全文获取类型
收费全文 | 1103篇 |
免费 | 44篇 |
国内免费 | 4篇 |
专业分类
化学 | 940篇 |
晶体学 | 6篇 |
力学 | 21篇 |
数学 | 89篇 |
物理学 | 95篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 18篇 |
2021年 | 22篇 |
2020年 | 34篇 |
2019年 | 24篇 |
2018年 | 29篇 |
2017年 | 11篇 |
2016年 | 32篇 |
2015年 | 42篇 |
2014年 | 40篇 |
2013年 | 58篇 |
2012年 | 83篇 |
2011年 | 109篇 |
2010年 | 55篇 |
2009年 | 39篇 |
2008年 | 86篇 |
2007年 | 72篇 |
2006年 | 64篇 |
2005年 | 55篇 |
2004年 | 61篇 |
2003年 | 41篇 |
2002年 | 42篇 |
2001年 | 15篇 |
2000年 | 16篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1937年 | 1篇 |
排序方式: 共有1151条查询结果,搜索用时 0 毫秒
81.
82.
83.
John?F?StinsEmail author G?Caroline?M?van Baal Tinca?JC?Polderman Frank?C?Verhulst Dorret?I?Boomsma 《BMC neuroscience》2004,5(1):49
Background
There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks. 相似文献84.
Hunter CA Low CM Rotger C Vinter JG Zonta C 《Chemical communications (Cambridge, England)》2003,(7):834-835
Chemical double mutant cycles have been used to quantify cation-pi interactions in chloroform as a function of the nature of the counteranion. The cation-pi interaction is -2.5 +/- 0.4 kJ mol(-1) and independent of the anion, even though the overall stability of the complexes varies by an order of magnitude due to competition of the anion for alternative binding sites. 相似文献
85.
Paul D Melin F Hirtz C Wytko J Ochsenbein P Bonin M Schenk K Maltese P Weiss J 《Inorganic chemistry》2003,42(12):3779-3787
The respective affinities of various imidazole derivatives, imidazole (ImH), 2-methylimidazole (2-MeImH), 2-phenylimidazole (2-PhImH), N-methylimidazole (N-MeIm), 2-methylbenzimidazole (2-MeBzImH), and 4,5-dimethylbenzimidazole (4,5-Me(2)BzImH), for two phenanthroline (Phen) strapped zinc(II) porphyrin receptors porphen-Zn 1-Zn and 2-Zn have been studied. The formation of a supplementary H-bond considerably enhances the affinity of the zinc(II)-porphen receptor for imidazoles unsubstituted on the pyrrolic nitrogen (ImH) versus N-substituted imidazoles such as N-MeIm. The ImHs subset porphen-Zn complexes are formed with association constants up to 4 orders of magnitude superior to those measured either for N-MeIm as substrate or TPP-Zn as receptor. Distal or proximal binding of the substrates was determined by (1)H NMR measurements and titration. In two cases, the very high stability of the inclusion complex enabled the use of 2D NMR techniques. Excellent correlation between solution and solid-state structures has been obtained. A total of six X-ray structures are detailed in this article showing that the evolution of the shape of the zinc(II) receptor is mostly dependent on the steric constraints induced by the substitution on the imidazole. Hindered guests also progressively induce considerable mobility restrictions and severe distortions on the receptor, especially in the case of 2-MeBzImH and 2-PhImH. 相似文献
86.
Chrystelle Brignone Caroline Grygar Manon Marcu Gaëlle Perrin Frédéric Triebel 《Journal of immune based therapies and vaccines》2007,5(1):5-15
Background
LAG-3 (CD223) is a natural high affinity ligand for MHC class II. The soluble form (sLAG-3) induces maturation of monocyte-derived dendritic cells in vitro and is used as a potent Th1-like immune enhancer with many antigens in animal models. To extend this observation to human, a proof of concept study was conducted with a clinical-grade sLAG-3, termed IMP321, coinjected with alum-non-absorbed recombinant hepatitis B surface antigen. 相似文献87.
Celso C. Ribeiro Daniel Aloise Thiago F. Noronha Caroline Rocha Sebastián Urrutia 《European Journal of Operational Research》2008
We address a multi-objective version of the car sequencing problem, which consists in sequencing a given set of cars to be produced in a single day, minimizing the number of violations of assembly constraints and the number of paint color changes in the production line. We propose a set of heuristics for approximately solving this problem, based on the paradigms of the VNS and ILS metaheuristics, to which further intensification and diversification strategies have been added. Computational results on real-life test instances are reported. The work presented in this paper obtained the second prize in the ROADEF challenge 2005 sponsored by Renault. 相似文献
88.
Franziska Emmerling Caroline Röhr 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1127-1128
The two title trialkaline trioxoantimonates(III), tripotassium trioxoantimonate(III), K3[SbO3], (I), and tricaesium trioxoantimonate(III), Cs3[SbO3], (II), crystallize in the cubic Na3[AsS3] structure type in space group P213. The structures show discrete Ψ-tetrahedral [SbO3]3− anions with C3v point-group symmetry. The Sb—O distances are 1.923 (4) Å in (I) and 1.928 (2) Å in (II), and the O—Sb—O bond angles are 99.5 (2)° in (I) and 100.4 (1)° in (II). 相似文献
89.
A new cyclic nitrone spin trap, [4-(3′,3′-dibutyl-2′-oxy-3′H-isoindol-5′-yloxy)butyl]triphenylphosphonium bromide (MitoSpin), bearing a lipophilic cation has been prepared by a route that involves a novel Parham-type lithiation-cyclization of an isocyanate to give the isoindolinone core. MitoSpin accumulates in a membrane potential dependent way in energized mitochondria and its oxidation could potentially be used in the study of oxidative stress resulting from reactive oxygen species generated in mitochondria. 相似文献
90.