全文获取类型
收费全文 | 13214篇 |
免费 | 1045篇 |
国内免费 | 1051篇 |
出版年
2024年 | 26篇 |
2023年 | 175篇 |
2022年 | 459篇 |
2021年 | 779篇 |
2020年 | 482篇 |
2019年 | 603篇 |
2018年 | 603篇 |
2017年 | 419篇 |
2016年 | 591篇 |
2015年 | 900篇 |
2014年 | 1052篇 |
2013年 | 1023篇 |
2012年 | 1267篇 |
2011年 | 1118篇 |
2010年 | 674篇 |
2009年 | 583篇 |
2008年 | 655篇 |
2007年 | 577篇 |
2006年 | 469篇 |
2005年 | 398篇 |
2004年 | 347篇 |
2003年 | 362篇 |
2002年 | 327篇 |
2001年 | 241篇 |
2000年 | 197篇 |
1999年 | 202篇 |
1998年 | 108篇 |
1997年 | 102篇 |
1996年 | 90篇 |
1995年 | 73篇 |
1994年 | 60篇 |
1993年 | 43篇 |
1992年 | 61篇 |
1991年 | 47篇 |
1990年 | 36篇 |
1989年 | 47篇 |
1988年 | 23篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 27篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1956年 | 1篇 |
1952年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Wei Wu Xiao‐Hui Jia Sha Zhang Chun‐Mao Dong Feng‐Hua Kang Zhen‐Xing Zou Kang‐Ping Xu 《化学与生物多样性》2020,17(6)
Two new abietane diterpenoids, (3S,5R,10S)‐3‐hydroxy‐12‐O‐demethyl‐11‐deoxy‐19(4→3)‐abeo‐cryptojaponol, 12,19‐dihydroxyabieta‐8,11,13‐trien‐7‐one, were isolated from Selaginella moellendorffii Hieron., together with one known abietane diterpenoid and four known tetracyclic triterpenoids. Their structures were characterized by their 1D‐ and 2D‐NMR, ECD and mass spectral studies. All compounds were tested for their inhibitory effects on proliferation of three human cancer cells (human non‐small‐cell lung carcinoma cell lines A549 and human breast adenocarcinoma cell lines MDA‐MB‐231 and MCF‐7) in vitro. Among them, three compounds displayed modest cytotoxic activities against the above three human cancer cell lines with IC50 values ranging from 16.28 to 40.67 μM. 相似文献
132.
133.
Jia Lijia Jiang Mengwei Wu Ke Hu Juefu Wang Yang Quan Weipeng Hao Mengchan Liu Haizhou Wei Hongping Fan Wenhui Liu Wenjun Hu Rongliang Wang Depeng Li Jing Chen Jianjun Liu Di 《中国科学:生命科学英文版》2020,63(1):160-164
正Dear Editor,African swine fever (ASF) is one of the most pathogenic viral diseases in pigs caused by African swine fever virus(ASFV). The fatality rate is almost 100%, which brings huge economic losses to the hog industry in countries with epi- 相似文献
134.
肺癌是当今世界最常见的恶性肿瘤之一,其新发率和死亡率多年来都居于各类癌症之首,其中85%的肺癌都是非小细胞癌,而腺癌又是最常见的非小细胞癌。肺癌的高隐匿性是造成其高死亡率的最主要原因,因此为肺癌的早期诊断和病理分期寻求高效可靠的方法是十分必要的。代谢组学揭示了小分子代谢物的一系列变化,反映了生命活动的最终状态,因此也能直接反映疾病不同发展阶段的病理生理变化。本研究利用核磁共振氢谱(1H-NMR),对在我院就诊的27例不同病理分期的肺腺癌患者和13例健康志愿者进行了血清代谢物分析,运用正交偏最小二乘判别分析(OPLS-DA)对1H-NMR数据进行建模,单变量统计分析对模型进行评价。结果表明肺腺癌患者组的血清中有14种代谢物出现明显差异,其中丙酮酸、丙氨酸、NAC1、乳酸、GPC和甘氨酸比起对照组来有显著上升,而葡萄糖、谷氨酰胺、亮氨酸、异亮氨酸、缬氨酸、丙酮、乙酰乙酸和苏氨酸则显著下降。而在不同分期肺腺癌患者间进行比较后发现,异亮氨酸、乙酰乙酸、NAC1和乳酸的变化与肺腺癌的发展有相关性,可能是肺腺癌早期诊断和分期的潜在生物标志物。 相似文献
135.
136.
Hai‐Dong Li Linfang Tang Chenxi Jia Marcel Holyoak Jochen Fründ Xiaoqun Huang Zhishu Xiao 《Ecology letters》2020,23(8):1252-1262
Understanding how biodiversity and interaction networks change across environmental gradients is a major challenge in ecology. We integrated metacommunity and metanetwork perspectives to test species’ functional roles in bird–plant frugivory interactions in a fragmented forest landscape in Southwest China, with consequences for seed dispersal. Availability of fruit resources both on and under trees created vertical feeding stratification for frugivorous birds. Bird–plant interactions involving birds feeding only on‐the‐tree or both on and under‐the‐tree (shared) had a higher centrality and contributed more to metanetwork organisation than interactions involving birds feeding only under‐the‐tree. Moreover, bird–plant interactions associated with large‐seeded plants disproportionately contributed to metanetwork organisation and centrality. Consequently, on‐the‐tree and shared birds contributed more to metanetwork organisation whereas under‐the‐tree birds were more involved in local processes. We would expect that species’ roles in the metanetwork will translate into different conservation values for maintaining functioning of seed‐dispersal networks. 相似文献
137.
138.
Qi Li Ji Wang Tian Bai Ming Zhang Yuling Jia Danyu Shen Meixiang Zhang Daolong Dou 《Molecular Plant Pathology》2020,21(4):502-511
EDS1 (Enhanced Disease Susceptibility 1) plays a crucial role in both effector-triggered immunity activation and plant basal defence. However, whether pathogen effectors can target EDS1 or an EDS1-related pathway to manipulate immunity is rarely reported. In this study, we identified a Phytophthora capsici Avirulence Homolog (Avh) RxLR (Arg-any amino acid-Leu-Arg) effector PcAvh103 that interacts with EDS1. We demonstrated that PcAvh103 can facilitate P. capsici infection and is required for pathogen virulence. Furthermore, genetic evidence showed that PcAvh103 contributes to virulence through targeting EDS1. Finally, PcAvh103 specifically interacts with the lipase domain of EDS1 and can promote the disassociation of EDS1–PAD4 (Phytoalexin Deficient 4) complex in planta. Together, our results revealed that the P. capsici RxLR effector PcAvh103 targets host EDS1 to suppress plant immunity, probably through disrupting the EDS1–PAD4 immune signalling pathway. 相似文献
139.