首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   112篇
  免费   10篇
  2022年   2篇
  2021年   4篇
  2018年   1篇
  2017年   3篇
  2016年   2篇
  2015年   5篇
  2014年   7篇
  2013年   2篇
  2012年   6篇
  2011年   5篇
  2010年   9篇
  2009年   8篇
  2008年   4篇
  2007年   3篇
  2006年   6篇
  2005年   4篇
  2004年   3篇
  2003年   2篇
  2002年   4篇
  2001年   3篇
  2000年   5篇
  1999年   4篇
  1998年   6篇
  1997年   5篇
  1996年   5篇
  1994年   3篇
  1993年   1篇
  1987年   1篇
  1981年   1篇
  1977年   3篇
  1962年   1篇
  1955年   1篇
  1952年   1篇
  1948年   1篇
  1947年   1篇
排序方式: 共有122条查询结果,搜索用时 843 毫秒
91.
Accumulation of tumor‐associated macrophages (TAMs) associates with malignant progression in cancer. However, the mechanisms that drive the pro‐tumor functions of TAMs are not fully understood. ZEB1 is best known for driving an epithelial‐to‐mesenchymal transition (EMT) in cancer cells to promote tumor progression. However, a role for ZEB1 in macrophages and TAMs has not been studied. Here we describe that TAMs require ZEB1 for their tumor‐promoting and chemotherapy resistance functions in a mouse model of ovarian cancer. Only TAMs that expressed full levels of Zeb1 accelerated tumor growth. Mechanistically, ZEB1 expression in TAMs induced their polarization toward an F4/80low pro‐tumor phenotype, including direct activation of Ccr2. In turn, expression of ZEB1 by TAMs induced Ccl2, Cd74, and a mesenchymal/stem‐like phenotype in cancer cells. In human ovarian carcinomas, TAM infiltration and CCR2 expression correlated with ZEB1 in tumor cells, where along with CCL2 and CD74 determined poorer prognosis. Importantly, ZEB1 in TAMs was a factor of poorer survival in human ovarian carcinomas. These data establish ZEB1 as a key factor in the tumor microenvironment and for maintaining TAMs’ tumor‐promoting functions.  相似文献   
92.
EA Miller  MC Lee    MA Anderson 《The Plant cell》1999,11(8):1499-1508
The stigmas of the ornamental tobacco plant Nicotiana alata accumulate large quantities of a series of 6-kD proteinase inhibitors (PIs) in the central vacuole that are derived from a 40-kD precursor protein, Na-PI. The sorting information that directs Na-PI to the vacuole is likely to reside in a C-terminal propeptide domain of 25 amino acids that forms an amphipathic alpha helix. Using cell fractionation techniques, we have examined transit of Na-PI through the endomembrane system and have identified a prevacuolar compartment that contains Na-PI with an intact targeting signal. In contrast, the targeting signal is not present on the predominant form of Na-PI in the vacuole. The prevacuolar compartment is marked by the presence of homologs of both the t-SNARE, PEP12p, and the putative vacuolar sorting receptor BP-80. Cross-linking and affinity precipitation studies revealed that Na-PI associates with BP-80 within this compartment, providing in vivo evidence for the function of BP-80 as a sorting receptor for a protein with a C-terminal vacuolar targeting signal.  相似文献   
93.
19-Norandrosterone (19-NA) as its glucuronide derivative is the target metabolite in anti-doping testing to reveal an abuse of nandrolone or nandrolone prohormone. To provide further evidence of a doping with these steroids, the sulfoconjugate form of 19-norandrosterone in human urine might be monitored as well. In the present study, the profiling of sulfate and glucuronide derivatives of 19-norandrosterone together with 19-noretiocholanolone (19-NE) were assessed in the spot urines of 8 male subjects, collected after administration of 19-nor-4-androstenedione (100 mg). An LC/MS/MS assay was employed for the direct quantification of sulfoconjugates, whereas a standard GC/MS method was applied for the assessment of glucuroconjugates in urine specimens. Although the 19-NA glucuronide derivative was always the most prominent at the excretion peak, inter-individual variability of the excretion patterns was observed for both conjugate forms of 19-NA and 19-NE. The ratio between the glucuro- and sulfoconjugate derivatives of 19-NA and 19-NE could not discriminate the endogenous versus the exogenous origin of the parent compound. However, after ingestion of 100 mg 19-nor-4-androstenedione, it was observed in the urine specimens that the sulfate conjugates of 19-NA was detectable over a longer period of time with respect to the other metabolites. These findings indicate that more interest shall be given to this type of conjugation to deter a potential doping with norsteroids.  相似文献   
94.
Besides their important contribution to global biodiversity, mangroves provide many services. Nevertheless, due to an increase of human activities and to climate change, in less than 20 years these ecosystems have lost one fifth of their global surface area. In response to this decrease, mangrove reforestation incentives have spread throughout the world. The scientific and societal legitimacy of reforestation actions still remain in question. Focusing on two case studies, the Saloum Delta and Lower Casamance, Senegal, our methodology was mainly based on the analysis of environmental narratives and discourses between 2009 and 2013, and on reforestation campaigns conducted by NGOs. We highlight the complexity of the system of values associated with the mangroves, as well as the positive and negative interactions between the services. Even although the reforestation campaigns were generally successful in terms of reforested surfaces and international visibility, they were poor in terms of biological and cultural diversities and led to spatial injustice. Moreover, the extensive reforestation with a unique mangrove species, Rhizophora mangle, was perceived as means of ‘green grabbing’, and the simultaneous buying of carbon tax by industrial conglomerates induced disempowerment of the local communities. More integrated research programmes must be developed towards the extensive knowledge of the mangroves.  相似文献   
95.
