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   3020篇
  免费   36篇
  国内免费   4篇
电工技术   19篇
综合类   2篇
化学工业   191篇
金属工艺   15篇
机械仪表   18篇
建筑科学   46篇
能源动力   87篇
轻工业   95篇
水利工程   16篇
石油天然气   11篇
无线电   155篇
一般工业技术   183篇
冶金工业   2090篇
原子能技术   3篇
自动化技术   129篇
  2024年   3篇
  2023年   17篇
  2022年   28篇
  2021年   65篇
  2020年   44篇
  2019年   33篇
  2018年   51篇
  2017年   36篇
  2016年   44篇
  2015年   34篇
  2014年   54篇
  2013年   71篇
  2012年   54篇
  2011年   63篇
  2010年   51篇
  2009年   47篇
  2008年   41篇
  2007年   34篇
  2006年   37篇
  2005年   28篇
  2004年   16篇
  2003年   21篇
  2002年   12篇
  2001年   14篇
  2000年   11篇
  1999年   70篇
  1998年   642篇
  1997年   376篇
  1996年   228篇
  1995年   157篇
  1994年   110篇
  1993年   137篇
  1992年   27篇
  1991年   35篇
  1990年   29篇
  1989年   33篇
  1988年   26篇
  1987年   26篇
  1986年   26篇
  1985年   26篇
  1984年   3篇
  1982年   10篇
  1981年   18篇
  1980年   24篇
  1979年   4篇
  1978年   6篇
  1977年   45篇
  1976年   83篇
  1971年   2篇
  1969年   2篇
排序方式: 共有3060条查询结果,搜索用时 15 毫秒
961.
Faculty evaluation of the clinical performance of medical students and residents is a great responsibility. However, many faculty members are reluctant to fulfill this responsibility with complete candor because of the fear of legal liability and lawsuits by dissatisfied students. This article examines current methods and uses of evaluation and problems created when they are incomplete or disingenuous. Legal issues arising in this process are then discussed, with emphasis upon the Supreme Court's 1978 Horowitz decision. Finally, the substantive and procedural implications of Horowitz for faculty practice are explained. It is argued that the law permits and encourages full and honest faculty evaluation of clinical performance.  相似文献   
962.
963.
964.
Coping and adaptation theory is used to synthesis existing data concerning psychological recovery from acute spinal cord injury. Psychological reactions to spinal cord trauma are similar to those of mourning and other situations of severe loss. Each reaction plays a specific role in fostering or hindering recovery depending upon when it occurs. Premorbid personality and the influence of significant others play a central role in coping with injury. These factors partly explain why some patients cope better than others to equally serious disability. A critique of research methodologies and suggestions for new studies are provided.  相似文献   
965.
966.
The decline in birthrates in the developed countries of the world has forced multinational corporations engaged in the production of infant formula to seek out new markets in the developing countries, where burgeoning population rates potentially guarantee the long-term profitability of these corporations. This development, ostensibly benign and nutritionally advantageous to infants in developing countries, has serious public health consequences, due to the high relative cost of purchased formula and the paucity of hygienic facilities essential to the sterile preparation of bottle formula. This paper delineates in detail economic and contraceptive advantages of breast-feeding, and examines the role of health personnel and multinational advertising techniques which have catalyzed the decline in breast-feeding. In addition, the paper focuses on the question of cultural imperialism and current efforts to regulate the multinational firms through both United Nations groups and stock-holders' suits. Finally, some suggestions are made concerning ameliorative public policy approaches to the breast-feeding controversy.  相似文献   
967.
968.
Forty-three patients with aortic rupture secondardy to blunt trauma have been treated at the University of Micigan within the past 10 years with an overall salvage rate of 70%. The diagnosis should be suspected in anyone who has sustained a high speed decelerating injury, if the chest roentgenogram shows media-stinal widening, whether or not there is hypertension of the upper extremities; systolic murmur, or external evidence of chest injury. Aortography should be employed to confirm the diagnosis and to determine the site or sites of rupture. Repair of the lesion should be undertaken as soon as possible and takes priority in most instances over associated injuries. Repair in almost all cases can be accomplished safely and quickly using a bypass shunt without the aid of extracorporeal circulation.  相似文献   
969.
Plasma renin activity, renin substrate, angiotensin II, aldosterone and cortisol were measured concurrently and renin concentration calculated in plasma from mothers during labor and delivery, from cord and from newborn infants. The renin-angiotensin-aldosterone system was found strongly stimulated in both mother and fetus. The high values of plasma renin activity in fetus were due exclusively to the high renin concentrations the substrate concentration being normal. In the mother, however, the markedly elevated renin substrate resulted in a doubling of relative values of renin activity compared to renin concentration. Therefore gradients of renin and renin substrate across the placenta are established, but the resulting renin activity is similar on both sides and the levels of generated angiotensin II are also nearly indentical with a good correlation between these last parameters. Aldosterone is as elevated in mother as in fetus whereas cortisol, due to its binding to transcortin, is twice as high in mother as in fetus. No correlation was found between renin activity or concentration of angiotensin II and aldosterone or cortisol indicating that other factors controlling aldosterone are involved.  相似文献   
970.
The relationship between early and late epicardial electrocardiographic changes as well as those in regional myocardial blood flow (MBF) and the severity of myocardial damage was determined in 12 anesthetized dogs with left anterior descending coronary artery ligation. Radioactive microspheres (15 mum) were used to measure regional MBF at 15 min (early) and 24 h (late) after coronary occlusion. Severity of myocardial damage was assessed by the extent of myocardial creatine phosphokinase depletion 24 h after coronary ligation. There was a close linear correlation between myocardial creatine phosphokinase activity and regional MBF both early (r=0.93, 2P less than 0.001) and late (r=0.88, 2P less than 0.001). An inverse but less precise relationship existed between acute epicardial ST-segment elevation and early (r=-0.41, 2P less than 0.001), or late (r=0.35, 2P less than 0.05) regional MBF. Similarly, a weak correlation was found between myocardial creatine phosphokinase (IU/mg protein) at 24 h and early epicardial ST (millivolt) elevation (r=-0.36, 2P less than 0.02). In the center zones of the infarct with MBF 1/10 of normal, about 35% of the areas with normal QRS width had no epicardial ST-segment elevation 15 min after coronary occlusion. About 44% of the areas which developed pathological Q-waves in the electrocardiogram at 24 h had no ST elevation 15 min after coronary ligation. Late evolution of abnormal Q-waves occurred almost invariably in areas in which the early MBF was reduced to less than 50% of normal and in areas which subsequently had myocardial creatine phosphokinase levels reduced to less than 60% of normal. After coronary occlusion, the severity of the ultimate myocardial damage, which was directly proportional to the degree of reduction in MBF, was therefore not reliably predicted by the early epicardial ST-segment elevation. The data obtained in these studies suggest the need for caution in the use of acute ST-segment elevation as a predictive index of the extent or severity of myocardial ischemic damage.  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