全文获取类型
收费全文 | 2129篇 |
免费 | 195篇 |
国内免费 | 334篇 |
出版年
2024年 | 10篇 |
2023年 | 61篇 |
2022年 | 101篇 |
2021年 | 174篇 |
2020年 | 116篇 |
2019年 | 129篇 |
2018年 | 124篇 |
2017年 | 76篇 |
2016年 | 104篇 |
2015年 | 151篇 |
2014年 | 176篇 |
2013年 | 158篇 |
2012年 | 204篇 |
2011年 | 190篇 |
2010年 | 92篇 |
2009年 | 92篇 |
2008年 | 107篇 |
2007年 | 66篇 |
2006年 | 72篇 |
2005年 | 63篇 |
2004年 | 54篇 |
2003年 | 50篇 |
2002年 | 66篇 |
2001年 | 20篇 |
2000年 | 26篇 |
1999年 | 22篇 |
1998年 | 13篇 |
1997年 | 17篇 |
1996年 | 19篇 |
1995年 | 6篇 |
1994年 | 16篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有2658条查询结果,搜索用时 15 毫秒
61.
Luo Shengxue Zhang Panli Zou Peng Wang Cong Liu Bochao Wu Cuiling Li Tingting Zhang Ling Zhang Yuming Li Chengyao 《中国病毒学》2021,36(5):1113-1123
Virologica Sinica - SARS-CoV-2 has caused more than 3.8 million deaths worldwide, and several types of COVID-19 vaccines are urgently approved for use, including adenovirus vectored vaccines.... 相似文献
62.
63.
Haiyue Niu Xiaohong Zhou Xuguang Zhang Tongjie Liu Yifan Wu Linzheng Lyu Cong Liang Shiwei Chen Pimin Gong Jiliang Zhang Xue Han Shilong Jiang Lanwei Zhang 《Environmental microbiology》2021,23(3):1750-1764
Infants often experience complementary food-induced diarrhoea (CFID), which occurs when infants switch from breast milk to solid foods. The relative abundances of Prevotella and Rothia were higher in stools of infants with CFID, while the relative abundances of Enterococcus and Escherichia were higher in healthy infants. The abundance of Lactobacillus spp. normally found in breast milk fed to infants with CFID was significantly reduced, and Enterococcus spp. were less abundant when diarrhoea occurred. Furthermore, Lactobacillus and Enterococcus were present as shared bacteria in both mother and infant, and they were considered potential anti-CFID probiotics as their relative abundances in breast milk were negatively correlated to infant CFID. Kyoto encyclopedia of genes and genomes (KEGG) functional analysis showed that the function of amino acid metabolism differed between infants with CFID and healthy infants. Therefore, CFID might be related to the decomposition of proteins in food supplements. The screening revealed seven hydrolytic casein and five hydrolytic casein and rice protein isolates from 320 suspected Lactobacillus and Enterococcus isolates. The animal experiments demonstrated that a mixture of five isolates effectively hydrolysed the casein and rice protein and prevented diarrhoea in young rats. Thus, the occurrence of CFID was found to be closely related to the intestinal and breast milk microbiota, and bacteria that could assist in the digestion of cereal proteins were involved in CFID. 相似文献
64.
林窗环境异质性导致群落物种多样性与系统发育多样性(phylogenetic diversity, PD)存在差异, 研究不同大小的林窗中群落的物种多样性与系统发育多样性有助于揭示林下生物多样性的形成及维持机制。本文以格氏栲(Castanopsis kawakamii)天然林为研究对象, 通过Pearson相关性分析与广义线性模型探讨了林窗内物种多样性与系统发育多样性间的相互关系及其环境影响因素。结果表明: (1)大林窗(面积 > 200 m2)植物种类及多度均高于中林窗(50 m2 ≤ 面积 < 100 m2)、小林窗(30 m2 ≤ 面积 < 50 m2)和非林窗(面积 = 100 m2)。大林窗群落系统发育结构趋于发散, 中、小林窗和非林窗群落系统发育结构受到生境过滤和竞争排斥综合作用。(2)群落系统发育多样性指数与物种丰富度(species richness, SR)、Margalef丰富度指数和Shannon-Wiener指数均呈显著正相关, 这与林窗内稀有种种类组成多于优势种有关。(3)林窗面积对物种多样性存在显著正效应; 土壤全氮含量对系统发育多样性和系统发育结构存在显著正效应。林窗形成提高了格氏栲天然林群落物种多样性和系统发育多样性, 林窗面积与土壤全氮共同驱动了格氏栲天然林林窗物种多样性和系统发育多样性的变化。 相似文献
65.
