共查询到20条相似文献,搜索用时 15 毫秒
1.
药敏药片经临床对金黄色葡萄球菌、大肠埃希氏菌、铜绿假单胞菌等235株考核.表明药片工艺研究先进,药片与培养基结合牢固,无断裂、崩解,不渗出颗粒,抑菌圈呈同心园扩散.边缘清楚。药物含量均匀,释放度好。药片抑菌差仅1~3mm;而纸片抑菌差为2~12mm。药片变黑系数CV为2.71~4.21;而纸片CV为3.82~14.36。表明纸片片间差大,药片精密度明显好于纸片。 相似文献
2.
本文根据我们严密设计的小集水区径流场连续6年的水文测定数据,进行了杉木人工林水量平衡和蒸散的研究。结果表明:集水区年平均降雨量1065.5mm, 在林冠作用面降雨量的分配中,林冠截留雨量264.6mm,截留率24.8%;穿透过林冠层的雨量799.82mm,树干径流量1.08mm,分别占降雨量的75.1%和0.1%。林内降水到达林地时,在枯枝落叶层这个作用面上净降水进行再分配,其中,地表径流量9.27mm,地下径流量203.00mm,总径流系数0.199。土壤蓄水量月变化较大,但年变化很小,占降雨量的1.2%。系统水量最大的输出是蒸散,每年以气态形式返回大气的水量866.03mm,占降雨量81.3%。在蒸散的水量中,林冠截留雨量的直接物理蒸发量为264.6mm,占总蒸散量的31.6%。 相似文献
3.
4.
糖、糖、“糖”——什么是糖? 总被引:1,自引:0,他引:1
糖类是自然界中最常见的一类生物分子,但是糖类因不同的人群可以有三种不同的理解.一是科学上的糖类,二是生活中的糖类,三是作为甜味剂的"糖"类.因为甜味是一个生理上的感觉,凡能与甜味受体相互作用的均是甜味剂,其中有些是糖的"糖",也有不是糖的"糖". 相似文献
5.
扬子鳄视觉器官组织学研究 总被引:11,自引:0,他引:11
本文用光镜和电镜研究了扬子鳄(Alligator sinensis)的组织学,同时测量了其眼球的一些光学参数.扬子鳄眼球呈扁圆球形,角膜径与球径的比值为1:1.44;晶状体与角膜的比值为1:1.40。角膜内具鲍氏膜;虹膜内的括约肌、睫状体内的睫状肌均属横纹肌,视细胞椭圆体内线粒体嵴突与线粒体长轴相平行,这与报道的其它鳄类不同。虹膜内未见扩瞳肌纤维,角膜缘缺巩膜小骨片,晶状体环垫薄,因而其视觉调节能力仍然很弱。视网膜中视细胞由视杆细胞、单锥细胞、双锥细胞组成,其中以视杆细胞占多数。视细胞与神经节细胞核比值平均为2.5:1,表明扬子鳄的组织结构与其弱光视觉相适应。 相似文献
6.
7.
《Journal of biological dynamics》2013,7(4):415-427
A general three-stage discrete-time population model is studied. The inherent net reproductive number for this model is derived. Global stability of the origin is established provided that the inherent net reproductive number is less than one. If it is larger than one the existence of a unique positive fixed point is proved and the persistence of the system is established. Finally, for certain parameter ranges global stability of the positive fixed point is proved. 相似文献
8.
Failure to Maintain Glycolysis in Anoxic Nerve Terminals 总被引:8,自引:6,他引:2
Synaptosomal glycolysis is stimulated eight- to 10-fold when the respiratory chain is inhibited by cyanide or by anoxia. However, the stimulation is transient and after 15 min declines toward the preanoxic rate. The decline is not seen when Ca2+ is absent or when the respiratory chain is inhibited by rotenone. The decline in glycolysis is reversible, is not due to substrate exhaustion, and is the cause, rather than the effect, of lowered synaptosomal ATP/ADP ratios. The failure to maintain glycolysis when the terminal oxidase of the respiratory chain is inhibited may have relevance to the sensitivity of the brain to anoxic damage. 相似文献
9.
羚牛(Budorcas taxicolor)部分脏器特点的观察 总被引:2,自引:2,他引:0
本文对2只羚牛的雌性生殖器官及肝、肾、脾等脏器进行了形态描述,并与黄牛及羊的相应器官进行了比较,为探讨羚牛的分类地位提供了解剖学资料。 相似文献
10.
