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   1460篇
  免费   12篇
电工技术   4篇
化学工业   125篇
金属工艺   3篇
机械仪表   9篇
建筑科学   21篇
矿业工程   3篇
能源动力   12篇
轻工业   46篇
水利工程   10篇
石油天然气   2篇
无线电   51篇
一般工业技术   62篇
冶金工业   1054篇
原子能技术   5篇
自动化技术   65篇
  2022年   7篇
  2021年   18篇
  2020年   7篇
  2019年   11篇
  2018年   14篇
  2017年   16篇
  2016年   9篇
  2014年   12篇
  2013年   23篇
  2012年   11篇
  2011年   23篇
  2010年   32篇
  2009年   32篇
  2008年   17篇
  2007年   17篇
  2006年   15篇
  2005年   16篇
  2004年   13篇
  2003年   5篇
  2001年   9篇
  1999年   33篇
  1998年   290篇
  1997年   171篇
  1996年   114篇
  1995年   64篇
  1994年   57篇
  1993年   59篇
  1992年   12篇
  1991年   15篇
  1990年   20篇
  1989年   13篇
  1988年   17篇
  1987年   20篇
  1986年   13篇
  1985年   18篇
  1983年   8篇
  1982年   15篇
  1981年   13篇
  1980年   15篇
  1978年   7篇
  1977年   31篇
  1976年   70篇
  1973年   7篇
  1972年   5篇
  1971年   4篇
  1969年   5篇
  1968年   7篇
  1961年   4篇
  1954年   4篇
  1951年   5篇
排序方式: 共有1472条查询结果,搜索用时 0 毫秒
1.
2.
3.
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   
4.
We propose a new, less costly, design to test the equivalence of digital versus analogue mammography in terms of sensitivity and specificity. Because breast cancer is a rare event among asymptomatic women, the sample size for testing equivalence of sensitivity is larger than that for testing equivalence of specificity. Hence calculations of sample size are based on sensitivity. With the proposed design it is possible to achieve the same power as a completely paired design by increasing the number of less costly analogue mammograms and not giving the more expensive digital mammograms to some randomly selected subjects who are negative on the analogue mammogram. The key idea is that subjects who are negative on the analogue mammogram are unlikely to have cancer and hence contribute less information for estimating sensitivity than subjects who are positive on the analogue mammogram. To ascertain disease state among subjects not biopsied, we propose another analogue mammogram at a later time determined by a natural history model. The design differs from a double sampling design because it compares two imperfect tests instead of combining information from a perfect and imperfect test.  相似文献   
5.
6.
7.
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   
8.
Creation of a dynamic levator aponeurosis fold or double eye adds to the beauty of the East Asian. The eyes are larger and less puffy, and the eyelashes appear longer and curve up and out instead of down. The distance from the ciliary border to the eyebrow is decreased and more in proportion. The Mongolian trait is preserved.  相似文献   
9.
10.
A method for machine interpretation of architectural (or other) schematic drawings is presented. The central problem is to build an efficient drawing parser (i.e., a program that identifies the semantic entities, characteristics, and relationships that are represented in the drawing). The parser is built from specifications of the drawing grammar and an underlying spatial model. The grammar describes what to look for, and the spatial model enables the parser to find it quickly. Coupled with existing optical recognition technology, this technique enables the use of drawings directly as: (1) a database to drive various Architecture-Engineering-Construction (AEC) applications; (2) a communication protocol to integrate CAD systems; (3) a traditional user interface.  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