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   20925篇
  免费   2099篇
  国内免费   2906篇
  2024年   19篇
  2023年   372篇
  2022年   534篇
  2021年   1205篇
  2020年   1043篇
  2019年   1278篇
  2018年   1078篇
  2017年   806篇
  2016年   1080篇
  2015年   1538篇
  2014年   1831篇
  2013年   1856篇
  2012年   2194篇
  2011年   2043篇
  2010年   1238篇
  2009年   1075篇
  2008年   1183篇
  2007年   1004篇
  2006年   849篇
  2005年   634篇
  2004年   549篇
  2003年   485篇
  2002年   363篇
  2001年   245篇
  2000年   216篇
  1999年   196篇
  1998年   145篇
  1997年   111篇
  1996年   130篇
  1995年   107篇
  1994年   87篇
  1993年   52篇
  1992年   73篇
  1991年   65篇
  1990年   53篇
  1989年   37篇
  1988年   36篇
  1987年   23篇
  1986年   15篇
  1985年   37篇
  1984年   11篇
  1983年   9篇
  1982年   9篇
  1981年   6篇
  1978年   2篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1965年   1篇
  1938年   1篇
排序方式: 共有10000条查询结果,搜索用时 181 毫秒
1.
This study investigated the effects of high-intensity ultrasound and glycosylation on the structural and interfacial properties of the Maillard reaction conjugates of buckwheat protein isolate (BPI). The covalent attachment of dextran to BPI was confirmed by examination of the Fourier-transform infrared spectra. Emulsifying properties of the conjugates obtained by ultrasound treatment were improved as compared to those obtained by classical heating. Structural feature analyses suggested that conjugates obtained by ultrasound treatment had less α-helix and more random coil, higher surface hydrophobicity and less compact tertiary structure as compared to those obtained by classical heating. The surface activity measurement revealed that the BPI–dextran conjugates obtained by ultrasound treatment were closely packed and that each molecule occupied a small area of the interface. Combination of ultrasonic treatment and glycosylation was proved to be an efficient way to develop new stabilizers and thickening agents for food in this study.  相似文献   
2.
Neuroblastoma accounts for 15% of childhood cancer deaths and presents with metastatic disease of the bone and the bone marrow at diagnosis in 70% of the cases. Previous studies have shown that the Mesenchymal Stromal Cell (MSC) secretome, triggers metastases in several cancer types such as breast and prostate cancer, but the specific role of the MSC factors in neuroblastoma metastasis is unclear. To better understand the effect of MSC secretome on chemokine receptors in neuroblastoma, and its role in metastasis, we studied a panel of 20 neuroblastoma cell lines, and compared their invasive potential towards MSC-conditioned-RPMI (mRPMI) and their cytokine receptor expression profiles. Western blot analysis revealed the expression of multiple CXCR4 isoforms in neuroblastoma cells. Among the five major isoforms, the expression of the 47 kDa isoform showed significant correlation with high invasiveness. Pretreatment with mRPMI up-regulated the expression of the 47 kDa CXCR4 isoform and also increased MMP-9 secretion, expression of integrin α3 and integrin β1, and the invasive potential of the cell; while blocking CXCR4 either with AMD 3100, a CXCR4 antagonist, or with an anti-47 kDa CXCR4 neutralizing antibody decreased the secretion of MMP-9, the expression of integrin α3 and integrin β1, and the invasive potential of the cell. Pretreatment with mRPMI also protected the 47 kDa CXCR4 isoform from ubiquitination and subsequent degradation. Our data suggest a modulatory role of the MSC secretome on the expression of the 47 kDa CXCR4 isoform and invasion potential of the neuroblastoma cells to the bone marrow.  相似文献   
3.
4.
5.
MicroRNAs (miRNAs) regulate the progression of human malignancy by targeting oncogenes or tumor suppressors, which are 12 promising targets for cancer treatment. Increasing evidence has suggested the aberrant expression and tumor-suppressive function of miR-1298 in cancers, however, the regulatory mechanism of miR-1298 in breast cancer (BC) remains unclear. Here, our findings showed that miR-1298 was down-regulated in BC tissues and cell lines. Lower level of miR-1298 was significantly correlated with the advanced progression of BC patients. Experimental study showed that overexpression of miR-1298 inhibited the proliferation, induced apoptosis and cell cycle arrest in BC cells. The in vivo xenograft mice model showed that highly expressed miR-1298 significantly reduced the tumor growth and metastasis. Further mechanism analysis revealed that miR-1298 bound the 3′-untranslated region (UTR) of a disintegrin and metalloproteinase 9 domain (ADAM9) and suppressed the expression of ADAM9 in BC cells. ADAM9 was overexpressed in BC tissues and inversely correlated with miR-1298. Down-regulation of ADAM9 induced apoptosis and cell cycle arrest of BC cells. Moreover, ectopic expression of ADAM9 by transiently transfecting with vector encoding the full coding sequence of ADAM9 attenuated the inhibitory effects of miR-1298 on the proliferation and cell cycle progression of BC cells. Collectively, our results illustrated that miR-1298 played a suppressive role in regulating the phenotype of BC cells through directly repressing ADAM9, suggesting the potential application of miR-1298 in the therapy of BC.  相似文献   
6.
7.
The expression of the genes for two types of myrosinase (EC 3.2.3.1), designated MA and MB, during embryo and seedling development was investigated in Sinapis alba L. by in-situ and RNA slot-blot analyses. The expression of MA and MB genes followed similar temporal profiles during embryogenesis, but MB mRNA was present in considerably higher amounts than MA mRNA. In the embryo, both MA and MB genes are activated in cotyledons and axis. The MB genes are preferentially expressed in the cotyledons whereas MA genes are preferentially expressed in the axis. In the developing seedling, MA mRNA was not present in the organs investigated. By contrast, MB mRNA was found in appreciable amounts in hypocotyls, cotyledons and developing leaves. The MB genes seem to be activated preferentially in tissues undergoing rapid cell division and — or cell expansion.Abbreviations DAP days after pollination - MA, MB A type, B type myrosinases in Sinapis alba Anna-Stina Höglund (Uppsala Genetic Center) is gratefully acknowledged for valuable discussion, Anders Gobl (Department of Immunology, Uppsala University) for kindly advice with the labeling of probes and Qingzhu Zhai (Department of Pharmaceutical Biosciences, Uppsala University) for help with seed harvest. This work was supported by grants from the Swedish Research Council for Forestry and Agriculture.  相似文献   
8.
Yan  Xue  Liu  Jia  Wu  Ke-Xin  Yang  Nan  Pan  Li-Ben  Song  Ying  Liu  Yang  Tang  Zhong-Hua 《Journal of Plant Growth Regulation》2022,41(6):2421-2434
Journal of Plant Growth Regulation - Early-spring plants are a special type of plant that complete their life cycle promptly in cold, early spring. Very little effort has been made into researching...  相似文献   
9.
10.
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