全文获取类型
收费全文 | 86篇 |
免费 | 5篇 |
出版年
2022年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2011年 | 2篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1961年 | 1篇 |
1959年 | 8篇 |
1958年 | 6篇 |
1957年 | 6篇 |
1956年 | 4篇 |
1955年 | 6篇 |
1954年 | 5篇 |
1953年 | 1篇 |
1951年 | 1篇 |
1950年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有91条查询结果,搜索用时 218 毫秒
1.
This study was conducted in a secondary broad-leaved forestin northern Hokkaido, Japan, which burned on 2021 April1998. The study plot, set up on 13 July 1998, contained Quercusmongolica var. grosseserrata and Betula platyphylla var. japonicatrees. The latter were more severely damaged by the fire. Size-dependentsurvivorship was observed in both species with larger treesbeing more likely to survive the fire. However, many largeBetulatrees were completely destroyed. Both species developed abundantroot collar sprouts immediately after the fire. The number ofsprouts ranged from 0 to 296 in Betula and from 0 to 34 in Quercus.Trees with no sprouts were not necessarily dead. The frequencydistribution of the sprouting pattern in Betula was bimodal.This was related to damage severity, with the most abundantsprouting manifest in the most severely damaged trees. Thispattern was not observed inQuercus . Stem diameter also appearedto influence the extent of sprouting in Betula, while in Quercusthere was no distinct correlation between basal area and thenumber of sprouts. In Betula, the relationship between the numberof sprouts and the damage severity suggests a trade-off in resourceallocation for sprouting vs. shoot flushing in the crown. Copyright2000 Annals of Botany Company Betula platyphylla var. japonica, fire, fire tolerance, Quercus mongolica var.grosseserrata , resource allocation, root collar sprouting, stem diameter size. 相似文献
2.
3.
Role of Contents of the Germinal Vesicle in Male Pronuclear Development and Cleavage of Starfish Oocytes 总被引:1,自引:1,他引:0
During 1-methyladenine induced germinal vesicle breakdown, contents of the germinal vesicle of starfish oocytes are mixed with the surrounding cytoplasm. Upon injection of contents of the germinal vesicle from immature (fully grown) oocytes into enucleated and inseminated oocytes, incorporated spermatozoa were not observed to change structurally. Alternatively, after treatment of the above oocytes with 1-methyladenine, sperm asters and male pronuclei were developed and subsequent cleavage was also detected. From these results, it is concluded that both action of 1-methyladenine and participation of contents of the germinal vesicle are indispensable for male pronuclear development and subsequent cleavage. 相似文献
4.
5.
T. YAMADA R. MORET J. P. BRUN 《Differentiation; research in biological diversity》1979,12(1-3):191-193
Iris epithelial cells of adult newts, which are fully differentiated melanocytes and non-dividing, become dedifferentiated and converted into lens cells when put in culture. A recent study shows that this dedifferentiation is based on an autophagic process which is associated with proliferation and mainly affects melanosomes. The present report shows that in primary culture of iris epithelial cells after the majority of melanosomes have disappeared, myelinoid bodies, which are interpreted to be telolysosomes of autophagic nature, appear in high frequencies. This suggests that in these cells autophagy persists after the loss of melanosomes. A possible connection of this type of autophagy with the differentation of lens fiber which occurs in this culture is discussed. In the TVI cell line which is believed to be derived from the same cell type, but devoid of melanosomes, similar myelinoid bodies are a characteristic cell component, suggesting that the tendency for autophagy is inherited in this cell line. 相似文献
6.
We analyzed the spatial distributions of two congeneric tree species, Neolistea aciculata and Neolistea sericea (Lauraceae), in a warm‐temperate forest on Miyajima Island, south‐western Japan. Both species were mainly found in valley sites on the island. Hence, these species shared the same topographic habitat niche. However, we found a clear difference between the spatial distributions of the two species in relation to the light environment. Neolistea aciculata was predominantly found in stands with low light, such as beneath the canopy of dense evergreen broadleaved forest. In contrast, N. sericea was predominantly associated with ample light, such as in secondary Pinus densiflora forest. In stands with moderate light conditions, both species were found. This habitat niche segregation in relation to light conditions presumably allows the coexistence of these two species in the predominantly successional forest on Miyajima Island. 相似文献
7.
UEMURA TAKASHI; SUZUKI KOHICHI; NAGANO KEI; MORITA SHIGEHIRO 《Plant & cell physiology》1961,2(4):451-461
- Comparative studies were performed on growth, photosyntheticand respiratory activities, and pigment content in Rhodopseudomonaspalustris.
- The growth of the organism, as influenced by variousculturalconditions such as light, aerobiosis, anaerobiosisand nutritionalfactors was investigated.
- The respiratoryactivity of the bacterium was found to be higherin dark-growncells than in cells grown in the light. The photosyntheticactivitydid not significantly depend on the growth conditionsof theculture. Cells of younger cultures were found to be moreactivethan those of older cultures, with respect both to respirationand photosynthesis.
- The pigment content was found to be higherin the light-growncells than in the dark-grown ones. The ratiophotosyntheticactivity/bacteriochlorophyll was significantlyhigher in thelatter than in the former.
- Light, as well asvarious nutritional factors, was found toexert a marked accelerationon pigment formation, although ithas not yet been possibleto culture cells completely lackingin photosynthetic pigmentsand accordingly in photosyntheticactivity.
8.
9.
In the tadpole of the tree frog Hyla arborea, the color of the dorsal skin was dark brown. Dermal melanophores, xanthophores, and iridophores were scattered randomly under the subepidermal collagen layer (SCL). After metamorphosis, the dorsal color of the animal changed to green and the animal acquired the ability of dramatic color change, demonstrating that the dermal chromatophore unit (DCU) was formed at metamorphosis. Fibroblasts invaded the SCL and divided it into two parts: the stratum spongiosum (SS) and the stratum compactum (SC). The activity of collagenase increased at metamorphosis. The fibroblasts appeared to dissolve the collagen matrix as they invaded the SCL. Then, three types of chromatophores migrated through the SCL and the DCU was formed in the SS. The mechanism how the three types of chromatophores were organized into a DCU is uncertain, but different migration rates of the three chromatophore types may be a factor that determines the position of the chromatophores in the DCU. Almost an equal number of each chromatophore type is necessary to form the DCUs. However, the number of dermal melanophores in the tadpoles was less than the number of xanthophores and iridophores. It was suggested that epidermal melanophores migrated to the dermis at metamorphosis and developed into dermal melanophores. This change may account for smaller number of dermal melanophores available to form the DCUs. 相似文献
10.