全文获取类型
收费全文 | 94479篇 |
免费 | 20315篇 |
国内免费 | 6694篇 |
出版年
2024年 | 158篇 |
2023年 | 917篇 |
2022年 | 2321篇 |
2021年 | 4043篇 |
2020年 | 4492篇 |
2019年 | 6500篇 |
2018年 | 6349篇 |
2017年 | 6033篇 |
2016年 | 6898篇 |
2015年 | 8223篇 |
2014年 | 8809篇 |
2013年 | 9334篇 |
2012年 | 8273篇 |
2011年 | 7313篇 |
2010年 | 6567篇 |
2009年 | 5050篇 |
2008年 | 4474篇 |
2007年 | 3660篇 |
2006年 | 3207篇 |
2005年 | 2731篇 |
2004年 | 2271篇 |
2003年 | 2154篇 |
2002年 | 1717篇 |
2001年 | 1364篇 |
2000年 | 1255篇 |
1999年 | 1101篇 |
1998年 | 649篇 |
1997年 | 542篇 |
1996年 | 560篇 |
1995年 | 480篇 |
1994年 | 491篇 |
1993年 | 364篇 |
1992年 | 494篇 |
1991年 | 353篇 |
1990年 | 303篇 |
1989年 | 279篇 |
1988年 | 219篇 |
1987年 | 216篇 |
1986年 | 187篇 |
1985年 | 165篇 |
1984年 | 122篇 |
1983年 | 132篇 |
1982年 | 86篇 |
1981年 | 52篇 |
1980年 | 52篇 |
1979年 | 68篇 |
1976年 | 48篇 |
1974年 | 55篇 |
1973年 | 48篇 |
1972年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Oscar Fernandez‐Capetillo 《EMBO reports》2010,11(1):32-36
Ageing is an unavoidable corollary to being alive; the most intuitive interpretation of ageing being that it is the consequence of progressive body degeneration. In agreement with this, current models propose that ageing occurs through a stepwise accumulation of DNA damage, which ultimately limits the regenerative capacity of tissues. On the other hand, there is increasing evidence that fetal distress can influence the development of disease in adult life, a phenomenon known as ‘intrauterine programming’. The extent to which an intrauterine exposure to DNA damage can compromise lifespan remains unclear. My group has recently generated a murine model of a human syndrome linked to defective DNA repair and observed that these animals age prematurely, but the accumulation of DNA damage is restricted mostly to the embryonic period. Here, I discuss the implications of this finding and propose that ageing can be influenced by fetal distress. 相似文献
133.
134.
Véronique Lavoie Anne‐Elen Kernaleguen Guy Charron Nada Farhat Mariève Cossette Aida M. Mamarbachi Bruce G. Allen Eric Rhéaume Jean‐Claude Tardif 《Obesity (Silver Spring, Md.)》2011,19(4):722-728
Adiponectin is an adipokine whose plasma levels are inversely correlated to metabolic syndrome components. Adiponectin protects against atherosclerosis and decreases risks in myocardial infarction. Endothelial progenitor cells (EPCs) are a heterogeneous population of circulating cells involved in vascular repair and neovascularization. EPCs number is reduced in patients with cardiovascular disease. We hypothesize that the positive effects of adiponectin against atherosclerosis are explained in part by its interactions with EPCs. Cells were obtained from healthy volunteers' blood by mononuclear cell isolation and plating on collagen‐coated dishes. Three sub‐populations of EPCs were identified and characterized using flow cytometry. EPCs' expression of adiponectin receptors, AdipoR1, and AdipoR2 was evaluated by quantitative PCR. The effects of recombinant adiponectin on EPCs' susceptibility to apoptosis were assessed. Finally, expression of neutrophil elastase by EPCs and activity of this enzyme on adiponectin processing were assessed. Quantitative PCR analysis of EPCs mRNAs showed that AdipoR1 mRNA is expressed at higher levels than AdipoR2. Expression of AdipoR1 protein was confirmed by western blot. Adiponectin significantly increased survival of two sub‐populations of EPCs in conditions of serum deprivation. Such effect could not be demonstrated in the third EPCs sub‐population. We also demonstrated that EPCs, particularly one sub‐population, express neutrophil elastase. Neutrophil elastase activity was confirmed in EPCs' conditioned media. Adiponectin protects some EPCs sub‐populations against apoptosis and therefore could modulate EPCs ability to induce repair of vascular damage. Neutrophil elastase activity of EPCs could locally modulate adiponectin activity by its involvement in the generation of the globular form of adiponectin. 相似文献
135.
After observing specimens of Calligonum pumilum Losinsk. and C. juochiangense Y. X. Liou in both the field and in herbarium collections, it was found that the morphological characters of these two species are quite different, especially with respect of the twisted direction of fruit ribs, number of bristle rows along each rib, rigidity and degree of interweaving of bristles, as well as their geographic distribution. Therefore, it is concluded that C. pumilum and C. juochiangense should be accepted as two independent species. 相似文献
136.
137.
138.
Yao Chen Jie Zhu Jun Mo Hongyu Yang Xueyang Jiang Hongzhi Lin 《Journal of enzyme inhibition and medicinal chemistry》2018,33(1):290-302
Small molecule cholinesterases inhibitor (ChEI) provides an effective therapeutic strategy to treat Alzheimer’s disease (AD). Currently, the discovery of new ChEI with multi-target effect is still of great importance. Herein, we report the synthesis, structure–activity relationship study and biological evaluation of a series of tacrine-cinnamic acid hybrids as new ChEIs. All target compounds are evaluated for their in vitro cholinesterase inhibitory activities. The representatives which show potent activity on cholinesterase, are evaluated for the amyloid β-protein self-aggregation inhibition and in vivo assays. The optimal compound 19, 27, and 30 (human AChE IC50?=?10.2?±?1.2, 16.5?±?1.7, and 15.3?±?1.8?nM, respectively) show good performance in ameliorating the scopolamine-induced cognition impairment and preliminary safety in hepatotoxicity evaluation. These compounds deserve further evaluation for the development of new therapeutic agents against AD. 相似文献
139.
140.
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