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   7448篇
  免费   91篇
  国内免费   4篇
电工技术   48篇
综合类   6篇
化学工业   471篇
金属工艺   82篇
机械仪表   95篇
建筑科学   162篇
矿业工程   6篇
能源动力   138篇
轻工业   309篇
水利工程   17篇
石油天然气   10篇
无线电   355篇
一般工业技术   653篇
冶金工业   4749篇
原子能技术   61篇
自动化技术   381篇
  2022年   29篇
  2021年   39篇
  2020年   35篇
  2019年   47篇
  2018年   34篇
  2017年   42篇
  2016年   46篇
  2015年   43篇
  2014年   55篇
  2013年   130篇
  2012年   119篇
  2011年   143篇
  2010年   116篇
  2009年   109篇
  2008年   127篇
  2007年   138篇
  2006年   108篇
  2005年   87篇
  2004年   104篇
  2003年   100篇
  2002年   95篇
  2001年   80篇
  2000年   74篇
  1999年   225篇
  1998年   1435篇
  1997年   846篇
  1996年   582篇
  1995年   321篇
  1994年   276篇
  1993年   286篇
  1992年   91篇
  1991年   111篇
  1990年   115篇
  1989年   88篇
  1988年   112篇
  1987年   99篇
  1986年   63篇
  1985年   98篇
  1984年   31篇
  1983年   43篇
  1982年   49篇
  1981年   50篇
  1980年   60篇
  1979年   34篇
  1978年   41篇
  1977年   125篇
  1976年   280篇
  1975年   19篇
  1974年   23篇
  1973年   28篇
排序方式: 共有7543条查询结果,搜索用时 15 毫秒
81.
We describe a simple method for combining in situ hybridisation and immunohistochemistry on the same retinal section. The technique was developed using a radiolabelled cDNA probe for opsin and an antibody (ROS1F4) against rhodopsin. This method retains the antigenic sites if immunocytochemistry is performed prior to in situ hybridisation. Opsin mRNA was found in the photoreceptor inner segment with rhodopsin immunolocalised to the photoreceptor outer segments. The technique should be applicable to numerous situations including analysis of the sequence of events in the expression and synthesis of the various opsins during retinal development and degeneration.  相似文献   
82.
83.
Recent procedures for autologous repair of cartilage defects may be difficult in elderly patients because of the loss of stem cells and chondrocytes that occurs with age and the slow in vitro proliferation of chondrocytes from aged cartilage. In this study secondary chondroprogenitor cells were obtained by modulating the phenotype of articular chondrocytes with growth factors and stimulating the proliferation of these cells in culture. Chondrocytes isolated from the articular cartilage of mature New Zealand White rabbits were exposed to a combination of transforming growth factor beta and basic fibroblast growth factor treatment. These cells ceased the production of Collagen II (a marker for the chondrocyte phenotype) and underwent a 136-fold increase in cell number. Next, the cells were placed in high density culture and reexpressed the chondrocyte phenotype in vitro and formed hyaline cartilage in an in vivo assay. Primary chondrocytes obtained from articular cartilage of elderly humans could be manipulated in a similar fashion in vitro. These human secondary chondroprogenitor cells formed only cartilage tissue when assayed in vivo and in tissue bioreactors. This approach may be essential for autologous repair of degenerated articular cartilage in elderly patients with osteoarthritis.  相似文献   
84.
The Paired Associate Recognition Test (PART) was developed to measure declarative memory using Wisconsin Card Sorting Test (WCST) stimuli, so that both tasks could be administered during functional neuroimaging to differentiate memory and executive function, and associated frontal and temporal lobe activation in schizophrenia. The current study was designed to compare PART and WCST performance in schizophrenic patients and to examine effects of medication and symptomatology. The PART, WCST, and standard declarative memory tasks were administered to 30 chronic schizophrenic patients and 30 matched healthy control subjects. Supporting task validity was the finding that patients were equally impaired on the PART and the WCST. Neuroleptics did not appear to affect performance. The effect of anticholinergic medication correlated negatively with WCST performance in a small subsample. Severity of schizophrenia-specific symptoms measured at intake on the Brief Psychiatric Rating Scale correlated negatively with performance on the WCST. These results support the application of the PART and WCST in future functional neuroimaging studies.  相似文献   
85.
We report two patients with paraneoplastic limbic and brainstem encephalitis associated with occult nonmetastatic testicular seminoma. In each patient, the neoplasm was detectable only by testicular ultrasonography. Male patients with this syndrome in whom lung cancer is not found should undergo testicular ultrasonography as part of the search for an extrapulmonary neoplasm. A normal clinical testicular examination is insufficient to exclude an occult seminoma.  相似文献   
86.
We report a case of cervicofacial necrotizing fasciitis that developed after blepharoplasty, an occurrence that, to our knowledge, has not previously been reported in the medical literature. A patient who presented to our institution 3 days after undergoing blepharoplasty of the upper eyelid was diagnosed as having fulminant fasciitis involving extensive areas of the face, scalp, and neck. We review the case in detail and discuss clinical and radiological clues to diagnosis, surgical and medical management, wound care, and subsequent scar contracture. This case emphasizes the need for individualized, appropriate postoperative care and for an awareness of this rare, potentially fatal complication. Early recognition and aggressive treatment of cervicofacial fasciitis can arrest its rapid progression and prevent devastating sequelae.  相似文献   
87.
A method to analyze the accuracy of the extracted values for the channel length (Leff) and series resistance (Rs) of MOSFET devices is presented. The analysis is based on a statistical argument being the variance σ of the extracted results. This variance is found to be a good measure for the accuracy of the particular extraction method used. It is shown that, in the case of deep submicron technologies, errors as large as 200 nm for ΔL can be made for these extraction methods depending on the process design and the process control. The use of a single transistor method is suggested as a possible solution to the low accuracy of the L-array methods  相似文献   
88.
Access and visualization in the implant-abutment area are often compromised. Tissue impingement and lack of abutment position verification may result in inaccurate fit.  相似文献   
89.
90.
Although the banking industry plays a central role in the world economy and has traditionally been an innovative user of information technology, banks are struggling to develop mature Internet strategies. A model used to analyze the type of Internet activities among a sample of banks as well as their level of sophistication and customization is useful not only for revealing unexploited opportunities in the banking sector but also for guiding the strategy-building process of organizations in other industries.  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