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   722104篇
  免费   10994篇
  国内免费   1972篇
电工技术   13737篇
综合类   730篇
化学工业   105005篇
金属工艺   30176篇
机械仪表   23342篇
建筑科学   17302篇
矿业工程   3486篇
能源动力   18477篇
轻工业   58353篇
水利工程   7308篇
石油天然气   11968篇
武器工业   43篇
无线电   83545篇
一般工业技术   144185篇
冶金工业   137639篇
原子能技术   13571篇
自动化技术   66203篇
  2021年   6040篇
  2020年   4478篇
  2019年   5725篇
  2018年   15472篇
  2017年   15670篇
  2016年   13328篇
  2015年   7493篇
  2014年   11730篇
  2013年   31204篇
  2012年   20015篇
  2011年   30822篇
  2010年   25543篇
  2009年   27103篇
  2008年   27576篇
  2007年   28738篇
  2006年   19808篇
  2005年   20627篇
  2004年   18874篇
  2003年   18310篇
  2002年   16787篇
  2001年   16486篇
  2000年   15436篇
  1999年   16406篇
  1998年   42553篇
  1997年   29588篇
  1996年   22791篇
  1995年   17027篇
  1994年   14822篇
  1993年   14509篇
  1992年   10334篇
  1991年   9690篇
  1990年   9486篇
  1989年   9064篇
  1988年   8427篇
  1987年   7314篇
  1986年   7245篇
  1985年   8305篇
  1984年   7662篇
  1983年   6719篇
  1982年   6285篇
  1981年   6523篇
  1980年   6085篇
  1979年   5869篇
  1978年   5650篇
  1977年   6842篇
  1976年   9020篇
  1975年   4902篇
  1974年   4606篇
  1973年   4679篇
  1972年   3845篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
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   
85.
86.
87.
88.
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   
89.
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   
90.
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y...  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