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   682885篇
  免费   8774篇
  国内免费   1448篇
电工技术   12554篇
综合类   571篇
化学工业   106598篇
金属工艺   28508篇
机械仪表   21804篇
建筑科学   15231篇
矿业工程   5341篇
能源动力   17494篇
轻工业   53896篇
水利工程   8544篇
石油天然气   17927篇
武器工业   52篇
无线电   73010篇
一般工业技术   141029篇
冶金工业   117871篇
原子能技术   17342篇
自动化技术   55335篇
  2021年   6495篇
  2019年   6195篇
  2018年   10711篇
  2017年   10901篇
  2016年   11480篇
  2015年   7158篇
  2014年   12092篇
  2013年   31162篇
  2012年   18668篇
  2011年   25033篇
  2010年   19964篇
  2009年   22424篇
  2008年   22740篇
  2007年   22375篇
  2006年   19436篇
  2005年   17673篇
  2004年   16760篇
  2003年   16369篇
  2002年   15766篇
  2001年   15455篇
  2000年   14807篇
  1999年   14612篇
  1998年   34808篇
  1997年   24981篇
  1996年   19428篇
  1995年   14816篇
  1994年   13322篇
  1993年   13154篇
  1992年   10141篇
  1991年   9850篇
  1990年   9633篇
  1989年   9362篇
  1988年   9109篇
  1987年   8145篇
  1986年   7997篇
  1985年   9067篇
  1984年   8217篇
  1983年   7902篇
  1982年   7119篇
  1981年   7165篇
  1980年   6959篇
  1979年   7081篇
  1978年   6958篇
  1977年   7646篇
  1976年   9423篇
  1975年   6251篇
  1974年   5987篇
  1973年   6121篇
  1972年   5308篇
  1971年   4950篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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   
92.
Journal of Communications Technology and Electronics - Abstract—The two-dimensional diffraction problem of a plane polarized TM-wave on two identical solid silver nanocylinders is considered....  相似文献   
93.
Hassan  Lovelu  Khan  K. A. 《Microsystem Technologies》2020,26(3):1031-1041

The efficiency of any electric cell or battery is very important. To keep it in mind it has been studied the columbic efficiency, voltaic efficiency and energy efficiency of a PKL (Pathor Kuchi Leaf) Quasi Voltaic Cell or Modified Voltaic Cell. It was found that the columbic efficiency data illustrated that this efficiency was lower comparing to other efficiencies may be the absence of salt bridge or separator between the electrodes. Because, our designed and fabricated PKL cell does not have any salt bridge. So that the internal resistance is lower than the traditional voltaic cell and as a result more current was found. The voltage and current changes with time and I–V characteristics for PKL unit cell, module, panel and array have also been studied. It is shown that the voltaic and energy efficiency have been studied. However, the highest efficiency was obtained for 40% PKL sap with 5% secondary salt in 55% aqueous solution, which implies that the concentration of PKL juice can play an important role regarding efficiency. It was also found that the average energy efficiency was 97.43% and it was also found that the average voltaic efficiency was 57.29%. Finally, morphological study FESEM (Field Emission Scanning Electron Microscopy) has also been performed. It is seen that the results confirmed that Zn was deposited on the Cu surface during the electro deposition process in PKL solution. Using AAS, it has been measured the concentration of [Cu2+] as a reactant ion and the concentration of [Zn2+] as a product ion those have been tabulated and graphically discussed. The variation of pH has also been studied with time and which was also tabulated and graphically discussed.

  相似文献   
94.
95.
96.
97.
98.
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   
99.
100.
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