全文获取类型
收费全文 | 2190篇 |
免费 | 5篇 |
专业分类
化学工业 | 15篇 |
金属工艺 | 1篇 |
建筑科学 | 1篇 |
能源动力 | 1篇 |
轻工业 | 3篇 |
石油天然气 | 1篇 |
无线电 | 14篇 |
一般工业技术 | 9篇 |
冶金工业 | 2137篇 |
自动化技术 | 13篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2006年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
1999年 | 69篇 |
1998年 | 624篇 |
1997年 | 360篇 |
1996年 | 265篇 |
1995年 | 154篇 |
1994年 | 117篇 |
1993年 | 126篇 |
1992年 | 21篇 |
1991年 | 34篇 |
1990年 | 26篇 |
1989年 | 39篇 |
1988年 | 43篇 |
1987年 | 38篇 |
1986年 | 25篇 |
1985年 | 35篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1978年 | 3篇 |
1977年 | 40篇 |
1976年 | 88篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有2195条查询结果,搜索用时 0 毫秒
51.
52.
The temporal changes in progesterone (delta 4P), 20 alpha-dihydroprogesterone (20 alpha-DHP) and luteinizing hormone (LH) concentrations in pseudopregnant (PSP) rats after treatment with a single subcutaneous Silastic-PVP tube containing 600 micrograms PGF2 alpha were correlated. Progesterone levels fell and LH levels rose significantly 2h after initiation of treatment, while 20 alpha-DHP levels were found to increase significantly 12h after treatment. Since the changes in delta 4P and LH concentrations occurred concurrently, it seems that the increase in LH levels could have been due to a direct effect of PGF2 alpha on the ovary causing a reduction in delta 4P and thus a negative feedback effect on LH release. Alternatively, PGF2 alpha might exert a direct effect on LH secretion at the hypothalamic-pituitary level. 相似文献
53.
54.
55.
56.
7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline (DCTQ) (50 mg/kg i.p.) antagonized the inactivation of MAO by pargyline as measured by direct enzyme assays in brain homogenates and by accumulation of hypothalamic catecholamines. These findings lend credence to the earlier interpretation that changes in brain concentrations of biogenic amines and their metabolites in DCTQ-treated rats were due at least in part to MAO inhibition. 相似文献
57.
58.
59.
Polypropylene mesh, the routinely used material for mesh laparostomies is expensive. A economical and easily available substitute-nylon net was compared with polypropylene mesh with regard to efficacy and wound complications in a retrospective study. 51 patients, 25 in the polypropylene mesh group and 26 in the nylon net group were studied. The groups were matched with respect to age, sex, indication for surgery and mortality. The mean hospital stay (65 vs 54 days), fate of the wound, incidence of mesh extrusion (26% vs 20%), bowel perforation (1 vs none) and incisional hernia formation (21% vs 20%) in those with polypropylene mesh and nylon net respectively was similar. In conclusion, nylon net is an effective and inexpensive indigenous substitute for polypropylene mesh for mesh laparostomies. 相似文献
60.