全文获取类型
收费全文 | 26288篇 |
免费 | 2481篇 |
国内免费 | 3955篇 |
专业分类
32724篇 |
出版年
2024年 | 105篇 |
2023年 | 414篇 |
2022年 | 962篇 |
2021年 | 1423篇 |
2020年 | 1157篇 |
2019年 | 1286篇 |
2018年 | 1181篇 |
2017年 | 912篇 |
2016年 | 1251篇 |
2015年 | 1877篇 |
2014年 | 2188篇 |
2013年 | 2238篇 |
2012年 | 2741篇 |
2011年 | 2526篇 |
2010年 | 1567篇 |
2009年 | 1440篇 |
2008年 | 1638篇 |
2007年 | 1365篇 |
2006年 | 1204篇 |
2005年 | 1026篇 |
2004年 | 898篇 |
2003年 | 750篇 |
2002年 | 621篇 |
2001年 | 382篇 |
2000年 | 309篇 |
1999年 | 278篇 |
1998年 | 170篇 |
1997年 | 127篇 |
1996年 | 111篇 |
1995年 | 104篇 |
1994年 | 76篇 |
1993年 | 47篇 |
1992年 | 59篇 |
1991年 | 57篇 |
1990年 | 38篇 |
1989年 | 38篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1974年 | 2篇 |
1965年 | 4篇 |
1950年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Clinical application of free digital artery flap of the hand 总被引:1,自引:0,他引:1
82.
报道了发现于辽宁省的2种中国归化植物新记录:白毛马鞭草(Verbena stricta Vent.)和向日葵(Helianthus annuus L.),白毛马鞭草穗状花序粗壮而紧凑,单生枝顶或呈简单的聚伞状或圆锥状排列,且花序轴在果期显著延长,叶卵圆形,无柄,与中国有报道的本属其他物种区别明显。该种原产美国西部至中部地区,近来在辽宁省铁岭市发现有归化。向日葵原产于北美地区,被发现广泛归化于辽宁省大连市,营口市鲅鱼圈也有发现。归化种群形态特征与该地区栽培类型完全不同,其花序极多分枝,头状花序直径较小,瘦果极小,表面纹饰多样性很高。 相似文献
83.
Guiyuan Ji Yupei Zhang Qinhe Yang Shaobin Cheng Jing Hao Xihong Zhao Zhuoqin Jiang 《PloS one》2012,7(12)
Genistein, the major isoflavone in soybean, was recently reported to exert beneficial effects in metabolic disorders and inflammatory diseases. In the present study, we investigated the effects and mechanisms of a dietary concentration of genistein on the inflammatory response in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages. Our results demonstrated that genistein effectively inhibited the LPS-induced overproduction of tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6), as well as LPS-induced nuclear factor kappa B (NF-κB) activation. In addition, the data also showed that genistein prevented LPS-induced decrease in adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. These effects were obviously attenuated by an AMPK inhibitor. Taken together, our results suggest that the dietary concentration of genistein is able to attenuate inflammatory responses via inhibition of NF-κB activation following AMPK stimulation. The data provide direct evidence for the potential application of low concentrations of genistein in the prevention and treatment of inflammatory diseases. 相似文献
84.
Govindan Raghunathan Nagasundarapandian Soundrarajan Sriram Sokalingam Hyungdon Yun Sun-Gu Lee 《PloS one》2012,7(12)
Diversification of protein sequence-structure space is a major concern in protein engineering. Deletion mutagenesis can generate a protein sequence-structure space different from substitution mutagenesis mediated space, but it has not been widely used in protein engineering compared to substitution mutagenesis, because it causes a relatively huge range of structural perturbations of target proteins which often inactivates the proteins. In this study, we demonstrate that, using green fluorescent protein (GFP) as a model system, the drawback of the deletional protein engineering can be overcome by employing the protein structure with high stability. The systematic dissection of N-terminal, C-terminal and internal sequences of GFPs with two different stabilities showed that GFP with high stability (s-GFP), was more tolerant to the elimination of amino acids compared to a GFP with normal stability (n-GFP). The deletion studies of s-GFP enabled us to achieve three interesting variants viz. s-DL4, s-N14, and s-C225, which could not been obtained from n-GFP. The deletion of 191–196 loop sequences led to the variant s-DL4 that was expressed predominantly as insoluble form but mostly active. The s-N14 and s-C225 are the variants without the amino acid residues involving secondary structures around N- and C-terminals of GFP fold respectively, exhibiting comparable biophysical properties of the n-GFP. Structural analysis of the variants through computational modeling study gave a few structural insights that can explain the spectral properties of the variants. Our study suggests that the protein sequence-structure space of deletion mutants can be more efficiently explored by employing the protein structure with higher stability. 相似文献
85.
