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排序方式: 共有8526条查询结果,搜索用时 15 毫秒
981.
982.
A review of recent data concerning the apoptotic death of cells during senescence at the organismic level. The data analyzed suggest interrelations between apoptosis deregulation and some age-related pathologies and senescent phenotypes. Genetic aspects and possible mechanisms of age-related changes in the program of apoptosis are considered. It has been proposed that age-related deregulation of apoptosis is a mechanism of senescence. 相似文献
983.
984.
985.
Ricardo D. Otaíza Sebastián R. Abades Antonio J. Brante 《Journal of applied phycology》2001,13(2):161-171
The population dynamics of the carrageenophyte Sarcothalia crispatais described from subtidal beds at two localities in south-central Chile. Seasonal fluctuations in total density and biomass were not evident. Frondswere identified to phase by the presence of reproductive structures and theresorcinol reaction. The monthly changes in abundance of each kind offrond were determined. Permanent gametophytic or sporophyticdominance was not evident: the more exposed site showed a seasonal shiftfrom sporophytic dominance in summer to gametophytic dominance inwinter, whereas the more protected site showed an interannual shift fromgametophytic to sporophytic dominance. The differences between localitiesand years suggest a very local population dynamics with large contributionof self-seeding to the maintenance of the S. crispata beds. 相似文献
986.
Alain Dubreuil 《The International Journal of Life Cycle Assessment》2001,6(5):281-284
Publicly available databases are analysed to demonstrate their relevance to life cycle inventory for energy production in
the Canadian context. Site specific emissions along with sectoral emissions data are combined with production data to construct
an energy production model, which has been applied to air emissions. The allocation procedure leads to reasonable results
for coal, natural gas and electricity. The detailed allocation of the inventory among petroleum co-products is outside the
scope of this study as it requires incorporating knowledge of physical relationship (unit process) or using economic data. 相似文献
987.
988.
Kin selection theory states that when resources are limited and all else is equal, individuals will direct competition away
from kin. However, when competition between relatives is completely local, as is the case in granivorous insects whose larval
stages spend their lives within a single seed, this can reduce or even negate the kin-selected benefits. Instead, an increase
in competition may have the same detrimental effects on individuals that forage with kin as those that forage with non-kin.
In a factorial experiment we assessed the effects of relatedness and competition over food on the survival and on fitness-related
traits of the bruchid beetle Callosobruchus maculatus. Relatedness of competitors did not affect the survival of larvae. Larval survival substantially decreased with increasing
larval density, and we found evidence that beetles maturing at a larger size were more adversely affected by competition,
resulting in lower survival rates. Furthermore, females showed a reduction in their growth rate with increasing larval density,
emerging smaller after the same development time. Males increased their growth rate, emerging earlier but at a similar size
when food was more limited. Our results add to the growing number of studies that fail to show a relationship between relatedness
and a reduction in competition between relatives in closed systems, and emphasize the importance of the scale at which competition
between relatives occurs. 相似文献
989.
目的 旨在通过对我院岗前培训8年经验的总结,摸索出一套在医院文化背景下的岗前培训体系。方法 采用问卷方法对2007—2009年新员工岗前培训效果进行匿名调查,并使用Excel进行数据录入和统计。结果 调查对象中76.63%的员工对师资配置情况及课程设置情况表示满意,54.08%的员工对培训时间与进度表示很合适,69.47%的员工对培训保障措施表示满意,69.42%和80.08%的员工分别对授课形式和培训受益情况表示满意。结论 医院文化及人文医学培训是医院人力资源处岗前培训的核心内容,这对每个从医人员树立正确的职业价值观具有指导作用和现实意义。岗前培训中培训师的授课技巧、专业知识及能力有待进一步提高,今后应不断完善内部培训师的培养途径与方法。 相似文献
990.
Andrew Clarke 《Invertebrate reproduction & development.》2013,57(2):71-82
The life-history tactics of many Antarctic marine invertebrates suggest that the commonly observed slow rates of growth are adaptations to the pattern of food availability, and not due to low temperature per se. This implies that marine invertebrates have been able, over the course of evolutionary time, to compensate their rates of embryonic development for the effect of temperature. Data from north Atlantic copepods indicate that this is so. It is therefore suggested that the slow rates of embryonic development in many Antarctic marine invertebrates are the result of large egg size, and not the low temperature. Large, slowly developing eggs are part of a suite of tactics, often called K-strategies, which characterise many marine invertebrates in Antarctica. 相似文献