全文获取类型
收费全文 | 586篇 |
免费 | 37篇 |
国内免费 | 44篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 39篇 |
2013年 | 44篇 |
2012年 | 32篇 |
2011年 | 46篇 |
2010年 | 25篇 |
2009年 | 28篇 |
2008年 | 32篇 |
2007年 | 25篇 |
2006年 | 27篇 |
2005年 | 24篇 |
2004年 | 19篇 |
2003年 | 23篇 |
2002年 | 19篇 |
2001年 | 16篇 |
2000年 | 20篇 |
1999年 | 23篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1965年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有667条查询结果,搜索用时 15 毫秒
91.
东北小鲵中枢神经系统形态学与组织学初步研究 总被引:4,自引:1,他引:3
本文应用脊椎动物神经标本制作法和HE染色法,对东北小鲵中枢神经系统的外部形态和组织学结构进行了初步研究,描述了东北小鲵神经系统形态和组织学结构的特点,并与无尾两栖类和爬行类相对比,探讨了有尾两栖类的进化地位。结果表明:与无尾两栖类(如蛙)相比,东北小鲵中枢神经系统中,大脑半球较小,结构较为原始,小脑结构简单,是两栖类中较为原始的类群。此外,东北小鲵开始具有了臂神经丛和骶神经丛,但没有爬行类的发达,可作为两栖类向爬行类进化的证据之一。 相似文献
92.
Jose V Llorens Jonathan B Clark Isabel Martínez-Garay Sirena Soriano Rosa de Frutos María J Martínez-Sebastián 《BMC evolutionary biology》2008,8(1):302
Background
Sequences homologous to the gypsy retroelement from Drosophila melanogaster are widely distributed among drosophilids. The structure of gypsy includes an open reading frame resembling the retroviral gene env, which is responsible for the infectious properties of retroviruses. 相似文献93.
94.
95.
The bis(pyrazol-1-yl)azine ligands 2,3-bis(pyrazol-1-yl)quinoxaline (bpzqnx), 2,3-bis(pyrazol-1-yl)pyrazine (bpzprz) and 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine (bpz*pdz) were prepared by the reaction of pyrazolate salts and the corresponding azine dichloride derivatives. The reaction of these ligands with Ru(arene) precursors led to the mononuclear complexes [RuCl(arene)(L)]BPh4 (arene = p-cymene, L = bpzqnx, 1, bpzprz, 5, bpz*pdz, 7; arene = C6H6, L = bpzqnx, 2, bpzprz, 6, bpz*pdz, 8) with the N-donor ligand coordinated in a bidentate chelate way. In general, the ligands coordinate through one pyrazole ring and the azine, except in the cases of 1 and 2 where the two pyrazolyl rings are coordinated to the metal in a symmetrical way. When the reactions between the ruthenium precursors and bpzqnx are carried out in MeOH, the complexes [RuCl(arene)(OMepzqnx)]BPh4 with partially methanolyzed ligands are isolated (arene = p-cymene, 3; C6H6, 4). In this process a methoxy group has replaced one of the pyrazole groups in the ligand. The X-ray structures of 6 and 7 have been determined. These compounds have a three-legged piano-stool structure with cations and anions packed through weak interactions. Complexes 1-8 are active in ketone hydrogenation transfer processes even in the absence of base. 相似文献
96.
Mourad Chioua Abdelouahid Samadi Elena Soriano Olivier Lozach Laurent Meijer José Marco-Contelles 《Bioorganic & medicinal chemistry letters》2009,19(16):4566-4569
The synthesis and biological evaluation of a number of differently substituted 3,6-diamino-1H-pyrazolo[3,4-b]pyridine derivatives are reported. From the inhibition results on a selection of disease-relevant protein kinases [IC50 (μM) DYRK1A = 11; CDK5 = 0.41; GSK-3 = 1.5] we have observed that 3,6-diamino-4-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile (4) constitutes a potential new and simple lead compound in the search of drugs for the treatment of Alzheimer’s disease. 相似文献
97.
Indalecio Quesada‐Soriano Lorien J. Parker Alessandra Primavera Juan M. Casas‐Solvas Antonio Vargas‐Berenguel Carmen Barón Craig J. Morton Anna Paola Mazzetti Mario Lo Bello Michael W. Parker Luis García‐Fuentes 《Protein science : a publication of the Protein Society》2009,18(12):2454-2470
The effect of the Y108V mutation of human glutathione S‐transferase P1‐1 (hGST P1‐1) on the binding of the diuretic drug ethacrynic acid (EA) and its glutathione conjugate (EASG) was investigated by calorimetric, spectrofluorimetric, and crystallographic studies. The mutation Tyr 108 → Val resulted in a 3D‐structure very similar to the wild type (wt) enzyme, where both the hydrophobic ligand binding site (H‐site) and glutathione binding site (G‐site) are unchanged except for the mutation itself. However, due to a slight increase in the hydrophobicity of the H‐site, as a consequence of the mutation, an increase in the entropy was observed. The Y108V mutation does not affect the affinity of EASG for the enzyme, which has a higher affinity (Kd ~ 0.5 μM) when compared with those of the parent compounds, K ~ 13 μM, K ~ 25 μM. The EA moiety of the conjugate binds in the H‐site of Y108V mutant in a fashion completely different to those observed in the crystal structures of the EA or EASG wt complex structures. We further demonstrate that the ΔCp values of binding can also be correlated with the potential stacking interactions between ligand and residues located in the binding sites as predicted from crystal structures. Moreover, the mutation does not significantly affect the global stability of the enzyme. Our results demonstrate that calorimetric measurements maybe useful in determining the preference of binding (the binding mode) for a drug to a specific site of the enzyme, even in the absence of structural information. 相似文献
98.
99.
100.
JF Yuan SJ Zhang O Jafer RA Furlong OE Chausiaux CA Sargent GH Zhang NA Affara 《BMC microbiology》2009,9(1):246