全文获取类型
收费全文 | 274篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 177篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 25篇 |
物理学 | 78篇 |
出版年
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 24篇 |
2012年 | 22篇 |
2011年 | 13篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 19篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有287条查询结果,搜索用时 15 毫秒
11.
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12.
Yu. Kudriavtsev S. Gallardo A. Villegas G. Ramirez R. Asomoza 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(7):895-898
A new model of the depth-resolution function for secondary-ion mass spectrometry, which takes into account recoil implantation, ion mixing, and surface roughness formation under ion irradiation, is considered. A simple three-parameter equation is proposed to describe the depth-resolution function. Analytical expressions are obtained for two parameters. 相似文献
13.
14.
A synthesis of β-stannyl esters from ester enolates and iodomethyl (tri-n-butyl) stannane (3) is described. 相似文献
15.
M. I. Gallardo S. M. Lenzi A. Vitturi 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(4):269-274
We study pairing correlations in deformed nuclei in the framework of the Nilsson+BCS theory. As in the spherical case, the pairing interaction is found to induce strong spacial correlations between the partners of each paired couple. The presence of the deformed mean field gives rise to a non-spherical pair field, whose deformation is governed by the properties of a few single-particle orbitals around the Fermi surface and does not necessarily follow the shape of the mean field. Multipole expansion of the pair field yields all the pair densities associated with the direct two-particle transfer processes to the members of the g.s. rotational band in the A+2 system. The interplay of the deformations of the mean and the pair fields can lead to different relative magnitudes and phases of these densities and therefore to different excitation patterns of the rotational bands in two-particle transfer reactions. In the case of non-collective twoquasiparticles and bands the associated pair densities display large components with high multipoles and the associated transfer processes may be favoured in heavy-ion collisions by kinematical conditions. Examples corresponding to both prolate and oblate cases are considered. 相似文献
16.
Juan Alfonso Redondo Enrique Martínez‐Campos Laetitia Plet Mnica Prez‐Perrino Rodrigo Navarro Guillermo Corrales Abhay Pandit Helmut Reinecke Alberto Gallardo Jos Luis Lpez‐Lacomba Alfonso Fernndez‐Mayoralas Carlos Elvira 《Macromolecular rapid communications》2016,37(7):575-583
The incorporation of cyclodextrins (CDs) to nonviral cationic polymer vectors is very attractive due to recent studies that report a clear improvement of their cytocompatibility and transfection efficiency. However, a systematic study on the influence of the CD derivatization is still lacking. In this work, the relevance of β‐CD permethylation has been addressed by preparing and evaluating two series of copolymers of the cationic N‐ethyl pyrrolidine methacrylamide (EPA) and styrenic units bearing pendant hydroxylated and permethylated β‐CDs (HCDSt and MeCDSt, respectively). For both cell lines, CDs permethylation shows a strong influence on plasmid DNA complexation, “in vitro” cytocompatibility and transfection efficiency of the resulting copolymers over two murine cell lines. While the incorporation of the hydroxylated CD moiety increased the cytotoxicity of the copolymers in comparison with their homopolycationic counterpart, the permethylated copolymers have shown full cytocompatibility as well as superior transfection efficiency than the controls. This behavior has been related to the different chemical nature of both units and tentatively to a different distribution of units along the polymeric chains. Cellular internalization analysis with fluorescent copolymers supports this behavior.
17.
