全文获取类型
收费全文 | 538432篇 |
免费 | 67058篇 |
国内免费 | 188篇 |
出版年
2018年 | 4676篇 |
2016年 | 6209篇 |
2015年 | 8559篇 |
2014年 | 10332篇 |
2013年 | 14585篇 |
2012年 | 16124篇 |
2011年 | 16059篇 |
2010年 | 10472篇 |
2009年 | 9863篇 |
2008年 | 13904篇 |
2007年 | 14636篇 |
2006年 | 13521篇 |
2005年 | 13127篇 |
2004年 | 12931篇 |
2003年 | 12424篇 |
2002年 | 11931篇 |
2001年 | 22833篇 |
2000年 | 23345篇 |
1999年 | 18627篇 |
1998年 | 6486篇 |
1997年 | 6892篇 |
1996年 | 6664篇 |
1995年 | 6618篇 |
1994年 | 6587篇 |
1993年 | 6511篇 |
1992年 | 16326篇 |
1991年 | 16191篇 |
1990年 | 15851篇 |
1989年 | 15415篇 |
1988年 | 14436篇 |
1987年 | 13864篇 |
1986年 | 12967篇 |
1985年 | 13113篇 |
1984年 | 11016篇 |
1983年 | 9715篇 |
1982年 | 7497篇 |
1981年 | 7040篇 |
1980年 | 6604篇 |
1979年 | 10997篇 |
1978年 | 8531篇 |
1977年 | 7871篇 |
1976年 | 7468篇 |
1975年 | 8281篇 |
1974年 | 8574篇 |
1973年 | 8419篇 |
1972年 | 7964篇 |
1971年 | 6924篇 |
1970年 | 6065篇 |
1969年 | 5728篇 |
1968年 | 5215篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Iu V Ladilov B I Islamov S I Vorob'ev G R Ivanitski? 《Biulleten' eksperimental'no? biologii i meditsiny》1992,113(6):593-595
The effect of different doses of perfluorocarbon emulsion (5, 10, and 15 ml/kg) on the hemodynamics and contractility of heart was studied on anesthetized dogs. The emulsion was introduced intravenously by the 60th minute of acute myocardium ischemia caused by partial coronary occlusion. When pO2 = 120 mm Hg, the emulsion was efficient only at doses of 10 and 15 ml/kg (an increase in cardiac ejection, in the rate of contraction and relaxation of the myocardium, reduction of vascular resistance). However, the efficiency of the emulsion at a dose of 15 ml/kg was lower, possibly, due to hypervolemia and cardiodepressive effect of introduction of excess quantity of the surface-active substance proxanol, a component of the emulsion. 相似文献
63.
64.
65.
R K Daniel J Hodgson V S Lambros 《Plastic and reconstructive surgery》1990,85(6):859-66; discussion 867-8
The physical characteristics of the light reflexes of the nasal tip are defined in large part by the studio lighting configuration. By varying the lighting configuration, it is possible to alter the light reflexes as regards their number, distance apart, symmetry, and size. For the plastic surgeon, the quarter light system of the medical photographer has definite advantages over the key light system of the portrait photographer. The quarter light system consists of two lights of equal intensity with symmetrical angles of incidence placed at 45 degrees to the camera-subject axis. Measuring changes in the light reflexes as a method of determining the efficacy of surgical techniques is valid under very controlled conditions. 相似文献
66.
Characterisation of Pseudomonas rhamnolipids 总被引:5,自引:0,他引:5
N B Rendell G W Taylor M Somerville H Todd R Wilson P J Cole 《Biochimica et biophysica acta》1990,1045(2):189-193
The Gram negative organism, Pseudomonas aeruginosa, is often found in the lungs of patients with cystic fibrosis and other forms of severe bronchiectasis, where it secretes a number of extracellular toxins including the mono- and dirhamnolipids. The principal monorhamnolipid from P. aeruginosa has previously been identified as rhamnosyl-3-hydroxydecanoyl-3-hydroxydecanoate (Rh-C10.C10). A number of related mono- and dirhamnolipids have been purified from cultures of a clinical isolate of P. aeruginosa and identified by fast atom bombardment and electron impact mass spectrometry: these contain the 3-hydroxyoctanoyl-3-hydroxydecanoate (C8.C10) and 3-hydroxydecanoyl-3-hydroxydodecanoate (C10.C12) homologues. Structural isomers were also present where the order of the lipid linkage was transposed (Rh-C10.C8 and Rh-C12.C10). Unsaturated mono- and dirhamnolipids containing the 3-hydroxydecanoyl-3-hydroxydodec-5-enoate (C10.C12:1) lipid were also present. 相似文献
67.
The mitotic indices, villus heights, and crypt depths were determined in each of three jejunal regions (proximal, middle, and distal) for five animals each in the flight, vivarium, and synchronous groups. Because of the rapid turnover of intestinal mucosal cells and the delay in recovering the flight animals, it is not known whether the proliferation of jejunal mucosal cells is affected by microgravity conditions associated with spaceflight. However, since there were no consistent differences between animals in the flight group and those in the synchronous and vivarium control groups, it appears that any effects of microgravity on the turnover of jejunal mucosal cells are short-lived. Thus, this study represents an initial step in determining the effects of microgravity on the proliferation and turnover of intestinal mucosal cells. 相似文献
68.
Fusaric acid and other metabolite production in Fusarium oxysporum f. sp. vasinfectum 总被引:1,自引:0,他引:1
A thin layer chromatography system is described for the analysis of fusaric acid and other secondary metabolites, to assist in the identification of pathogenic races of Fusarium oxysporum f. sp. vasinfectum . There were differences in the metabolite profiles of the races grown on different media. 相似文献
69.
70.