Yun Wang Hong-Jie Yan Shu-Yan Zhou Yun-Shuang Wang Hui Qi Chun-Yan Deng Fu-Rong Li 《PloS one》2014,9(4)
Islet transplantation has considerable potential as a cure for diabetes. However, the difficulties that arise from inflammation and the immunological rejection of transplants must be addressed for islet transplantation to be successful. Alpha 1-antitrypsin (AAT) inhibits the damage on β cells caused by inflammatory reactions and promotes β-cell survival and proliferation. This protein also induces specific immune tolerance to transplanted β cells. However, whether the expression of AAT in β cells themselves could eliminate or decrease immunological rejection of transplants is not clear. Therefore, we established a β cell line (NIT-hAAT) that stably expresses human AAT. Interestingly, in a cytotoxic T lymphocyte (CTL)-killing assay, we found that hAAT reduced apoptosis and inflammatory cytokine production in NIT-1 cells and regulated the Th1/Th2 cytokine balance in vitro. In vivo transplantation of NIT-hAAT cells into mice with diabetes showed hAAT inhibited immunological rejection for a short period of time and increased the survival of transplanted β cells. This study demonstrated that hAAT generated remarkable immunoprotective and immunoregulation effects in a model of β cell islet transplantation for diabetes model. 相似文献
86.
87.
目的用micro-CT方法,评估中等强度跑台运动对去卵巢大鼠腰椎微结构的影响。方法将30只3月龄雌性SD大鼠按体重分层后随机分为假手术、去卵巢静止和去卵巢运动三个组。运动组每周进行4次45min、速度18 m/min、坡度5°的跑台训练。正式运动处理14周时,取第2腰椎检测骨密度,取第4腰椎行micro-CT分析及三维结构重建;取第3腰椎椎体进行椎体压缩实验。结果去卵巢运动组第2腰椎骨密度、第3腰椎最大载荷、最大应力和弹性模量以及第4腰椎骨小梁体积和骨小梁数目显著高于去卵巢静止组,骨小梁分离度显著低于去卵巢静止组,而骨小梁厚度无显著变化。结论中等强度跑台运动能改善去卵巢大鼠腰椎的微结构。 相似文献
88.
Mitigation of ammonia inhibition by internal dilution in high‐rate anaerobic digestion of food waste leachate and evidences of microbial community response 下载免费PDF全文
89.
细胞外基质不仅维持着体内细胞微环境的稳定,还在细胞的正常生长、增殖以及细胞之间的信号传导中起着重要作用。肿瘤发生时,基质中的分子组分发生了改变,这些改变朝着有利于肿瘤细胞生长侵袭的方向发展。在这个过程中,细胞外基质的主要成分在合成和分解上发生巨大变化,胶原分子便是其中之一,胶原分子作为细胞外基质中的主要成分,对细胞的黏附、运动、迁移等活动起着重要作用。随着研究的深入,发现越来越多的胶原分子参与了肿瘤的发生发展。基质中还存在着一些分子,它们在结构上和胶原蛋白一样含有三螺旋胶原结构域,在肿瘤的发生发展过程中同样发挥着重要作用。本文就包括胶原分子在内的含有胶原结构的分子在肿瘤中的作用做一综述。 相似文献
90.
Xun Wang Nora Fung-Yee Tam Shi Fu Aray Ametkhan Yun Ouyang Zhihong Ye 《Annals of botany》2014,114(2):271-278