Edwin Weber Claus Wimmer Ingeborg Csöregh Olga Gallardo 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(2):141-153
A novel host molecule, 1, suitable for crystalline lattice-type inclusion, has been synthesized, and its cocrystal formation ability has been investigated. Host 1 proved to be of potential use for organic solvent separation and retrieval, and a promising auxiliary for solidification of certain odorous substances. The crystal structures of the solvent-free host 1, and its complex with 1,4-dioxane (1 : 1), have been determined by single crystal X-ray diffraction. The structure of 1 (guest-free) is triclinic, P
, with a = 9.452(2), b = 10.359(3), c = 13.116(3) Å, = 101.80(2), = 106.53(1) and = 104.32(1)°. The spacious, propeller-like molecules are held together by weak van der Waals' forces. The dioxane inclusion compound is monoclinic, P21/a, with a = 15.050(1), b = 8.641(1) and c = 20.658(1) Å, and = 94.56(1)°, and contains two crystallographically independent guest molecules, both located around symmetry centres. The molecular packing seems to be governed by C—H···O type bonds (C···O = 3.31 and 3.48 Å) from the host to the dioxane oxygens. 相似文献
18.
Mykola Telychko Jie Su Aurelio Gallardo Yanwei Gu Jesús I. Mendieta‐Moreno Dongchen Qi Anton Tadich Shaotang Song Pin Lyu Zhizhan Qiu Hanyan Fang Ming Joo Koh Jishan Wu Pavel Jelínek Jiong Lu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(51):18764-18770
The ability to use mechanical strain to steer chemical reactions creates completely new opportunities for solution‐ and solid‐phase synthesis of functional molecules and materials. However, this strategy is not readily applied in the bottom‐up on‐surface synthesis of well‐defined nanostructures. We report an internal strain‐induced skeletal rearrangement of one‐dimensional (1D) metal–organic chains (MOCs) via a concurrent atom shift and bond cleavage on Cu(111) at room temperature. The process involves Cu‐catalyzed debromination of organic monomers to generate 1,5‐dimethylnaphthalene diradicals that coordinate to Cu adatoms, forming MOCs with both homochiral and heterochiral naphthalene backbone arrangements. Bond‐resolved non‐contact atomic force microscopy imaging combined with density functional theory calculations showed that the relief of substrate‐induced internal strain drives the skeletal rearrangement of MOCs via 1,3‐H shifts and shift of Cu adatoms that enable migration of the monomer backbone toward an energetically favorable registry with the Cu(111) substrate. Our findings on this strain‐induced structural rearrangement in 1D systems will enrich the toolbox for on‐surface synthesis of novel functional materials and quantum nanostructures. 相似文献
19.
C.?LaluceEmail author A.?C.?G.?Schenberg J.?C.?M.?Gallardo L.?F.?C.?Coradello S.?R.?Pombeiro-Sponchiado 《Applied biochemistry and biotechnology》2012,166(8):1908-1926
The conversion of biomass into ethanol using fast, cheap, and efficient methodologies to disintegrate and hydrolyse the lignocellulosic
biomass is the major challenge of the production of the second-generation ethanol. This revision describes the most relevant
advances on the conversion process of lignocellulose materials into ethanol, development of new xylose-fermenting strains
of Saccharomyces cerevisiae using classical and modern genetic tools and strategies, elucidation of the expression of some complex industrial phenotypes,
tolerance mechanisms of S. cerevisiae to lignocellulosic inhibitors, monitoring and strategies to improve fermentation processes. In the last decade, numerous
engineered pentose-fermenting yeasts have been developed using molecular biology tools. The increase in the tolerance of S. cerevisiae to inhibitors is still an important issue to be exploited. As the industrial systems of ethanol production operate under
non-sterile conditions, microbial subpopulations are generated, depending on the operational conditions and the levels of
contaminants. Among the most critical requirements for production of the second-generation ethanol is the reduction in the
levels of toxic by-products of the lignocellulosic hydrolysates and the production of low-cost and efficient cellulosic enzymes.
A number of procedures have been established for the conversion of lignocellulosic materials into ethanol, but none of them
are completely satisfactory when process time, costs, and efficiency are considered. 相似文献
20.
I Gallardo G Guirado M Moreno G Prats M Takeshita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9807-9812
A reversible bidirectional ring-opening and ring-closing system triggered by electricity has been prepared by using metacyclophan-1-enes, a known thermo-photochromic molecular switch system. 相似文献