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排序方式: 共有1230条查询结果,搜索用时 31 毫秒
1.
辽宁省菜田生态系统组分优势值与系统优势度分析   总被引:2,自引:1,他引:1  
辽宁省菜田生态系统组分优势值与系统优势度分析周宝利,葛晓光李宁义(沈阳农业大学园艺系,110161)(沈阳市城建中专,110013)AnalysisonSuperiorityValueandDominanceDegreeofVariousCompon...  相似文献   
2.
In this study, the fractionation and distribution of phosphorus (P) in the core sediments of the Shanmei reservoir were investigated by using the chemical extraction method in directions for the first time in order to understand its bio-availability, adsorption characteristics, potential release and environmental significance. The results of the study showed that P in the sediments mainly consisted of inorganic phosphorus (IP) and that IP mainly consisted of non-apatite phosphorus (NAIP). The horizontal and temporal distributions of the P fractions were different from each other, but the vertical distribution was similar, which indicated a trend of stabilization after falling. The content of total phosphorus (TP), IP, organic phosphorus (OP), NAIP, apatite phosphorus (AP), and bio-available phosphorus (BAP) in the sediments during the three seasons ranged from 193.85 to 1664.05 mg·kg?1, 126.90 to 1127.70 mg·kg?1, 43.74 to 669.29 mg·kg?1, 57.62 to 937.07 mg·kg?1, 32.58 to 250.71 mg·kg?1, and 41.06 to 871.82 mg·kg?1, respectively. NAIP contents in the sediments accounted for more than 50% of TP. Using an analysis from three aspects, the eutrophication risk index (ERI) could be used to assess the potential release of P in the sediments, and there was a high release risk of P in the sediments in the Shanmei reservoir.  相似文献   
3.
As a key issue in China’s urban development, urbanization creates increasing pressure on the environment. Thus, a better understanding of the relationship between urbanization and the eco-environment is necessary for Chinese policy makers to realize sustainable urbanization development. Making reference to physical coupling models, we developed a coupling coordination degree model in order to examine the relationship between urbanization and the eco-environment in Shanghai, using data from 1980 to 2013. The comprehensive level of Shanghai’s urbanization process during the study period was estimated using an index composed of four primary indicators, namely: demographic urbanization, spatial urbanization, social urbanization, and economic urbanization. We also developed an index system for the eco-environment, which was based on four primary indicators: the environmental level, eco-environmental endowment, eco-environmental pressure and eco-environment response. The entropy method was subsequently employed in order to identify the contribution made by each indicator to the compound system during the study period. The results show that: (1) economic urbanization and eco-environmental response made the greatest contributions to the urbanization subsystem and the eco-environmental subsystem, respectively—these are thus the key factors to consider in policy decisions aiming to adjust the coupling coordination degree between the two subsystems; (2) the two parameters α-urbanization and β-eco-environment were found to have minimal effect on the coupling coordination system; (3) the coupling coordination between urbanization and the eco-environment produced an S-shaped curve, and both subsystems were found to have evolved from seriously unbalanced development at the start of the study period into superiorly balanced development at the close of the study period. The results of this study hold important implications for efforts to achieve the coordinated development of both urbanization and the eco-environment.  相似文献   
4.
庐山蕨类植物区系研究   总被引:2,自引:1,他引:1  
庐山共有蕨类植物39科87属247种(含变种、变型),其区系带有热带和温带双重性。其中鳞毛蕨科、水龙骨科、蹄盖蕨科、金星蕨科和铁角蕨科属种优势明显,共有38属160种,分别占总属数的43.7%和种数的64.8%,代表了该地区蕨类植物区系的一个重要特征。该区区系地理成分复杂,相互交错,其中热带性属占总属数的64.2%,温带性属占总属数的35.8%。东亚成分在该区系占有绝对优势,共有14属,占总属数的20.9%,中国特有属缺乏,特有种丰富,表明成分具有多样性并具有热带亲缘性,是亚热带向北温带的过渡地区。该区与井冈山、武夷山关系密切,与鼎湖山、秦岭和横断山关系疏远。  相似文献   
5.
步长稳心颗粒治疗136例心律失常的临床疗效观察   总被引:1,自引:0,他引:1  
目的:观察步长稳心颗粒对心律失常的治疗效果。方法:将心律失常患者136例随机分成两组,治疗组68例用稳心颗粒治疗,对照组68例用胺碘酮治疗,治疗4周观察静息心电图、动态心电图、Q-T离散度,平均心室率,不良反应的变化。结果:治疗4周后,治疗组总有效率优于对照组,差异有统计学意义(P<0.05)。治疗组治疗后Q-T离散度减小,差异有统计学意义(P<0.05);对照组胺碘酮治疗后Q-T离散度变化不大。治疗组和对照组治疗后平均心室率均下降,差异有统计学意义(P<0.05),但两组间平均心室率比较差异无统计学意义(P>0.05);治疗组不良反应发生率明显低于对照组(P<0.05)。结论:稳心颗粒能有效治疗心律失常,毒副作用小,安全可靠。  相似文献   
6.
