全文获取类型
收费全文 | 1781篇 |
免费 | 143篇 |
国内免费 | 89篇 |
专业分类
2013篇 |
出版年
2024年 | 5篇 |
2023年 | 36篇 |
2022年 | 97篇 |
2021年 | 111篇 |
2020年 | 61篇 |
2019年 | 75篇 |
2018年 | 86篇 |
2017年 | 63篇 |
2016年 | 78篇 |
2015年 | 87篇 |
2014年 | 120篇 |
2013年 | 129篇 |
2012年 | 163篇 |
2011年 | 147篇 |
2010年 | 81篇 |
2009年 | 59篇 |
2008年 | 95篇 |
2007年 | 71篇 |
2006年 | 58篇 |
2005年 | 62篇 |
2004年 | 37篇 |
2003年 | 35篇 |
2002年 | 31篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 21篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1994年 | 4篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 5篇 |
1971年 | 6篇 |
排序方式: 共有2013条查询结果,搜索用时 15 毫秒
1.
2.
c-Myc binds to 5' flanking sequence motifs of the dihydrofolate reductase gene in cellular extracts: role in proliferation. 总被引:3,自引:1,他引:2 下载免费PDF全文
The dihydrofolate reductase is a key enzyme of the folate metabolism which supplies the cell with dTTPs for DNA synthesis. Using cellular extracts, we demonstrate the formation of c-Myc/Max heterodimers at the dihydrofolate reductase (DHFR) 5' flanking CANNTG (E-box) motifs. The presence of these complexes correlates with c-Myc levels and active cellular proliferation. 相似文献
3.
Wang Zunxin Wang Xianyu Liu Siqin Yang Ying Li Yang Chen Siyuan Wang Guangpeng Zhang Xincheng Ye Yuxiu Hu Laibao Zhou Qing Wang Feibing Chen Xinhong 《Journal of Plant Growth Regulation》2023,42(1):294-303
Journal of Plant Growth Regulation - Zinc is an important micronutrient for the growth and development of human body and plants. Proper use of nitrogen fertilizer and foliar application of Zn have... 相似文献
4.
Doan Minh Sang Ik Ho Na Dr. Duong Tien Anh Do Thi Mai Dung Nguyen Thi Thu Hang Nguyen T. Phuong-Anh Assoc. Prof. Dr. Pham-The Hai Assoc. Prof. Dr. Dao Thi Kim Oanh Dr. Truong Thanh Tung Soo Jung Lee Joo Hee Kwon Prof. Dr. Jong Soon Kang Prof. Dr. Sang-Bae Han Assoc. Prof. Dr. Dinh Thi Thanh Hai Prof. Dr. Nguyen-Hai Nam 《化学与生物多样性》2023,20(5):e202201030
Herein, we report the design, synthesis and evaluation of novel (E)-3-(3-oxo-4-substituted-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)-N-hydroxypropenamides ( 4 a – i , 7 a – g ) targeting histone deacetylases. Three human cancer cell lines were used to test the cytotoxicity of the synthesized compounds (SW620, colon; PC-3, prostate; NCI−H23, lung cancer); inhibitory activity towards HDAC; anticancer activity; as well as their impact on the cell cycle and apoptosis. As a result, compounds 4 a – i bearing the alkyl substituents seemed to be less potent than the benzyl-containing compounds 7 a – g in all biological assays. Compounds 7 e – f were found to be the most active HDAC inhibitors with IC50 of 1.498±0.020 μM and 1.794±0.159 μM, respectively. In terms of cytotoxicity and anticancer assay, 7 e and 7 f also showed good activity with IC50 values in the micromolar range. In addition, the cell cycle and apoptosis of SW620 were affected by compound 7 f in almost a similar manner to that of reference compound SAHA. Docking assays were carried out for analysis the binding mode and selectivity of this compound toward 8 HDAC isoforms. Overall, our data confirmed that the inhibition of HDAC plays a pivotal role in their anticancer activity. 相似文献
5.
The sequences of the entire blue opsin gene in the squirrel monkey (Saimiri boliviensis) and the five introns of the human blue opsin gene were obtained. Intron 3 of these genes contains an Alu sequence and intron
4 contains a partial mer13 sequence. A comparison of the squirrel monkey opsin sequence with published mammalian opsin sequences
shows that features believed to be functionally critical are all conserved. However, the blue opsin has evolved twice as fast
as rhodopsin and is only as conservative as the β globin, which has evolved at the average rate of mammalian proteins. Interestingly,
the interhelical loops are, on average, actually more conservative than the transmembrane α helical regions. The introns of
the blue opsin gene have evolved at the average rate of introns in primate genes.
