全文获取类型
收费全文 | 248篇 |
免费 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 26篇 |
2012年 | 18篇 |
2011年 | 14篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 17篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1967年 | 1篇 |
1962年 | 1篇 |
1927年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有262条查询结果,搜索用时 281 毫秒
21.
J. M. Hibberd R. A. Bungard M. C. Press W. D. Jeschke J. D. Scholes W. P. Quick 《Planta》1998,205(4):506-513
Cells capable of photosynthesis in the parasitic angiosperm Cuscuta reflexa Roxb. (dodder) are highly localized. Immunolocalization of ribulose-1,5 bisphosphate carboxylase-oxygenase (Rubisco) and
autofluorescence of chlorophyll in transverse sections of stems showed that they were largely restricted to a band of cells
adjacent to the vascular bundles, consequently, the concentrations of Rubisco and chlorophyll were low per unit area or fresh
weight. When 14CO2 was supplied to stem segments of C. reflexa it preferentially accumulated in these cells adjacent to the vasculature. Although the conductance for CO2 movement to the cells containing chlorophyll and Rubisco was very low, both the light reactions and dark reactions of photosynthesis
appeared to be functional. De-epoxidation of the xanthophyll-cycle pigments after exposure to high light, and the chlorophyll
fluorescence parameters, photochemical quenching (qP), non-photochemical quenching (NPQ) and the quantum efficiency of photosystem
II (φPSII) responded normally to changes in photon flux density, indicating functional light-driven electron transport. The
response of CO2 exchange to photon flux density followed a typical hyperbolic curve, and positive rates of CO2 fixation occurred when external CO2 was increased to 5%. We propose that CO2 for carbon assimilation is derived from internally respired CO2 and that this layer of photosynthetic cells makes a positive contribution to the carbon budget of C. reflexa.
Received: 23 October 1997 / Accepted: 16 December 1997 相似文献
22.
23.
Lourdais O Hoffman TC Denardo DF 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(5):569-577
Parental care provides considerable benefits to offspring and is widespread among animals, yet it is relatively uncommon among
squamate reptiles (e.g., lizards and snakes). However, all pythonine snakes show extended maternal egg brooding with some
species being facultatively endothermic. While facultative endothermy provides thermal benefits, the presence of brooding
in non-endothermic species suggests other potential benefits of brooding. In this study we experimentally tested the functional
significance of maternal brooding relative to water balance in the children’s python, Antaresia childreni, a small species that does not exhibit facultative endothermy. Clutch evaporative water loss (EWL) was positively correlated
with clutch mass and was much lower than expected values based on individual eggs. The conglomerate clutch behaved as a single
unit with a decreasing surface area to volume ratio as clutch size increased. Maternal brooding had a dramatic impact on evaporation
from eggs, reducing and possibly eliminating clutch EWL. In a separate experiment, we found that viability of unattended eggs
is highly affected by humidity level, even in the narrow range from 75 to 100% relative humidity at 30.5°C (20–33 mg m−3 absolute humidity). However, the presence of the brooding female ameliorated this sensitivity, as viability of brooded clutches
at 75% relative humidity was higher than that of non-brooded eggs at either the same absolute humidity or at near-saturated
conditions. Overall, these results demonstrate that brooding behavior strongly promotes egg water balance (and thus egg viability)
in children’s pythons. 相似文献
24.
Identification of the IL-17 receptor related molecule IL-17RC as the receptor for IL-17F 总被引:2,自引:0,他引:2
Kuestner RE Taft DW Haran A Brandt CS Brender T Lum K Harder B Okada S Ostrander CD Kreindler JL Aujla SJ Reardon B Moore M Shea P Schreckhise R Bukowski TR Presnell S Guerra-Lewis P Parrish-Novak J Ellsworth JL Jaspers S Lewis KE Appleby M Kolls JK Rixon M West JW Gao Z Levin SD 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(8):5462-5473
The proinflammatory cytokines IL-17A and IL-17F have a high degree of sequence similarity and share many biological properties. Both have been implicated as factors contributing to the progression of inflammatory and autoimmune diseases. Moreover, reagents that neutralize IL-17A significantly ameliorate disease severity in several mouse models of human disease. IL-17A mediates its effects through interaction with its cognate receptor, the IL-17 receptor (IL-17RA). We report here that the IL-17RA-related molecule, IL-17RC is the receptor for IL-17F. Notably, both IL-17A and IL-17F bind to IL-17RC with high affinity, leading us to suggest that a soluble form of this molecule may serve as an effective therapeutic antagonist of IL-17A and IL-17F. We generated a soluble form of IL-17RC and demonstrate that it effectively blocks binding of both IL-17A and IL-17F, and that it inhibits signaling in response to these cytokines. Collectively, our work indicates that IL-17RC functions as a receptor for both IL-17A and IL-17F and that a soluble version of this protein should be an effective antagonist of IL-17A and IL-17F mediated inflammatory diseases. 相似文献
25.