66.
67.
Cong Jiang Robert J. Suhadolnik David C. Baker 《Nucleosides, nucleotides & nucleic acids》2013,32(3):271-294
Abstract [2′-18O]- and [3′-18O]-Adenosine and [2′-18O]- and [3′-18O]-9-(β-D-arabinofuranosyl) adenine were synthesized from?appropriate nucleoside precursors. The sites of 18O-incorporation were determined by mass spectrometry. 18O-Induced 13C NMR shifts were measured for 2′-and 3′-labeled adenosines as 1.2 and 1.6 Hz, respectively. 相似文献
68.
Lihua Hou Xiaoyang Li Cong Wang Xiaohong Cao Haiyong Wang 《Journal of industrial microbiology & biotechnology》2013,40(3-4):393-397
An effective approach, using the plasmid YCplac33-GHK, is developed to construct a ploidy series of Saccharomyces cerevisiae. YCplac33-GHK harbors the HO gene under the control of galactose-inducible promoter and KanMX4 as the selective marker. The simple method can solve the problem of industrial applications of strains with resistance genes. 相似文献
69.
70.
Cong Cao Mengia S. Rioult-Pedotti Paolo Migani Crystal J. Yu Rakesh Tiwari Keykavous Parang Mark R. Spaller Dennis J. Goebel John Marshall 《PLoS biology》2013,11(2)
Angelman syndrome (AS) is a neurodevelopment disorder characterized by severe cognitive impairment and a high rate of autism. AS is caused by disrupted neuronal expression of the maternally inherited Ube3A ubiquitin protein ligase, required for the proteasomal degradation of proteins implicated in synaptic plasticity, such as the activity-regulated cytoskeletal-associated protein (Arc/Arg3.1). Mice deficient in maternal Ube3A express elevated levels of Arc in response to synaptic activity, which coincides with severely impaired long-term potentiation (LTP) in the hippocampus and deficits in learning behaviors. In this study, we sought to test whether elevated levels of Arc interfere with brain-derived neurotrophic factor (BDNF) TrkB receptor signaling, which is known to be essential for both the induction and maintenance of LTP. We report that TrkB signaling in the AS mouse is defective, and show that reduction of Arc expression to control levels rescues the signaling deficits. Moreover, the association of the postsynaptic density protein PSD-95 with TrkB is critical for intact BDNF signaling, and elevated levels of Arc were found to impede PSD-95/TrkB association. In Ube3A deficient mice, the BDNF-induced recruitment of PSD-95, as well as PLCγ and Grb2-associated binder 1 (Gab1) with TrkB receptors was attenuated, resulting in reduced activation of PLCγ-α-calcium/calmodulin-dependent protein kinase II (CaMKII) and PI3K-Akt, but leaving the extracellular signal-regulated kinase (Erk) pathway intact. A bridged cyclic peptide (CN2097), shown by nuclear magnetic resonance (NMR) studies to uniquely bind the PDZ1 domain of PSD-95 with high affinity, decreased the interaction of Arc with PSD-95 to restore BDNF-induced TrkB/PSD-95 complex formation, signaling, and facilitate the induction of LTP in AS mice. We propose that the failure of TrkB receptor signaling at synapses in AS is directly linked to elevated levels of Arc associated with PSD-95 and PSD-95 PDZ-ligands may represent a promising approach to reverse cognitive dysfunction. 相似文献