全文获取类型
收费全文 | 133篇 |
免费 | 5篇 |
国内免费 | 9篇 |
学科分类
生物科学 | 147篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 5篇 |
2011年 | 2篇 |
2010年 | 2篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 2篇 |
排序方式: 共有147条查询结果,搜索用时 31 毫秒
71.
Malcolm B. Wilkins 《Planta》1991,185(3):425-431
The role of the epidermis in the generation of the endogenous circadian rhythm of CO2 exchange in leaves of Bryophyllum fedtschenkoi has been examined. At 25° C the rhythm of CO2 output exhibited by whole leaves kept in continuous darkness and an initially CO2-free air stream also occurs in isolated pieces of mesophyll. The sensitivity to light of the rhythms in whole leaves and in isolated mesophyll appears to be identical. At 15° C, however, no rhythm is observed in isolated mesophyll tissue, despite there being a conspicuous rhythm in intact leaves. The rhythm of net CO2 assimilation in whole leaves kept in continuous light and a stream of normal air at either 25° C or at 15° C is abolished by removal of the epidermis, although at 15° C and under the higher of the two light levels used, there is an indication that rhythmicity may begin to reappear after the third day of the experiment. Thus, only under certain environmental conditions is the rhythm of CO2 exchange in Bryophyllum leaves independent of the epidermis. The results indicate that the rhythm of carbon dioxide fixation in continuous darkness and CO2-free air is generated primarily in the mesophyll cells, whereas the rhythm in continuous light and normal air is generated in the stomatal guard cells or in an interaction of these cells with the mesophyll cells.Abbreviation PEPCase
phosphoenolpyruvate carboxylase 相似文献
72.
Epidermis is easily detached from both adaxial and abaxial surfaces of leaf four of the Argenteum mutant of Pisum sativum L. The isolated epidermis has stomata with large, easily-measured pores. Hairs and glands are absent. The density of stomata is high and contamination by mesophyll cells is low. In the light and in CO2-free air, stomata in isolated adaxial epidermis of Argenteum mutant opened maximally after 4 h incubation at 25°C. The response of stomata to light was dependent on the concentration of KCl in the incubation medium and was maximal at 50 mol m-3 KCl. Stomata did not respond to exogenous kinetin, but apertures were reduced by incubation of epidermis on solutions containing between 10-5 and 10-1 mol m-3 abscisic acid (ABA). The responses of stomata of Argenteum mutant to light, exogenous KCl, ABA and kinetin were comparable with those described previously for stomata in isolated epidermis of Commelina communis. A method for preparing viable protoplasts of guard cells from isolated epidermis of Argenteum mutant is described. The response of guard cell protoplasts to light, exogenous KCl, ABA and kinetin were similar to those of stomata in isolated epidermis except that the increase in volume of the protoplasts in response to light was maximal at a lower concentration of KCl (10 mol m-3) and that protoplasts responded more rapidly to light than stomata in isolated epidermis. The protoplasts did not respond to exogenous kinetin, but when incubated for 1 h in the light and in CO2-free air on a solution containing 10-3 mol m-3 ABA, they decreased in volume by 30%. The advantages of using epidermis from Argenteum mutant for experiments on stomatal movements are discussed.Abbreviations ABA
abscisic acid
- MES
2-(N-morpholino)ethanesulfonic acid 相似文献
73.
Summary Potted cuttings of a 12-year-old, and grafts of an 80-year-old, Norway spruce (Picea abies (L.) Karst.) were subjected to 100 or 300 g O3·m–3 for 1215 h (45 h of daylight per week) during the growing season of 1985. At the end of the fumigation the plants did not exhibit any visible signs of injury. Whereas in the fumigation with 100g O3·m–3 we did not detect any significant change in gas exchange, 300 g O3·m–3 did alter the CO2 uptake after 27 weeks, and in one clone transpiration was also altered. Stomatal reaction to a change of light suggested sluggishness, but the change was not statistically significant. 相似文献
74.
