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221.
农业科技进步是农业经济增长的主要影响因素。 在探讨农业科技进步内涵、借鉴以前学者提出的农业
科技进步评价指标的基础上、收集 2007-2011 年的数据、采用主成分分析法比较重庆 13 个区县在农业科技进步上
的差距、从而找出对农业科技进步产生影响的主要因素、并根据重庆各区县农业科技进步的现状、提出今后重庆农
业科技进步的对策与建议。 相似文献
222.
基于 VSM 的农机作业精益管理模式研究 总被引:1,自引:0,他引:1
我国农机作业正向社会化服务迈进、农机作业组织呈现数量增长快、服务方式多、服务能力和水平不断
提高的特点;但也存在由于服务组织结构不合理、管理不规范等因素造成的服务水平低、服务收益波动大等问题。 为
了规范农机作业过程管理、提高作业绩效、应用基于活性系统模型(VSM )的组织设计方法、将多种精益管理手段和
方法引入农机作业服务管理中、构建了面向农机作业服务精益管理的活性系统模型。 案例研究结果表明、该模型可
用于指导我国农机作业服务组织实施精益管理的组织结构设计和运作诊断。 相似文献
223.
通过对伦敦奥运会男篮比赛分析发现,来源于欧美职业篮球联赛队员数量决定各队竞技实力,体现各国运动员国际流动与交融发展新趋势;欧、美球队呈现“高、快、灵、准、全、悍、变、星”的进攻特征及防守“以球权争夺为核心,球、人、区、时空兼顾”的先进理念;当前世界篮球区域发展不均衡,美洲占据竞技优势,欧洲整体水平高,亚、非洲实力弱,呈欧美全面抗衡格局;中国男篮竞技水平和成绩下滑明显,运动员身体机能指标和得分、失分、投篮次数、命中率、篮板球、助攻、失误、抢断指标与世界强队存在显著性差异(P﹤0.05),盖帽、犯规无显著性差异(P>0.05),表现出个人能力、技战术风格、整体攻防与世界强队全方位差距,并呈逐步拉大趋势。 相似文献
224.
225.
K. David Hyrenbach Zora McGinnis Kathleen Page Dan Rapp F. David Horgen Jennifer M. Lynch 《水产资源保护:海洋与淡水生态系统》2021,31(2):408-419
- Although the frequency of occurrence of plastic ingestion in the large-sized dolphinfish and tunas taken by the Hawai'i longline fishery is very low (frequency of occurrence < 5% of sampled individuals), the ingestion of plastic in smaller-sized specimens caught with pole-and-line gear by commercial and recreational fishers has not been investigated.
- This study examined ingestion of >0.25 mm marine plastic debris (MPD) by four predatory fish species caught by commercial fishers around the Main Hawaiian Islands, and documented ingestion in three species: 85.7% of albacore tuna (n = 7), 40.0% of skipjack tuna (n = 10) and 12.5% of dolphinfish (n = 8).
- Yellowfin tuna (n = 10) did not contain any MPD, probably owing to the high proportion of empty stomachs (60%).
- For skipjack tuna, the frequency of occurrence of MPD ingestion was significantly higher for the smaller-sized specimens caught with pole-and-line (40%), compared with the larger-sized specimens caught with longlines (0%).
- For dolphinfish, the frequency of occurrence of MPD ingestion was similar for the similar-sized specimens caught with pole-and-line and with longlines.
- The ingested MPD items were micro–meso plastics, between 1 and 25 mm. While most ingested items were fragments, albacore also ingested line and skipjack also ingested sheets.
- The predatory fishes ingested light MPD items that float in sea water, but there were species-specific differences in their polymer composition: albacore contained more polypropylene and polyethylene, and skipjack contained more elastomers, characterized by a high percentage of ester plasticizers.
- Altogether, these results suggest that albacore and skipjack tunas ingest plastic of different types and polymers. Yet more research is needed to understand how differences in vertical distribution, foraging ecology and diet influence the MPD sampled by these predatory fish species.
226.
