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51.
胡红晓 《农业图书情报学刊》2010,22(8):260-262,290
通过对某专业院校图书馆文献借阅情况调查,就改进院校图书馆管理,优化读者服务谈了一些看法。侧重于研究教学型的专业院校图书馆作讨论。 相似文献
52.
从活跃农民群众文化生活、发展和繁荣农村文化的角度出发,从促进社会主义农村经济的协调发展、全面提高农民综合素质入手,对当前“农家书屋”发展现状以及存在的问题进行分析,探讨了高校图书馆对“农家书屋”工程建设的优势和促进“农家书屋”工程建设的有效方法和途径。 相似文献
53.
Mohamed Neji Mohamed Moncef Serbaji Olivier Hardy Mohamed Chaieb 《Arid Land Research and Management》2018,32(3):291-315
Knowledge about vegetation patterns along disturbance gradients is essential for conservation and management of coastal habitats in arid regions. This study focuses on the floristic diversity and the factors controlling the vegetation structure in the Gulf of Gabès (Tunisia). For this purpose, the floristic diversity of 120 relevés belonging to three coastal sites with different disturbance levels (40 relevés per site) was analyzed in relation with 10 environmental and anthropogenic factors. Therophytes constitute 54% of the 237 plants species belonging to 44 families identified in the present study. The species richness and floristic diversity indices exhibited a similar trend and peaked in the slightly disturbed site (H′?=?3.38; S?=?176). The similarity between sites was relatively low and reached its maximum between the little and the highly disturbed sites. Two-way indicator species analysis and detrended correspondence analysis applied on the floristic data resulted in groups mainly determined by disturbance level by explicitly segregating the three sites. Canonical correspondence analysis (CCA) indicated that the spatial pattern of species composition was mainly influenced by anthropogenic variables. Partial CCA revealed that the effect of anthropogenic variables on floristic composition was thrice higher than the effect of environmental variables (57.5% vs. 18.4%, respectively). Overall, this study provides a broad understanding of the floristic diversity and vascular plant richness in the Gulf of Gabès. The obtained results reflected a disturbance–diversity pattern and thus revealed the obvious importance of maintaining the intermediate disturbance for biodiversity conservation and monitoring. 相似文献
54.
To clarify the relationship between the phylogeny and infectivity of isolates of Podosphaera fuliginea s. lat. (= Sphaerotheca fuliginea s. lat.) from cosmos and cucumber, more than 50 powdery mildew isolates from these two plants were subjected to nucleotide sequencing
or PCR-RFLP analysis of the rDNA internal transcribed spacer (ITS) region and cross-inoculation tests. The isolates from both
cosmos and cucumber are genetically monotypic, and there are six nucleotide substitutions in the rDNA ITS region between isolates
from cosmos and cucumber. Cross-inoculation tests of these isolates revealed that isolates from cosmos are not pathogenic
on cucumber. Although isolates from cucumber produced conidia on leaves of cosmos in the laboratory, the conidial density
was much lower than that from isolates from cosmos. This result, as well as the fact that the cucumber strain was not isolated
from cosmos in fields, suggests that isolates from cucumber do not infect cosmos in the field. Therefore, powdery mildews
on cosmos and cucumber can be regarded to have become specialized for their hosts both genetically and pathogenically. The
present study reconfirms the close relationship between phylogeny and infectivity of powdery mildew fungi. Host specialization
may be a trigger that causes genetic divergence of powdery mildew fungi.
Received 28 June 2000/ Accepted in revised form 4 September 2000 相似文献
55.
张静互 《湖南农业大学学报(自然科学版)》2003,(2)
作为儒家哲学的一个重要范畴,"礼"是先秦儒家教育理论及其实践的核心范畴。儒家的教育理论是完全依靠"礼"如何与其他范畴互相关联而形成发展的。尤其是孔子、孟子和荀子所提出的"仁"、"人性"和"文"等范畴对体现出"礼"的教育内涵是不可缺少的。"仁"只有通过"礼"才能实现自己的价值,"人性"也依靠"礼"的内化过程而能够获得真正的发展。在这一点上,可以说"礼"是文明化了的传统中分化、发展下来的一切标准,"礼教"是以"博文"与"约礼"为主要内容而培养君子的先秦儒家的教育传统。 相似文献
56.
