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   1314篇
  免费   161篇
  国内免费   120篇
电工技术   63篇
综合类   114篇
化学工业   221篇
金属工艺   48篇
机械仪表   39篇
建筑科学   71篇
矿业工程   24篇
能源动力   13篇
轻工业   104篇
水利工程   22篇
石油天然气   27篇
武器工业   7篇
无线电   246篇
一般工业技术   95篇
冶金工业   20篇
原子能技术   7篇
自动化技术   474篇
  2024年   3篇
  2023年   13篇
  2022年   26篇
  2021年   33篇
  2020年   28篇
  2019年   37篇
  2018年   33篇
  2017年   53篇
  2016年   54篇
  2015年   41篇
  2014年   55篇
  2013年   99篇
  2012年   99篇
  2011年   61篇
  2010年   48篇
  2009年   45篇
  2008年   46篇
  2007年   54篇
  2006年   78篇
  2005年   87篇
  2004年   109篇
  2003年   102篇
  2002年   71篇
  2001年   55篇
  2000年   60篇
  1999年   27篇
  1998年   12篇
  1997年   13篇
  1996年   19篇
  1995年   14篇
  1994年   15篇
  1993年   10篇
  1992年   9篇
  1991年   4篇
  1990年   10篇
  1989年   5篇
  1988年   6篇
  1987年   5篇
  1986年   10篇
  1985年   17篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1979年   3篇
  1977年   3篇
  1975年   3篇
  1974年   3篇
  1973年   2篇
  1972年   1篇
排序方式: 共有1595条查询结果,搜索用时 15 毫秒
1.
The microbial transformation of l‐menthol ( 1 ) was investigated by using 12 isolates of soil‐borne plant pathogenic fungi, Rhizoctonia solani (AG‐1‐IA Rs24, Joichi‐2, RRG97‐1; AG‐1‐IB TR22, R147, 110.4; AG‐1‐IC F‐1, F‐4, P‐1; AG‐1‐ID RCP‐1, RCP‐3, and RCP‐7) as a biocatalyst. Rhizoctonia solani F‐1, F‐4 and P‐1 showed 89.7–99.9% yields of converted product from 1 , RCP‐1, RCP‐3, and RCP‐7 26.0–26.9% and the other isolates 0.1–12.0%. In the cases of F‐1, F‐4 and P‐1, substrate 1 was converted to (?)‐(1S,3R,4S,6S)‐6‐hydroxymenthol ( 2 ), (?)‐(1S,3R,4S)‐1‐hydroxymenthol ( 3 ) and (+)‐(1S,3R,4R,6S)‐6,8‐dihydroxymenthol ( 4 ), which was a new compound. Substrate 1 was converted to 2 and/or 3 by RRG97‐1, 110.4, RCP‐1, RCP‐3 and RCP‐7. The structures of the metabolic products were elucidated on the basis of their spectral data. In addition, metabolic pathways of the biotransformation of 1 by Rhizoctonia solani are discussed. Finally, from the main component analysis and the differences in the yields of converted product from 1 , the 12 isolates of Rhizoctonia solani were divided into three groups based on an analysis of the metabolites. Copyright © 2003 Society of Chemical Industry  相似文献   
2.
介绍I/A’S系统在巨化热电厂八号50MW供热机组上应用实例,并从DCS系统的整体设计到实现的功能、控制效果等多方面进行了分折,总结了调试和运行经验。  相似文献   
3.
提出了一种基于小波变换的多分辨率数字水印隐藏与检测新算法,算法的优点在于其算法简单。利用小波变换的快速、简单和多分辨率特点,将水印信号隐藏在第1、2、3级的详细分量(细节信号)中保证了水印的稳健性,具有很强的抵御各种信号处理变换的能力,适用于数字语音等信号的版权保护。最后给出了计算机仿真实验结果,证明了本算法的有效性。  相似文献   
4.
王根平 《矿山机械》2003,31(8):26-27
介绍了溜井振动放矿机设计时的埋设参数选择,阐述了其设计和安装的基本原则和要求,简明而系统地论述了振动放矿机使用维护的注意事项以及常见故障的处理方法。  相似文献   
5.
In this paper, we propose an ID-based non-interactive zero-knowledge proof system based on the 1-out-of-2 noninteractive oblivious transfer protocol. This zero-knowledge proof system is secure against a newly discovered cheating attack.  相似文献   
6.
7.
The distribution of anthocyanins in methanolic skin extracts of 16 grape cultivars used for port wine production and grown at five sites in the Douro Valley in Northern Portugal has been assessed by high performance liquid chromatography. Results are confined to the seven most readily separated and identified anthocyanins and are expressed as percentages of their total (88–99% of the total integrated area). Anthocyanins based on malvidin (Mv) predominated. Of these, Mv 3-glucoside was the major pigment (33–60%), being exceeded by Mv 3-p-coumarylglucoside (2–51%) in only two cultivars; Mv 3-acetylglucoside (1–15%) was consistently the lowest. Peonidin 3-glucoside (1–27%) was prominent in four cultivars, but delphinidin 3-glucoside (1–11%), petunidin 3-glucoside (2–11%) and cyanidin 3-glucoside (trace-6%) were of low proportions throughout. The ratio Mv 3-acetylglucoside/total Mv glucosides appeared characteristic of cultivar, independent of site, and a useful aid to identification of grape cultivars. The coloured pulp of some cultivars contained peonidin 3-glucoside as a major component, present in greater proportions than in the skin; the percentage of Mv 3-p-coumarylglucoside was lower in pulp than in skin. The identities of six of the seven anthocyanins were confirmed by fast atom bombardment mass spectrometry and the structures of the Mv derivatives were determined by nuclear magnetic resonance. The formation of formyl and acetyl anthocyanin artefacts is described.  相似文献   
8.
冷硬树脂砂增韧机理的研究   总被引:2,自引:1,他引:1  
系统地研究了附加物对冷硬树脂砂的增韧作用,探讨了附加物对冷硬树脂砂的增韧机理  相似文献   
9.
Games such as CHESS, GO and OTHELLO can be represented by minimax game trees. Among various search procedures to solve such game trees,- and SSS* are perhaps most well known. Although it is proved that SSS* explores only a subset of the nodes explored by-, - is commonly believed to be faster in real applications, since it requires very little memory space and hence its storage management cost is low. Contrary to this folklore, however, this paper reports, using the OTHELLO game as an example, that SSS* is much faster than-. It is also demonstrated that SSS* can be modified to make the required memory space controllable to some extent, while retaining the high efficiency of the original SSS*.This research was partially supported by the Ministry of Education, Science and Culture of Japan, under a Scientific Grant-in-Aid.  相似文献   
10.
随着信息化浪潮的发展,SSL协议的应用非常普遍,但是在SSL协议应用的工程实践中也发现了一些应用模式所导致的问题,文章首先介绍了SSL协议的安全技术应用,重点分析了其中安全技术问题的表现,并通过国产密码算法与SSL协议之间应用兼容性的问题分析,提出了一些SSL协议应用模式的建议。  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