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   211867篇
  免费   2559篇
  国内免费   578篇
电工技术   3242篇
综合类   995篇
化学工业   31590篇
金属工艺   10261篇
机械仪表   6714篇
建筑科学   4028篇
矿业工程   2401篇
能源动力   3196篇
轻工业   10932篇
水利工程   3385篇
石油天然气   8947篇
武器工业   29篇
无线电   16512篇
一般工业技术   41830篇
冶金工业   47786篇
原子能技术   7146篇
自动化技术   16010篇
  2021年   1755篇
  2018年   3509篇
  2017年   3913篇
  2016年   4504篇
  2015年   2562篇
  2014年   3560篇
  2013年   6986篇
  2012年   6598篇
  2011年   7913篇
  2010年   5193篇
  2009年   5725篇
  2008年   5602篇
  2007年   5539篇
  2006年   4743篇
  2005年   7144篇
  2004年   6258篇
  2003年   5726篇
  2002年   4581篇
  2001年   4452篇
  2000年   3735篇
  1999年   3847篇
  1998年   12702篇
  1997年   8626篇
  1996年   6155篇
  1995年   4285篇
  1994年   3599篇
  1993年   3734篇
  1992年   2490篇
  1991年   2599篇
  1990年   2692篇
  1989年   2571篇
  1988年   2576篇
  1987年   2390篇
  1986年   2422篇
  1985年   2439篇
  1984年   2269篇
  1983年   2210篇
  1982年   2105篇
  1981年   2360篇
  1980年   2238篇
  1979年   2326篇
  1978年   2520篇
  1977年   3005篇
  1976年   4338篇
  1975年   2333篇
  1974年   2344篇
  1973年   2384篇
  1972年   2194篇
  1971年   1953篇
  1970年   1737篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Russian Engineering Research - Models based on regression analysis for predicting the operational efficiency of high-pressure roller crushers are considered. A systematized and structured...  相似文献   
22.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
23.
24.
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the...  相似文献   
25.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation...  相似文献   
26.
Russian Journal of Non-Ferrous Metals - Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of...  相似文献   
27.
28.
29.
30.
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   
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