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1.
内蒙古欧李生长结果特性研究   总被引:1,自引:0,他引:1  
试验主要对内蒙古呼和浩特北郊生长的欧李实生群体植株的生长结果特性进行了调查研究。对其物候期、枝条生长、果实性状等特性进行了观察测定,为制定优质欧李丰产栽培技术提供参考,同时为进一步进行欧李种质资源多样性的研究奠定了理论基础。  相似文献   

2.
温度、降水与树木径向生长关系研究进展   总被引:1,自引:0,他引:1  
本文综述了树木径向生长与温度、降水之间的关系及在温度、降水等方面的应用研究,针对我国树木年轮宽度研究现状提出了扩大研究区域和研究树种、对不同生长环境的树种进行分析比较、学科交叉进行研究等建议,为我国树木年轮径向生长的进一步分析研究提供一定的参考.  相似文献   

3.
基于Xfrog的树木建模及生长模拟   总被引:2,自引:0,他引:2  
为探讨树木模型和生长动画的模拟,真实简单的模拟植物模型及其生长,对Xfrog植物模型生成软件进行研究。在客观分析树木建模及生长模拟难点的基础上,研究了Xfrog中表达树木拓扑结构的核心原理及其制作树木生长动画的基本方法;详细探讨了采用Xfrog进行树木建模和生长模拟的流程及其关键问题;并基于Xfrog实现了油松、侧柏、栓皮栎等多种北京山区的代表性树种的建模和生长模拟,取得了逼真的模拟效果。该法可用于树木几何模型及其生长动画的快速制作,并对研究树木模型表达和生长模拟具有借鉴意义。  相似文献   

4.
动物生长模型研究进展(综述)   总被引:1,自引:0,他引:1  
本文综述了动物生长方程的研究历史和现状,并对动物生长模拟模型的形成和发展以及近十年来的研究概况进行了总结,同时对生长模拟模型的各个组成部分进行了详细的分析和讨论。  相似文献   

5.
以树木生长的理论方程为基础,对树木生长方程的参数进行了研究,给出了树木生长方程参数的一种估计方法。  相似文献   

6.
本文研究了树莓的扦插技术、管理技术,对扦插苗的根系生长情况进行了研究,并对扦插后覆膜和不覆膜的生长和成活率进行了对比,以对树莓的扦插繁殖有指导作用。  相似文献   

7.
《农技服务》2015,(9):37-38
笔者阐述了火龙果茎枝生长研究,水分胁迫下果树生长发育和作物生长模型研究进展,并进行了展望。  相似文献   

8.
本文通过对引种的42个杨树无性系苗期形态特征进行观测,对苗期生长表现进行系统研究,初步掌握了引进杨树品种的生长差异,为苗期栽培管理提供了依据。通过对42个品种高生长和径生长进行对比分析,初步选出苗期表现较好的品种,为下一步栽培试验做准备。  相似文献   

9.
不同密度湿地松纸浆原料试验林早期冠幅生长模型研究   总被引:2,自引:0,他引:2  
应用回归分析方法,对鄂中丘陵岗地下不同密度湿地松纸浆原料试验林前4年冠幅生长与树龄的关系进行了研究。结果表明,高密度湿地松幼林冠幅生长遵循逻辑斯蒂生长模型,中等密度湿地松幼林冠幅生长遵循严格苏玛克生长模型,低密度湿地松幼林冠幅生长则遵循指数生长模型,并对各密度冠幅生长模型进行了比较分析。  相似文献   

10.
抚育间伐对林分生长的效应及其模型研究   总被引:4,自引:0,他引:4  
简述了抚育间伐对林分生长的一般效应,着重分析了林分生长和收获模型研究中的间伐考虑,并就以往间伐研究中存在的问题和今后的研究发展趋势进行了讨论  相似文献   

