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   1873篇
  免费   5篇
  国内免费   1篇
电工技术   1篇
综合类   2篇
化学工业   89篇
金属工艺   20篇
机械仪表   27篇
建筑科学   21篇
能源动力   3篇
轻工业   2篇
水利工程   3篇
石油天然气   31篇
无线电   17篇
一般工业技术   101篇
冶金工业   1517篇
原子能技术   8篇
自动化技术   37篇
  2020年   6篇
  2019年   5篇
  2018年   7篇
  2017年   6篇
  2016年   5篇
  2015年   8篇
  2014年   8篇
  2013年   22篇
  2012年   5篇
  2011年   13篇
  2010年   7篇
  2009年   15篇
  2008年   10篇
  2007年   14篇
  2006年   7篇
  2005年   9篇
  2004年   8篇
  2003年   12篇
  2002年   7篇
  2000年   6篇
  1999年   55篇
  1998年   472篇
  1997年   260篇
  1996年   152篇
  1995年   97篇
  1994年   91篇
  1993年   97篇
  1992年   28篇
  1991年   28篇
  1990年   24篇
  1989年   23篇
  1988年   18篇
  1987年   23篇
  1986年   17篇
  1985年   23篇
  1984年   5篇
  1983年   13篇
  1982年   12篇
  1981年   18篇
  1980年   24篇
  1979年   6篇
  1978年   6篇
  1977年   48篇
  1976年   89篇
  1975年   10篇
  1974年   8篇
  1972年   9篇
  1970年   7篇
  1969年   5篇
  1968年   5篇
排序方式: 共有1879条查询结果,搜索用时 31 毫秒
141.
142.
The patients treated for oesophageal atresia present a correlation between the clinical sintomatology after recanalization characterized by disfagia, dispnea, recurrent cough, chronic pneumopaties and oesophageal anomalies. Where morphological alterations accounting for the presence of gastro-oesophageal reflux (GOR) were not evident, possible functional alterations of the motility were considered. The incidence of GOR was considerably high and, expression of a congenital alteration of the lower oesophageal sphincter and of oesophageal peristalsis, becomes even more severe due to further stretching of the gastro-esophageal junction. The authors underline that the early demonstration of histological changes, even before recanalization, and the motility disorders of the oesophagus have to be well studied, while the LES is normalized, in order to prevent and treat the possible appearance of the well-known complications of GOR.  相似文献   
143.
The adenovirus type 5 243R E1A protein induces p53-dependent apoptosis in the absence of the 19- and 55-kDa E1B polypeptides. This effect appears to result from an accumulation of p53 protein and is unrelated to expression of E1B products. We now report that in the presence of the E1B 55-kDa polypeptide, the 289R E1A protein does not induce such p53 accumulation and, in fact, is able to block that induced by E1A 243R. This inhibition also requires the 289R-dependent transactivation of E4orf6 expression. E4orf6 is known to form complexes with the E1B 55-kDa protein and to function both in the transport and stabilization of viral mRNA and in shutoff of host cell protein synthesis. We demonstrated that the block in p53 accumulation is not due to the generalized shutoff of host cell metabolism. Rather, it appears to result from a mechanism targeted specifically to p53, most likely involving a decrease in the stability of p53 protein. The E1B 55-kDa protein is known to interact with both E4orf6 and p53, and as demonstrated recently by others, we showed that E4orf6 also binds directly to p53. Thus, multiple interactions between all three proteins may regulate p53 stability, resulting in the maintenance of low levels of p53 following virus infection.  相似文献   
144.
We report 18 patients who presented prior to age 20 years with epilepsy or fixed neurologic deficits. MRI showed signal abnormality extending from the cortex to the superolateral wall of the lateral ventricle. Histology showed cortical disorganization, neuronal cytomegaly, balloon cells, indistinct cortical gray matter-white matter junctions, and variable accompanying astrogliosis. We propose that this transmantle dysplasia is a specific anomaly resulting from abnormal stem cell development.  相似文献   
145.
We consider the classification of detonation logic elements (DLE), that is, devices in which logical operations are effected by means of explosive signals. The technical implementation of the DLE studied is based on the physical principle of the “corner effect.” Methods of describing the functional properties of DLE using Boolean functions are analyzed. Examples are given of the application of Boolean functions to detonation elements of single-step and two-step logic. Institute of Specialized Mechanical Engineering, N. é. Bauman Moscow State Technical University, Moscow 107005. Translated from Fizika Goreniya i Vzryva. Vol. 30, No. 5, pp. 123–126, September–October, 1994.  相似文献   
146.
147.
OBJECTIVE: To report our clinical experience on the use of oral erythromycin for the treatment of severe gastrointestinal dysmotility in preterm infants. METHODOLOGY: A case series study of seven preterm infants (six were very low birthweight) with severe intestinal dysmotility in a tertiary neonatal centre. RESULTS: All responded favourably without adverse effects and tolerated full enteral feeding within 1-2 weeks of the commencement of the drug. CONCLUSIONS: As prolonged total parenteral nutrition carries significant risk of complications, this therapy could be considered in selected preterm infants who fail to establish enteral feeding after an extended period, and in whom an anatomically obstructive lesion of the gastrointestinal tract has been excluded. Meanwhile, we would caution against the widespread implementation of this therapeutic approach until formal evaluation by randomized controlled trials have established the exact role of erythromycin, or its analogues, in the treatment of intestinal dysmotility in preterm infants.  相似文献   
148.
The authors report the case study of a 13-year-old girl, suffering from epigastric pain related to an important infectious syndrome and from marked hypertrophic pneumosteopathy (clubbed fingers, diffuse cortical hyperostosis). Radiological examination (chest x-ray and computed tomography scan) showed a partly calcified right posterior mediastinal mass. The esophagoscopy showed a fistular emanation from the esophagus to the tumor. The biopsy results were of no diagnostic significance, and the samples demonstrated a bacterial and fungal colonization. An endoscopic sonogram showed an inhomogeneous mass with hyperechoic structures developed between the mucosa and the outer muscular coat of the esophagus. The patient underwent surgery, which showed a large intraparietal tumor of the esophagus, which, through pathological examination, was confirmed to be a benign leiomyoma. Postoperative follow-up was simple and the pneumosteopathic symptoms regressed rapidly. This disease is rare in children under 15 years of age. It is only exceptionally associated with a hypertrophic pneumosteopathy. This pathology is diagnostically challenging to the surgeon. The endoscopic ultrasonography is the best procedure in the assessment of subepithelial tumor and extrinsic compressions of the oesophagus.  相似文献   
149.
OBJECTIVE: The purpose of this study was to show the usefulness of MR imaging with a transrectal coil (TRC) in the management of various urethral abnormalities. This report also reveals the appearance of various postsurgical changes relating to the therapy of urethral abnormality. CONCLUSION: The high-resolution images obtained with TRC MR imaging were useful in evaluating urethral abnormalities. The imaging guided therapy in most cases. In two patients, TRC MR imaging more accurately depicted abnormality than did voiding cystourethrography and transvaginal sonography. In one case, TRC MR imaging was the only imaging technique that revealed the abnormality of periurethral scarring.  相似文献   
150.
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