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   1197篇
  免费   97篇
  2022年   21篇
  2021年   39篇
  2020年   11篇
  2019年   8篇
  2018年   18篇
  2017年   16篇
  2016年   25篇
  2015年   35篇
  2014年   52篇
  2013年   57篇
  2012年   81篇
  2011年   71篇
  2010年   31篇
  2009年   36篇
  2008年   50篇
  2007年   55篇
  2006年   64篇
  2005年   52篇
  2004年   55篇
  2003年   40篇
  2002年   35篇
  2001年   24篇
  2000年   23篇
  1999年   19篇
  1997年   9篇
  1996年   15篇
  1995年   8篇
  1994年   9篇
  1993年   12篇
  1992年   19篇
  1991年   18篇
  1990年   14篇
  1989年   12篇
  1988年   15篇
  1987年   12篇
  1986年   13篇
  1985年   11篇
  1984年   15篇
  1983年   10篇
  1982年   13篇
  1981年   13篇
  1980年   8篇
  1979年   18篇
  1977年   9篇
  1976年   13篇
  1975年   8篇
  1974年   10篇
  1973年   8篇
  1971年   8篇
  1969年   7篇
排序方式: 共有1294条查询结果,搜索用时 15 毫秒
971.
Multiple myeloma (MM) is a malignant clonal expansion of plasma cells in the bone marrow and belongs to the mature B-cell neoplams. The pathogenesis of MM is associated with constitutive NF-κB activation. However, genetic alterations causing constitutive NF-κB activation are still incompletely understood. Since A20 (TNFAIP3) is a suppressor of the NF-κB pathway and is frequently inactivated in various lymphoid malignancies, we investigated the genetic and epigenetic properties of A20 in MM. In total, of 46 patient specimens analyzed, 3 single base pair exchanges, 2 synonymous mutations and one missense mutation were detected by direct sequencing. Gene copy number analysis revealed a reduced A20 gene copy number in 8 of 45 (17.7%) patients. Furthermore, immunohistochemical staining confirmed that A20 expression correlates with the reduction of A20 gene copy number. These data suggest that A20 contributes to tumor formation in a significant fraction of myeloma patients.  相似文献   
972.
Neisseria meningitidis, a major cause of bacterial meningitis and septicaemia, secretes multiple virulence factors, including the adhesion and penetration protein (App) and meningococcal serine protease A (MspA). Both are conserved, immunogenic, type Va autotransporters harbouring S6‐family serine endopeptidase domains. Previous work suggested that both could mediate adherence to human cells, but their precise contribution to meningococcal pathogenesis was unclear. Here, we confirm that App and MspA are in vivo virulence factors since human CD46‐expressing transgenic mice infected with meningococcal mutants lacking App, MspA or both had improved survival rates compared with mice infected with wild type. Confocal imaging showed that App and MspA were internalized by human cells and trafficked to the nucleus. Cross‐linking and enzyme‐linked immuno assay (ELISA) confirmed that mannose receptor (MR), transferrin receptor 1 (TfR1) and histones interact with MspA and App. Dendritic cell (DC) uptake could be blocked using mannan and transferrin, the specific physiological ligands for MR and TfR1, whereas in vitro clipping assays confirmed the ability of both proteins to proteolytically cleave the core histone H3. Finally, we show that App and MspA induce a dose‐dependent increase in DC death via caspase‐dependent apoptosis. Our data provide novel insights into the roles of App and MspA in meningococcal infection.  相似文献   
973.
Coral Reefs - Understanding the structural and mechanical properties of coral skeletons is important to assess their responses to natural and anthropogenic challenges and to predict the long-term...  相似文献   
974.