Susan Lurie 《Planta》1978,140(3):245-249
The effect of broad band green, blue and red light on stomatal opening of Vicia faba L. (broad bean) leaves was examined. In air, blue light caused greater stomatal opening than red light. In air with green light stomata were only slightly opened. In a nitrogen atmosphere red light caused greater opening than blue light, and green light caused only slight opening. Opening in air or nitrogen atmosphere in red or blue light was inhibited by the uncoupler CCCP, while the photosynthetic inhibitor DCMU inhibited opening in air but not in nitrogen atmosphere. We concluded that more than one light activated metabolic pathway can supply the energy needed to effect stomatal opening and that different pathways are operative under different conditions. 相似文献
75.
Differential cell wall thickening in developing guard cells of Polypodium vulgare L. has been studied with particular reference to guard cell protoplast deformation and the eventual formation of the stomatal pore. Concomitant studies on the development of guard cell chloroplasts and their starch inclusions during ontogeny of the stomatal complex have provided data which have been incorporated into a model to account for the formation of the pore. Guard cell starch inclusions reach a maximum density per unit volume at the same time as the guard cell walls achieve maximum differential thickening. These events coincide with the development of the pore. It is suggested that, whilst pore formation is initiated enzymatically, the mechanical forces required to bring about the separation of the two guard cells are of an osmotic nature derived from starch hydrolysis. The development of the mesophyll in relation to the epidermis is examined in respect of the formation of substomatal chambers. 相似文献
76.
77.
Odair J.G. Almeida J. Hugo Cota-Sánchez Adelita A.S. Paoli 《Perspectives in Plant Ecology, Evolution and Systematics》2013,15(5):255-268
A long-standing interest in cactus taxonomy has existed since the Linnaean generation, but an appreciation of the reproductive biology of cacti started early in the 1900s. Numerous studies indicate that plant reproductive traits provide valuable systematic information. Despite the extensive reproductive versatility and specializations in breeding systems coupled with the striking floral shapes, the reproductive biology of the Cactaceae has been investigated in approximately 10% of its species. Hence, the systematic value of architectural design and organization of internal floral parts has remained virtually unexplored in the family. This study represents the most extensive survey of flower and nectary morphology in the Cactaceae focusing on tribes Hylocereeae and Rhipsalideae (subfamily Cactoideae). Our objectives were (1) to conduct comparative morphological analyses of flowers and floral nectaries and (2) to compare nectar solute concentration in these two tribes consisting of holo- and semi-epiphytic species. Flower morphology, nectary types, and sugar concentration of nectar have strong taxonomic implications at the tribal, generic and specific levels. Foremost, three types of nectaries were found, namely chamber nectary (with the open and diffuse subtypes), furrow nectary (including the holder nectary subtype), and annular nectary. All Hylocereeae species possess chamber nectaries, in which the nectarial tissue has both trichomes and stomata. The Rhipsalideae are distinguished by two kinds of floral nectaries: furrow and annular, both nectary types with stomata only. The annular nectary type characterizes the genus Rhipsalis. Nectar concentration is another significant taxonomic indicator separating the Hylocereeae and Rhipsalideae and establishing trends linked to nectar sugar concentration and amount of nectar production in relation to flower size. There is an inverse relationship between flower size and amount of nectar production in the smaller Rhipsalideae flowers, in which nectar concentration is more than two-fold higher despite the smaller volume of nectar produced when compared to the large Hylocereeae flowers. Variability of nectary morphology and nectar concentration was also evaluated as potential synapomorphic characters in recent phylogenies of these tribes. In conclusion, our data provide strong evidence of the systematic value of floral nectaries and nectar sugar concentration in the Cactaceae, particularly at different taxonomic levels in the Hylocereeae and Rhipsalideae. 相似文献
78.
