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   315452篇
  免费   4092篇
  国内免费   925篇
电工技术   5376篇
综合类   391篇
化学工业   50334篇
金属工艺   12557篇
机械仪表   9200篇
建筑科学   7789篇
矿业工程   1929篇
能源动力   7633篇
轻工业   29506篇
水利工程   3424篇
石油天然气   7245篇
武器工业   22篇
无线电   33636篇
一般工业技术   60744篇
冶金工业   57718篇
原子能技术   7723篇
自动化技术   25242篇
  2021年   2845篇
  2019年   2553篇
  2018年   4336篇
  2017年   4364篇
  2016年   4605篇
  2015年   2995篇
  2014年   5050篇
  2013年   13435篇
  2012年   8020篇
  2011年   10736篇
  2010年   8691篇
  2009年   9782篇
  2008年   9974篇
  2007年   9724篇
  2006年   8575篇
  2005年   8106篇
  2004年   7654篇
  2003年   7334篇
  2002年   7377篇
  2001年   7179篇
  2000年   6690篇
  1999年   6728篇
  1998年   16689篇
  1997年   12310篇
  1996年   9454篇
  1995年   7118篇
  1994年   6397篇
  1993年   6302篇
  1992年   4697篇
  1991年   4724篇
  1990年   4518篇
  1989年   4507篇
  1988年   4460篇
  1987年   3769篇
  1986年   3768篇
  1985年   4346篇
  1984年   4102篇
  1983年   3728篇
  1982年   3556篇
  1981年   3679篇
  1980年   3546篇
  1979年   3462篇
  1978年   3524篇
  1977年   4082篇
  1976年   5274篇
  1975年   3228篇
  1974年   3050篇
  1973年   3071篇
  1972年   2694篇
  1971年   2509篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The authors address using the concept of multimodal bioimage integration at the local area network level, using 3D MRI and PET data of the human head. Here, integration is intended between structural and functional multidimensional images of the same body area of a patient. They analyze the role of present technology and standards (such as the X Window protocol) in providing the physician with a better understanding of the structure-to-function relationships of a given biological organ. They analyze the concept of integration intended as a tool to extract the significative information content from bioimages, i.e. to perform image analysis. The fusion of visual eidetic and linguistic knowledge, which plays an important role in medical diagnosis formation, is seen as a significant step towards obtaining quantitative evaluation of the relevant information content of bioimages  相似文献   
993.
OBJECTIVE: To determine the effect on oxygen saturation of instilling a saline bolus into artificial airways prior to suctioning, as measured by pulse oximeter. DESIGN: Quasi-experimental, single-case, counterbalanced design. SETTING: The surgical, medical and coronary intensive care units of a federal, teaching medical center. SUBJECTS: Subjects were 40 men, more than 40 years old, in need of intensive care nursing and mechanical ventilation. INTERVENTIONS: Subjects were suctioned as needed for 24 hours. A 5-mL saline bolus was instilled every other time the subject was suctioned. Outcome measurements were done immediately before and after suctioning and at 1-minute intervals for 5 minutes after suctioning. MAIN OUTCOME MEASURES: Noninvasive oxygen saturation values. RESULTS: The instillation of a saline bolus was found to have an adverse effect on oxygen saturation that worsened over time. Significant changes in oxygen saturation as a result of saline bolus instillation were found at 2,3,4 and 5 minutes after instillation. CONCLUSIONS: These results indicate that instilling saline prior to suctioning has an adverse effect on oxygen saturation. These results support the recommendation that the practice of instilling saline prior to suctioning should be abandoned as a routine procedure. More study is needed to investigate whether a specific group of patients may actually benefit from this procedure.  相似文献   
994.
995.
A clinical study was carried out in an attempt to assess the efficacy of a newly designed electric toothbrush compared to a conventional manual toothbrush using the American Dental Association's protocol for evaluating toothbrushes. An Oral-B 35 manual toothbrush, which served as the control, was compared to the Plaq & White125 electric toothbrush. Examinations were performed by two calibrated examiners at baseline, day 15 and day 30. Examinations included the gingival index, plaque index and bleeding index. Mean indices were calculated and compared between the two brushes using the repeated measures multiple analysis of variance. No statistically significant differences between the mean indices on the three examination days were observed following the use of the manual or the electric toothbrushes. The results of this study demonstrate that the electric toothbrush was numerically more effective than the manual toothbrush in reducing supragingival plaque levels, either before or after brushing, at each examination date compared to baseline plaque values. However, this difference was not statistically significant. This and other findings concluded that the Plaq & White toothbrush is comparable to the control ADA-accepted toothbrush.  相似文献   
996.
Thermochemical constants for specimens of alumogoethite and alumohematite are determined. Limited miscibility of solid solutions and their thermodynamic stability are shown. Their possible effect on the properties of bauxite refractories is estimated. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 7, pp. 35–39, July, 1996.  相似文献   
997.
998.
999.
Translated from Steklo i Keramica, No. 3, pp. 7–10, March, 1993.  相似文献   
1000.
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