全文获取类型
收费全文 | 143篇 |
免费 | 15篇 |
专业分类
158篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 3篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 1篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 4篇 |
1975年 | 1篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有158条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
Rob Noorlag Pauline MW van Kempen Cathy B Moelans Rick de Jong Laura ER Blok Ronald Koole Wilko Grolman Paul J van Diest Robert JJ van Es Stefan M Willems 《Epigenetics》2014,9(9):1220-1227
Silencing of tumor suppressor genes (TSGs) by DNA promoter hypermethylation is an early event in carcinogenesis and a potential target for personalized cancer treatment. In head and neck cancer, little is known about the role of promoter hypermethylation in survival. Using methylation specific multiplex ligation-dependent probe amplification (MS-MLPA) we investigated the role of promoter hypermethylation of 24 well-described genes (some of which are classic TSGs), which are frequently methylated in different cancer types, in 166 HPV-negative early oral squamous cell carcinomas (OSCC), and 51 HPV-negative early oropharyngeal squamous cell carcinomas (OPSCC) in relation to clinicopathological features and survival. Early OSCC showed frequent promoter hypermethylation in RARB (31% of cases), CHFR (20%), CDH13 (13%), DAPK1 (12%), and APC (10%). More hypermethylation (≥ 2 genes) independently correlated with improved disease specific survival (hazard ratio 0.17, P = 0.014) in early OSCC and could therefore be used as prognostic biomarker. Early OPSCCs showed more hypermethylation of CDH13 (58%), TP73 (14%), and total hypermethylated genes. Hypermethylation of two or more genes has a significantly different effect on survival in OPSCC compared with OSCC, with a trend toward worse instead of better survival. This could have a biological explanation, which deserves further investigation and could possibly lead to more stratified treatment in the future. 相似文献
85.
86.
87.
Interactions of Photobleaching and Inorganic Nutrients in Determining Bacterial Growth on Colored Dissolved Organic Carbon 总被引:8,自引:0,他引:8
Abstract Bacteria are key organisms in the processing of dissolved organic carbon (DOC) in aquatic ecosystems. Their growth depends on both organic substrates and inorganic nutrients. The importance of allochthonous DOC, usually highly colored, as bacterial substrate can be modified by photobleaching. In this study, we examined how colored DOC (CDOC) photobleaching, and phosphorus (P) and nitrogen (N) availability, affect bacterial growth. Five experiments were conducted, manipulating nutrients (P and N) and sunlight exposure. In almost every case, nutrient additions had a significant, positive effect on bacterial abundance, production, and growth efficiency. Sunlight exposure (CDOC photobleaching) had a significant, positive effect on bacterial abundance and growth efficiency. We also found a significant, positive interaction between these two factors. Thus, bacterial use of CDOC was accelerated under sunlight exposure and enhanced P and N concentrations. In addition, the accumulation of cells in sunlight treatments was dependent on nutrient availability. More photobleached substrate was converted into bacterial cells in P- and N-enriched treatments. These results suggest nutrient availability may affect the biologically-mediated fate (new biomass vs respiration) of CDOC. 相似文献
88.
Crustacean and cheliceratan hemocyanins (oxygen-transport proteins) and
insect hexamerins (storage proteins) are homologous gene products, although
the latter do not bind oxygen and do not possess the copper- binding
histidines present in the hemocyanins. An alignment of 19 amino acid
sequences of hemocyanin subunits and insect hexamerins was made, based on
the conservation of elements of secondary structure observed in X-ray
structures of two hemocyanin subunits. The alignment was analyzed using
parsimony and neighbor-joining methods. Results provide strong indications
for grouping together the sequences of the 2 crustacean hemocyanin
subunits, the 5 cheliceratan hemocyanin subunits, and the 12 insect
hexamerins. Within the insect clade, four methionine- rich proteins, four
arylphorins, and two juvenile hormone-suppressible proteins from
Lepidoptera, as well as two dipteran proteins, form four separate groups.
In the absence of an outgroup sequence, it is not possible to present
information about the ancestral state from which these proteins are
derived. Although this family of proteins clearly consists of homologous
gene products, there remain striking differences in gene organization and
site of biosynthesis of the proteins within the cell. Because studies on
18S and 12S rRNA sequences indicate a rather close relationship between
insects and crustaceans, we propose that hemocyanin is the ancestral
arthropod protein and that insect hexamerins lost their copper-binding
capability after divergence of the insects from the crustaceans.
相似文献
89.
90.
M Barathan V Mariappan E M Shankar B JJ Abdullah K L Goh J Vadivelu 《Cell death & disease》2013,4(6):e697
Photodynamic therapy (PDT) has emerged as a capable therapeutic modality for the treatment of cancer. PDT is a targeted cancer therapy that reportedly leads to tumor cell apoptosis and/or necrosis by facilitating the secretion of certain pro-inflammatory cytokines and expression of multiple apoptotic mediators in the tumor microenvironment. In addition, PDT also triggers oxidative stress that directs tumor cell killing and activation of inflammatory responses. However, the cellular and molecular mechanisms underlying the role of PDT in facilitating tumor cell apoptosis remain ambiguous. Here, we investigated the ability of PDT in association with hypericin (HY) to induce tumor cell apoptosis by facilitating the induction of reactive oxygen species (ROS) and secretion of Th1/Th2/Th17 cytokines in human hepatocellular liver carcinoma cell line (HepG2) cells. To discover if any apoptotic mediators were implicated in the enhancement of cell death of HY-PDT-treated tumor cells, selected gene profiling in response to HY-PDT treatment was implemented. Experimental results showed that interleukin (IL)-6 was significantly increased in all HY-PDT-treated cells, especially in 1 μg/ml HY-PDT, resulting in cell death. In addition, quantitative real-time PCR analysis revealed that the expression of apoptotic genes, such as BH3-interacting-domain death agonist (BID), cytochrome complex (CYT-C) and caspases (CASP3, 6, 7, 8 and 9) was remarkably higher in HY-PDT-treated HepG2 cells than the untreated HepG2 cells, entailing that tumor destruction of immune-mediated cell death occurs only in PDT-treated tumor cells. Hence, we showed that HY-PDT treatment induces apoptosis in HepG2 cells by facilitating cytotoxic ROS, and potentially recruits IL-6 and apoptosis mediators, providing additional hints for the existence of alternative mechanisms of anti-tumor immunity in hepatocellular carcinoma, which contribute to long-term suppression of tumor growth following PDT. 相似文献