11.
经济新常态背景下,税收增速下滑,探索税收新的增长点就显得非常必要。运用LMDI指数分解方法,从宏观角度分解出税收增长的影响因素,并以2005~2012年的省际数据为基础,测算出我国区域税收增长的宏观因素影响效应值。研究发现:经济产出因素和产业税负因素是推动区域税收增长主要动因,不过前者累计贡献度更大;产业结构因素和税收结构因素的效应累计贡献度则产生了区域分化;研究进一步发现,各因素效应变动的深层次原因也呈现出地区性差异。  相似文献   

12.
Nerve growth factor of very high yield and specific activity   总被引:1,自引:0,他引:1  
Nerve growth factor has been isolated from submaxillary glands of mnature male mice at specific activities about a million times, and in yields of biological activity ten million times, greater than best previous results. The major improvement in the isolation is related to the separation of a highly active tosylarginine methyl esterase present in cruder preparations. The new nerve growth factor may be an entity different from the older one, although no gross differences in the qualitative aspects of their actions are apparent on superficial examination of chick ganglia influenced by them. The neurites which develop from a ganglion in the presence of nerve growth factor are of nearly equal length. The amount of nerve growth factor determines the number of neurites but not the extent of individual development. The amount of the new nerve growth factor which evokes the appearance of a hundred neurites from a single ganglion appears to be about ten molecules. Since each neurite seems to arise from a different neuron each molecule of nerve growth factor must affect several cells. This result can be rationalized by a catalytic mechanism or by indirect action of nerve growth factor through a hypothetical cell which produces a neurite evocator on contact with the molecule of nerve growth factor.  相似文献   

13.
Neutrophil migration inhibition factor from T lymphocytes (NIF-T) is a lymphokine that acts to localize granulocytes. Medium conditioned by the Mo human T-lymphoblast cell line was used to purify NIF-T, a glycoprotein with a molecular weight of 22,000. The NIF-T was found to potently stimulate the growth of granulocyte and macrophage colonies from human bone marrow and colony formation by the KG-1 myeloid leukemia cell line. Thus a human lymphokine (NIF-T) that modulates the activities of mature neutrophilic granulocytes is also a colony-stimulating factor acting on precursors to induce growth and differentiation of new effector cells.  相似文献   

14.
该项研究是佳木斯市林科所于1981—1987年在黑龙江省桦南县开展的。经过观察分析,A_(15)(小黑×波)等十个杨树新品系的树高、胸径年生长季节周期性节律是同步的,大部分品系的速生期具有一个生长高峰。其生长与气温、降水、日照时数的回归分析表明,日照时数是影响树高、胸径生长的重要因子。A_(15)等十个杨树新品系的大部分树高生长从第三年开始加速,第六年左右出现高峰;胸径生长从第二年开始加速,第六年左右出现高峰,而材积生长是逐年增加的,其高峰也在第六年出现。在研究涉及的时间范围内,材积连年生长量始终大于平均生长量,说明各品系的数量成熟龄尚未到来。  相似文献   

15.
Macrophage-like U-937 cells secrete a 22-kilodalton heparin-binding growth factor that is mitogenic for BALB-3T3 fibroblasts and smooth muscle cells, but not endothelial cells. The amino acid sequence predicted from complementary DNA clones indicates that the mitogen is a new member of the epidermal growth factor (EGF) family. This heparin-binding EGF-like growth factor (HB-EGF) binds to EGF receptors on A-431 epidermoid carcinoma cells and smooth muscle cells, but is a far more potent mitogen for smooth muscle cells than is EGF. HB-EGF is also expressed in cultured human macrophages and may be involved in macrophage-mediated cellular proliferation.  相似文献   