Received: 5 August 1996 / Accepted: 2 October 1996 相似文献
6.
Ribosomal DNA and ITS-2 sequence comparisons as a tool for predicting genetic relatedness 总被引:14,自引:0,他引:14
The determination of the secondary structure of the internal transcribed spacer (ITS) regions separating nuclear ribosomal
RNA genes of Chlorophytes has improved the fidelity of alignment of nuclear ribosomal ITS sequences from related organisms.
Application of this information to sequences from green algae and plants suggested that a subset of the ITS-2 positions is
relatively conserved. Organisms that can mate are identical at all of these 116 positions, or differ by at most, one nucleotide
change. Here we sequenced and compared the ITS-1 and ITS-2 of 40 green flagellates in search of the nearest relative to Chlamydomonas reinhardtii. The analysis clearly revealed one unique candidate, C. incerta. Several ancillary benefits of the analysis included the identification of mislabelled cultures, the resolution of confusion
concerning C. smithii, the discovery of misidentified sequences in GenBank derived from a green algal contaminant, and an overview of evolutionary
relationships among the Volvocales, which is congruent with that derived from rDNA gene sequence comparisons but improves
upon its resolution. The study further delineates the taxonomic level at which ITS sequences, in comparison to ribosomal gene
sequences, are most useful in systematic and other studies.
Received: 14 February 1997 / Accepted: 28 March 1997 相似文献
7.
建立了一种改良的血清1,25-双羟胆钙化醇(1,25-Dihydroxycholecalciferol,DHCC)超微量放射受体检测(RRA)技术。完成了灵敏度、精密度、准确度、稳定性及特异性等技术指标。报告了我国健康青年血清DHCC正常值;检测了先天性佝偻病、青春期佝偻病病人及患肾性骨病奶牛等血清DHCC水平。 根据配体与受体相互结合的定量关系,建立了DHCCR(DHCC受体)检测技术。在游离与结合配基分离方面,除建立与比较了DCC(葡聚糖包埋的活性炭)及HAP(羟基磷灰石)方法外,还首次将IEF(等电聚焦电泳)应用于DHCCR分离技术。对佝偻病鸡小肠粘膜上皮细胞受体含量进行了检测并比较了鸡小肠、输卵管壳腺及肝组织DHCCR含量。 相似文献
8.
9.
K Yasumoto S Okamoto N Mukaida S Murakami M Mai K Matsushima 《The Journal of biological chemistry》1992,267(31):22506-22511
10.
Summary An approach is described whereby cells with definitive markers are followed from their source through dissociation and fractionation, then during long-term maintenance in vitro. Such sequential studies should enable investigators to define factors regulating proliferation and function of specific cells since ambiguity concerning identity is readily avoided.Pancreatic cells of guinea pigs were isolated by enzymic dissociation, and exocrine cells were enriched by centrifugation with solutions of serum albumin. Resulting populations consisting of up to 95% exocrine cells were then incubated with gyration to produce aggregates, and these were seeded to standard culture plates for further study. Colonial aggregates of exocrine epithelia develop in culture and can be maintained for 20–30 days. The cells exhibit changes with time that are qualitatively similar to those known to occur during serial cultivation of diploid fibroblastlike cells from human and other species. The uptake of tritiated thymidine decreases with maintenance time. Autoradiographic examination indicates that this is due to a reduction in the number of epithelial cells incorporating the isotope. Cell diameters increase from an average of 21 m at day 0 to 44 m by day 26, and a marked increase in heterogeneity of this parameter is also evident. Cellular DNA and protein accumulate during the same interval. Incorporation of tritiated leucine during 24-h exposures increases until about the 10th day in vitro and remains relatively constant for at least 2 weeks thereafter.The data are consistent with the hypothesis that exocrine pancreatic cells like other diploid cells in culture, progress to terminal differentiation under the culture conditions employed. The role of physical, nutritional, and humoral evironmental factors on this process will be the subject of future reports.Supported in part by National Cancer Institute Contracts NO1-CP-43231 and NO1-CP-65751 相似文献