全文获取类型
收费全文 | 178篇 |
免费 | 20篇 |
专业分类
198篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 16篇 |
2011年 | 12篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1955年 | 1篇 |
1951年 | 1篇 |
1948年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有198条查询结果,搜索用时 0 毫秒
81.
Background
Bone resorption displays marked diurnal variation. Reversible inhibition of bone resorption may result in best possible efficacy when bone resorption peaks. The aim of the study was to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of 0.8 mg of oral salmon calcitonin (sCT) and the effect of timing of drug intake. 相似文献82.
Derek J Sloan Andrew Nicolson Alastair RO Miller Nick J Beeching Mike BJ Beadsworth 《Journal of medical case reports》2008,2(1):1-5
Introduction
Electrocardiogram (ECG) abnormalities in patients with blunt chest trauma are diverse and non-specific, but may be indicative of potentially life-threatening conditions.Case presentation
We report a rare case of pneumopericardium with extreme ECG abnormalities after blunt chest trauma in a 22-year-old male. The diagnosis was confirmed using computed tomography (CT) scanning. The case is discussed, together with its differential diagnosis and the aetiology of pneumopericardium and tension pneumopericardium.Conclusion
Pneumopericardium should be distinguished from other pathologies such as myocardial contusion and myocardial infarction because of the possible development of tension pneumopericardium. Early CT scanning is important in the evaluation of blunt chest trauma. 相似文献83.
A model of embryo energetics was fitted to data from the literature for species as different as snails and mammals. The model
is based on assumptions about energy uptake, storage and utilization. It describes the animal by two state variables: volume
and energy storage. Embryo weight is taken to be proportional to volume, yolk weight to energy storage, and respiration rate
to storage utilization rate. The fits were good, with minor deviations occurring only in the early phases of development.
For altricial birds, good model fits were obtained, but the parameter values markedly differed from those of other species.
We hypothesized that, due to an increase in energy utilization towards hatching, the temperature of the embryo increases.
As a result, metabolic processes are accelerated. When this was taken into account, parameter values were obtained that correspond
better with those of other animals. 相似文献
84.
85.
Bridging molecular genetics and participatory research: how access and benefit‐sharing stimulate interdisciplinary research for tropical biology and conservation 下载免费PDF全文
Maarten van Zonneveld Judy Loo Silvana Maselli Julio Javier Madrid José Luis Echeverria 《Biotropica》2018,50(1):178-186
Molecular genetics research can benefit efforts to conserve the genetic diversity of tropical plant species. Clear and efficient procedures are needed to access DNA samples, while respecting tropical countries’ and local communities’ rights on genetic resource usage. The Nagoya Protocol on Access and Benefit‐Sharing, which took effect in 2014, provides an opportunity to establish such procedures. However, scientists are concerned that its emphasis on monetary gains restricts research focused on scientific, societal, and environmental benefits. Despite much political and scientific debate, few concrete cases have demonstrated the practical functioning of the Nagoya Protocol. This paper describes the first application of the Protocol in Guatemala, where it was used to grant permission to a non‐commercial study on gene flow in mahogany (Swietenia macrophylla King) populations in the Maya Biosphere Reserve of Petén. On the basis of this study, we discuss five strategies to enhance the application of molecular genetics to conservation biology under the Nagoya Protocol: (1) generate short and standardized procedures; (2) enable science communication; (3) cultivate a common understanding between users, providers, and potential beneficiaries; (4) involve local research and practitioner organizations; and (5) integrate participatory research. Positive societal views on the application of molecular genetics to conservation biology generate further support for work in this discipline and promote adoption of research results for the conservation of genetic diversity of tropical plant species. 相似文献
86.
Regulation of mRNA levels of rat liver carbamoylphosphate synthetase by glucocorticosteroids and cyclic AMP as estimated with a specific cDNA 总被引:3,自引:0,他引:3
C J de Groot A J van Zonneveld P G Mooren D Zonneveld A van den Dool A J van den Bogaert W H Lamers A F Moorman R Charles 《Biochemical and biophysical research communications》1984,124(3):882-888
The construction and cloning of a cDNA complementary to the mRNA of rat liver carbamoylphosphate synthetase (ammonia) is described. Using this cDNA, the size of the mature, cytosolic carbamoylphosphate synthetase (ammonia) mRNA is estimated to be 6.0 Kb. The levels of carbamoylphosphate synthetase (ammonia) mRNA in liver are shown to be regulated by glucocorticosteroids and cyclic AMP. By studying mRNA levels of carbamoylphosphate synthetase, albumin and phosphoenolpyruvate carboxykinase, using specific cDNA clones, we show that carbamoylphosphate synthetase gene expression, like that of albumin is liver-specific. 相似文献
87.