《Journal of biological education》2012,46(1):19-27
The treatment of technical vocabulary largely deter-mines its effectiveness as a medium of communication. The present paper describes how six O-level1 Biology texts were analysed, to discover how they dealt with terminology. Two categories of vocabulary were recognised: the terms peculiar to individual books and those common to all books. Individual vocabu-laries were of different sizes because of divergences in style and the use of various synonyms to express the same idea. (Synonyms also increase vocabulary burden and make it more difficult for a pupil to pass from one book to another.) The common vocabulary was thought to contain the most important terms, and the authors' treatment of them seemed to bear this out: a large majority were both explained and emphasised. Technical vocabulary would be used even more effectively if synonyms were eliminated and all the remaining terms were explained and emphasised at their first appearance. 相似文献
79.
Meinzer FC Woodruff DR Domec JC Goldstein G Campanello PI Gatti MG Villalobos-Vega R 《Oecologia》2008,156(1):31-41
Stomatal regulation of transpiration constrains leaf water potential (ΨL) within species-specific ranges that presumably avoid excessive tension and embolism in the stem xylem upstream. However,
the hydraulic resistance of leaves can be highly variable over short time scales, uncoupling tension in the xylem of leaves
from that in the stems to which they are attached. We evaluated a suite of leaf and stem functional traits governing water
relations in individuals of 11 lowland tropical forest tree species to determine the manner in which the traits were coordinated
with stem xylem vulnerability to embolism. Stomatal regulation of ΨL was associated with minimum values of water potential in branches (Ψbr) whose functional significance was similar across species. Minimum values of Ψbr coincided with the bulk sapwood tissue osmotic potential at zero turgor derived from pressure–volume curves and with the
transition from a linear to exponential increase in xylem embolism with increasing sapwood water deficits. Branch xylem pressure
corresponding to 50% loss of hydraulic conductivity (P
50) declined linearly with daily minimum Ψbr in a manner that caused the difference between Ψbr and P
50 to increase from 0.4 MPa in the species with the least negative Ψbr to 1.2 MPa in the species with the most negative Ψbr. Both branch P
50 and minimum Ψbr increased linearly with sapwood capacitance (C) such that the difference between Ψbr and P
50, an estimate of the safety margin for avoiding runaway embolism, decreased with increasing sapwood C. The results implied a trade-off between maximizing water transport and minimizing the risk of xylem embolism, suggesting
a prominent role for the buffering effect of C in preserving the integrity of xylem water transport. At the whole-tree level, discharge and recharge of internal C appeared to generate variations in apparent leaf-specific conductance to which stomata respond dynamically. 相似文献
80.
Saji S Bathula S Kubo A Tamaoki M Kanna M Aono M Nakajima N Nakaji T Takeda T Asayama M Saji H 《Plant & cell physiology》2008,49(1):2-10
To understand better the plant response to ozone, we isolated and characterized an ozone-sensitive (ozs1) mutant strain from a set of T-DNA-tagged Arabidopsis thaliana ecotype Columbia. The mutant plants show enhanced sensitivity to ozone, desiccation and sulfur dioxide, but have normal sensitivity to hydrogen peroxide, low temperature and high light levels. The T-DNA was inserted at a single locus which is linked to ozone sensitivity. Identification of the genomic sequences flanking the T-DNA insertion revealed disruption of a gene encoding a transporter-like protein of the tellurite resistance/C(4)-dicarboxylate transporter family. Plants with either of two different T-DNA insertions in this gene were also sensitive to ozone, and these plants failed to complement ozs1. Transpiration levels, stomatal conductance levels and the size of stomatal apertures were greater in ozs1 mutant plants than in the wild type. The stomatal apertures of ozs1 mutant plants responded to light fluctuations but were always larger than those of the wild-type plants under the same conditions. The stomata of the mutant and wild-type plants responded similarly to stimuli such as light, abscisic acid, high concentrations of carbon dioxide and ozone. These results suggest that OZS1 helps to close stomata, being not involved in the responses to these signals. 相似文献