Environmental Monitoring of Mycobacterium bovis in Badger Feces and Badger Sett Soil by Real-Time PCR, as Confirmed by Immunofluorescence, Immunocapture, and Cultivation 下载免费PDF全文
F. P. Sweeney O. Courtenay V. Hibberd R. G. Hewinson L. A. Reilly W. H. Gaze E. M. H. Wellington 《Applied microbiology》2007,73(22):7471-7473
Real-time PCR was used to detect and quantify Mycobacterium bovis cells in naturally infected soil and badger feces. Immunomagnetic capture, immunofluorescence, and selective culture confirmed species identification and cell viability. These techniques will prove useful for monitoring M. bovis in the environment and for elucidating transmission routes between wildlife and cattle. 相似文献
26.
27.
Astley HM Parsley K Aubry S Chastain CJ Burnell JN Webb ME Hibberd JM 《The Plant journal : for cell and molecular biology》2011,68(6):1070-1080
Pyruvate orthophosphate dikinase (PPDK) is a key enzyme in C(4) photosynthesis and is also found in C(3) plants. It is post-translationally modified by the PPDK regulatory protein (RP) that possesses both kinase and phosphotransferase activities. Phosphorylation and dephosphorylation of PPDK lead to inactivation and activation respectively. Arabidopsis thaliana contains two genes that encode chloroplastic (RP1) and cytosolic (RP2) isoforms of RP, and although RP1 has both kinase and phosphotransferase activities, to date RP2 has only been shown to act as a kinase. Here we demonstrate that RP2 is able to catalyse the dephosphorylation of PPDK, although at a slower rate than RP1 under the conditions of our assay. From yeast two-hybrid analysis we propose that RP1 binds to the central catalytic domain of PPDK, and that additional regions towards the carboxy and amino termini are required for a stable interaction between RP2 and PPDK. For 21 highly conserved amino acids in RP1, mutation of 15 of these reduced kinase and phosphotransferase activity, while mutation of six residues had no impact on either activity. We found no mutant in which only one activity was abolished. However, in some chimaeric fusions that comprised the amino and carboxy termini of RP1 and RP2 respectively, the kinase reaction was severely compromised but phosphotransferase activity remained unaffected. These findings are consistent with the findings that both RP1 and RP2 modulate reversibly the activity of PPDK, and possess one bifunctional active site or two separate sites in close proximity. 相似文献
28.
Raghwani J Rambaut A Holmes EC Hang VT Hien TT Farrar J Wills B Lennon NJ Birren BW Henn MR Simmons CP 《PLoS pathogens》2011,7(6):e1002064
Dengue is one of the most important infectious diseases of humans and has spread throughout much of the tropical and subtropical world. Despite this widespread dispersal, the determinants of dengue transmission in endemic populations are not well understood, although essential for virus control. To address this issue we performed a phylogeographic analysis of 751 complete genome sequences of dengue 1 virus (DENV-1) sampled from both rural (Dong Thap) and urban (Ho Chi Minh City) populations in southern Viet Nam during the period 2003-2008. We show that DENV-1 in Viet Nam exhibits strong spatial clustering, with likely importation from Cambodia on multiple occasions. Notably, multiple lineages of DENV-1 co-circulated in Ho Chi Minh City. That these lineages emerged at approximately the same time and dispersed over similar spatial regions suggests that they are of broadly equivalent fitness. We also observed an important relationship between the density of the human host population and the dispersion rate of dengue, such that DENV-1 tends to move from urban to rural populations, and that densely populated regions within Ho Chi Minh City act as major transmission foci. Despite these fluid dynamics, the dispersion rates of DENV-1 are relatively low, particularly in Ho Chi Minh City where the virus moves less than an average of 20 km/year. These low rates suggest a major role for mosquito-mediated dispersal, such that DENV-1 does not need to move great distances to infect a new host when there are abundant susceptibles, and imply that control measures should be directed toward the most densely populated urban environments. 相似文献
29.
Advances in sequencing technology and genome-wide association studies are now revealing the complex interactions between hosts
and pathogen through genomic variation signatures, which arise from evolutionary co-existence. 相似文献
30.