Identification of regulatory sequences in the type 1 plasminogen activator inhibitor gene responsive to transforming growth factor beta. 总被引:17,自引:0,他引:17
M R Keeton S A Curriden A J van Zonneveld D J Loskutoff 《The Journal of biological chemistry》1991,266(34):23048-23052
Regulation of the human type 1 plasminogen activator inhibitor (PAI-1) promoter by transforming growth factor-beta (TGF beta) was studied. An 800-base pair fragment from the PAI-1 promoter and 5'-flanking region was fused to the firefly luciferase reporter gene and transfected into Hep3B human hepatoma cells. Treatment of the cells with TGF beta induced luciferase activity by more than 50-fold. Transfection studies using constructs with 5' or 3' deletions through this region revealed that two sequences were important in the TGF beta response. The first sequence was located in the proximal promoter (-49 to -87) and mediated an 11-fold induction with TGF beta, while the second more distal region (-636 to -740) contained two sequences which together mediated a 50-fold or greater response. Sequence comparison indicated that both of the responsive regions contained sequences with high homology to the AP-1 consensus binding site. Moreover, gel retardation analysis experiments demonstrated that both sequences bound a common nuclear protein, and that an oligonucleotide containing a consensus AP-1 sequence was able to compete for the binding of this common protein. Thus, the response of the PAI-1 gene to TGF beta is mediated by at least two separate regions, and both of these regions contain DNA sequences homologous to the AP-1 binding site. 相似文献
88.
89.
Water hyacinth Eichhornia crassipes (Pontederiaceae) is one of the world's worst invasive species, responsible for damaging aquatic systems in many warmer parts of the globe including north America, Africa, Asia and Australia. The planthopper Megamelus scutellaris Berg (Delphacidae) has been released in USA and approved for release in South Africa for biocontrol of water hyacinth. We assessed this agent for suitability for release in Australia and found that a related native aquatic plant, Monochoria cyanea (Pontederiaceae) is within the fundamental host range of this insect. Adult survival, oviposition and development of nymphs to adult was equally high on M. cyanea as on the target species, although the quality of these next generation adults was lower than those reared on the target species. This demonstrates that M. scutellaris is not sufficiently specific for release in Australia. Nymphal development to adults occurred only in very low numbers on the three other Australian species of Monochoria. M. cyanea only occurs in Australia so M. scutellaris is still a possible water hyacinth biocontrol candidate for other regions depending on the results of assessment of the risk to local species of Monochoria. This study demonstrates the effectiveness of modern biocontrol agent assessment and reinforces the importance of testing of local non-target species. 相似文献
90.
MATS BJÖRKLUND IKER RUIZ JUAN CARLOS SENAR 《Biological journal of the Linnean Society. Linnean Society of London》2010,99(1):9-19
The increase of urban areas has led to a fragmentation of habitats for many forest‐living species. Man‐made parks might be a solution, but they can also act as sinks that are unable to maintain themselves without immigration from natural areas. Alternatively, parks might act as true metapopulations with extinctions and colonizations. In both cases, we can expect genetic variation to be reduced in the parks compared to the natural habitat. A third alternative is that the parks have sufficient reproduction to maintain themselves. To test these hypotheses, we analysed the pattern of genetic variation in the great tit (Parus major) in 12 parks in central Barcelona, and in an adjacent forest population using microsatellites. Genetic variation was not lower in the parks compared to the forest population, but larger, and gene flow was higher from the town to the forest compared to vice versa. We found a significant genetic differentiation among the parks, with a structure that only partly reflected the geographic position of the parks. Relatedness among individuals within parks was higher than expected by chance, although we found no evidence of kin groups. Assignment tests suggest that some parks are acting as net donors of individuals to other parks. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 9–19. 相似文献