全文获取类型
收费全文 | 478篇 |
免费 | 24篇 |
国内免费 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 12篇 |
2021年 | 15篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 9篇 |
2015年 | 23篇 |
2014年 | 35篇 |
2013年 | 30篇 |
2012年 | 39篇 |
2011年 | 39篇 |
2010年 | 10篇 |
2009年 | 22篇 |
2008年 | 15篇 |
2007年 | 20篇 |
2006年 | 9篇 |
2005年 | 22篇 |
2004年 | 22篇 |
2003年 | 23篇 |
2002年 | 19篇 |
2001年 | 17篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 13篇 |
1996年 | 2篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有533条查询结果,搜索用时 93 毫秒
11.
Chromosomes of root tip cells ofAllium cepa andAllium sativum were studied in early, middle and late telophase to examine the organization of mitotic chromosomes, taking advantage of the naturally occurring chromosome dispersion during the process of decondensation in telophase. Longitudinal and transverse sections of telophase chromosomes viewed under the transmission electron microscope showed that mitotic chromosomes inAllium were composed of helically coiled 400–550 nm chromatin fibres. In some regions of the longitudinal sections, these chromatin fibres were seen to be orientated parallel to one another but formed roughly a right angle to the long axis of the chromosome. In transverse sections, the telophase chromosome appeared to have a hollow centre encircled by the 400–550 nm chromatin fibre which in turn was a hollow tube structure formed by the coiling of a thinner fibre of 170–200 nm. In addition, cross views of chromatin fibres of 170–200 nm and 50–70 nm were also identified in telophase chromosome preparations. These two organizational levels of chromatin fibres also showed a hollow centre. The process of decondensation of telophase chromosomes is described, and some morphological characteristics associated with the activities of chromosome decondensation are analysed. Based on the observations made onAllium chromosomes in this study, various models of chromosome organization are discussed. 相似文献
12.
Nancy Shui Fong Ma 《American journal of physical anthropology》1981,54(3):293-303
We have reported nine distinct karyotypes for Aotus, of four pelagic phenotypes, and suggest that this single species has undergone extensive subspeciation. We reconstruct the mechanism of chromosomal evolution and propose a hypothesis about the events of subspeciation in Aotus. We speculate that isolated groups of ancestral individuals living in several confined areas have separately accumulated a fusion or inversion pair as a result of inbreeding. A subsequent reassociation of descendants from these individuals led to the formation of offspring with mixtures of fusion or inversion pairs in their complements. They, in turn, radiated into different ecological niches accompanied by adaptive genetic changes and eventually gave rise to the present forms of Aotus distinguishable by their karyotypes, but not easily recognizable by ordinary taxonomic criteria. 相似文献
13.
Mingxing Li Zhihui Wang Lixu Zhu Yifang Shui Shuijun Zhang Wenzhi Guo 《Bioscience reports》2021,41(4)
Recent research has indicated that metabolically related genes play crucial roles in the pathogenesis of hepatocellular carcinoma (HCC). We evaluated the associations between novel biomarkers and retinol-binding protein 4 (RBP4) for predicting clinical HCC outcomes, hub-related genes, pathway regulation, and immune cells infiltration. Bioinformatic analyses based on data from The Cancer Genome Atlas were performed using online analysis tools. RBP4 expression was low in HCC and was also down-regulated in pan-cancers compared with normal tissues. RBP4 expression was also significantly different based on age (41–60 years old versus 61–80 years old), and low RBP4 expression levels were associated with advanced tumor stages and grades. Higher RBP4 expression was associated with better overall survival time in HCC patients, and we identified a deletion-mutation rate of 1.4% in RBP4. We also identified ten co-expressed genes most related to RBP4 and explored the relationships between six hub genes (APOB, FGA, FGG, SERPINC1, APOA1, and F2) involved in RBP4 regulation. A pathway enrichment analysis for RBP4 indicated complement and coagulation cascades, metabolic pathways, antibiotic biosynthesis pathways, peroxisome proliferator-activated receptor signaling pathways, and pyruvate metabolism pathways. These results suggest that RBP4 may be a novel biomarker for HCC prognosis, and an indicator of low immune response to the disease. 相似文献
14.
