全文获取类型
收费全文 | 128篇 |
免费 | 13篇 |
专业分类
141篇 |
出版年
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 6篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1959年 | 5篇 |
1958年 | 9篇 |
1957年 | 2篇 |
1956年 | 2篇 |
1955年 | 8篇 |
1954年 | 12篇 |
1953年 | 6篇 |
1952年 | 3篇 |
1951年 | 5篇 |
1950年 | 10篇 |
1949年 | 4篇 |
1948年 | 3篇 |
1941年 | 1篇 |
排序方式: 共有141条查询结果,搜索用时 15 毫秒
1.
Carbonic Anhydrase and the Regulation of Photosynthesis 总被引:14,自引:0,他引:14
THE role of CO2 in the regulation of photosynthetic and respiratory metabolism in plants is little understood in the unicellular alga Chlorella pyrenoidosa; for example, after autotrophic growth in high CO2 (5·5% by volume), transfer to a CO2 concentration about ten times less than the concentration in air results initially in low rates of photosynthesis characterized by the virtual absence of the Calvin cycle1 of CO2 fixation2. An induction period of about 2 h is necessary before normal photosynthetic rates are established. Cells grown in air (0.03% CO2) do not show this effect and photosynthesize at comparatively high rates even in very low concentrations of CO2. 相似文献
2.
3.
4.
5.
CHARLES A. REED 《American anthropologist》1972,74(4):944-945
6.
7.
Abstract Changes in cell volume and solute content upon hyperosmotic shock have been studied for six unicellular blue-green algae (cyanobacteria): Synechococcus PCC 6301, PCC 6311; Synechocystis PCC 6702, PCC 6714, PCC 6803 and PCC 7008. The extent of change in volume was shown to be dependent upon the solute used to establish the osmotic gradient, with cells in NaCl showing a reduced shrinkage when compared to cells in media containing added sorbitol and sucrose. Uptake of extracellular solutes during hyperosmotic shock was observed in Synechocystis PCC 6714, with maximum accumulation of external solutes in NaCl and minimum solute uptake in sucrose solutions. Conversely, solute loss from the cells (K+ and amino acids) was greatest in sucrose-containing media and least in NaCl. The results show that these blue-green algae do not behave as ‘ideal osmometers’ in media of high osmotic strength. It is proposed that short-term changes in plasmalemma permeability in these organisms may be due to transient membrane instability resulting from osmotic imbalance between the cell and its surrounding fluid at the onset of hyperosmotic shock. 相似文献
8.
Marie GB Hansen Mette Christoffersen Line R Thuesen Morten R Petersen Anders M Bojesen 《Acta veterinaria Scandinavica》2010,52(1):3
Background
Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum are able to infect horses. However, the extend to which Danish horses are infected and seroconvert due to these two bacteria is unknown. The aim of the present study was to evaluate the seroprevalence of B. burgdorferi sensu lato and A. phagocytophilum in Danish horses.Methods
A total of 390 blood samples collected from all major regions of Denmark and with a geographical distribution corresponding to the density of the Danish horse population were analyzed. All samples were examined for the presence of antibodies against B. burgdorferi sensu lato and A. phagocytophilum by the use of the SNAP®4DX ® ELISA test.Results
Overall, 29.0% of the horses were seropositive for B. burgdorferi sensu lato whereas 22.3% were seropositive for A. phagocytophilum.Conclusions
Antibodies against B burgdorferi sensu lato and A. phagocytophilum are commonly found among Danish horses thus showing that Danish horses are frequently infected by these organisms.9.
TIMOTHY M. REED 《Biological journal of the Linnean Society. Linnean Society of London》1984,21(4):431-437
A multiple regression analysis was performed to establish relationships between the number of breeding landbird species and selected environmental variables for the Isles of Scilly, England.
Two analyses were made: the first with all variables log converted, the second without log conversion. In the log model the number of landbird species ( S ) was correlated with island area, r2 = 85.98. In the non-log model, S was most highly correlated with the number of habitats on an island.
Partial correlation analyses confirmed the importance of habitats, rejecting the importance of island area, and indicating that increasing intra-archipelagal isolation alone does not reduce the number of breeding species. 相似文献
Two analyses were made: the first with all variables log converted, the second without log conversion. In the log model the number of landbird species ( S ) was correlated with island area, r
Partial correlation analyses confirmed the importance of habitats, rejecting the importance of island area, and indicating that increasing intra-archipelagal isolation alone does not reduce the number of breeding species. 相似文献
10.
Antagonism between local dispersal and self-incompatibility systems in a continuous plant population
REED A. CARTWRIGHT 《Molecular ecology》2009,18(11):2327-2336
Many self-incompatible plant species exist in continuous populations in which individuals disperse locally. Local dispersal of pollen and seeds facilitates inbreeding because pollen pools are likely to contain relatives. Self-incompatibility promotes outbreeding because relatives are likely to carry incompatible alleles. Therefore, populations can experience an antagonism between these forces. In this study, a novel computational model is used to explore the effects of this antagonism on gene flow, allelic diversity, neighbourhood sizes, and identity by descent. I confirm that this antagonism is sensitive to dispersal levels and linkage. However, the results suggest that there is little to no difference between the effects of gametophytic and sporophytic self-incompatibility systems (GSI and SSI) on unlinked loci. More importantly, both GSI and SSI affect unlinked loci in a manner similar to obligate outcrossing without mating types. This suggests that the primary evolutionary impact of self-incompatibility systems may be to prevent selfing, and prevention of biparental inbreeding might be a beneficial side-effect. 相似文献