全文获取类型
收费全文 | 3020篇 |
免费 | 36篇 |
国内免费 | 4篇 |
专业分类
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 |
出版年
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.
MB Kapp 《Canadian Metallurgical Quarterly》1981,56(7):559-564
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.
MB Bader 《Canadian Metallurgical Quarterly》1976,6(4):609-626
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.
MM Kirsh DM Behrendt MB Orringer O Gago LA Gray LJ Mills JF Walter H Sloan 《Canadian Metallurgical Quarterly》1976,184(3):308-316
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