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   1769篇
  免费   80篇
  国内免费   54篇
电工技术   42篇
综合类   29篇
化学工业   161篇
金属工艺   44篇
机械仪表   48篇
建筑科学   59篇
矿业工程   21篇
能源动力   15篇
轻工业   77篇
水利工程   9篇
石油天然气   31篇
武器工业   2篇
无线电   121篇
一般工业技术   131篇
冶金工业   982篇
原子能技术   17篇
自动化技术   114篇
  2024年   5篇
  2023年   24篇
  2022年   27篇
  2021年   28篇
  2020年   21篇
  2019年   28篇
  2018年   19篇
  2017年   40篇
  2016年   33篇
  2015年   41篇
  2014年   22篇
  2013年   60篇
  2012年   40篇
  2011年   77篇
  2010年   37篇
  2009年   50篇
  2008年   50篇
  2007年   29篇
  2006年   42篇
  2005年   50篇
  2004年   30篇
  2003年   19篇
  2002年   27篇
  2001年   11篇
  2000年   16篇
  1999年   43篇
  1998年   275篇
  1997年   165篇
  1996年   123篇
  1995年   60篇
  1994年   59篇
  1993年   65篇
  1992年   17篇
  1991年   14篇
  1990年   21篇
  1989年   15篇
  1988年   17篇
  1987年   17篇
  1986年   13篇
  1985年   16篇
  1983年   10篇
  1982年   4篇
  1981年   15篇
  1980年   12篇
  1979年   2篇
  1978年   7篇
  1977年   27篇
  1976年   69篇
  1975年   2篇
  1974年   3篇
排序方式: 共有1903条查询结果,搜索用时 15 毫秒
1.
The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits.  相似文献   
2.
3.
4.
Osteomyelitis in uncommon locations can present unusual diagnostic difficulties. A patient with primary sternal osteomyelitis who presented with pain over the right supraclavicular area and a radiologic picture of a pleural-based right upper lung mass is discussed. A triple-phase bone scan was consistent with the diagnosis, and a needle aspiration of the mass revealed a staphylococcal abscess. Percutaneous drainage of the contiguous abscess and a prolonged course of antibiotic therapy cured the infection.  相似文献   
5.
6.
7.
8.
9.
张志波  陈建平  魏伴云 《爆破》2002,19(1):11-13
在现场试验的基础上,对气相起爆系统的实际应用性能进行了初步研究.分析和探讨了该系统安全使用条件和尚存在的诸多技术问题.此外,还介绍了我国首批研制成功的气相雷管及其性能.  相似文献   
10.
In response to a light pulse, hamsters normally generate phase advances that are positively correlated with the length of their circadian period (tau). To determine whether this is a general property of the phase-shifting oscillator, the present study looked for a correlation between tau and phase-advance size not only for photic but also for nonphotic shifts. Syrian hamsters, Mesocricetus auratus, were entrained to light-dark cycles with a periodicity of either 23.67 h (the short-T group) or 24.33 h (the long-T group); after release into constant darkness, the short-T and long-T groups exhibited short and long taus, respectively. These animals were then induced to run in a novel exercise wheel for 3 h, starting at circadian time (CT) 7, or were exposed to 20 min of light, starting at CT 19. The size of the ensuing phase advances did not differ between the short-T and long-T groups not only for the nonphotic stimulus but also for the photic one, an unexpected result for the photic stimulus. Within the short-T groups for photic and nonphotic stimuli, the shorter tau was, the larger the phase advances were, another unexpected relationship. Another experiment where phase delays were induced by light pulses at CT 15 also failed to yield significant differences between the short-T and long-T groups. Independently of their after-effects on tau, T cycles may influence the capacity of the pacemaker to phase shift in ways that are still unclear but at least similar for both photic and nonphotic shifts.  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