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191.
河南省入境旅游市场时空演变规律研究 总被引:1,自引:0,他引:1
在分析河南省入境旅游市场发展现状的基础上,应用地理集中指数、亲景度和竞争态三种市场指标体系和EXCEL统计软件对河南入境旅游客源市场进行分析,揭示了河南入境旅游市场时空演替规律.据此划分河南入境旅游的重点市场、主要市场、潜在市场和机会市场,并提出了进一步拓展河南入境旅游客源市场的几点建议. 相似文献
192.
Woon-Seok Cho 《Ecological modelling》2011,222(3):407-418
The genotypic and phenotypic processes were incorporated into one system in the gene-individual-population relationships under the framework of Individual based models (IBMs). The gene types addressing different degrees of metabolic efficiency and toxin susceptibility were provided as attributes in the individuals. Subsequently ecological processes such as food competition and movement were allowed concurrently on the 2-D space to determine the suitable species adapted to the system. The integrative gene-individual-population model accordingly responded to gene exchanges between the neighboring individuals through conjugation. At a substantially low level of gene exchange, system heterogeneity increased to produce high levels of eco-exergy, being presented by species diversity and total population size in the system. The issues related to genetic and ecological effects in the integrative gene-individual-population relationships were further discussed. 相似文献
193.
D.N. Mungai C.L. Coulson J.K. Ng'' Ang'' A G.W.S. Netondo G.O. Umay C.J. Stigter 《环境科学学报(英文版)》2001,13(3):291-298
IntroductionOnlyabout 2 0 %ofKenya’stotallandareahashighpotentialforagriculturalproduction ,therestbeingaridorsemi arid .TheannualpopulationgrowthrateinKenyaofcloseto 4 %isoneofthehighestintheworld (e .g .UnitedNationsDevelopmentProgramme ,1990 ) .Thissituationhasl… 相似文献
194.
T. I. Pisman 《Russian Journal of Ecology》2003,34(4):267-270
The functioning of a closed aquatic consumer–producer system with spatially separated links, with each link consisting of two species, is considered. Competition between the consumers (infusorians Paramecium caudatum and rotifers Brachionus sp.) feeding on a mixed algal culture (Chlorella vulgaris and Scenedesmus sp.) and competition between these algae under conditions of limited nitrogen supply are analyzed. It is shown that Scenedesmus algae have an advantage over C. vulgaris in terms of competitiveness, and their metabolic products have an adverse effect on reproduction in infusorians. 相似文献
195.
间接竞争ELISA法测定稻田土壤中除草剂毒莠定的残留量 总被引:6,自引:1,他引:6
通过对反应体系中酶标二抗(辣根过氧化物酶标记羊抗兔IgG)和抗体的最佳稀释浓度等条件的筛选和确定,最终建立了一种快速灵敏地测定污染稻田土壤中毒莠定残留量的方法--间接竞争ELISA分析方法.结果表明,酶标二抗和抗体的最佳稀释度均为1:500(体积比),毒莠定的检出下限达到5 ng·mL-1,在0.07~0.7μg·mL-1浓度范围内有良好的线性;土壤浸出液加样的平均回收率为104.11%,变异系数在3.13%~11.13%之间,符合农药残留分析的要求;样品基质对检测结果没有干扰. 相似文献
196.
复杂网络视角下世界石油流动的竞合态势演变及对中国石油合作的启示 总被引:2,自引:0,他引:2
世界石油流动的规模和复杂性日益增加,从复杂网络分析视角考察石油流动中主要贸易国及其所处地缘区之间的相对地位及变动,并分析中国在其中的竞合关系,有利于从与出口地缘区合作和与进口地缘区合作两个方面,全面审视中国石油合作的总体格局、重点合作国家和可能的模式创新。研究结果表明:(1)世界石油流动仍由主要出口地缘区主导,逐步演变为俄罗斯—中亚、美国—加拿大和中东三足鼎立的出口竞争格局,但出口地缘区的多元化和地位相对变动也为进口国调整合作关系提供了机遇;(2)亚太地区逐步成为世界石油流动的竞合焦点,但由于区内大国缺乏互济交流,降低了地区的整体核心地位和对石油流动的调控力,中国也深陷进口分散化、出口大国博弈和进口大国制衡三大困境中;(3)中国应与核心出口地缘区重点合作,与其他出口地缘区稳定合作并创新合作模式,与亚太其他进口国基于进口份额协调机制、来源错位竞争机制和国际贸易中心分工协作机制,开展区内互济交流合作,以改善中国在世界石油流动格局中的竞合环境,保障石油供需平衡、降低供给风险。 相似文献
197.
We investigated the fledging probability of oystercatcher, Haematopus ostralegus, chicks as a function of hatching order, brood size, territory quality and food availability. Sibling dominance was related
to the hatching order in both low- (’leapfrogs’) and high-quality (’residents’) territories. Differences in hatchling mass
might have aided the establishment of a dominance hierarchy, since breeders produced small late eggs and hatchlings. These
mass differences were most pronounced in leapfrogs, and in large broods in years with lower food availability (’poor’ years).
Late hatchlings fledged less often and with lower body masses compared to early hatchlings in all situations. Leapfrogs produced
smaller broods and hatched their broods more asynchronously in poor years than leapfrogs breeding in years with more available
food (’good’ years) and residents breeding in both poor and good years. Large brood sizes resulted in lower survival of hatchlings
in poor years. These results favour the ’brood reduction’ hypothesis. However, contrary to the expectations of this hypothesis,
hatching order also affected fledging success in residents. Moreover, large brood size resulted in higher survival of hatchlings
in good years, particularly in residents. Thus, although large broods experienced losses due to sibling competition in some
years, they nevertheless consistently produced more fledglings per brood in all years, both as leapfrogs and residents. We
believe this effect is due to parental quality correlating with initial brood size. Most leapfrogs, at best, fledged one chick
successfully each year, losing chicks due to starvation. Nevertheless, leapfrog broods were reduced in size after hatching
significantly less quickly than resident broods. These results suggest that breeders lay and hatch insurance eggs to compensate
for unpredictable losses due to the high predation rates on both nests (ca 50%) and chicks (ca 90%), in accordance with the
’nest failure’ hypothesis.
Received: 14 February 2000 / Revised: 27 September 2000 / Accepted: 10 June 2000 相似文献
198.
199.
200.
There is evidence to suggest that males of various species can respond to the threat of sperm competition by varying the
amount of sperm transferred during copulation. We tested this in two species of cricket, Acheta domesticus and Gryllodes supplicans (Orthoptera: Gryllidae) by varying the apparent threat of intermale competition experimentally. The results showed that males
of both species increased the amount of sperm transferred as apparent competition increased and that male A. domesticus transferred more sperm when encountering larger females. The results also showed that male G. supplicans produced a larger spermatophylax when a larger ampulla was transferred, a relationship consistent with a sperm protection
function.
Received: 5 May 1995/Accepted after revision: 27 January 1996 相似文献