A water-soluble arabinogalactan-peptide from wheat endosperm was degraded by treatment with mild acid, alkali and enzymes. 4-Hydroxyproline-galactoside was isolated from the degradation products and was shown to be identical with synthetic trans-4-hydroxyproline-β-d-galactopyranoside. This linkage compound connects the arabinogalactan side chains to the peptide core in the arabinogalactan-peptide. A possible structural model for this glycoprotein is discussed.  相似文献   
96.
Sustainable development of a bioenergy industry will require low‐cost, high‐yielding biomass feedstock of desirable quality. Switchgrass (Panicum virgatum L.) is one of the primary feedstock candidates in North America, but the potential to grow this biomass crop using fertility from biosolids has not been fully explored. The objective of this study was to examine the effects of harvest frequency and biosolids application on switchgrass in Virginia, USA. ‘Cave‐in‐Rock’ switchgrass from well‐established plots was cut once (November) or twice (July and November) per year between 2010 and 2012. Class A biosolids were applied once at rates of 0, 153, 306, and 459 kg N ha?1 in May 2010. Biomass yield, neutral and acid detergent fiber, cellulose, hemicellulose, lignin, and ash were determined. Theoretical ethanol potential (TEP, l ethanol Mg?1 biomass) and yield (TEY, l ethanol ha?1) were calculated based on cellulose and hemicellulose concentrations. Cutting twice per season produced greater biomass yields than one cutting (11.7 vs. 9.8 Mg ha?1) in 2011, but no differences were observed in other years. Cutting once produced feedstock with greater TEP (478 vs. 438 l Mg?1), but no differences in TEY between cutting frequencies. Biosolids applied at 153, 306, and 459 kg N ha?1 increased biomass yields by 25%, 37%, and 46%, and TEY by 25%, 34%, and 42%, respectively. Biosolids had inconsistent effects on feedstock quality and TEP. A single, end‐of‐season harvest likely will be preferred based on apparent advantages in feedstock quality. Biosolids can serve as an effective alternative to N fertilizer in switchgrass‐to‐energy systems.  相似文献   
97.
Piper T  Baume N  Strahm E  Emery C  Saugy M 《Steroids》2012,77(6):644-654
Several factors influencing the carbon isotope ratios (CIR) of endogenous urinary steroids have been identified in recent years. One of these should be the metabolism of steroids inside the body involving numerous different enzymes. A detailed look at this metabolism taking into account differences found between steroids excreted as glucuronides or as sulphates and hydrogen isotope ratios of different steroids pointed out possibility of unequal CIR at the main production sites inside the male body - the testes and the adrenal glands. By administration of β-HCG it is possible to strongly stimulate the steroid production within the testes without influencing the production at the adrenal glands. Therefore, this treatment should result in changed CIR of urinary androgens in contrast to the undisturbed pre-treatment values. Four male volunteers received three injections of β-HCG over a time course of 5 days and collected their urine samples at defined intervals after the last administration. Those samples showing the largest response in contrast to the pre-administration urines were identified by steroid profile measurements and subsequent analysed by GC/C/IRMS. CIR of androsterone, etiocholanolone, testosterone, 5α- and 5β-androstanediol and pregnanediol were compared. While pregnanediol was not influenced, most of the investigated androgens showed depleted values after treatment. The majority of differences were found to be statistically significant and nearly all showed the expected trend towards more depleted δ(13)C-values. These results support the hypothesis of different CIR at different production sites inside the human body. The impact of these findings on doping control analysis will be discussed.  相似文献   
98.
Cardiovascular death is frequently associated with atherosclerosis, a chronic multifactorial disease and a leading cause of death worldwide. Genetically engineered mouse models have proven useful for the study of the mechanisms underlying cardiovascular diseases. The apolipoprotein E-deficient mouse has been the most widely used animal model of atherosclerosis because it rapidly develops severe hypercholesterolemia and spontaneous atherosclerotic lesions similar to those observed in humans. In this review, we provide an overview of the cardiac and vascular phenotypes and discuss the interplay among nitric oxide, reactive oxygen species, aging and diet in the impairment of cardiovascular function in this mouse model.  相似文献   
99.
In the post-genome era, high throughput gene expression profiling has been successfully used to develop genomic biomarker panels (GBP) that can be integrated into clinical decision making. The development of GBPs in the context of personalized medicine is a scientifically challenging and resource-intense process. It needs to be accomplished in a systematic phased approach to address biological variation related to a clinical phenotype (e.g. disease etiology, gender, etc.) and minimize technical variation (noise). Here we present the methodological aspects of GBP development based on the experience of the Cardiac Allograft Rejection Gene Expression Observation (CARGO) study, a study that lead to the development of a molecular classifier for rejection screening in heart transplant patients.  相似文献   
100.

Background  

Methodologies like phage display selection, in vitro mutagenesis and the determination of allelic expression differences include steps where large numbers of clones need to be compared and characterised. In the current study we show that high-resolution melt curve analysis (HRMA) is a simple, cost-saving tool to quickly study clonal variation without prior nucleotide sequence knowledge.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号