8株光合细菌的鉴定及其系统进化关系分析   总被引:1,自引:0,他引:1  
目的为8株光合细菌(photosynthetic bacteria,PSB)作为益生菌株提供系统资料。方法用常规方法对8株PSB菌株的形态、培养特性及生理生化特征进行鉴定,同时定性分析菌株产生的类胡萝卜素和CoQ,测定菌株16S DNA序列并分析其系统进化关系,在GenBank中获取了8个16S DNA序列号。结果菌株鉴定结果表明:菌株2C、2c和13ing为沼泽红假单胞菌,Ga、Il106、WS8N为类球红细菌,MT1131为荚膜红细菌,rub为深红红螺菌。基于菌株16S DNA序列的系统进化树显示,同一种菌并不总是聚为一簇,但相隔较近;种属完全不同的菌株,尽管序列相似性高达97%以上,在系统进化树上相隔较远。结论8株PSB菌株的鉴定和系统进化关系分析结果为后续研究提供了背景资料,同时菌株在GenBank中获得的16S DNA序列号为菌株作上了生物标记,也为菌株的产权保护提供了依据。  相似文献   
7.
The temporal variation of stoichiometry between consumed oxygen and oxidized carbon was investigated for the aerobic mineralization of leachates from aquatic macrophytes. Seven species of aquatic plants, viz. Cabomba piauhyensis, Cyperus giganteus, Egeria najas, Eichhornia azurea, Salvinia auriculata, Scirpus cubensisand Utricularia breviscapa, were collected from Òleo lagoon located in the floodplain of Mogi-Guacu river (São Paulo State, Brazil). After being collected, the plants were washed, oven-dried and triturated. In order to obtain the leachate, the fragments were submitted to an aqueous extraction (cold). Mineralization chambers were incubated at 20 °C containing leachates dissolved in water samples from Òleo lagoon to a final concentration of ca. 200 mg l–1on carbon basis. The chambers were maintained under aerobic conditions; the concentrations of the organic carbon (particulate and dissolved) and the dissolved oxygen were measured during approximately 80 days. Elemental analysis of the detritus and the concentrations of the remaining material (DOC and POC) were used to determine the amounts of mineralized organic carbon. The data were analyzed with first-order kinetics models, from which the daily rates of consumption (carbon and oxygen) and the stoichiometry (O/C) were determined. In the early phase of mineralization the O/C rates increased before reaching a maximum, after which they tended to decrease. For the mineralization of leachates from C. giganteus, S. auriculata and U. breviscapa, the decrease was relatively slow. For all substrata the initial values were smaller than 1, and ranged from 0.42 (S. cubensis) to 0.81 (C. piauhyensis). The maximum values were within the range from 0.58 (U. breviscapa) to 23.1 (E. najas) and at their highest 26th (C. piauhyensis) and 106th (C. giganteus) days. These variations are believed to be associated with the chemical composition of the leachates, with their transformations and alterations of metabolic pathways involved in the mineralization.  相似文献   
8.
目的:分析医疗指标与平均住院日的关联程度,为医院有效缩短平均住院日提供参考依据。方法:建立基于灰熵优化的加权灰色关联度模型,对影响平均住院日的医疗指标进行重要程度的分析。结果:根据关联程度分析,可知影响平均住院日的医疗指标重要程度依次为开放床位数、床位周转次数、治疗有效率、床位使用率、年门诊量、住院手术人次和出院人数。结论:基于灰熵优化的加权灰色关联分析方法可以有效分析医疗指标对平均住院日的影响程度,提高医疗服务质量。  相似文献   
9.
10.
东北地区部分大型藓类植物遗传多样性的RAPD研究   总被引:1,自引:1,他引:0  
李晶  沙伟 《植物研究》2008,28(6):689-692
采用RAPD标记构建了东北地区20种大型藓类植物的系统关系。从200个随机引物中筛选出清晰且多态性高的7个引物,共产生了82条DNA片段,其中79条谱带具有遗传多态性,约占96.34%,平均每个引物扩增的DNA片段数为11.71条。采用NTSYS-pc数据分析软件,计算Nei氏相似性系数,建立了UPGMA聚类图。结果表明:以遗传相似性系数0.27为界限划分,可将20种苔藓植物分为二大类,即泥炭藓类和真藓类。以遗传相似性系数0.42为界限划分,可将20种苔藓植物划分为四大类群,即泥炭藓类、顶蒴单齿亚类、顶蒴双齿亚类和侧蒴双齿类。从整个聚类图可以看出,泥炭藓类是较原始的类群,而金发藓类是较进化的类群,这一结果和大多数苔藓植物经典分类系统相同。  相似文献   
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