全文获取类型
收费全文 | 512篇 |
免费 | 26篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 55篇 |
2012年 | 33篇 |
2011年 | 26篇 |
2010年 | 24篇 |
2009年 | 16篇 |
2008年 | 31篇 |
2007年 | 37篇 |
2006年 | 34篇 |
2005年 | 28篇 |
2004年 | 27篇 |
2003年 | 31篇 |
2002年 | 30篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 3篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1951年 | 1篇 |
1943年 | 1篇 |
1898年 | 1篇 |
排序方式: 共有538条查询结果,搜索用时 62 毫秒
21.
22.
23.
Alexander J Oseroff C Dahlberg C Qin M Ishioka G Beebe M Fikes J Newman M Chesnut RW Morton PA Fok K Appella E Sette A 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(12):6189-6198
Proteins are generally regarded as ineffective immunogens for CTL responses. We synthesized a 100-mer decaepitope polypeptide and tested its capacity to induce multiple CD8(+) IFN-gamma and Th lymphocyte (HTL) responses in HLA transgenic mice. Following a single immunization in the absence of adjuvant, significant IFN-gamma in vitro recall responses were detected for all epitopes included in the construct (six A2.1-, three A11-restricted CTL epitopes, and one universal HTL epitope). Immunization with truncated forms of the decaepitope polypeptide was used to demonstrate that optimal immunogenicity was associated with a size of at least 30-40 residues (3-4 epitopes). Solubility analyses of the truncated constructs were used to identify a correlation between immunogenicity for IFN-gamma responses and the propensity of these constructs to form particulate aggregates. Although the decaepitope polypeptide and a pool of epitopes emulsified in IFA elicited similar levels of CD8(+) responses using fresh splenocytes, we found that the decaepitope polypeptide more effectively primed for in vitro recall CD8(+) T cell responses. Finally, immunogenicity comparisons were also made between the decaepitope polypeptide and a corresponding gene encoding the same polypeptide delivered by naked DNA immunization. Although naked DNA immunization induced somewhat greater direct ex vivo and in vitro recall responses 2 wk after a single immunization, only the polypeptide induced significant in vitro recall responses 6 wk following the priming immunization. These studies support further evaluation of multiepitope polypeptide vaccines for induction of CD8(+) IFN-gamma and HTL responses. 相似文献
24.
Vento G Matassa PG Ameglio F Capoluongo E Tortorolo L Romagnoli C 《European cytokine network》2002,13(2):207-214
Corticosteroid administration may prevent chronic lung disease in premature newborns, perhaps by modulating the synthesis of various cytokines, including those involved in fibrogenic processes. This study analyses the levels of three fibrogenic cytokines, namely vascular endothelial growth factor, transforming growth factor-beta 1 and basic fibroblast growth factor in tracheobronchial aspirate fluids collected from 20 premature newborns randomly assigned to the early dexamethasone group or to the control group. Furthermore, pulmonary function tests were performed on days 0 and 2 following the start of therapy. The results show that early corticosteroid administration reduces transforming growth factor-beta 1 and basic fibroblast growth factor levels, and abolishes the spontaneous vascular endothelial growth factor increase observed in untreated patients, concomitantly with significant improvement of dynamic lung compliance and shorter duration of the intubation period in the treated group of patients. Significant correlations were observed between the levels of transforming growth factor-beta 1 and vascular endothelial growth factor, indicating that the production of both these cytokines is coordinated. Finally, transforming growth factor-beta 1 ratios (day 2/day 0), representing early variations of the cytokine levels, were significantly different between treated and untreated subjects and correlated with the dynamic lung compliance ratios and the extubation day, suggesting that the downmodulation of some fibrogenic mediators may be involved in the mode of action of dexamethasone. 相似文献
25.
Downstream E-box-mediated regulation of the human telomerase reverse transcriptase (hTERT) gene transcription: evidence for an endogenous mechanism of transcriptional repression 总被引:26,自引:0,他引:26 下载免费PDF全文
Horikawa I Cable PL Mazur SJ Appella E Afshari CA Barrett JC 《Molecular biology of the cell》2002,13(8):2585-2597
26.
Autonomic nerves supplying mammalian male internal genital organs have an important role in the regulation of reproductive function. To find out the relationships between the neurochemical content of these nerves and the reproductive activity, we performed a histochemical and immunohistochemical study in a species, the water buffalo, exhibiting a seasonal sexual behaviour. The distribution of noradrenergic and nitric oxide synthase (NOS)- and peptide-containing nerves was evaluated during the mating and non-mating periods. Fresh segments of vas deferens and accessory genital glands were collected immediately after slaughter and immersed in 4% paraformaldehyde. Frozen sections were obtained and processed according to single and double labelling immunofluorescent procedures or NADPH-diaphorase histochemistry. During the mating period, a dense noradrenergic innervation was observed to supply the vas deferens as well as the accessory genital glands. NOS- and peptide-containing nerves were also observed but with a lower density. During the non-mating period noradrenergic nerves dramatically reduced. In addition, neuropeptide Y (NPY)- and vasoactive intestinal peptide (VIP)-containing nerves were also reduced. These findings suggest the presence of complex interactions between androgen hormones and the autonomic nerve supply in the regulation of male water buffalo reproductive functions. 相似文献
27.
