全文获取类型
收费全文 | 496篇 |
免费 | 39篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 27篇 |
2020年 | 11篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 33篇 |
2014年 | 38篇 |
2013年 | 46篇 |
2012年 | 38篇 |
2011年 | 33篇 |
2010年 | 19篇 |
2009年 | 11篇 |
2008年 | 18篇 |
2007年 | 34篇 |
2006年 | 24篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有535条查询结果,搜索用时 15 毫秒
1.
Vikas Yadav Patade Sujata Bhargava Penna Suprasanna 《Plant Cell, Tissue and Organ Culture》2012,108(2):279-286
In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) calli were cultured on media containing NaCl or polyethylene glycol (PEG) 8000 that exerted the same osmotic
pressure (−0.7 MPa). PEG stress exposure for 15 days led to significant growth reduction and loss in water content than salt
stressed and control tissues. Osmotic adjustment (OA) was observed in callus tissues grown on salt, but was not evident in
callus grown on PEG. Oxidative damage to membranes, estimated in terms of accumulation of thiobarbituric acid reactive substances-TBARS
and electrolytic leakage was significantly higher in both the stressed calli than the control however, the extent of damage
was more in the PEG stressed calli. The stressed callus tissues showed inhibition of ascorbate peroxidase activity, while
catalase activity was increased. These results indicate sensitivity of cells to PEG-mediated stress than salt stress and differences
in their OA to these two stress conditions. The sensitivity to the osmotic stress indicate that expression of the stress tolerance
response requires the coordinated action of different tissues in a plant and hence was not expressed at the cellular level. 相似文献
2.
Elvira D'Alessandro Corinna De Matteis Vaccarella Maria Luisa Lo Re Francesco Cappa Angela D'Alfonso Stefania Discepoli Maria Rosa Della Penna Giuseppe Del Porto 《Human genetics》1988,80(2):203-204
Summary Pericentric inversion of chromosome 19 has been found in several members of three unrelated families from a restricted geographical region. In one of the families, an additional pericentric inversion of chromosome 9 was observed. Reproductive problems, multiple abortions in two families and a neonatal death in the third, were present. A review of previously described cases is included, and the genetic risk connected with this type of rearrangement is also discussed. 相似文献
3.
It is known that the 40s ribosomal protein S6 undergoes a dramatic increase in its level of phosphorylation during Xenopus oocyte meiotic maturation in response to progesterone stimulation. During prophase arrest, the majority of S6 has 0 moles phosphate per mole protein; this increases to 4-5 moles phosphate per mole protein by the time of germinal vesicle breakdown (GVBD). Our in vitro and in vivo studies indicate that the accumulation of phosphate on S6 is the net result of a 4-5-fold increase in S6 kinase activity and a 30-50% decrease in the rate of dephosphorylation and/or turnover of phosphate groups on S6 in maturing oocytes. In addition, the level of phosphorylation of S6 on 80s monosomes injected into non-hormone-stimulated oocytes was unexpectedly high. This indicates that the S6 kinase/phosphatase ratio in prophase arrested oocytes is higher than anticipated from previous studies. This observation implies that the majority of the oocyte ribosomes may be sequestered from any S6 kinase during meiotic prophase. Furthermore, these observations suggest that a portion of the increased accumulation of phosphate on S6 may be the result of increased accessibility of the ribosomes to S6 kinase during oocyte meiotic maturation. 相似文献
4.
Mario Penna Robert R. Capranica Jane Somers 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(1):73-82
Summary Twenty four castrated male, 6 intact male, and 11 intact female Hyla cinerea were injected subcutaneously with 25 g arginine-vasotocin (AVT) and induced to call 1 h later in response to the playback of a conspecific mating call. Eighteen castrated males and 8 intact females were implanted 5 mg androgen pellets for 3 weeks prior to the neuropeptide injection. Among castrated males, 6/9 testosterone (T) implanted, 4/9 dihydrotestosterone (DHT) implanted and 2/6 non implanted individuals produced calls after being administered AVT. 5/6 intact non implanted males and 6/8 T intact implanted females also called, and 3 intact non implanted females remained silent after the injection. Evoked calls had a mid-frequency spectral peak at about 1900 Hz which is absent in field-recorded mating calls of this species. Calls of implanted females and castrated non implanted males were shorter than those of castrated implanted and intact non implanted males. Audiograms measured before hormone implants showed dips of enhanced sensitivity at about 0.5, 0.9 and 3.0 kHz in males and females. After AVT injection, thresholds at frequencies within the 0.7–1.5 kHz range were increased in castrated males. Such reduction in sensitivity points to an inhibition of the auditory system during hormone induced vocal activation.Abbreviations
AVT
arginine-vasotocin
-
DHT
dihydrotestosterone
-
T
testosterone
-
TS
torus semicircularis 相似文献
5.
