全文获取类型
收费全文 | 185617篇 |
免费 | 14864篇 |
国内免费 | 52篇 |
专业分类
200533篇 |
出版年
2018年 | 1856篇 |
2017年 | 1799篇 |
2016年 | 2304篇 |
2015年 | 2239篇 |
2014年 | 3084篇 |
2013年 | 4356篇 |
2012年 | 4998篇 |
2011年 | 5472篇 |
2010年 | 3820篇 |
2009年 | 3478篇 |
2008年 | 5055篇 |
2007年 | 5324篇 |
2006年 | 4976篇 |
2005年 | 4709篇 |
2004年 | 4855篇 |
2003年 | 4749篇 |
2002年 | 4714篇 |
2001年 | 8519篇 |
2000年 | 8724篇 |
1999年 | 6431篇 |
1998年 | 2054篇 |
1997年 | 2101篇 |
1996年 | 1852篇 |
1995年 | 1735篇 |
1992年 | 5315篇 |
1991年 | 5459篇 |
1990年 | 5218篇 |
1989年 | 5210篇 |
1988年 | 4823篇 |
1987年 | 4574篇 |
1986年 | 4139篇 |
1985年 | 4291篇 |
1984年 | 3461篇 |
1983年 | 2969篇 |
1982年 | 1986篇 |
1981年 | 1772篇 |
1980年 | 1759篇 |
1979年 | 3270篇 |
1978年 | 2592篇 |
1977年 | 2315篇 |
1976年 | 2124篇 |
1975年 | 2593篇 |
1974年 | 2920篇 |
1973年 | 2850篇 |
1972年 | 2676篇 |
1971年 | 2446篇 |
1970年 | 2156篇 |
1969年 | 2037篇 |
1968年 | 1931篇 |
1967年 | 1754篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Blood smears of both male and female chicken Gallus domesticus were analysed by using the following topochemical methods: a) Periodic acid-Schiff (PAS) for glycogen. b) Mercury-bromophenol blue for protein. c) O-Toluidine for myeloperoxidase. d) Sudan black B for lipid. The PAS reaction revealed glycogen in the cytoplasm of all thrombocytes and in a few heterophils. The presence of proteins was evidenced in all types of cells. However variation in the intensity of staining of protein granules was observed in the fusiform structures of the heterophils. A negative reaction for myeloperoxidase was found in all cells. Although some evidence of myeloperoxidase activity was show in the polymorphonuclears it was not enough to ascertain a positive reaction. Lipids were detected in the cytoplasm of few heterophils, eosinophils and monocytes. 相似文献
82.
The potent rat-liver mitogen 4-acetylaminofluorene (4AAF) is shown here to provide an effective replacement for the surgical procedure of 2/3 partial hepatectomy (2/3PH) in the in vivo rat-liver micronucleus assay described by Tates and his colleagues. This protocol modification enables the assay to be conducted on a routine basis. Control observations for both 2/3PH and 4AAF-treated rats are presented, together with evidence indicating 4AAF itself to be without activity in the assay, irrespective of the mitogenic stimulus. The activities of the rat carcinogens DMN, 2AAF, DMH and 6BT, and of the non-carcinogens 4AAF and 4N are demonstrated. Recommendations for the conduct of the modified assay are made. 相似文献
83.
84.
85.
86.
87.
88.
89.
90.
The dopamine metabolite, homovanillic acid, decreases in concentration in plasma between 8:30 A.M. and 12:30 P.M. In patients with schizophrenia this cyclic change is attenuated by chronic neuroleptic treatment; however, if the 8 A.M. dose of neuroleptic is omitted, the decrease in level occurs. Presuming that neuroleptics attenuate the decline through a receptor mediated compensatory increase in dopamine release, it would appear that receptors are not fully occupied by neuroleptics even at therapeutically effective doses. The usual morning decrease in plasma cortisol levels was unaffected by neuroleptics. 相似文献