15.
Degang Yang Tiejun Shui Jake W. Miranda Danny J. Gilson Zhengyu Song Jia Chen Chao Shi Jianyu Zhu Jun Yang Zhichun Jing 《PLoS neglected tropical diseases》2016,10(1)
Background
The persistence of Mycobacterium leprae (M. leprae) infection is largely dependent on the types of host immune responses being induced. Macrophage, a crucial modulator of innate and adaptive immune responses, could be directly infected by M. leprae. We therefore postulated that M. leprae-infected macrophages might have altered immune functions.Methodology/Principal Findings
Here, we treated monocyte-derived macrophages with live or killed M. leprae, and examined their activation status and antigen presentation. We found that macrophages treated with live M. leprae showed committed M2-like function, with decreased interleukin 1 beta (IL-1beta), IL-6, tumor necrosis factor alpha (TNF-alpha) and MHC class II molecule expression and elevated IL-10 and CD163 expression. When incubating with naive T cells, macrophages treated with live M. leprae preferentially primed regulatory T (Treg) cell responses with elevated FoxP3 and IL-10 expression, while interferon gamma (IFN-gamma) expression and CD8+ T cell cytotoxicity were reduced. Chromium release assay also found that live M. leprae-treated macrophages were more resistant to CD8+ T cell-mediated cytotoxicity than sonicated M. leprae-treated monocytes. Ex vivo studies showed that the phenotype and function of monocytes and macrophages had clear differences between L-lep and T-lep patients, consistent with the in vitro findings.Conclusions/Significance
Together, our data demonstrate that M. leprae could utilize infected macrophages by two mechanisms: firstly, M. leprae-infected macrophages preferentially primed Treg but not Th1 or cytotoxic T cell responses; secondly, M. leprae-infected macrophages were more effective at evading CD8+ T cell-mediated cytotoxicity. 相似文献16.
17.
18.
Ling P Meyer CF Redmond LP Shui JW Davis B Rich RR Hu MC Wange RL Tan TH 《The Journal of biological chemistry》2001,276(22):18908-18914
Hematopoietic progenitor kinase 1 (HPK1), a mammalian Ste20-related serine/threonine protein kinase, is a hematopoietic-specific upstream activator of the c-Jun N-terminal kinase. Here, we provide evidence to demonstrate the involvement of HPK1 in T cell receptor (TCR) signaling. HPK1 was activated and tyrosine-phosphorylated with similar kinetics following TCR/CD3 or pervanadate stimulation. Co-expression of protein-tyrosine kinases, Lck and Zap70, with HPK1 led to HPK1 activation and tyrosine phosphorylation in transfected mammalian cells. Upon TCR/CD3 stimulation, HPK1 formed inducible complexes with the adapters Nck and Crk with different kinetics, whereas it constitutively interacted with the adapters Grb2 and CrkL in Jurkat T cells. Interestingly, HPK1 also inducibly associated with linker for activation of T cells (LAT) through its proline-rich motif and translocated into glycolipid-enriched microdomains (also called lipid rafts) following TCR/CD3 stimulation, suggesting a critical role for LAT in the regulation of HPK1. Together, these results identify HPK1 as a new component of TCR signaling. T cell-specific signaling molecules Lck, Zap70, and LAT play roles in the regulation of HPK1 during TCR signaling. Differential complex formation between HPK1 and adapters highlights the possible involvement of HPK1 in multiple signaling pathways in T cells. 相似文献
19.
20.
Orthologous gene-expression profiling in multi-species models: search for candidate genes 总被引:2,自引:0,他引:2 下载免费PDF全文
Microarray-driven gene-expression profiles are generally produced and analyzed for a single specific experimental model. We have assessed an analytical approach that simultaneously evaluates multi-species experimental models within a particular biological condition using orthologous genes as linkers for the various Affymetrix microarray platforms on multi-species models of ventilator-associated lung injury. The results suggest that this approach may be a useful tool in the evaluation of biological processes of interest and selection of process-related candidate genes. 相似文献