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   819453篇
  免费   11791篇
  国内免费   2678篇
电工技术   15424篇
综合类   790篇
化学工业   125014篇
金属工艺   30415篇
机械仪表   25242篇
建筑科学   20742篇
矿业工程   3170篇
能源动力   22236篇
轻工业   72789篇
水利工程   7364篇
石油天然气   9769篇
武器工业   34篇
无线电   101182篇
一般工业技术   157061篇
冶金工业   154293篇
原子能技术   14651篇
自动化技术   73746篇
  2021年   6434篇
  2020年   4737篇
  2019年   6173篇
  2018年   9950篇
  2017年   10041篇
  2016年   10867篇
  2015年   7632篇
  2014年   12467篇
  2013年   39284篇
  2012年   20736篇
  2011年   28972篇
  2010年   22649篇
  2009年   25812篇
  2008年   26942篇
  2007年   27044篇
  2006年   24335篇
  2005年   22140篇
  2004年   21411篇
  2003年   21037篇
  2002年   20257篇
  2001年   20093篇
  2000年   18859篇
  1999年   19838篇
  1998年   47168篇
  1997年   33853篇
  1996年   26539篇
  1995年   20364篇
  1994年   18171篇
  1993年   17799篇
  1992年   13295篇
  1991年   12600篇
  1990年   12299篇
  1989年   11842篇
  1988年   11322篇
  1987年   9899篇
  1986年   9728篇
  1985年   11409篇
  1984年   10607篇
  1983年   9527篇
  1982年   8884篇
  1981年   8857篇
  1980年   8254篇
  1979年   8052篇
  1978年   7729篇
  1977年   9218篇
  1976年   12159篇
  1975年   6644篇
  1974年   6267篇
  1973年   6259篇
  1972年   5154篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
83.
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   
84.
85.
86.
87.
Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019  相似文献   
88.
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   
89.
Fefelov  S. A.  Kazakova  L. P.  Bogoslovskiy  N. A.  Bylev  A. B.  Yakubov  A. O. 《Semiconductors》2020,54(4):450-453
Semiconductors - The current–voltage characteristics measured on Ge2Sb2Te5 thin films in the current mode are studied. The effect of multilevel recording is established when applying...  相似文献   
90.
Hussien  O. S.  Elamy  M. I. 《Strength of Materials》2020,52(3):470-479
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which...  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