Isabela Tagomori Vassilis Daioglou Pedro Rochedo Gerd Angelkorte Roberto Schaeffer Detlef van Vuuren Alexandre Szklo 《Global Change Biology Bioenergy》2023,15(2):116-127
Bioenergy could play a major role in decarbonizing energy systems in the context of the Paris Agreement. Large-scale bioenergy deployment could be related to sustainability issues and requires major infrastructure investments. It, therefore, needs to be studied carefully. The Bioenergy and Land Optimization Spatially Explicit Model (BLOEM) presented here allows for assessing different bioenergy pathways while encompassing various dimensions that influence their optimal deployment. In this study, BLOEM was applied to the Brazilian context by coupling it with the Brazilian Land Use and Energy Systems (BLUES) model. This allowed investigating the most cost-effective ways of attending future bioenergy supply projections and studying the role of recovered degraded pasture lands in improving land availability in a sustainable and competitive manner. The results show optimizing for limiting deforestation and minimizing logistics costs results in different outcomes. It also indicates that recovering degraded pasture lands is attractive from both logistics and climate perspectives. The systemic approach of BLOEM provides spatial results, highlighting the trade-offs between crop allocation, land use and the logistics dynamics between production, conversion, and demand, providing valuable insights for regional and national climate policy design. This makes it a useful tool for mapping sustainable bioenergy value chain pathways. 相似文献
6.
C Ferrari M Pilli A Penna A Bertoletti A Valli A Cavalli G Pasetti F Fiaccadori 《Journal of virology》1992,66(4):2536-2540
Processing and presentation by T cells appear to be limited to antigens that can directly interact with the T-cell surface, thereby overcoming the T-cell inefficiency in antigen capture and internalization. Our study provides evidence that the hepatitis B virus (HBV) envelope proteins can also be efficiently processed and presented by CD4+ and CD8+ T cells to other T cells in a human leukocyte antigen class II-restricted fashion. This phenomenon suggests a receptor-mediated interaction between T cells and the HBV envelope and defines a system that can, we hope, be exploited for the identification of the receptor binding site within the HBV envelope and for the characterization of the putative cellular HBV receptor. 相似文献
7.
Ogaki Mayara B. Coelho Lívia C. Vieira Rosemary Neto Arthur A. Zani Carlos L. Alves Tânia M. A. Junior Policarpo A. S. Murta Silvane M. F. Barbosa Emerson C. Oliveira Jaquelline G. Ceravolo Isabela P. Pereira Patrícia O. Cota Betania B. Viana Roberta O. Alves Viviane S. Rosa Luiz H. 《Extremophiles : life under extreme conditions》2020,24(2):227-238
Extremophiles - We accessed the culturable mycobiota present in marine sediments at different depths in Antarctica Ocean. Acremonium fusidioides, Penicillium allii-sativi, Penicillium chrysogenum,... 相似文献
8.
9.
Isabela P. Gomes Talita L. Santos Amanda N. de Souza Lúcio O. Nunes Gabriele A. Cardoso Carolina O. Matos Lívia M.F. Costa Luciano M. Lião Jarbas M. Resende Rodrigo M. Verly 《生物化学与生物物理学报:生物膜》2021,1863(1):183449
Studies have suggested that antimicrobial peptides act by different mechanisms, such as micellisation, self-assembly of nanostructures and pore formation on the membrane surface. This work presents an extensive investigation of the membrane interactions of the 14 amino-acid antimicrobial peptide hylaseptin P1-NH2 (HSP1-NH2), derived from the tree-frog Hyla punctata, which has stronger antifungal than antibacterial potential. Biophysical and structural analyses were performed and the correlated results were used to describe in detail the interactions of HSP1-NH2 with zwitterionic and anionic detergent micelles and phospholipid vesicles. HSP1-NH2 presents similar well-defined helical conformations in both zwitterionic and anionic micelles, although NMR spectroscopy revealed important structural differences in the peptide N-terminus. 2H exchange experiments of HSP1-NH2 indicated the insertion of the most N-terminal residues (1–3) in the DPC-d38 micelles. A higher enthalpic contribution was verified for the interaction of the peptide with anionic vesicles in comparison with zwitterionic vesicles. The pore formation ability of HSP1-NH2 (examined by dye release assays) and its effect on the size and surface charge as well as on the lipid acyl chain ordering (evaluated by Fourier-transform infrared spectroscopy) of anionic phospholipid vesicles showed membrane disruption even at low peptide-to-phospholipid ratios, and the effect increases proportionately to the peptide concentration. On the other hand, these biophysical investigations showed that a critical peptide-to-phospholipid ratio around 0.6 is essential for promoting disruption of zwitterionic membranes. In conclusion, this study demonstrates that the binding process of the antimicrobial HSP1-NH2 peptide depends on the membrane composition and peptide concentration. 相似文献
10.