全文获取类型
收费全文 | 2051篇 |
免费 | 0篇 |
专业分类
化学工业 | 9篇 |
金属工艺 | 2篇 |
建筑科学 | 5篇 |
轻工业 | 2篇 |
无线电 | 2篇 |
一般工业技术 | 1篇 |
冶金工业 | 2030篇 |
出版年
2020年 | 3篇 |
2019年 | 1篇 |
2011年 | 1篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 57篇 |
1998年 | 621篇 |
1997年 | 363篇 |
1996年 | 216篇 |
1995年 | 151篇 |
1994年 | 108篇 |
1993年 | 134篇 |
1992年 | 21篇 |
1991年 | 33篇 |
1990年 | 29篇 |
1989年 | 30篇 |
1988年 | 25篇 |
1987年 | 22篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 20篇 |
1978年 | 4篇 |
1977年 | 45篇 |
1976年 | 82篇 |
1975年 | 1篇 |
排序方式: 共有2051条查询结果,搜索用时 15 毫秒
81.
The use of bone grafts is the basis of all craniofacial surgery. Bone grafts are used to stabilize the open segments, expand the patient's structural boundaries, and fill defects created by trauma or congenital malformations. Bone grafts are harvested from local or distant sites as indicated. Biomaterial implants are used as bone substitutes when it is not possible to use bone grafts. 相似文献
82.
83.
84.
85.
86.
The seasonal distribution of cryptosporidiosis in children in Aragón, a region in northeastern Spain, was determined. Over a period of six years (October 1988 to September 1994), 10,034 stool samples from 4,508 children with gastrointestinal symptoms were analyzed for this purpose. The age of the patients ranged from 1 month to 14 years. Cryptosporidium oocysts were identified in 87 (1.93%) patients. Prevalence was highest (6.20%) in children aged 1 to 3 years old. The prevalence was significantly higher in the autumn-winter period (October to March) than in the spring-summer period (April to September) in the whole population (2.41% vs. 1.35%, p = 0.010) and in the 1- to 3-year-old age group (8.44% vs. 3.20%, p = 0.002), but not in the other age groups. A possible relationship of this pattern to attendance at child care centres is suggested. 相似文献
87.
Spore cortex of conditional cortexless mutants of Bacillus sphaericus 9602 was not detectable by electron microscopy unless the medium was supplemented with meso-alpha,epsilon-diaminopimelic acid during sporulation. Other spore structures appeared normal. Spore shape was quite irregular in the absence of meso-alpha,epsilon-diaminopimelic acid. 相似文献
88.
89.
90.