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   2510篇
  免费   8篇
  国内免费   1篇
电工技术   1篇
化学工业   18篇
金属工艺   2篇
机械仪表   14篇
建筑科学   11篇
能源动力   2篇
轻工业   54篇
水利工程   2篇
石油天然气   17篇
无线电   2篇
一般工业技术   6篇
冶金工业   2382篇
原子能技术   2篇
自动化技术   6篇
  2022年   4篇
  2021年   2篇
  2020年   3篇
  2017年   7篇
  2016年   2篇
  2015年   3篇
  2013年   14篇
  2012年   4篇
  2011年   7篇
  2010年   11篇
  2009年   5篇
  2008年   3篇
  2007年   4篇
  2006年   5篇
  2005年   3篇
  2004年   2篇
  2003年   8篇
  2002年   2篇
  2001年   2篇
  2000年   2篇
  1999年   68篇
  1998年   722篇
  1997年   398篇
  1996年   276篇
  1995年   168篇
  1994年   114篇
  1993年   159篇
  1992年   20篇
  1991年   19篇
  1990年   33篇
  1989年   28篇
  1988年   32篇
  1987年   14篇
  1986年   20篇
  1985年   14篇
  1984年   2篇
  1983年   4篇
  1982年   11篇
  1981年   17篇
  1980年   26篇
  1979年   3篇
  1978年   9篇
  1977年   77篇
  1976年   179篇
  1975年   5篇
  1974年   1篇
  1968年   1篇
  1965年   2篇
  1962年   1篇
  1955年   1篇
排序方式: 共有2519条查询结果,搜索用时 553 毫秒
111.
The objective of the study was to evaluate the walking ability and the energy cost of walking in patients before and after total hip replacement. The oxygen intake and the maximum walking speed were measured immediately before and 6 months after operation in 25 patients. Although the oxygen intake did not change significantly in most patients it was decreased in those patients who before surgery had had the worst walking capacity. The average maximum walking speed almost doubled in the 25 patients.  相似文献   
112.
113.
The time and age dependence of cancer incidence rates resulting from various type of carcinogenic exposure are calculated and compared with observed cancer incidence rates. Implications for the detection of increased cancer incidence are discussed. The calculations assume that exposure affects one of several changes necessary for malignant cell transformation.  相似文献   
114.
The authors present an analysis of the causes of radiation induced complications in 383 patients referred to the Chair of Clinical Radiology from different medical institutions of the country. It was found that under distant gamma therapy, to prevent the development of complications the value of TDF-factor should not exceed 105--110, for the associated radiotherapy--130--140, and that for close focal roentgenotherapy--130--150. In vast majority of patients (95.3%) the complications resulted from surpassing the normal tissue tolerance. To prevent radiation injuries it is suggested to take into consideration the TDF-factor values, while in planning radiotherapy to choose such schedules of irradiation, which preclude any surpassing of the tolerance of normal tissues and organs adjacent to the tumor.  相似文献   
115.
116.
117.
118.
OBJECTIVE: The purpose of this study is to determine the efficacy of initial trabeculotomy in the patient with aniridic glaucoma. DESIGN: Clinical charts were reviewed. PARTICIPANTS: Twenty-nine eyes of 16 patients with aniridia were studied. INTERVENTION: Glaucoma surgery was performed. As an initial procedure, trabeculotomy was performed in 12 eyes, other surgery was performed in 17 eyes (trabeculectomy, 5; goniotomy, 5; other, 7). MAIN OUTCOME MEASURES: Success was defined as an intraocular pressure (IOP) of 21 mmHg or lower, and no further surgery was performed. RESULTS: Ten (83%) of 12 eyes obtained IOP control after first (6 eyes) or second (4 eyes) trabeculotomy with a mean follow-up period of 9.5 years. Five eyes maintained visual acuity of 20/40 to 20/200. No serious complications were found after trabeculotomy. Three (18%) of 17 eyes were controlled with the first glaucoma surgery other than trabeculotomy (goniotomy, trabeculectomy, trabeculectomy combined with trabeculotomy, and Molteno implant). Good IOP control was obtained in 8 (47%) of 17 eyes after several surgeries with a mean follow-up period of 10.4 years. Four of 17 eyes became phthisical. CONCLUSION: This study suggests that trabeculotomy is the preferred initial operation for uncontrolled glaucoma with aniridia.  相似文献   
119.
We report a 10-year-old boy who presented with a piece of chicken stuck in his throat. He had similar episodes in the past that resolved spontaneously. The foreign body was removed and oesophagoscopy revealed no abnormality. Post-operative barium swallow showed oesophageal intramural pseudodiverticulosis.  相似文献   
120.
Glaucoma reportedly affects motion perception. As an initial step in characterizing glaucoma-induced changes in the motion system, we determined the range of temporal frequencies that the motion system could process. A noise-masking paradigm was used to measure contrast energy thresholds of 26 glaucoma patients at various stages of the disease and 16 age-similar subjects with normal vision. Using a sinusoidal stimulus, thresholds were measured for the discrimination of motion direction and for the stimulus embedded within a pattern of dynamic spatial noise. The noise was filtered to contain only low spatial frequencies, and the temporal-frequency spectrum of the noise was manipulated across conditions to derive the temporal filter shape of the most efficient motion sensor. The results show that the range of temporal frequencies processed by the motion system is diminished in the glaucoma group. The filters of the glaucoma subjects have reduced bandwidths compared with the normal-vision group. In addition, the upper cut-off frequency of the filters of the glaucoma subjects is correlated with stage of disease as indexed by the mean deviation of the Humphrey Visual Field Analyzer program 24-2, as well as the cup-to-disk ratio.  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