全文获取类型
收费全文 | 71篇 |
免费 | 3篇 |
国内免费 | 25篇 |
专业分类
99篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 11篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有99条查询结果,搜索用时 10 毫秒
61.
62.
ABSTRACT Cupressus sempervirens L. var. pyramidalis and C. sempervirens var. horizontalis were examined for their pollen morphometry and ultrastructure to verify whether, in addition to phenotype, pollen could also show characteristics useful to discriminate the two infraspecific taxa. C. sempervirens var. pyramidalis compared to C. sempervirens var. horizontalis has mainly larger, subcircular pollen with a higher percentage of apolar and germinating grains, and a wall with thicker intine; the cytoplasm has a greater number of callose-containing vesicles. C. sempervirens var. horizontalis has pollen distributed in five classes of shape. In addition it is smaller and shows a higher percentage of ruptured grains, and a lower percentage of germination in vitro. The cytoplasm contains vesicles rich in callose and also a higher amount of osmophilic bodies. Pollen grains in both varietas contain only one cell at dispersal. The reported differences in pollen morphometry, structure and biology, together with the phenotypic characteristics of the tree, support the validity of two infraspecific taxa. 相似文献
63.
Chemical Composition and Biological Activities of Tunisian Cupressus arizonica Greene Essential Oils
下载免费PDF全文
![点击此处可从《化学与生物多样性》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Amri Ismail Emilia Mancini Laura De Martino Lamia Hamrouni Mohsen Hanana Bassem Jamoussi Samia Gargouri Mariarosa Scognamiglio Vincenzo De Feo 《化学与生物多样性》2014,11(1):150-160
The chemical composition of the essential oils obtained by hydrodistillation of leaves, stems, and female cones of Cupressus arizonica Greene , grown in Tunisia, was studied by GC‐FID and GC/MS analyses. Altogether, 62 compounds were identified, 62 in the leaf oil, 19 in the cone oil, and 24 in the stem oil. The cone and stem oils were mainly composed by monoterpene hydrocarbons (96.6 and 85.2%, resp.). In the leaf oil, the total sesquiterpene fraction constituted 36.1% and that of the monoterpene hydrocarbons 33.8% of the total oil composition. The three oils were evaluated for their in vitro herbicidal activity by determining their influence on the germination and the shoot and root growth of the four weed species Sinapis arvensis L., Lolium rigidum Gaudin , Trifolium campestre Schreb ., and Phalaris canariensis L. At the highest doses tested (0.8 and 1.0 mg/ml), the leaf essential oil inhibited either totally or almost completely the seed germination and the shoot and root growth of S. arvensis and T. campestre. The oils were also tested for their antifungal activity; however, their effects on the fungal growth were statistically not significant. 相似文献
64.
Cupressus chenggiana S. Y. Hu (Cupressaceae) is an endemic and endangered conifer species in southwest China. In order to study the population
genetics and design the effective conservation methods, we aimed to develop microsatellite primers for this species in the
present study. We developed eight new microsatellite loci for this species through biotin capture method. Polymorphism of
each locus was further assessed in 18 individuals from three geographically distant populations. The number of alleles per
locus ranged from 6 to 11 with an average of 8.13. The observed and expected heterozygosities ranged from 0.219 to 0.296 and
from 0.374 to 0.470, with averages of 0.254 and 0.417, respectively. We further found that three of nine microsatellite loci
developed previously for another congeneric species showed polymorphic banding patters. We performed primer-crossing tests
of these loci in the other two congeneric species which are closely related to C. chenggiana (C. gigantea and C. duclouxiana). These microsatellite markers would be effective for analyzing genetic diversity and population genetic structure of this
species and its morphological differentiation with the close relatives. 相似文献
65.
温度对四川小金县岷江柏种子发芽的影响 总被引:1,自引:0,他引:1
通过对采自四川小金县的岷江柏(Cupressus chenggiana S. Y. Hu)种子发芽特征的研究,分析不同温度对种子发芽的影响.结果表明,采自四川小金县的岷江柏种子发芽周期为20 d,其中0 ~5 d为萌动期,5 ~15 d为高峰期;发芽温度为5℃~30℃,适宜发芽温度为10℃~25℃,种子最适发芽温度在2003年1、4、7和10月分别为25℃、15℃、20℃和20℃.岷江柏种子的最适发芽温度和贮藏过程中的发芽特征与环境温度有着密切的关系. 相似文献
66.
