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   11119篇
  免费   17篇
电工技术   45篇
综合类   1篇
化学工业   226篇
金属工艺   26篇
机械仪表   20篇
建筑科学   9篇
能源动力   22篇
轻工业   49篇
水利工程   1篇
无线电   101篇
一般工业技术   125篇
冶金工业   10415篇
原子能技术   15篇
自动化技术   81篇
  2022年   10篇
  2021年   11篇
  2019年   6篇
  2018年   8篇
  2017年   12篇
  2016年   15篇
  2015年   6篇
  2014年   16篇
  2013年   33篇
  2012年   28篇
  2011年   34篇
  2010年   26篇
  2009年   33篇
  2008年   33篇
  2007年   30篇
  2006年   34篇
  2005年   33篇
  2004年   27篇
  2003年   40篇
  2002年   20篇
  2001年   15篇
  2000年   20篇
  1999年   308篇
  1998年   3404篇
  1997年   1994篇
  1996年   1220篇
  1995年   700篇
  1994年   559篇
  1993年   651篇
  1992年   74篇
  1991年   143篇
  1990年   119篇
  1989年   130篇
  1988年   137篇
  1987年   107篇
  1986年   91篇
  1985年   70篇
  1984年   6篇
  1983年   17篇
  1982年   52篇
  1981年   54篇
  1980年   71篇
  1979年   5篇
  1978年   24篇
  1977年   194篇
  1976年   469篇
  1975年   14篇
  1974年   4篇
  1955年   8篇
  1954年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This paper reviews the pathogenesis of Mycobacterium bovis infection in cattle, focusing on aspects relating to the host rather than the organism. A broad concept of pathogenesis has been considered and information is presented on sources and routes of infection, as well as the immune responses and pathology. In addition, data is presented on the excretion of M. bovis from tuberculous cattle.  相似文献   
82.
83.
84.
The aqueous solution structure of the cyclic pentapeptide cyclo(-Ser-D-Leu-Asp-Val-Pro-) has been determined by two-dimensional 1H-NMR spectroscopy, combined with a conformational search and distance-geometry calculations. As many as five conformers in slow exchange were observed, and the rate of interconversion between components was measured from the build-up rates of exchange peaks. NMR data allowed the structures of the two predominant conformers to be determined. The major component (66%) contained a cis-proline as part of a type-VIa2 beta-turn encompassing residues Asp-Val-cis-Pro-Ser. The second component (16%) contained only trans-amide bonds, and a type-VIII beta-turn formed by residues Val-Pro-Ser-D-Leu. These structures are discussed in relation to the (phi, psi), space available to the cyclic pentapeptide, determined by a conformational search, and in relation to previously published cyclic-pentapeptide structures. The molecule exhibits activity in a scintillation-proximity assay for the inhibition of the interaction between the integrin very-late antigen-4 (VLA-4; alpha 4 beta 1) and vascular-cell-adhesion molecule-1 (VCAM-1). The structure/activity relationship of the LDV sequence is discussed and related to the recently published X-ray structure of VCAM-1. The relevance of the work to the design of anti-inflammatory drugs is discussed.  相似文献   
85.
Earlier studies have established that mutant strains of Azotobacter vinelandii that do not synthesize ferredoxin I (AvFdI) overexpress another protein designated Protein X (Morgan, T. V., Lundell, P. J., and Burgess, B. K. (1988) J. Biol. Chem. 263, 1370-1375). This protein has now been purified using two-dimensional gel electrophoresis as an assay. The purified protein is a monomer with M(r) approximately 29,000 which degrades slowly to a specific M(r) approximately 22,000 form when stored in solution. The native protein is bright yellow and contains noncovalently attached FAD that is reduced by either dithionite or NADPH without formation of a stable semiquinone. Titration with NADP+/NADPH gives an E0' value of approximately -327 mV versus SHE. Because this E0' is so close to that of the NADP+/NADPH couple it is not clear if Protein X is an NADPH oxidase or an NADP+ reductase in vivo. Comparison of the NH2-terminal sequence and other properties of Protein X with those of other proteins, suggests that it is likely to be related to the Escherichia coli ferredoxin NADP+ reductase (the fpr gene product), and affinity chromatography shows that Protein X binds specifically to AvFdI.  相似文献   
86.
87.
88.
89.
90.
High-temperature and controlled humidity treatment before drying has proven to be highly effective in preventing surface checks by forming drying sets in the surface layer of boxed-heart square timber in Japan. In this study, we examined the differences of the surface drying sets on sugi timber under different treatment temperatures. As a result, the width of a surface check after drying was much smaller at a treatment temperature of 120°C than at 80°C, and this indicates that the drying set with 120°C treatment would be larger than that with 80°C treatment. Also we observed that treatment temperature had a greater effect on the drying set as the drying advanced.  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