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   4837篇
  免费   3篇
电工技术   5篇
综合类   1篇
化学工业   44篇
金属工艺   10篇
机械仪表   10篇
建筑科学   16篇
能源动力   1篇
轻工业   23篇
水利工程   4篇
无线电   55篇
一般工业技术   68篇
冶金工业   4556篇
原子能技术   5篇
自动化技术   42篇
  2021年   4篇
  2018年   3篇
  2014年   7篇
  2013年   10篇
  2012年   6篇
  2011年   7篇
  2010年   9篇
  2009年   7篇
  2008年   9篇
  2007年   3篇
  2006年   8篇
  2004年   11篇
  2003年   14篇
  2002年   4篇
  2001年   3篇
  2000年   9篇
  1999年   142篇
  1998年   1414篇
  1997年   860篇
  1996年   508篇
  1995年   273篇
  1994年   261篇
  1993年   288篇
  1992年   42篇
  1991年   58篇
  1990年   83篇
  1989年   66篇
  1988年   75篇
  1987年   69篇
  1986年   50篇
  1985年   41篇
  1984年   5篇
  1983年   11篇
  1982年   15篇
  1981年   31篇
  1980年   47篇
  1979年   4篇
  1978年   13篇
  1977年   102篇
  1976年   215篇
  1975年   10篇
  1974年   7篇
  1973年   3篇
  1971年   3篇
  1969年   2篇
  1968年   4篇
  1967年   2篇
  1966年   2篇
  1964年   2篇
  1955年   3篇
排序方式: 共有4840条查询结果,搜索用时 0 毫秒
51.
52.
Pre-clerking of all patients undergoing elective general surgical operations was introduced at our hospital in an attempt to reduce an unacceptably high operation cancellation rate. A prospective audit has been performed on the effect of this policy on the cancellation rate. Before the introduction of pre-clerking there was a marked seasonal variation in the number of patients who failed to attend for surgery, which could be explained by absence on holiday. This seasonal variation disappeared after the start of pre-clerking clinics, but there has been no reduction in the number of cancellations for medical reasons.  相似文献   
53.
54.
55.
56.
LA Mastaj  DJ Tartakow  AJ Borislow  MS Fogel 《Canadian Metallurgical Quarterly》1994,15(1):74, 76, 78-80, passim; quiz 86
Infections present a significant hazard in the orthodontic office because they can be transmitted by blood or saliva through direct or indirect contact, droplets, aerosols, or contaminated instruments and equipment. Because the incidence of certain microbial cross-infections in the dental environment has not been well documented, orthodontic personnel may not take the problem of cross-infection as seriously as they should, and they may transmit or contract more infections than they realize. The use of effective infection-control procedures in the orthodontic office and laboratory will prevent cross-contamination that may extend to the orthodontist, office staff, assistants, and patients. The goal of this article is to present infection control in a simple, yet comprehensive, manner, and to encourage all orthodontic practitioners to implement essential infection-control procedures in their practices.  相似文献   
57.
58.
Calmodulin and de-phosphorylated B-50/growth-associated protein-43 (GAP-43) have been shown to bind in vitro in a molecular complex, but evidence for an in situ association in the nervous system does not exist. Previously, we have reported that, in the model of the regenerating rat sciatic nerve, the B-50/GAP-43 immunoreactivity is increased and concentrated at the axolemma of unmyelinated axons located proximal to the site of injury and axon outgrowth. To explore a putative function of B-50/GAP-43, namely, the capacity of binding calmodulin to the plasma membrane, we examined the ultrastructural distribution of calmodulin in the proximal unmyelinated axon shafts of this model, using double immunolabelling and detection by fluorescent or gold probes conjugated to second antibodies. Immunofluorescence showed that seven days post-sciatic nerve crush the calmodulin immunoreactivity, similar to B-50/GAP-43 immunoreactivity, was intense in unmyelinated axon shafts located proximal to the site of injury of the regenerating nerve. Ultrastructurally, calmodulin was located at the axolemma of these regenerating unmyelinated axon shafts and inside the axoplasm, where it was associated with vesicles and microtubules. The plasma membrane labelling (approximately 69%) was significantly higher than the axoplasmic labelling. Over 60% of the plasma membrane-associated calmodulin co-localized with B-50/GAP-43 in a non-random distribution. Since normally calmodulin is largely present in the cytoplasm, these data suggest that calmodulin has been concentrated at the plasma membrane of unmyelinated axons, most probably by B-50/GAP-43. If the concentrating effect is due to B-50/GAP-43, then there is a possibility that these proteins may be present as a molecular complex in situ. The physiological significance could be that this association regulates the local availability of both B-50/GAP-43 and calmodulin for other interactions.  相似文献   
59.
The paper describes a high-capacity blind video watermarking system invariant to geometrical attacks such as shift, rotation, scaling and cropping. A spatial domain reference watermark is used to obtain invariance to geometric attacks by employing image registration techniques to determine and invert the attacks. A second, high-capacity watermark, which carries the data payload, is embedded in the wavelet domain according to a human visual system model. This is protected by a state-of-the-art error correction code (turbo code). For a false detection probability of 10/sup -8/, the proposed system is invariant to scaling up to 180%, rotation up to 70/spl deg/, and arbitrary aspect ratio changes up to 200% on both axes. Furthermore, the system is virtually invariant to any shifting, cropping, or combined shifting and cropping. The system is also robust to MPEG2 compression, even when combined with shifting and cropping.  相似文献   
60.
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