28.
Goloudina A Yamaguchi H Chervyakova DB Appella E Fornace AJ Bulavin DV 《Cell cycle (Georgetown, Tex.)》2003,2(5):473-478
Degradation of Cdc25A phosphatase is an ubiquitous feature of stress. There are some discrepancies in the reported roles for different phosphorylation sites in the regulation of Cdc25A stability. Using a panel of doxycycline-inducible phosphorylation mutants we show that the stability of human Cdc25A protein is dependent upon phosphorylation at S75. In non-stressed conditions and in non-mitotic cells, Cdc25A is unstable and its stability is regulated in a Chk1-dependent manner. During mitosis, Cdc25A becomes stable and does not undergo degradation after DNA damage. We further show that Chk1 kinase regulates Cdc25A stability after UV irradiation. Similar to Chk1 kinase, p38 MAPK controls Cdc25A protein level after osmotic stress. Using phospho-specific antibodies, we find that both kinases can phosphorylate S75 and S123 in vitro. Inactivation of either Chk1 after UV-irradiation or p38 MAPK after osmotic stress prevents activation of a S phase checkpoint and S75 and S123 phosphorylation. However, introduction of stable Cdc25A (S75A or S75/123A) proteins is not sufficient to overcome this checkpoint. We propose that regulation of human Cdc25A stability by its phosphorylation at S75 may contribute to S phase checkpoint activation only in cooperation with other regulatory mechanisms. 相似文献
29.
Capoluongo E Giglio A Belardi M Leonetti F Frasca A Giannetti A Ameglio F 《The new microbiologica》2000,23(1):21-27
Contrasting data are reported in the literature on the percent positivity rates (13.5%-100%) of exfoliative toxin (ET) production by S. aureus strains isolated from impetigo patients in Japan and in France. In the present study, by means of a recently available latex-test, toxin-A (ETA) or toxin-B (ETB) production was found in 67.6% of the 34 S. aureus strains isolated from 19 lesional (63.2%) and 15 non-lesional (nose or pharynx, 73.3%) areas of patients with impetigo (with no significant difference between the lesional and non-lesional isolates). ETA + ETB were produced by 44.1% of the strains, while 32.4% were non-producers. In contrast, the percent positivity rate observed in 40 [20 lesional and 20 non-lesional (nose or pharynx)] strains isolated in patients with atopic dermatitis was 15.0% (p < 0.001 both for the lesional and non-lesional strains versus impetigo, with no significant difference between lesional and non lesional strains). Finally, 26 strains from other types of specimens (abscesses, hemocultures, urine, central venous catheters, bronchoalveolar lavages) showed an 11.5% production rate of ETA or ETB (p < 0.001 versus impetigo strains, no significance versus atopic dermatitis). These data point to a significant association between exfoliative toxin production and S. aureus strains isolated in impetigo, both in lesional areas and in nasal/pharyngeal reservoirs. An attempt to correlate SmaI pulsed-field gel electrophoresis (PFGE) restriction patterns and exfoliative toxin production showed no significant association in either group. 相似文献
30.
Ivana Sirangelo Ettore Bismuto Simona Tavassi G. Irace 《European biophysics journal : EBJ》1998,27(1):27-31
The individual tryptophanyl contributions to the near-ultraviolet circular dichroic activity of apomyoglobin in its native
conformation have been resolved by studying recombinant proteins with single tryptophanyl substitutions. Site-directed mutagenesis
of sperm whale apomyoglobin was performed in order to obtain proteins containing only Trp A-5 or Trp A-12. These amino acid
substitutions have very little effect on the overall globin fold as indicated by comparing the spectroscopic properties of
the mutants with those of the wild type protein. The circular dichroism spectra of the two apomyoglobin mutants in the near
ultraviolet were found to be significantly different, both indole residues having significant activity but of opposite sign.
In particular, Trp A-5 shows the presence of a main positive peak centered near 294 – 295 nm with a marked shoulder at 285
nm, ascribed to the 1LBtransition. The spectrum of the mutant protein containing only Trp A-12 shows a large negative contribution with a minimum
near 283 nm and a marked shoulder at 293 nm. The broadness of the negative contribution exhibited by Trp A-12 suggests that
it may originate mainly from the 1LA transition.
Received: 17 February 1997 / Accepted: 14 August 1997 相似文献