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1.
通过对日本林蛙早期胚胎发育的观察和出膜至变态蝌蚪、幼蛙及成体的系统解剖,对呼吸,循环、泌尿、生殖系统和感觉器官的发生,发展与变化过程进行了描述和讨论.  相似文献   

2.
本文对采集于青海西宁地区产中国林蛙的输卵管的显微结构进行了观察研究。  相似文献   

3.
性激素对中国林蛙性腺分化的影响   总被引:5,自引:0,他引:5  
在我国要蛙养殖地区,性别比例失调问题十分严重,部分地区紫蛙和雄蛙的比例只有3:7,严重影响养殖效益,制约养蛙业的发展。为调整林蛙性别比例,分别在实验室内和抚松林蛙养殖场采用在蝌蚪饵料中添加性激素的方法,诱导性腺分化,达到了调整林蛙性别的目的,并对激素诱导的合适浓度和最佳时期进行了研究。为促进林蛙养殖业的发展提供了切实可行的诱导技术。  相似文献   

4.
辽宁产中国林蛙早期胚胎发育研究   总被引:12,自引:0,他引:12  
在恒温条件下,观察了辽宁产中国林蛙的正常胚胎发育。根据基外形变化和胚胎主要特征的出现以及胚胎的行为,将其胚胎发育划分为25个期。从卵子受精开始至蝌蚪的鳃盖闭合,出水孔形成止。18℃时共历时151.56h。  相似文献   

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辽宁产中国林蛙染色体核型及银带研究   总被引:5,自引:0,他引:5  
通过对染色体核型及银带的研究来建筑辽宁产中国林蛙在染色体水平上的雌雄差异。核型分析表明,辽宁产中国林蛙有12对染色体,根据相对长度可以分为组:A为相对长度〉10%者;B为相对长度在7%-10%之间者;C为相对长度〈7%者,第11对染色体长臂中部有明显的次缢痕,雌雄个体间略有差异。  相似文献   

8.
目前对徂徕林蛙的描述仅限形态学分析,对其与近缘物种的分化及物种有效性尚缺乏分子生物学研究。笔者对徂徕林蛙所属长肢林蛙种组物种及其他林蛙属物种的线粒体16SrRNA基因部分序列进行分析,得到序列长度521bp。遗传变异分析显示徂徕林蛙与镇海林蛙以及峨眉林蛙遗传距离很近(均为0.9%),表明徂徕林蛙在进化过程中是一个紧密连接镇海林蛙与峨眉林蛙的物种。系统发育树分析显示徂徕林蛙与镇海林蛙构成姐妹群,徂徕林蛙与镇海林蛙处于物种分化过程中的并系阶段,其物种分化还未完全完成。  相似文献   

9.
东北地区有中国林蛙和黑龙江林蛙的分布.根据“取输卵管后林蛙残体的营养成份”一文提供的数据,本文建立了这两种林蛙判别分类的数学模型,为中国林蛙和黑龙江林蛙的识别提供了一个有效的数学方法.  相似文献   

10.
本文介绍我们对日本林蛙(Rana j.japonica)在冬眠期(12~2月,5.5~8.5℃)与活动期(9~11月,12.5~24℃)的部分生理生化指标的比较.测定了血清、肝、脑、心肌和骨骼肌的乳酸脱氢酶(LDH)同工酶的相对活力(±SD)、血红蛋白浓度及红细胞数等指标.这些指标不仅存在明显的组织差异,也存在季节差异和种群差异.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

17.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.  相似文献   

18.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

19.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

20.
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that  相似文献   

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