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   449906篇
  免费   6503篇
  国内免费   1847篇
电工技术   8321篇
综合类   1030篇
化学工业   64824篇
金属工艺   18141篇
机械仪表   13101篇
建筑科学   11299篇
矿业工程   2113篇
能源动力   11052篇
轻工业   39900篇
水利工程   4390篇
石油天然气   5279篇
武器工业   15篇
无线电   52063篇
一般工业技术   82188篇
冶金工业   97362篇
原子能技术   8538篇
自动化技术   38640篇
  2021年   3086篇
  2019年   2876篇
  2018年   5069篇
  2017年   5200篇
  2016年   5926篇
  2015年   4225篇
  2014年   6244篇
  2013年   18938篇
  2012年   11621篇
  2011年   15887篇
  2010年   11608篇
  2009年   13064篇
  2008年   13582篇
  2007年   13706篇
  2006年   12235篇
  2005年   13994篇
  2004年   12859篇
  2003年   12361篇
  2002年   10879篇
  2001年   10996篇
  2000年   9908篇
  1999年   10859篇
  1998年   30216篇
  1997年   21027篇
  1996年   16075篇
  1995年   11646篇
  1994年   10264篇
  1993年   9990篇
  1992年   6983篇
  1991年   6843篇
  1990年   6299篇
  1989年   6287篇
  1988年   6106篇
  1987年   5155篇
  1986年   5036篇
  1985年   5908篇
  1984年   5332篇
  1983年   4924篇
  1982年   4512篇
  1981年   4690篇
  1980年   4422篇
  1979年   4216篇
  1978年   4236篇
  1977年   5412篇
  1976年   8020篇
  1975年   3654篇
  1974年   3437篇
  1973年   3456篇
  1972年   2818篇
  1971年   2586篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Topics in Catalysis - In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this...  相似文献   
32.
The role of the following factors in the selection of technological bases for manufacturing is considered: the accessibility of the machined surfaces; their parameters and dimensional relationships; their position relative to the forces acting; and the uniformity of the margin distribution.  相似文献   
33.
The price of cobalt has increased by some 450% in the past two years, mainly due to increasing demand for lithium–ion batteries. With an official 2017 production of 64 kt, the Democratic Republic of Congo produces more than half of the world’s cobalt. African Copperbelt operations have traditionally focused on copper production; however, it has now become imperative to also consider cobalt recovery from these ores. A plethora of processing routes is possible. Most hydrometallurgical flowsheets recover cobalt from the raffinate of the low-grade copper solvent-extraction circuit. Downstream purification processes include sequential precipitation with a variety of reagents, solvent extraction, and ion exchange. Product choices include hydroxide, carbonate, sulfate, and metal cathode. This study assesses technical and economic advantages and limitations of various approaches to the hydrometallurgical processing of cobalt in an African context.  相似文献   
34.
Wireless Personal Communications - The orthogonal frequency division multiplexing (OFDM) is the most encouraging multi-carrier modulation system chosen for the high data rates but the objective is...  相似文献   
35.
Multidimensional Systems and Signal Processing - The paper is devoted to the development of the octonion Fourier transform (OFT) theory initiated in 2011 in articles by Hahn and Snopek. It is also...  相似文献   
36.
37.
38.
39.
40.
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