共查询到20条相似文献，搜索用时 390 毫秒
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不育控制是一种新的鼠害治理方法,需要研究不育控制下害鼠的种群动态以及与之相关的其他生物种群的动态。论述建立了一类对害鼠进行不育控制的竞争模型,得到了系统平衡点的存在条件,证明了平衡点的渐近稳定性。在一定的条件下,对害鼠的控制可以使其他种群规模增大。 相似文献
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语文要在初中阶段过关，许多语文界人士早就这样呼吁。可是初中语文教学的现状却不尽人意，甚至令人担忧。现有对中考语文答卷的分析显示：卷面书写工整、规范的不到３％，书写潦草、字形较差的超过一半，其中有１０％的字迹难以辨认；一篇作文错别字数在５～９个的占２０％，在１０个以上的仍有１０％。这一统计提供的虽然只是学生对汉字的学习和掌握情况，但对其他语文基础知识的学习，甚至基本技能的养成也就不难想象了。应该指出，统计所反映出来的问题是具有普遍性的。这就清清楚楚地告诉我们：初中语文教学非但没有过关，而且这样的语… 相似文献
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多媒体教学方式探讨 总被引：7，自引：0，他引：7
陈璞 《高等工程教育研究》1995,(3):93-96
多媒体教学方式探讨陈璞现代教育学实验证明：学生获得知识，只靠听觉，所获的信息经过３小时后可保持２０％，３日后可保持１０％；只靠视觉，３小时后可保持７２％，３日后可保持２０％；视觉和听觉相结合，３小时后可保持８５％，３日后可保持６５％。由此可见，不同的... 相似文献
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王磊 《昭通师范高等专科学校学报》1995,(3)
本文采用滑鼠蛇作为鼠类的天敌,对农田害鼠采用滑鼠蛇进行生物防治的可行性在实验室内进行了模拟实验,从能量分析的角度认为滑鼠蛇对农田害鼠的生物防治意义不大。 相似文献
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五种猛禽的食性食量分析 总被引：1，自引：0，他引：1
五种猛禽——领角、燕隼、省鹰、松雀鹰和草均具有捕食农田害鼠的习性，但各自对不同种类的鼠类的嗜食程度不同。领角喜食小家鼠和板齿鼠，不喜食褐家鼠；燕隼喜食板齿鼠、黄毛鼠和褐家鼠．不喜食小家鼠；雀鹰对褐家鼠的嗜食性对比于平均食量的差异并不显著；松雀鹰极喜食小家鼠和板齿鼠，不食褐家鼠． 相似文献
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珠江三角洲黄毛鼠发生规律与防治措施 总被引：1，自引：0，他引：1
本文从不同侧面研究黄毛鼠发生规律．每年3～10月是黄毛鼠繁殖盛期．数量不断上升．年底达到高峰．将作物大面积连片种植．消灭弃耕地，减少、恶化害鼠栖息地；打破行业界限．全面灭鼠又突出重点．全面灭鼠与挑治相结合；优化灭鼠时机；下半年使用饱和间歇投饵技术．提高毒杀幼鼠的效果是当前控制鼠害行之有效的策略及技术． 相似文献
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试验通过在肥有猪日粮中添加１０％、２０％、３０％发酵稻草粉，结果表明：发酵活干菌对改变秸秆饲料的适口性；提高营养价值有较为明显的作用，有一定的饲用价值。 相似文献
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浅析教师应具备的素质杨富田植物病虫害和杂草严重威胁农业生产。据联合国粮农组织统计，世界上农作物因病虫危害所造成的损失：粮食作物约２０％，棉花３０％左右，果树４０％左右。一般杂草造成减产１０～１５％。因此，加强病虫害的防治工作是发展农业生产的一项重要措... 相似文献
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采用严格的田间小区品比试验对5个津巴布韦引进烤烟品种（系）和2个对照取样,对其9项重要化学成分进行检测．通过对比分析表明：津引烤娴资源的化学成分与K326相比,呈现“两糖低、烟碱低、氧化钾高”的三大显著特征;与云烟87相比,呈现“两糖低、淀粉低、氧化钾高、石油醚提取物高”的四大显著特征;在云南高原种植条件下,津引良种的烟叶氧化钾含量（质量分数）超过2％,石油醚提取物含量超过5％,总糖、还原糖分别低于31％和26％,淀粉含量低于3％和上部叶的烟碱含量低于2．5％．这说明,云南现有种植品种与津引品种有差异明显,在云南种植津巴布韦品种可以生产出类似津巴布韦的优质烟叶． 相似文献
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本研究采用二次通用旋转组合设计的方法,建立了以小麦产量和野燕麦防除率(％)为目标函数,考虑“燕麦枯”药剂施药量(公斤/公顷),喷液量(公斤/公顷)和施药时期(月/日)三个决策变量的数学模型。通过对模型的综合分析寻优提出:在麦田野燕麦危害严重地区(减产30％以上),“燕麦枯”施药量为8.25——10.05公斤/公顷,喷液量为450——675公斤/公顷,施药时期为12月/10日或翌年3月/10日前后的优化技术方案。运用此“燕麦枯”麦田施用技术,可获小麦每公顷产量4050公斤以上和野燕麦防除率75％以上。 相似文献
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温度对TiO2-膨润土紫外光降解十二烷基苯磺酸钠的影响 总被引：1，自引：1，他引：0
投加0.5‰的TiO2-膨润土光催化剂于浓度为20 mg/L的十二烷基苯磺酸钠(SDBS)溶液中,在紫外光照射下,在温度分别为10、20、30℃下,反应2 h后的溶液中的SDBS分别降解了86.0%,89.5%和90.5%,反应6 h后降解率分别达98.0%,98.8%和99.3%,可见温度对TiO2-膨润土复合光催化剂降解水溶液中的SDBS的影响不明显。溶液的COD值受温度影响较大,温度越高,COD值降低越多,在10、20、30℃条件下,反应6 h后溶液的COD值分别降低50.6%,58.1%和97.0%。TiO2-膨润土光催化剂降解水溶液中SDBS的反应为一级反应,符合Langmuir-Hinshelwood方程。同样条件下,环境温度由10℃增加到30℃时光催化反应速率常数由0.0105增大到0.0137,增加了30%。 相似文献
