全文获取类型
收费全文 | 5428篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 19篇 |
建筑科学 | 4篇 |
轻工业 | 2篇 |
无线电 | 4篇 |
一般工业技术 | 5篇 |
冶金工业 | 5391篇 |
原子能技术 | 1篇 |
自动化技术 | 3篇 |
出版年
2014年 | 1篇 |
2013年 | 1篇 |
2011年 | 1篇 |
2009年 | 1篇 |
2006年 | 3篇 |
2004年 | 2篇 |
2003年 | 8篇 |
2000年 | 1篇 |
1999年 | 157篇 |
1998年 | 1645篇 |
1997年 | 893篇 |
1996年 | 636篇 |
1995年 | 324篇 |
1994年 | 313篇 |
1993年 | 330篇 |
1992年 | 36篇 |
1991年 | 57篇 |
1990年 | 77篇 |
1989年 | 65篇 |
1988年 | 62篇 |
1987年 | 82篇 |
1986年 | 58篇 |
1985年 | 57篇 |
1984年 | 1篇 |
1983年 | 11篇 |
1982年 | 30篇 |
1981年 | 34篇 |
1980年 | 39篇 |
1979年 | 1篇 |
1978年 | 8篇 |
1977年 | 143篇 |
1976年 | 336篇 |
1975年 | 10篇 |
1965年 | 1篇 |
1955年 | 5篇 |
排序方式: 共有5429条查询结果,搜索用时 15 毫秒
21.
22.
Three cases of haematemesis associated with alcohol abuse are described. Early fibreoptic endoscopical examination in each showed a focal, well demarcated area of gastric mucosal haemorrhage, close to the oesophagogastric junction. Two patients showed prolapse of the lesion into the lower part of the oesophagus, and the third had coexistent Mallory-Weiss tears. Our observations suggest that forceful vomiting is responsible for this lesion, by causing abrupt retrograde gastrooesophageal prolapse. The prognosis of the lesion appears good. 相似文献
23.
Commercially available lots of plasma derivatives prepared between 1957 and 1975 were tested for hepatitis B surface antigen (HBsAg) by radioimmunoassay. In all, 69 per cent of lots of plasma protein fraction, 40 per cent of factor IX concentrate, 20 per cent of normal serum albumin, 13 per cent of antihemophilic factor, 3 per cent of fibrinogen, and 0.7 per cent of immune serum globulin lots tested were HBsAg-positive. There was great variation in the prevalence of HBsAg-positive lots of each product among the different manufacturers, reflecting not only differences in methods of processing plasma, but also differences in donor populations. Those manufacturers relying upon volunteer donor plasma or placental source material demonstrated lower rates of HBsAg-positive lots of final products than those relying upon commercial donor plasma. There was a marked decrease in the prevalence of positive lots during the period 1971 to 1973, coincident with the onset of routine plasma donor screening for HBsAg. However, current requirements for plasma screening have not resulted in totally HBsAg-free plasma products. Use of more sensitive and more reliable tests for HBsAg will probably reduce contamination of plasma pools with HBsAg to undetectable levels. Despite HBsAg-status, however, the "high-risk" plasma products (fibrinogen, antihemophilic factor, factor IX concentrate) must still be considered capable of transmitting hepatitis and used only with the strictest indications. 相似文献
24.
25.
26.
RJ Harris 《Canadian Metallurgical Quarterly》1976,62(2):287-298
27.
28.
29.
30.