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   25823篇
  免费   2050篇
  国内免费   395篇
  2023年   78篇
  2022年   311篇
  2021年   571篇
  2020年   394篇
  2019年   486篇
  2018年   704篇
  2017年   545篇
  2016年   862篇
  2015年   1395篇
  2014年   1503篇
  2013年   1668篇
  2012年   2227篇
  2011年   2069篇
  2010年   1353篇
  2009年   1151篇
  2008年   1625篇
  2007年   1414篇
  2006年   1260篇
  2005年   1198篇
  2004年   1179篇
  2003年   1003篇
  2002年   993篇
  2001年   785篇
  2000年   736篇
  1999年   520篇
  1998年   217篇
  1997年   171篇
  1996年   146篇
  1995年   107篇
  1994年   107篇
  1993年   77篇
  1992年   176篇
  1991年   140篇
  1990年   97篇
  1989年   110篇
  1988年   83篇
  1987年   70篇
  1986年   74篇
  1985年   60篇
  1984年   48篇
  1983年   42篇
  1982年   30篇
  1979年   27篇
  1978年   34篇
  1977年   27篇
  1976年   36篇
  1975年   33篇
  1973年   39篇
  1970年   26篇
  1969年   29篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Due to the highly immunogenic nature of renal cell carcinoma (RCC), the tumor microenvironment (TME) is enriched with various innate and adaptive immune subsets. In particular, gamma-delta (γδ) T cells can act as potent attractive mediators of adoptive cell transfer immunotherapy because of their unique properties such as non-reliance on major histocompatibility complex expression, their ability to infiltrate human tumors and recognize tumor antigens, relative insensitivity to immune checkpoint molecules, and broad tumor cytotoxicity. Therefore, it is now critical to better characterize human γδ T-cell subsets and their mechanisms in RCCs, especially the stage of differentiation. In this study, we aimed to identify γδ T cells that might have adaptive responses against RCC progression. We characterized γδ T cells in peripheral blood and tumor-infiltrating lymphocytes (TILs) in freshly resected tumor specimens from 20 RCC patients. Furthermore, we performed a gene set enrichment analysis on RNA-sequencing data from The Cancer Genome Atlas (TCGA) derived from normal kidneys and RCC tumors to ascertain the association between γδ T-cell infiltration and anti-cancer immune activity. Notably, RCC-infiltrating CD3low Vγ9Vδ1 T cells with a terminally differentiated effector memory phenotype with up-regulated activation/exhaustion molecules were newly detected as predominant TILs, and the cytotoxic activity of these cells against RCC was confirmed in vitro. In an additional analysis of the TCGA RCC dataset, γδ T-cell enrichment scores correlated strongly with those for CTLs, Th1 cells, “exhausted” T cells, and M1 macrophages, suggesting active involvement of γδ T cells in anti-tumor rather than pro-tumor activity, and Vδ1 cells were more abundant than Vδ2 or Vδ3 cells in RCC tumor samples. Thus, we posit that Vγ9Vδ1 T cells may represent an excellent candidate for adoptive immunotherapy in RCC patients with a high risk of relapse after surgery.  相似文献   
932.
933.
In vivo imaging of model organisms is heavily reliant on fluorescent proteins with high intracellular brightness. Here we describe a practical method for rapid optimization of fluorescent proteins via directed molecular evolution in cultured mammalian cells. Using this method, we were able to perform screening of large gene libraries containing up to 2 × 107 independent random genes of fluorescent proteins expressed in HEK cells, completing one iteration of directed evolution in a course of 8 days. We employed this approach to develop a set of green and near‐infrared fluorescent proteins with enhanced intracellular brightness. The developed near‐infrared fluorescent proteins demonstrated high performance for fluorescent labeling of neurons in culture and in vivo in model organisms such as Caenorhabditis elegans, Drosophila, zebrafish, and mice. Spectral properties of the optimized near‐infrared fluorescent proteins enabled crosstalk‐free multicolor imaging in combination with common green and red fluorescent proteins, as well as dual‐color near‐infrared fluorescence imaging. The described method has a great potential to be adopted by protein engineers due to its simplicity and practicality. We also believe that the new enhanced fluorescent proteins will find wide application for in vivo multicolor imaging of small model organisms.  相似文献   
934.
935.
We visualized the distribution of heterochromatin in a single nucleus using plasmonic nanoparticle-conjugated H3K9me3 and H3K27me3 antibodies. Due to distance-dependent plasmonic coupling effects between nanoprobes, their scattering spectra shift to longer wavelengths as the distance between heterochromatin histone markers reduced during oncogene-induced senescence (OIS). These observations were supported by simulating scattering profiles based on considerations of particle numbers, interparticle distances, and the spatial arrangements of plasmonic nanoprobes. Using this plasmon-based colourimetric imaging, we estimated changes in distances between H3K9me3 and H3K27me3 during the formation of senescence-associated heterochromatin foci in OIS cells. We anticipate that the devised analytical technique combined with high-spatial imaging and spectral simulation will eventually lead to a new means of diagnosing and monitoring disease progression and cellular senescence.  相似文献   
936.
毛蕊花糖苷是由咖啡酸、羟基酪醇、葡萄糖和鼠李糖组成的苯乙醇苷类衍生物,广泛存在于多种天然药用植物中,具有抗炎、抗菌、抗病毒、抗肿瘤、抗氧化、镇痛、神经保护、改善性功能、免疫调节和改善细胞记忆等多方面的生物活性.然而,植物提取来源的毛蕊花糖苷存在含量低、环境污染问题,无法实现绿色可持续的规模化生产.利用合成生物学成功构建...  相似文献   
937.
1. Colchicine and related anti-microtubular drugs impair plasma protein secretion from adult rat liver explants 2-3-fold more than from fetal tissue. 2. Indirect immunofluorescence microscopy of cultured adult and fetal hepatocytes demonstrated that hepatocytes of both ages contain large numbers of densely packed microtubules which are equally disassembled by 10 microM colchicine. 3. Colchicine (10 microM) reduced secretion of [14C]leucine-labelled proteins from cultured adult hepatocytes by about 50% but did not significantly impede fetal secretion. 4. These results confirmed that plasma protein secretion can proceed without an intact microtubular system in fetal hepatocytes.  相似文献   
938.
A method was devised for collecting phloem sap from the CAMspecies Opuntia ficus-indica using severed stylets of a scaleinsect (Dactylopius opuntiae), for which exudation could continuefor up to 5 d. For both basal (planted) cladodes and first-orderdaughter cladodes, the concentrations of sucrose and total aminoacids in the phloem exudate were virtually constant over 24-hperiods whereas the chlorenchyma osmolality had sizeable increasesduring the night under both current and doubled atmosphericCO2 concentrations. Sucrose, total amino acids, and potassiumaccounted for 56, 21, and 9%, respectively, of the osmolalityof the phloem exudate, which was about 350 mOsm at the two CO2concentrations; valine, isoleucine, leucine, tyrosine, glutamine,and lysine accounted for about 70% of the total amino acids.Doubling the CO2 concentration led to approx. 5% more sucrose,560% more mannose and 17% less amino acids in the phloem exudateand also significantly increased mannose, starch and glucomannanin the chlorenchyma. Atmospheric CO2 concentrations thus affectedvarious solute properties in the phloem and the chlorenchymaof O. ficus-indica.Copyright 1995, 1999 Academic Press Dactylopius opuntiae, Opuntia ficus-indica, cladode, CO2 concentrations, Crassulacean acid metabolism, phloem exudate  相似文献   
939.
940.
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