC) is a potent CCR5 coreceptor antagonist that is in clinical testing for daily oral pre-exposure prophylaxis (PrEP) for HIV prevention. We used a macaque model consisting of weekly SHIV162p3 exposures to evaluate the efficacy of oral MVC in preventing rectal SHIV transmission. MVC dosing was informed by the pharmacokinetic profile seen in blood and rectal tissues and consisted of a human-equivalent dose given 24 h before virus exposure, followed by a booster postexposure dose. In rectal secretions, MVC peaked at 24 h (10,242 ng/ml) with concentrations at 48 h that were about 40 times those required to block SHIV infection of peripheral blood mononuclear cells (PBMCs) in vitro. Median MVC concentrations in rectal tissues at 24 h (1,404 ng/g) were 30 and 10 times those achieved in vaginal or lymphoid tissues, respectively. MVC significantly reduced macrophage inflammatory protein 1β-induced CCR5 internalization in rectal mononuclear cells, an indication of efficient binding to CCR5 in rectal lymphocytes. The half-life of CCR5-bound MVC in PBMCs was 2.6 days. Despite this favorable profile, 5/6 treated macaques were infected during five rectal SHIV exposures as were 3/4 controls. MVC treatment was associated with a significant increase in the percentage of CD3+/CCR5+ cells in blood. We show that high and durable MVC concentrations in rectal tissues are not sufficient to prevent SHIV infection in macaques. The increases in CD3+/CCR5+ cells seen during MVC treatment point to unique immunological effects of CCR5 inhibition by MVC. The implications of these immunological effects on PrEP with MVC require further evaluation.  相似文献   
45.
Feeding ecology of the African civet, Civettictis civetta (Schreber, 1778), was studied in selected coffee forest habitat for two seasons between December 2012 and October 2013. The study was conducted in Limu Seka district, south‐west Ethiopia. Faecal analysis was employed to assess the diet spectrum, seasonal abundance and relative importance of food items. Over 55 different food items were identified from the analysis of 387 scat samples collected during the dry and wet seasons. In the coffee forest habitat, African civets showed omnivorous feeding habit with plant‐to‐animal diet biomass ratio of 1 : 1.36. A slight diet specialization was observed during the wet season (BA = 0.46) favouring animal prey. However, during the dry season, they showed generalist feeding habit (BA = 0.87) with more plant biomass in their diet. With over 64% occurrence and 14.4% biomass, coffee berries significantly contributed to the civets dry season plant diets. The excreted coffee beans, after civets ingested ripe coffee berries, are the tastiest product used by farmers for consumption and market. Seasonal collection of civet coffee from coffee forest floor economically supports the farmers while increasing the importance of civets in the habitat and hence contributing for its conservation.  相似文献   
46.
Les urgences biologiques représentent une valorisation de l’activité biologique, car elles influencent directement la prise en charge des patients. Elles s’accompagnent souvent d’un contact direct entre cliniciens et biologistes. L’unité de lieu que représente le laboratoire est un avantage; le gain de temps permettra un transfert rapide du patient si les résultats le nécessitent.  相似文献   
47.
The highlands of Eastern Africa are characterized by high population densities and tightly coupled interactions between adjacent landscape units and users. Effective formal or informal natural resource governance is necessary to mitigate the potential negative social and environmental effects of individuals’ behavior. Yet many natural resource management and development problems that require or benefit from collective solutions remain unresolved (German et al. Environ Dev Sustain 8: 535–552, 2006a; German et al. 2006b; German et al. Q J Int Agr 47(3): 191–216, 2008). We argue that many of the more intractable problems in improving governance stem from the trade-offs that underlie them, which may include a loss of livelihood options for at least some households, leading to governance break down. Following a brief introduction to natural resource management and governance in Eastern Africa, we analyze the results of participatory by-law deliberations by distilling the restrictions proposed governance reforms pose to certain local stakeholders. We recommend that future policy for improved landscape governance couple institutional reforms with livelihood alternatives that reduce the burden of good governance on households.  相似文献   
48.
The hydrogen content of whole human breath (not concentrated or end-expiratory samples), useful as an index of carbohydrate malabsorption, can be determined accurately by gas chromatographic analysis using a thermal conductivity detector and, for the first time, and electronic peak integrator. Standard gas mixtures (H2Ar or preferably H2N2) give peak areas linearly related to hydrogen content. For repeatable results, it is necessary to pressurize samples in a 0.5-ml sample loop. Five minutes are required for the analysis of a sample with a printed report of the area of the H2 peak (arbitrary units) and concentration of H2 (parts per million). Standard samples can be stored in special impervious bags for up to 3 days without loss. Details of bag construction are given.  相似文献   
49.
50.
For commercial protein therapeutics, Chinese hamster ovary (CHO) cells have an established history of safety, proven capability to express a wide range of therapeutic proteins and high volumetric productivities. Expanding global markets for therapeutic proteins and increasing concerns for broadened access of these medicines has catalyzed consideration of alternative approaches to this platform. Reaching these objectives likely will require an order of magnitude increase in volumetric productivity and a corresponding reduction in the costs of manufacture. For CHO-based manufacturing, achieving this combination of targeted improvements presents challenges. Based on a holistic analysis, the choice of host cells was identified as the single most influential factor for both increasing productivity and decreasing costs. Here we evaluated eight wild-type eukaryotic micro-organisms with prior histories of recombinant protein expression. The evaluation focused on assessing the potential of each host, and their corresponding phyla, with respect to key attributes relevant for manufacturing, namely (a) growth rates in industry-relevant media, (b) adaptability to modern techniques for genome editing, and (c) initial characterization of product quality. These characterizations showed that multiple organisms may be suitable for production with appropriate engineering and development and highlighted that yeast in general present advantages for rapid genome engineering and development cycles.  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