大黄鱼精子的超微结构 总被引:44,自引:1,他引:43
大黄鱼的精子由头产和尾部两部分组成。头部结构较为独特,其腹侧有一较大的细胞核,背部有中心粒复合体。头部的后端是袖套。细胞核的腹面稍向外突出背面则稍向内凹。细胞核中的染以质浓缩成致密的团块状。团块状的染色质之间分布着松散的纤维状染色质。植入窝位于细胞核的背部表面,由细胞核背面向内凹陷而成,呈一沟状,其走向与精子的长轴平行。 相似文献
11.
沙冬青淀粉粒及其与叶绿体发育的关系 总被引:5,自引:0,他引:5
沙冬青叶绿体中的淀粉粒一般为1-3个,主要有4种类型。第1种外周部分电子密度较高,中央部分较低,但每个部分的电子密度十分均匀。它们近似椭圆形,附近的类囊体形态正常,结构清晰。第2种电子密度由外向内逐渐变低,多为椭圆形,附近的类囊体较清晰。第3种外周部分的电子密度很高,中央部分不均匀,形状多种多样,附近的类囊体有的不清晰。第4种电子密度很低,十分均匀,形状不规则,附近的类囊体已经解体或正在解体。分析表明,淀粉的形态变化明显与叶绿体发育有关。 相似文献
12.
Site of graviperception in roots: a re-examination 总被引:1,自引:0,他引:1
Two lines of evidence have been cited to support the assertion that the root cap is the sole site of graviperception in the root. The first evidence is based on surgical removal of the cap, which abolishes the response to gravity. This is sufficient to conclude that the cap is involved in gravitropism, but not to conclude that the cap is the site of graviperception. The second is based on the results of centrifugation experiments, in which different parts of the plant are subjected to different centrifugal forces. The data from such experiments have been cited to support the conclusion that the perception of gravity is limited to the rootcap. However, these data actually support the conclusion that gravity is perceived throughout the root tip, and not only in the root cap. We believe that the data support the conclusion that the root cap is involved in root gravitropism, but that there is inadequate evidence to conclude that the cap is the sole site of graviperception. 相似文献
13.
短柄五加大,小孢子发生和雌,雄配子体发育的研究 总被引:6,自引:2,他引:4
短柄五加花药5枚,每个花药四个花粉囊。小孢子母细胞减数分裂时,胞质分裂为同时型,产生正四面体形的四分体。花药壁由表皮、药室内壁、中层和绒毡层四层细胞组成,其发育类型为双子叶型。腺质绒毡层,其细胞为二核。三细胞型花粉。子房5室,每室两个胚珠,上胚珠败育,下胚珠可育。下胚珠倒生,具单珠被,厚珠心。大孢子母细胞减数分裂形成线性排列的四个大孢子,雌配子体发育属蓼型。开花当天,花粉散开,雌配子体尚未成熟,处 相似文献
14.
The taxonomy and biology of further aeolidacean and arminacean nudibranch molluscs with symbiotic zooxanthellae 总被引:1,自引:0,他引:1
W. B. RUDMAN 《Zoological Journal of the Linnean Society》1982,74(2):147-196
The occurrence of symbiotic zooxanthellae in further aeolid and arminacean nudibranch molluscs is described for the first time. The aeolid Aeolidiopsis ransoni Pruvot-Fol is redescribed, and a new species of Aeolidiopsis , also feeding on the colonial zoantharian Palythoa , is described. Both have symbiotic zooxanthellae. The taxonomy of the family Aeolidiidae is discussed and the genus Berghia Trinchese, 1877 is considered a synonym of Spurilla Bergh, 1864. Spurilla major (Eliot, 1903) and a new species of Spurilla are reported to have zooxanthellae while another new species of Spurilla is without zooxanthellae. The glaucid aeolid Pteraeolidia ianthina (Angas) is shown to have symbiotic zooxanthellae, as is the arminacean Doridomorpha gardineri Eliot, which is reported to feed on the alcyonarian blue coral, Heliopora. In all cases, the morphological adaptations developed for this symbiosis are described. Further notes on the Porites-fetding arminacean Pinufius rebus Marcus & Marcus and the aeolid Phestilla lugubris (Bergh) are included and a facultative symbiosis with zooxanthellae is suggested for the latter. The tion of symbiosis with zooxanthellae within nudibranchs is discussed and it is suggested that the relationship has evolved independently on several occasions. 相似文献
15.