The Caulerpa taxifolia is excellent marine green algae, which produced enormous bioactive compounds with more biological activities. Also, it is an excellent source for synthesis of Ag NPs with increased bioactivity against various infections. In our study, the marine algae marine algae Caulerpa taxifolia mediated Ag NPs was synthesized effectively. The synthesized Ag NPs was characterized well using UV-spectrometer and X-ray powder diffraction (XRD) and confirmed as synthesized particle was Ag NPs. The available structure of the Ag NPs was morphologically identified by scanning electron microscope (SEM), and exact minimum size, polydispersive spherical shape of the entire Ag NPs structure was confirmed by Transmission electron microscope (TEM). Further, the anti-cancer efficiency of biosynthesized Ag NPs against A549 lung cancer cells was found at 40 µg/mL concentration by cytotoxicity experiment. In addition, the phase contrast images of the result were supported the Ag NPs, which damaged the A549 morphologically clearly. Finally, florescence microscopic images were effectively proved the anti-cancerous effect against A549 lung cancer cells due to the condensed morphology of increased death cells. All the confirmed in-vitro results were clearly stated that the Caulerpa taxifolia mediated Ag NPs has superior anti-cancer agent against A549 lung cancer cells.  相似文献   
975.
The aims of the present study were to characterize ticks infesting the dromedary camel and cattle in Hofuf, Eastern Saudi Arabia and to determine the piroplasms that they may harbor. DNA was extracted from ticks, collected from camels and cattle, using commercial kits and subjected to polymerase chain reaction using specific primers for the amplification of ticks and piroplasms DNA. The cytochrome oxidase subunit I mitochondrial gene (COI) was used for characterization of ticks whereas partial 18S rRNA gene (18S rRNA) was used for piroplasms characterization. Ticks were genetically identified as Hyalomma dromedarii and Hyalomma anatolicum. Both cattle and camel in Hofuf, were found to be infested with both species. Both ticks identified as H. dromedarii and H. anatolicum from camels and cows showed 100% identity to COI sequences from the same species available in GenBank. Only Theileria annulata DNA was amplified from both H. anatolicum and H. dromedarii infesting cattle. None of the ticks collected from camels revealed DNA of piroplasms. T. annulata DNA was reported for the first time from Hofuf and the role of both H. anatolicum and H. dromedarii as potential vectors for this parasite in cattle in Saudi Arabia has been documented for the first time.  相似文献   
976.
977.
Policies supporting the rapid and open sharing of proteomic data are being implemented by the leading journals in the field. The proteomics community is taking steps to ensure that data are made publicly accessible and are of high quality, a challenging task that requires the development and deployment of methods for measuring and documenting data quality metrics. On September 18, 2010, the United States National Cancer Institute convened the "International Workshop on Proteomic Data Quality Metrics" in Sydney, Australia, to identify and address issues facing the development and use of such methods for open access proteomics data. The stakeholders at the workshop enumerated the key principles underlying a framework for data quality assessment in mass spectrometry data that will meet the needs of the research community, journals, funding agencies, and data repositories. Attendees discussed and agreed up on two primary needs for the wide use of quality metrics: 1) an evolving list of comprehensive quality metrics and 2) standards accompanied by software analytics. Attendees stressed the importance of increased education and training programs to promote reliable protocols in proteomics. This workshop report explores the historic precedents, key discussions, and necessary next steps to enhance the quality of open access data. By agreement, this article is published simultaneously in the Journal of Proteome Research, Molecular and Cellular Proteomics, Proteomics, and Proteomics Clinical Applications as a public service to the research community. The peer review process was a coordinated effort conducted by a panel of referees selected by the journals.  相似文献   
978.
979.
This study aimed to determine the existence and distribution of certain neuropeptides in endocrine and exocrine pancreas of the long-legged buzzard by using immunohistochemical methods. SOM-14-, NPY- and CGRP-IR endocrine cells were determined in both central and peripheral regions in A-islets within the pancreas, while SP-IR endocrine cells were found only in the central region, and CCK-8- and galanin-IR endocrine cells were only detected in peripheral region. On the other hand, in B-islets; SP-, NPY- and CGRP-IRendocrine cells were determined in both central and peripheral regions, while SOM-14- CCK-8- and galanin-IRendocrine cells were found only in the peripheral region. In addition; SOM-14-, NPY-, CGRP-, CCK-8- and galanin-IR cells were also observed in exocrine pancreas. This distribution pattern in the pancreas of the long-legged buzzard demonstrates that neuropeptides perform their probable affects through endocrine and/or paracrine mechanisms. In conclusion, the existence and distribution of neuropeptides in the pancreas of long-legged buzzard have been introduced in this study for the first time and this bird species has also been found to differ from other types of avian species.  相似文献   
980.
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