In Italian nurseries and young groves of evergreen cypress(Cupressus sempervirens L.), the eriophyoid miteTrisetacus juniperinus (Nal.) is considered a very serious pest. A rating system of damage symptoms was developed to investigate the susceptibility
of different cypress seedling families to the mite. Based on this system, the seedlings were evaluated for three years in
the nursery and in two field locations after transplanting. Data obtained in the nursery allowed the cypress families to be
allocated to at least two different levels of susceptibility. These levels of susceptibility were generally also maintained
in the field. However, the environmental conditions of the two transplanting localities significantly affected the susceptibility
of each family. In all families, scores for each of the damage categories were strongly correlated positively to each other
and negatively with the average increment in the height of plant over the duration of the field experiment. Assessment of
the intensity of the symptoms peculiar to damage category A (buds enlarged, deformed, russet and/or branch apex folded) was
sufficient to give the same susceptibility evaluation as if data for all damage categories were used. The evaluation of susceptibility
on the basis of injury pattern may return very useful information for selection and certification of families of known susceptibility
to eriophyoid mites.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
67.
Suspension cell cultures of Cupressus lusitanica produce beta-thujaplicin, a tropolone found mostly in Cupressaceae heartwood. The factors controlling beta-thujaplicin accumulation in this cell culture system were investigated. Initial cell density of the cultures did not affect beta-thujaplicin levels, though initial addition of beta-thujaplicin suppressed its de novo production. When beta-thujaplicin accumulation reached a certain level (ca. 40 mg/l) in the medium, the cultures seemed to cease beta-thujaplicin production. However, beta-thujaplicin productivity was restored when the beta-thujaplicin-containing medium was exchanged for fresh medium; the formation of 2-methoxy-6-(methylethyl)cyclohepta-2,4,6-trien-1-one, an isomer of methylated beta-thujaplicin, in medium was also observed. These results suggest that beta-thujaplicin synthesis was regulated by product feedback mechanism in this cell line, and that excess accumulation of beta-thujaplicin is relieved by conversion of beta-thujaplicin to its methyl ether. 相似文献
68.
桤柏混交林种群生物量动态与密度调节 总被引:20,自引:5,他引:15
研究了四川省盐亭县桤柏混交林中桤木和柏木种群的生物量动态、密度动态及 种群密度对生物量动态的调节.结果表明,桤木种群生物量在18 a内符合逻辑斯蒂增长, 柏木种群生物量在20 a内呈幂函数增长.而种群密度在 18 a内均呈负幂函数降低在桤 柏混交林中.密度制约是决定种群生物量动态的主要因素,棺木和柏本平均单株生物量较 符合Yoda提出的-3/2自疏定律为快,其自疏系数分别为一2.33和一3.97.个体平均生 物量的增长比由密度下降引起的生物量降低快,因此,两种群生物量在密度调节过程中仍 然保持增长状态.其中柏木是生物量增长旺盛的种群. 相似文献
69.
Species richness and diversity and soil physical and chemical properties were compared between a mature lower montane rain forest (LMRF) and abandoned 21-year-old plantations of introduced Pinus patula and Cupressus lusitanica in the central Andes of Colombia (2000m). In 0.1ha plots, species richness (number of species) and diversity (Shannon and Simpson indexes) were higher in the LMRF, followed by P. patula and C. lusitanica plantations. There were 56species and 30families of higher plants in the LMRF, 26species and 15families in the P. patula plantation, and 18species and 10families in the C. lusitanica plantation. There were no statistically significant differences (p<0.05) in soil physical or chemical properties between P. patula, C. lusitanica and native LMRF. Nevertheless, soil carbon, the C/N ratio and total bases tended to be higher in the native forest than in the plantations. Available P tended to be higher in the P. patula plantation. These results show that, although abandoned plantations can support some native species, particularly in the understorey, species richness is far from that of the native forest. 相似文献
70.
I. Chraif H. Ben Jannet M. Hammami M.L. Khouja Z. Mighri 《Biochemical Systematics and Ecology》2007,35(12):813-820
The chemical composition of the essential oils obtained by hydrodistillation from leaves, branches and female cones of Cupressus arizonica Greene cultivated in Tunisia was determined by GC and GC/MS analysis. Significant differences were found between the constituent percentages of the different oils. Among the 87 identified components α-pinene (60.5% in female cones), umbellulone (18.4% in leaves), δ-3-carene (15.6% in branches) and cis-muurola-4(14),5-diene (9.4% in leaves) were found to be the major ones.Composition of essential oils extracted from different organs of C. arizonica Greene growing in Tunisia showed remarkable differences from the same species cultivated in Algeria, Argentina, Iran, Italy, France and Texas based on a comparison with published results. The in vitro antibacterial activity of the essential oils samples was evaluated against some Gram positive and negative bacteria. 相似文献