16.
Cho HS  Leahy DJ 《Science (New York, N.Y.)》2002,297(5585):1330-1333
We have determined the 2.6 angstrom crystal structure of the entire extracellular region of human HER3 (ErbB3), a member of the epidermal growth factor receptor (EGFR) family. The structure consists of four domains with structural homology to domains found in the type I insulin-like growth factor receptor. The HER3 structure reveals a contact between domains II and IV that constrains the relative orientations of ligand-binding domains and provides a structural basis for understanding both multiple-affinity forms of EGFRs and conformational changes induced in the receptor by ligand binding during signaling. These results also suggest new therapeutic approaches to modulating the behavior of members of the EGFR family.  相似文献   

17.
The key parameters to technological growth have been identified as societal resources and societal expectations. Both of these are evident functions of technology, and their combined effects can be expected to continue technology's historical exponential growth. This growth pattern would be substantially altered only if we assume that knowledge is bounded or if society makes a conscious decision to stop the flow of resources into the production of new technological options. Although such conscious selection among individual technical fields is to be expected, it is very unlikely to apply to the totality of technology since, as society grows more complex it continuously creates new needs (priority factor), which in turn provide new opportunities for the application of technological options (payoff factor). The analysis also clearly emphasizes the important role which awareness of new technologies plays in forming societal expectations. These considerations indicate that the technological component of the world simulation model proposed by Meadows et al. (1) and Forrester (2) is best represented by an exponential growth function. The importance of this has been shown by Boyd (3) (Fig. 1), whose "technological optimist" curve has slightly less than exponential growth. Private comnmunication with Boyd indicates that an exponential assumption would reduce the time for equilibrium by several decades. Boyd also indicated that in his modification of the world dynamics model, an exponential technological growth would eventually dominate all other parameters in determining the long-term approach to a steady state. It is evident that the behavior of any world system model is very sensitive to the growth and interaction assumptions for its principal parameters. Thus, model studies should not be easily presumed to represent reality. The one conclusion that appears to be valid regardless of approach is the evident merit of reducing population growth. The parameter for quality of life shown in Fig. 1, parts 2 and 5, is the product of material levels, overcrowding, food, and pollution. The one factor that a "technological optimist" cannot expect to substantially alter in this model is the effect of overcrowding (Fig. 1, parts 3 and 6). Certainly, the many clear values of reducing population growth and improving the environment do not appear to require the justification of a world system analysis. In like manner, it seems appropriate to encourage the "technological optimist" to provide future options for societal choice, even though there may be present philosophical uncertainties as to their eventual merits. Unlike resources found in nature, technology is a manmade resource whose abundance can be continuously increased, and whose importance in determining the world's future is also increasing.  相似文献   

18.
The growth of new axonal sprouts was studied from transected, ascending noradrenergic axons into transplants of iris tissue in the caudal hypothalamus of the rat. A single intraventricular injection of nerve growth factor, given at the time of axonal damage, resulted in an increased formation and growth of new noradrenaline sprouts 7 days later. The effect seemed to be proportional to the administered dose of nerve growth factor.  相似文献   

19.
石榴黄蓟马生物学特性研究   总被引:1,自引:0,他引:1  
笔者于2005—2007年采用在果园中定点观察、采集标本回实验室制片后通过显微镜进行形态观察等方法对石榴新害虫黄蓟马Thrips flavus Schrank的生物学特性进行了系统研究。结果表明,黄蓟马在四川省凉山州1年发生17—19代,有较为明显的世代重叠现象;越冬虫态为成虫和若虫;温、湿度对石榴黄蓟马生长发育有显著影响,干旱季节往往猖獗为害,多雨季节则对其生长发育不利,其发育最适温度范围为25~30℃。  相似文献   

20.
将模糊认知图引入虚拟桃树建模的研究之中,在研究的基础上,提出了一种基于模糊认知图的桃树生长数学模型。模糊认知图模型通过在传统认知图模型中引入模糊测度来量化概念间因果关系的影响程度,用简单数值运算代替了复杂的符号逻辑来实现智能推理和决策。这个模型为虚拟植物提供了一种新的方法。通过试验表明,该模型设计简单、易于扩展、适用性好。  相似文献   

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