汪一江 《安徽农业大学学报》2003,(4):102-104,107
优秀教师是高等教育事业建设的宝贵财富,高校领导必须尊重他们,使用他们。这样,就得创造一个让他们尽情发挥才能的环境。要做到这些,高校领导需要有尊师爱才之心,有识才之智,有容才之量,有用人之识。只有创造一个优秀教师人才脱颖而出的环境,我们的高校才能兴旺发达,才能步入“世界一流”的行列。 相似文献
57.
58.
- 1. Dabry's sturgeon, a large, long‐lived migratory fish is endemic to the Yangtze River. Over‐fishing and habitat destruction have caused large‐scale declines in natural stocks in the last two decades.
- 2. Examining patterns of genetic diversity has become an integral component of many management plans for endangered species. DNA fingerprinting was applied to detect genetic diversity in Dabry's sturgeon collected in 1958–1959, 1980–1981 and 1998–1999.
- 3. Studies on direct genetic parameters (genetic variability, hypervariable loci and heterozygosity) and indirect parameters (band‐sharing coefficient and allelic frequency) showed that the continuous decline in wild populations has caused the loss of genetic diversity in present‐day sturgeon.
- 4. The present‐day populations have the lowest genetic variability; thus, effective management is needed to preserve genetic diversity.
- 5. A conservation strategy is urgently required, comprising artificial rearing facilities coupled with breeding management plans.
59.
通过招商引资壮大雅安市现有乳品加工企业的能力与水平,带动奶业基地发展;建立奶业协会,破除当前条块分割、体制不顺等问题,提高农民养奶牛奶羊的组织化程度;建设奶业高种园区,提高科技贡献率,充分利用雅安发展奶业得天独厚的优越条件及大好机遇,超常规跨越式发展,使雅安市成为四川奶业强市. 相似文献
60.
Many chlorine-containing pesticides, for example 2-chloro-s-triazines, are of great concern both environmentally and toxicologically. As a result, ascertaining or predicting the fate and transport of these compounds in soils and water is of current interest. Transformation pathways for 2-chloro-s-triazines in the environment include dealkylation, dechlorination (hydrolysis), and ring cleavage. This study explored the feasibility of using computational chemistry, specifically the hybrid density functional theory method, B3LYP, to predict hydrolysis trends of atrazine (2-chloro-N4-ethyl-N6-isopropyl-1,3,5-triazine-2,4-diamine) and related 2-chloro-s-triazines to the corresponding 2-hydroxy-s-triazines. Gas-phase energetics are described on the basis of calculations performed at the B3LYP/6-311++G(d,p)//B3LYP/6-31G* level of theory. Calculated free energies of hydrolysis (delta h G298) are nearly the same for simazine (2-chloro-N4,N6-diethyl-1,3,5-triazine-2,4-diamine), atrazine, and propazine (2-chloro-N4,N6-di-isopropyl-1,3,5-triazine-2,4-diamine), suggesting that hydrolysis is not significantly affected by the side-chain amine-nitrogen alkyl substituents. High-energy barriers also suggest that the reactions are not likely to be observed in the gas phase. Aqueous solvation effects were examined by means of self-consistent reaction field methods (SCRF). Molecular structures were optimized at the B3LYP/6-31G* level using the Onsager model, and solvation energies were calculated at the B3LYP/6-311++G(d,p) level using the isodensity surface polarizable continuum model (IPCM). Although the extent of solvent stabilization was greater for cationic species than neutral ones, the full extent of solvation is underestimated, especially for the transition state structures. As a consequence, the calculated hydrolysis barrier for protonated atrazine is exaggerated compared with the experimentally determined one. Overall, the hydrolysis reactions follow a concerted nucleophilic aromatic substitution (SNAr) pathway. 相似文献