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   1825篇
  免费   10篇
  国内免费   2篇
电工技术   4篇
化学工业   50篇
金属工艺   11篇
机械仪表   3篇
建筑科学   3篇
能源动力   14篇
轻工业   21篇
水利工程   2篇
无线电   29篇
一般工业技术   51篇
冶金工业   1627篇
原子能技术   4篇
自动化技术   18篇
  2022年   2篇
  2021年   2篇
  2020年   5篇
  2019年   4篇
  2018年   8篇
  2017年   7篇
  2016年   7篇
  2015年   9篇
  2014年   5篇
  2013年   22篇
  2012年   10篇
  2011年   10篇
  2010年   13篇
  2009年   10篇
  2008年   9篇
  2007年   10篇
  2006年   10篇
  2005年   3篇
  2004年   9篇
  2003年   10篇
  2002年   8篇
  2001年   3篇
  2000年   3篇
  1999年   51篇
  1998年   428篇
  1997年   273篇
  1996年   194篇
  1995年   116篇
  1994年   98篇
  1993年   99篇
  1992年   9篇
  1991年   43篇
  1990年   39篇
  1989年   25篇
  1988年   26篇
  1987年   23篇
  1986年   25篇
  1985年   32篇
  1983年   3篇
  1982年   7篇
  1981年   8篇
  1980年   14篇
  1979年   2篇
  1978年   3篇
  1977年   53篇
  1976年   83篇
  1975年   4篇
排序方式: 共有1837条查询结果,搜索用时 0 毫秒
71.
One hundred consecutive patients (81 male and 19 female) with unstable angina pectoris undergoing coronary angiography were divided according to Braunwald's clinical classification. Seventeen (17%) patients had new onset angina (class I), 68 (68%) sub-acute angina (class II) and 15 (15%) had acute rest angina (class III). Twenty-seven (27%) patients had secondary unstable angina pectoris (class A), 49 (49%) primary unstable angina (class B) and 24 (24%) had post-infarction unstable angina (class C). ST-T wave changes on ECG were present in 54 (54%) while absent in 46 (46%) patients. On coronary angiography, 26 (26%) patients had single vessel disease, 30 (30%) double vessel disease and 39 (39%) patients had triple vessel disease. Five (5%) patients were found to have normal coronaries. Classification of patients according to Braunwald's clinical classification showed single vessel disease to be higher in class I as compared to class II (47% vs 22%; p = 0.04) and classes III (47% vs 20%; p<0.01). Single vessel disease was found to be higher in class C as compared to class B (41.7% vs 16.4; p = 0.01). Double vessel disease was higher in class B as compared to class A (40.8% vs 18.5%, p = 0.04). Triple vessel disease incidence was not found to be significantly different among different clinical classes. Morphology of coronary artery lesions was classified according to Ambrose's classification. Out of the total of 248 lesions in the whole study group, there were 68 (27.42%) concentric lesions, 55 (22.18%) eccentric type I lesions, 23 (9.27%) eccentric type II lesions, 42 (16.94%) multiple irregularity lesions and 60 (24.19%) totally occluded lesions. Concentric lesions were found to be higher in class C as compared to class B (40% vs 19.8%; p = 0.014). Statistically significant difference was not present in the distribution of other morphological type of lesions among different clinical classes. In the whole study group, intra-luminal thrombus was found to be present in 17 (17%) of patients. Distribution of intra-luminal thrombus according to Braunwald's classification showed that none of the patients in class I had intra-luminal thrombus, while 13 (19.1%) patients in class II and 4(26.7%) in class III had intra-luminal thrombus. The difference in the occurrence of intra-luminal thrombus between class I and class II (p = 0.004) and class I and class III (p = 0 .03 was found to be significant. Thus, majority of patients undergoing coronary angiography had primary sub-acute rest angina. Single vessel disease was higher in new onset angina. Patients with unstable angina pectoris and ST-T changes on ECG had higher number of lesions per patient and higher eccentric type I lesions. Intra-luminal thrombus was more frequently encountered with acute rest angina. However, the distribution of different morphological type of lesions on coronary angiography did not differ significantly in different clinical classes of unstable angina pectoris divided according to Braunwald's classification.  相似文献   
72.
73.
74.
75.
76.
77.
78.
79.
A trajectory defined by three time-ordered events was offered as a useful adjunct to building a development theory about antisocial behaviors. A sequence was defined with significant linkages between antisocial childhood behavior and early arrest and between early arrest and chronic offending. The majority of chronic offenders traveled through all three events in the sequence. Each event in the sequence shared a common process of disrupted family process plus frequent family transitions and marked social disadvantage. The findings support the hypothesis that the process that leads to antisocial behaviors at grade four may also maintain the entire sequence. The level of disrupted process at initiation and a time-based measure of involvement with deviant peers predicted which individuals moved forward in the sequence and which did not. The findings are consistent with the idea that the majority of chronic offending juveniles follow a trajectory that can be explained by a single theory.  相似文献   
80.
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