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   621篇
  免费   54篇
  2023年   27篇
  2022年   26篇
  2021年   54篇
  2020年   29篇
  2019年   23篇
  2018年   18篇
  2017年   30篇
  2016年   38篇
  2015年   38篇
  2014年   31篇
  2013年   43篇
  2012年   71篇
  2011年   38篇
  2010年   17篇
  2009年   16篇
  2008年   13篇
  2007年   15篇
  2006年   18篇
  2005年   10篇
  2004年   8篇
  2003年   12篇
  2002年   11篇
  2001年   4篇
  1998年   3篇
  1997年   3篇
  1992年   2篇
  1991年   4篇
  1989年   2篇
  1988年   6篇
  1987年   3篇
  1986年   2篇
  1985年   2篇
  1984年   3篇
  1982年   3篇
  1981年   4篇
  1980年   5篇
  1978年   2篇
  1977年   2篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1970年   2篇
  1969年   2篇
  1968年   2篇
  1967年   2篇
  1966年   4篇
  1965年   3篇
  1964年   2篇
  1963年   2篇
  1962年   3篇
排序方式: 共有675条查询结果,搜索用时 15 毫秒
81.
We present a new strategy for the detection of subtelomeric rearrangements. This approach is based on two hybridizations with different probe sets. The first set consists of microdissected subtelomeric probes (each 5-10 megabases in size) labeled combinatorially employing 7 different fluorochromes. With this set, subtelomeric interchromosomal exchanges can be detected in a 24-color experiment. The second set comprises a second generation of subtelomeric PAC-, P1- and BAC-clones. Probes for p- and q-arms are labeled with two different colors. This second set detects small deletions; in addition it provides regional information, so that translocated material identified by the first probe set can be assigned to the p- or q-arm of a chromosome. The test has been evaluated in a blind study on a series of subtle translocations and deletions.  相似文献   
82.
Molecular Biology Reports - Tropomyosin is a major allergen in crustaceans, including mud crab species, but its molecular and allergenic properties in Scylla olivacea are not well known. Thus, this...  相似文献   
83.
84.
85.
The potential of the nitrogen fixing bacteriumAzospirillum brasilense to enhance development and increase growth of several gramineae was investigated. In both sterilized and non-sterilized systems heading and flowering occurred earlier in the inoculated plants as compared to the noninoculated ones. Total shoot and root weights, total-N content, plant height and leaf length were significantly increased by inoculation.From the Department of Agricultural Botany.  相似文献   
86.
The diagnosis of Parkinson’s disease (PD) remains primarily a clinical issue, based mainly on phenotypic patterns. The identification of biomarkers capable of permitting the preclinical detection of PD is critically needed. α-Synuclein is a key protein in PD, with missense and multiplication mutations in the gene encoding α-synuclein (SNCA) having been reported in familial cases of PD, and accumulation of the protein identified in Lewy bodies (LBs) and Lewy neurites (LNs) in affected brain regions. With the objective of validating the use of α-synuclein as a clinical or progressive biomarker in an accessible tissue, we used an enzyme-linked immunosorbent assay (ELISA) to measure α-synuclein levels in the peripheral blood plasma of idiopathic PD and LRRK2 mutation carrier patients and compared our findings with healthy control subjects. Compared to healthy controls, we found a significant decrease in plasma total α-synuclein levels in idiopathic PD (iPD) patients (n = 134, p = 0.010). However, the reduction was less significant in patients who were LRRK2 mutation carriers (n = 32, p = 0.133). This lack of significance could be due to the small number of individuals employed in this group. No predictive value of total α-synuclein in the diagnosis of PD was found in a receiver operating characteristic (ROC) curve analysis. Although this is a pilot study requiring corroboration on a larger cohort of patients, our results highlight the possible use of plasma α-synuclein as a biomarker for PD.  相似文献   
87.
88.
Different types of genetic and epigenetic changes are associated with HNSCC. The molecular mechanisms of HNSCC carcinogenesis are still undergoing intensive investigation. WWOX gene expression is altered in many cancers and in a recent work reduced WWOX expression has been associated with miR-134 expression in HNSCC. In this study we investigated the WWOX messenger RNA expression levels in association with the promoter methylation of the WWOX gene and miR-134 expression levels in 80 HNSCC tumor and non-cancerous tissue samples. Our results show that WWOX expression is down-regulated especially in advanced-stage tumor samples or in tumors with SCC. This down-regulation was associated with methylation of the WWOX promoter region but not with miR-134 expression. There was an inverse correlation between the expression level and promoter methylation. We also analyzed whole exons and exon/intron boundries of the WWOX gene by direct sequencing. In our study group we observed 10 different alterations in the coding sequences and 18 different alterations in the non-coding sequences of the WWOX gene in HNSCC tumor samples. These results indicate that the WWOX gene can be functionally inactivated by promoter methylation, epigenetically or by mutations affecting the sequences coding for the enzymatic domain of the gene, functionally. We conclude that inactivation of WWOX gene contributes to the progression of HNSCC.  相似文献   
89.
Steroidal and non-steroidal aromatase inhibitors target the suppression of estrogen biosynthesis in the treatment of breast cancer. Researchers have increasingly focused on developing non-steroidal derivatives for their potential clinical use avoiding steroidal side-effects.Non-steroidal derivatives generally have planar aromatic structures attached to the azole ring system. One part of this ring system comprises functional groups that inhibit aromatization through the coordination of the haem group of the aromatase enzyme. Replacement of the triazole ring system and development of aromatic/cyclic structures of the side chain can increase selectivity over aromatase enzyme inhibition.In this study, 4-(aryl/heteroaryl)-2-(pyrimidin-2-yl)thiazole derivatives were synthesized and physical analyses and structural determination studies were performed. The IC50 values were determined by a fluorescence-based aromatase inhibition assay and compound 1 (4-(2-hydroxyphenyl)-2-(pyrimidine-2-yl)thiazole) were found potent inhibitor of enzyme (IC50:0.42?nM). Then, their antiproliferative activity over MCF-7 and HEK-293 cell lines was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Compounds 1, 7, 8, 13, 15, 18, 21 were active against MCF-7 breast cancer cells. Lastly, a series of docking experiments were undertaken to analyze the crystal structure of human placental aromatase and identify the possible interactions between the most active structure and the active site.  相似文献   
90.
The seaweed genus Gracilaria is a potential candidate for the production of bioethanol due to its high carbohydrate content. Gracilaria is abundant throughout the world and can be found in both wild and cultivated forms. Differences in the ecological factors such as temperature, salinity, and light intensity affecting wild and cultivated specimens may influence the biochemical content of seaweeds, including the carbohydrate content. This study aimed to investigate the proximate composition and potential bioethanol production of wild and cultivated G. gigas and G. verrucosa. Bioethanol was produced using separate hydrolysis fermentation (SHF), employing a combination of enzymatic and acid hydrolysis, followed by fermentation with Saccharomyces cerevisiae ATCC 200062. The highest carbohydrate content was found in wild G. gigas. The highest galactose and glucose contents (20.21 ± 0.32 and 9.70 ± 0.49 g L?1, respectively), as well as the highest production of bioethanol (3.56 ± 0.02 g L?1), were also found in wild G. gigas. Thus, we conclude that wild G. gigas is the most promising candidate for bioethanol production. Further research is needed to optimize bioethanol production from wild G. gigas. Domestication of wild G. gigas is a promising challenge for aquaculture to avoid overexploitation of this wild seaweed resource.  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