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Hans G. K. Hummel Rob J. Nadolski Jannes Eshuis Aad Slootmaker Jeroen Storm 《British journal of educational technology : journal of the Council for Educational Technology》2021,52(1):125-141
Introductory Psychology courses in Higher Education lack application of knowledge in solving work-based problems. We develop and study mini-games that support a more active and experiential way of learning to increase professional awareness. This paper describes the instructional design and the factors under study: learner control and authenticity. We compared professional awareness and perceived authenticity for the old (without game, n = 130) and new course (with game, n = 197) by administering pre- and post-questionnaires. Participants were allocated to game variants, differing in freedom of assignment order (less or more learner control) and number of sources available (less or more authentic). We computer logged their game actions, and asked them additional questions about gameplay that concerned aspects like motivation, flow, performance, learnability and usability. Both courses improved professional awareness (knowledge gains of 4% for the old and 12% for the new course), but only in the new course with mini-games this was significant. Students evaluated gameplay and their content as “more than sufficient” to “good.” A free order of assignments was found to produce more effective (in-game) performance, and the provision of more sources was found to improve learnability, authentic learning and appreciations of gameplay. 相似文献
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在反应温度20℃、紫外光强度700～750μW/cm2、照射时间2h、电磁搅拌时间2h、溶液初始浓度20mg/L的实验条件下,TiO2-膨润土的投加量对光催化降解十二烷基苯磺酸钠(SDBS)的效果有影响:随着TiO2-膨润土投加量由0.01‰增加到0.5‰,SDBS的降解率逐渐提高,当投加量为0.5‰时,光催化降解率最高,达92％,以后随着投加量的增加(从0.5‰到6‰),降解效率反而下降.可见,最佳投加量为0.5‰.在相同实验条件下,投加0.17‰的TiO2(与0.5‰的TiO2 -膨润土中含Ti量相同),SDBS的降解率只有40％.可见,相比TiO2,TiO2-膨润土具有投加量小,降解效率高的优点,更实用. 相似文献
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何凤琴 《西安文理学院学报》2009,12(4):1-5
为了验证雷公藤混合饵料和莪术葡萄糖注射液的混合饵料对农田害鼠的防治效果,在种植小麦的农田中进行了大面积的实验.实验结果表明害鼠对0.3 mg/kg雷公藤混合饵料、30 mg/kg莪术葡萄糖注射液混合饵料及0.3 mg/kg雷公藤和30 mg/kg莪术葡萄糖注射液的混合饵料的适口性没有显著性差异;3种混合饵料发挥作用后,害鼠数量明显少于混合饵料发挥作用前,实验结果进一步表明：3种混合饵料均可以作为环保型鼠药加以推广应用.由于30 mg/kg莪术葡萄糖注射液混合饵料实验产品成本最低,可以重点推荐使用. 相似文献
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This research examined children between 13 and 23 months of age with developmental delays in walking. Children in the experimental group received intensive infant stimulation and, subsequently approximately 71% were able to walk by themselves. In contrast, 32% of those children receiving only verbal instruction were able to achieve this important milestone. There was a significant difference (p less than 0.05) between the control and experimental group in acquiring walking skills. Mothers' lack of awareness about infant stimulation and lack of supervision on the part of health workers are the major contributing factors to delayed walking skill in these children. The study highlights the importance of taking health care to the home of clients, the most neglected aspect of primary health in this part of the world. 相似文献
