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   851201篇
  免费   12240篇
  国内免费   2109篇
电工技术   15552篇
综合类   718篇
化学工业   132271篇
金属工艺   33652篇
机械仪表   26930篇
建筑科学   19179篇
矿业工程   5466篇
能源动力   22883篇
轻工业   68100篇
水利工程   9730篇
石油天然气   18254篇
武器工业   51篇
无线电   93952篇
一般工业技术   171433篇
冶金工业   154390篇
原子能技术   19201篇
自动化技术   73788篇
  2021年   8245篇
  2020年   6267篇
  2019年   7942篇
  2018年   13488篇
  2017年   13548篇
  2016年   14327篇
  2015年   9291篇
  2014年   15153篇
  2013年   40930篇
  2012年   23766篇
  2011年   31876篇
  2010年   25490篇
  2009年   28405篇
  2008年   28910篇
  2007年   28390篇
  2006年   24758篇
  2005年   22359篇
  2004年   21354篇
  2003年   21062篇
  2002年   20026篇
  2001年   19508篇
  2000年   18531篇
  1999年   18815篇
  1998年   46612篇
  1997年   33040篇
  1996年   25533篇
  1995年   19243篇
  1994年   17191篇
  1993年   17054篇
  1992年   12628篇
  1991年   12028篇
  1990年   11854篇
  1989年   11452篇
  1988年   10881篇
  1987年   9815篇
  1986年   9451篇
  1985年   10790篇
  1984年   9821篇
  1983年   9165篇
  1982年   8368篇
  1981年   8553篇
  1980年   7995篇
  1979年   8016篇
  1978年   7857篇
  1977年   8992篇
  1976年   11604篇
  1975年   6941篇
  1974年   6658篇
  1973年   6774篇
  1972年   5699篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
122.
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   
123.
124.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  相似文献   
125.
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   
126.
127.
128.
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   
129.
130.
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