全文获取类型
收费全文 | 45047篇 |
免费 | 6116篇 |
国内免费 | 20568篇 |
出版年
2024年 | 504篇 |
2023年 | 1390篇 |
2022年 | 2351篇 |
2021年 | 2808篇 |
2020年 | 2446篇 |
2019年 | 2816篇 |
2018年 | 2144篇 |
2017年 | 1896篇 |
2016年 | 2114篇 |
2015年 | 2882篇 |
2014年 | 3924篇 |
2013年 | 3507篇 |
2012年 | 4700篇 |
2011年 | 4501篇 |
2010年 | 3486篇 |
2009年 | 3560篇 |
2008年 | 3865篇 |
2007年 | 3628篇 |
2006年 | 3325篇 |
2005年 | 2755篇 |
2004年 | 2203篇 |
2003年 | 1927篇 |
2002年 | 1747篇 |
2001年 | 1644篇 |
2000年 | 1510篇 |
1999年 | 975篇 |
1998年 | 551篇 |
1997年 | 319篇 |
1996年 | 313篇 |
1995年 | 225篇 |
1994年 | 223篇 |
1993年 | 167篇 |
1992年 | 147篇 |
1991年 | 156篇 |
1990年 | 133篇 |
1989年 | 116篇 |
1988年 | 102篇 |
1987年 | 82篇 |
1986年 | 69篇 |
1985年 | 91篇 |
1984年 | 43篇 |
1983年 | 51篇 |
1982年 | 64篇 |
1981年 | 35篇 |
1980年 | 14篇 |
1958年 | 21篇 |
1957年 | 19篇 |
1955年 | 16篇 |
1954年 | 19篇 |
1950年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
An interspecific somatic hybrid between Actinidia chinensis and Actinidia kolomikta and its chilling tolerance 总被引:2,自引:0,他引:2
Protoplasts isolated from cotyledon-derived callus of Actinidia chinensisPlanch. var. chinensis (2N=2x=58) were fused with mesophyll protoplasts of Actiniadia kolomikta(Maxim. et Rupr.) Maxim (2N=2x=58) using a PEG method. Plantlets were regenerated from the fusion product clone 11. RAPD analyses, chromosome numbers of root tip cells and fluorescence peak position of leaf nuclei confirmed that clone 11 was an interspecific somatic hybrid (2N=4x=116) between A. chinensis and A. kolomikta. The chilling tolerance of the somatic hybrid was tested with in vitro leaves at low temperatures. Based on data of leaf thickness, electroconductivity, proline levels, malondialdehyde content and activity of superoxide dismutase, dendrogram cluster analysis suggested that the interspecific somatic hybrid was similar to A. kolomikta, and might have a higher capacity of cold resistance than A. chinensis. 相似文献
22.
23.
Xiao Zhang Jinpeng Li Bo Yang Qina Leng Ji Li Xintuan Wang Junyao Lu Opeyemi Joshua Olatunji Jian Tang 《化学与生物多样性》2021,18(5):e2100065
This study investigated the protective effects of two polysaccharides (CPA-1 and CPB-2) from Cordyceps cicadae against high fructose/high fat diet (HF/HFD) induced obesity and metabolic disorders in rats. Rats were either fed with normal diet or HF/HFD and treated with CPA-1 and CPB-2 (100 and 300 mg/kg) for 11 weeks. Administration of CPA-1 and CPB-2 significantly and dose dependently reduced body and liver weight, insulin and glucose tolerance, serum insulin and glucose levels. Furthermore, serum and hepatic lipid profiles, liver function enzymes and proinflammatory cytokines (TNF-α, IL-1β and IL-6) were markedly reduced. Additionally, CPA-1 and CPB-2 treatment alleviated hepatic oxidative stress by reducing lipid peroxidation level (MDA) and upregulating glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activities as well as ameliorated histological alterations through the reduction of hepatic lipid accumulation. These results suggested that the polysaccharides from C. cicadae showed protective effects against HF/HFD induced metabolic disturbances and may be considered as a dietary supplement for treating obesity. 相似文献
24.
25.
26.
27.
28.
29.
30.