Bechir Saidi Khaled Echwikhi Samira Enajjar Sami Karaa Imed Jribi Mohamed N. Bradai 《水产资源保护:海洋与淡水生态系统》2020,30(6):1172-1181
- This study evaluated the circle hook use as a tool for shark management in the pelagic longline fishery in the Gulf of Gabès.
- The usual J‐hook No. 2 with 10° offset, which has been traditionally used by the fishery, was compared to the 18/0 non‐offset circle hook in an alternating fashion along the main line. In total, 22 experimental longline sets were deployed through the shark fishing seasons of 2016 and 2017 to examine the effects of hook types on the catch composition, the catch rates, the hooking location, and the status at haulback.
- The catch composition differed significantly among hook types. Moreover, an overall increase in catch rates for the main species, the sandbar shark Carcharhinus plumbeus, and the shortfin mako shark Isurus oxyrinchus, was observed when using circle hooks.
- There was no size‐selective effect of circle hooks for the common species. The circle hooks were not effective at reducing at‐haulback mortality of sandbar shark. Conversely, shortfin mako and smooth‐hound shark Mustelus mustelus showed significantly lower relative mortality at haulback with circle hooks than with J‐hooks. Furthermore, circle hooks were more frequently hooked externally than the J‐hooks for the three shark species.
- Results demonstrated that the use of 18/0 non‐offset circle hooks in the pelagic shark longline fishery can reduce mortality at haulback for some species without any benefit for the dominant species, the sandbar shark.
- Overall, it is difficult to promote the adoption of the use of circle hooks as a management measure in this specialized fishery. Management measures focusing on fishing effort controls, fishing closures in critical habitats, and size limits could have significant benefits for the conservation of shark species and may help to improve the sustainability of the shark fishery in the Gulf of Gabès.
227.
Dr. John F. Burka Heather A. Briand Cheryl Ann Wartman Jeffrey G. Hogan William P. Ireland 《Fish physiology and biochemistry》1996,15(2):95-104
Mediators and mechanisms responsible for the inhibitory modulation of trout intestinal smooth muscle were examined using a series of putative mediators and substances known to modulate neurotransmission in mammalian systems. Frequency response relationships to transmural stimulation and concentration response relationships to 5-hydroxytryptamine, carbachol, and substance P were established on paired segments of rainbow trout intestinein vitro in the presence and absence of putative modulatory agents. Modulation of neurally-mediated contractions of trout intestine was achieved with dibutyryl cyclic AMP and forskolin, agents that increase intracellular levels of cyclic AMP. The effect appears to be at the level of the smooth muscle, since the adenylate cyclase activator, forskolin, inhibited muscarinic and serotoninergic contractions as well as transmurally stimulated contractions. Substance P-induced contractions were unaffected by forskolin. The endogenous agonists/neurotransmitters which would increase cyclic AMP levels in rainbow trout intestinal smooth muscle are as yet unknown. The effects do not appear to be modulated by vasoactive intestinal peptide (VIP), calcitonin, calcitonin gene-related peptide (CGRP), or agents that activate -adrenoceptors. Prostaglandin E2 (PGE2) and 2-adrenergenic agonists are possible agents which will decrease contractility of the smooth muscle. They were only active in the proximal intestine and on transmurally stimulated contractions. The effects of both PGE2 and 2-agonists appear to be prejunctional, decreasing release of contractile neurotransmitters in the enteric nervous system. 相似文献
228.
229.
黄朝霞 《厦门水产学院学报》2011,(2):141-144
在Lω-空间中引进加强了的ωTi(i=1,2)-分离性等概念,系统地讨论了这些概念的特征性质,得出它们保持了LF拓扑空间中Ti-分离性的主要结论,进而说明加强了的ωTi(i=1,2)-分离性是L-好的推广. 相似文献
230.
姜红 《安徽农业大学学报》2000,(4):89-91
本文从人物塑造、文化修养、语言风格及创作心态四方面对金庸小说进行了分析,进而指出在人物塑造方面的求真、以现代的观点诊释历史、对传统的白话文加以发展及将自由写作的精神与严肃的态度相结合是金庸小说沟通雅俗、超越古今的重要原因。 相似文献