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   1533301篇
  免费   27580篇
  国内免费   7116篇
电工技术   34780篇
综合类   6679篇
化学工业   271253篇
金属工艺   65072篇
机械仪表   44330篇
建筑科学   46785篇
矿业工程   11635篇
能源动力   50311篇
轻工业   117819篇
水利工程   15421篇
石油天然气   37943篇
武器工业   210篇
无线电   197755篇
一般工业技术   289463篇
冶金工业   173477篇
原子能技术   34209篇
自动化技术   170855篇
  2021年   15509篇
  2020年   11869篇
  2019年   14635篇
  2018年   16799篇
  2017年   16237篇
  2016年   21758篇
  2015年   17459篇
  2014年   28744篇
  2013年   87842篇
  2012年   36320篇
  2011年   49734篇
  2010年   43559篇
  2009年   51741篇
  2008年   46133篇
  2007年   43589篇
  2006年   45535篇
  2005年   40573篇
  2004年   42395篇
  2003年   42201篇
  2002年   41207篇
  2001年   38017篇
  2000年   36349篇
  1999年   35486篇
  1998年   47924篇
  1997年   40846篇
  1996年   36464篇
  1995年   31505篇
  1994年   29374篇
  1993年   29214篇
  1992年   26523篇
  1991年   23632篇
  1990年   23950篇
  1989年   22952篇
  1988年   21476篇
  1987年   19757篇
  1986年   19193篇
  1985年   22503篇
  1984年   22580篇
  1983年   20545篇
  1982年   19407篇
  1981年   19504篇
  1980年   18157篇
  1979年   18695篇
  1978年   17905篇
  1977年   17901篇
  1976年   19184篇
  1975年   16147篇
  1974年   15700篇
  1973年   15780篇
  1972年   13215篇
排序方式: 共有10000条查询结果,搜索用时 981 毫秒
231.
232.
RCAS1 is a protein that participates in regulation of the tumor microenvironment and its immune responses, all in order to evade the immune system. The aim of this study was to analyze RCAS1 expression in urothelial bladder cancer cells (and in fibroblasts and macrophages of the tumor stroma) and its relationship with the histological pattern of malignancy. Eighty-three postcystectomy patients were enrolled. We analyzed the histological maturity (grade), progress (pT stage), tissue invasion type (TIT), nonclassic differentiation number (NDN), and the ability to metastasize (pN). The expression of RCAS1 protein was analyzed by immunohistochemistry. Indicators of histological malignancy were observed solely in association with the RCAS1 expression in cells in the border parts (BPs) of the tumor. Histological malignancy of the tumor, indicated by the pT and pN, and metastasis-free survival time, correlated significantly with RCAS1 expression in tumor neoplastic cells, whereas malignancy determined by grade, TIT, and NDN correlated with RCAS1 expression in fibroblasts and macrophages in the tumor microenvironment. These findings suggest that the increased RCAS1 expression depends on its cellular source and that RCAS1 expression itself is a component of various signaling pathways. The immune escape occurs within the tumor BPs, where the increase in the RCAS1 expression occurs within tumor cells and stromal cells in its microenvironment. We conclude that the histological pattern of tumor malignancy, indicated by grade, TIT, NDN, pT, and pN is a morphological indicator of immune escape.  相似文献   
233.
234.
235.
236.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  相似文献   
237.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  相似文献   
238.
239.
240.
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.  相似文献   
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