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   474216篇
  免费   51320篇
  国内免费   296篇
  2018年   4711篇
  2016年   6511篇
  2015年   8765篇
  2014年   10152篇
  2013年   13814篇
  2012年   15953篇
  2011年   16182篇
  2010年   10892篇
  2009年   9804篇
  2008年   14561篇
  2007年   15039篇
  2006年   14199篇
  2005年   13545篇
  2004年   13504篇
  2003年   12679篇
  2002年   12454篇
  2001年   18725篇
  2000年   18812篇
  1999年   15012篇
  1998年   5466篇
  1997年   5642篇
  1996年   5255篇
  1995年   4943篇
  1994年   4826篇
  1993年   4849篇
  1992年   12309篇
  1991年   12201篇
  1990年   11917篇
  1989年   11510篇
  1988年   11011篇
  1987年   10556篇
  1986年   9861篇
  1985年   9698篇
  1984年   8155篇
  1983年   7074篇
  1982年   5504篇
  1981年   4959篇
  1980年   4727篇
  1979年   7837篇
  1978年   6200篇
  1977年   5683篇
  1976年   5434篇
  1975年   5918篇
  1974年   6610篇
  1973年   6445篇
  1972年   6043篇
  1971年   5507篇
  1970年   4851篇
  1969年   4819篇
  1968年   4691篇
排序方式: 共有10000条查询结果,搜索用时 346 毫秒
991.
Carcinoma tissue consists of not only tumor cells but also fibroblasts, endothelial cells or vascular structures, and inflammatory cells forming the supportive tumor stroma. Therefore, the spatial distribution of proteins that promote growth and proliferation in these complex functional units is of high interest. Matrix-assisted laser desorption/ionization imaging mass spectrometry is a newly developed technique that generates spatially resolved profiles of protein signals directly from thin tissue sections. Surface-enhanced laser desorption/ionization mass spectrometry (MS)combined with tissue microdissection allows analysis of defined parts of the tissue with a higher sensitivity and a broader mass range. Nevertheless, both MS-based techniques have a limited spatial resolution. IHC is a technique that allows a resolution down to the subcellular level. However, the detection and measurement of a specific protein expression level is possible only by semiquantitative methods. Moreover, prior knowledge about the identity of the proteins of interest is necessary. In this study, we combined all three techniques to gain highest spatial resolution, sensitivity, and quantitative information. We used frozen tissue from head and neck tumors and chose two exemplary proteins (HNP1–3 and S100A8) to highlight the advantages and disadvantages of each technique. It could be shown that the combination of these three techniques results in congruent but also synergetic data. (J Histochem Cytochem 58:929–937, 2010)  相似文献   
992.
Epithelial cell islets in primary monolayer cultures of human breast biopsies were characterized by combined immuno-, enzyme- and DNA cytochemistry as well as by analysis of attachment-, spread- and growth patterns. For cultivation we used explants from reduction mammoplasties, benign lesions, primary carcinomas and metastases. Milk fat globule membrane antigen (MFGM-A) was detected with a monoclonal antibody, and the tetrazolium reaction for glucose 6-phosphate dehydrogenase (G6PDH) as well as DNA content of the cultured cells were quantified. Spreading and growth of individual islets were studied by image analysis. Fibroblast-like cells did not express MFGM-A, and whereas epithelial (MFGM-A positive) cell islets of normal and benign origin showed cells with no or low G6PDH reaction, respectively, the majority of epithelial cell islets from 11 out of 21 carcinomas showed strong reaction. Cell islets with strong G6PDH reaction were sometimes hyperdiploid. Moreover, whereas cell islets with no or low reaction from both benign lesions and carcinomas readily attached and spread in a serum-free medium and showed population doubling times of 30 to 110 h, cell islets with strong reaction from carcinomas and metastatic lesions required serum for attachment and their growth rate was too low to be determined.  相似文献   
993.
994.
995.
Electron microscopic studies of the leg ciliary epithelium was carried out in two mollusks. In the epithelium of the leg of adult animals, the centrioles were mostly formed de novo with participation of deuterosomes during the formation of basal bodies. Transformation of the centriolar cylinder in a mature basal body is accompanied by the cylinder elongation and appearance of pericentriolar structures, such as rootlet system, basal legs, and basal plate. Centriolegenesis proceeds in both ciliate and nonciliate (with microvilli) cells of the epithelium. It has been proposed that the cell with microvilli represent a transitional stage in differentiation of the ciliary cells.  相似文献   
996.
997.
998.
999.
Janospira is described from early Ordovician (Arenig) rocks of northern Spitsbergen. It is a curious microfossil, probably calcareous, about 1 mm in length, made up of an initial coil which expands distally into a straight tube, at the same time as producing a narrower tube almost in line with the first but in the opposite direction. Although showing some similarities to Foraminifera, molluscs and polychaetes, there are objections to its inclusion in any of these groups, and it is equally probable that it belongs to an unknown group with a planktic early growth stage.  相似文献   
1000.
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