In the present paper, the morphology and structure of the flower, fruit
and seed of Kingdonia uniflora are reported. Each part of the flower is usually indefinite and is spirally arranged. The venation of the tepals is open-dichotomous and classified into three types. There are two types of the stamens, which have a solitary bundle; the sterile stamens bear nectaries in the ventral furrows of the apex, and the pollen
sacs of the fertile ones are lateral-extrose. The carpel is differentiated into three parts,
and is not completely closed in flower, which represents a half-opened type and is simillar to that of Coptis. The fruit is an achene. The embryo is at the stage of proembryo when the fruit is mature. The endosperm is copious. In this paper, some problems
concerning morphological evolution are also discussed. 相似文献
16.
Gerhard Wiegleb 《Plant Ecology》1989,83(1-2):17-34
A definition of vegetation science is given, spanning 6 levels of integration and stressing the interrelations among them. The problems of realism are discussed. The selection of levels is related to the adequate correspondence between conceptualization and research aims. Pattern and process are introduced as the central concepts of vegetation science. The perception of reality is dependent on the spatial and temporal scale chosen. The concept of noise is discussed in relation to stochasticity and randomness of events. Traces of essentialism are found both in classification of communities and habitat ecology. Classification is important, particularly the coexistence of alternative classification approaches. Organicism as a basis of vegetation research is rejected because the organismic view is inadequate on higher integration levels. The concept of function is redefined in a non-teleologic way.Present vegetation ecological research is inductivistic. One possible alternative to inductivism is falsificationism. The major domain of this approach is hypothesis testing, which will become more important. Progress can only be reached by a maximum degree of communication among scientific individuals.Predictive ecology is partly based on historic explanation, partly on complementary approaches. Characters of vegetation worthwhile to be predicted are listed and the necessary requirements for vegetation science to become predictive are discussed. A major requirement is the development of succession and life-history theory. A further elaboration of the individualistic concept will be a main task of vegetation science in the near future. 相似文献
17.
The variogram is a standard tool in the analysis of spatial data, and its shape provides useful information on the form of spatial correlation that may be present. However, it is also useful to be able to assess the evidence for the presence of any spatial correlation. A method of doing this, based on an assessment of whether the true function underlying the variogram is constant, is proposed. Nonparametric smoothing of the squared differences of the observed variables, on a suitably transformed scale, is used to estimate variogram shape. A statistic based on a ratio of quadratic forms is proposed and the test is constructed by investigating the distributional properties of this statistic under the assumption of an independent Gaussian process. The power of the test is investigated. Reference bands are proposed as a graphical follow-up. An example is discussed. 相似文献
18.
19.
两型豆花粉和叶表皮的扫描电镜观察 总被引:5,自引:1,他引:4
两型豆花粉和叶表皮在扫描电镜下的形态特征:花粉近球形至矩球形,三孔沟,外壁表面较粗糙,侧壁具疣状突起至块状突起,极面具粗网状纹饰,但两型豆祖山居群属于萌发沟不明显型,两型豆燕塞湖居群属于萌发沟明显型。叶表皮细胞不规则,排列紧密,叶脉表皮细胞长圆柱形,长轴与叶脉平行,角质膜薄,表皮毛均为单细胞非腺毛,气孔器仅分布在下表皮,属于平列型,偶见不规则型。表皮毛和气孔器在叶片上分布不均匀,两型豆祖山居群叶表皮毛和气孔器的平均密度大于两型豆燕塞湖居群叶表皮毛和气孔器的平均密度,自然生长的两型豆叶表皮毛和气孔器的平均密度大于遮光条件下的两型豆。 相似文献
20.
从姜黄中提取姜黄素的研究 总被引:13,自引:1,他引:12
本文利用75%乙醇浸提姜黄得到姜黄素粗提物,然后分别采用吸附分离法和沉淀法对粗提物进一步分离提纯得到纯度较高的姜黄素产品。在吸附分离法提取姜黄素实验中,考察了不同洗脱剂组成对洗脱率的影响,实验发现90%乙醇洗脱效果最好;在沉淀法实验中,考察了不同pH值条件下的姜黄素沉淀量,发现pH值为7.0时,姜黄素沉淀量最大。实验结果表明,沉淀法得到的姜黄素产品纯度比吸附分离法得到的高,但沉淀法产品收率比吸附分离法低,吸附分离法比沉淀法更适合工业应用。 相似文献