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The purpose of this study was to compare the effects of four item selection rules—(1) Fisher information (F), (2) Fisher information with a posterior distribution (FP), (3) Kullback-Leibler information with a posterior distribution (KP), and (4) completely randomized item selection (RN)—with respect to the precision of trait estimation and the extent of item usage at the early stages of computerized adaptive testing. The comparison of the four item selection rules was carried out under three conditions: (1) using only the item information function as the item selection criterion; (2) using both the item information function and content balancing; and (3) using the item information function, content balancing, and item exposure control. When test length was less than 10 items, FP and KP tended to outperform F at extreme trait levels in Condition 1. However, in more realistic settings, it could not be concluded that FP and KP outperformed F, especially when item exposure control was imposed. When test length was greater than 10 items, the three nonrandom item selection procedures performed similarly no matter what the condition was, while F had slightly higher item usage. 相似文献
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This study is a detailed look at the level of understanding of fundamental ideas about blackbody radiation (BBR) among physics teachers. The aim is to explore associations and ideas that teachers have regarding blackbody radiation: a concept used routinely in physics and chemistry, which is necessary to understand fundamentals of quantum physics. In this explorative study, the responses of 106 high school physics teachers from 18 different cities in Turkey were examined using an online questionnaire during the 2014/2015 academic year. Male (88 %) and female (12 %) teachers with an average teaching experience of 17 years participated in this study. Teachers were asked about the concept of a “blackbody” and its radiation as well as about the closely related topics such as Wien’s law and the historic effect of understanding BBR on the development of modern physics. In this study, teachers’ spontaneous ideas about the BBR are depicted by “answer sculptures.” The answer sculpture is a new way of representing and categorizing responses provided by the participants. The analysis of answer sculptures revealed that the physics teachers’ factual knowledge and their conceptual understanding of the BBR are incomplete and even misleading. Here is what teachers we surveyed make of BBR as presented in our answer sculptures. This study is left at investigating teachers’ understandings of (1) blackbody radiation and (2) the significance of this scientific breakthrough. 相似文献