全文获取类型
收费全文 | 369篇 |
免费 | 19篇 |
国内免费 | 5篇 |
专业分类
化学 | 275篇 |
晶体学 | 1篇 |
力学 | 15篇 |
数学 | 40篇 |
物理学 | 62篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 7篇 |
2016年 | 19篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 27篇 |
2012年 | 21篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 8篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 15篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有393条查询结果,搜索用时 468 毫秒
81.
François Piriou Karl Lintner Hung Lam-Thanh Flavio Toma Serge Fermandjian 《Tetrahedron》1978,34(5):553-556
In order to analyze completely the ring conformation of [S]-Proline (l-thiazolidine-4-carboxylic acid) this compound has been synthesized with its Cδ atom enriched at 90% in 13C. The 1H-1H, 13C-1H, 13C-13C vicinal coupling constants measured at several pH values describe well the geometry of the thiazolidine ring. The results suggest that the ring has an average planar conformation only in a narrow range of pH close to the pK of the amine group. Above and below this pH the ring tends to adopt preferentially the Sγendo and Sγexo puckered conformations respectively. It is concluded that a good correlation exists between the value of the dihedral angle ø and the character Sγendo or Sγexo of the ring. 相似文献
82.
83.
Flavio Della Foglia Tonia Losco Paolo Piseri Paolo Milani Elena Selli 《Journal of nanoparticle research》2009,11(6):1339-1348
The photocatalytic activity of thin, nanostructured films of titanium dioxide, synthesized by supersonic cluster beam deposition
(SCBD) from the gas phase, has been investigated employing the photodegradation of salicylic acid as test reaction. Because
of the low deposition energy, the so-deposited highly porous TiO2 films are composed of nanoparticles maintaining their original properties in the film, which can be fully controlled by tuning
the deposition and post-deposition treatment conditions. A systematic investigation on the evolution of light absorption properties
and photoactivity of the films in relation to their morphology, determined by AFM analysis, and phase composition, determined
by Raman spectroscopy, has been performed. The absorption and photocatalytic activity of the nanostructured films in the visible
region could be enhanced either through post-deposition annealing treatment in ammonia containing atmosphere or employing
mild oxidation conditions, followed by annealing in N2 at 600 °C. 相似文献
84.
85.
Flavio Pressacco Marcellino Gaudenzi Antonino Zanette Laura Ziani 《European Journal of Operational Research》2008
With reference to the evaluation of the speed–precision efficiency of pricing and hedging of American Put options, we present and discuss numerical results obtained on the basis of four different large enough random samples according to the relevance of the American quality (relative importance of the early exercise opportunity) of the options. Here we provide a comparison of the best methods (lattice based numerical methods and an approximation of the American Premium analytical procedure) known in literature along with some key methodological remarks. 相似文献
86.
Teodosio Luigi Alferi Giuseppe Genovese Andrea Farroni Flavio Mele Benedetto Timpone Francesco Sakhnevych Aleksandr 《Meccanica》2021,56(3):549-567
Meccanica - The characterization and reproduction of tyre behaviour for vehicle modelling is a topic of particular interest both for real-time driver in the loop simulations and for offline... 相似文献
87.
Alditols have been obtained in very high yield using an excess of electron-rich furans with respect to the protected sugars. The scope and limitation of the reaction have been explored. 相似文献
88.
Paulo Eliandro da Silva Júnior Natlia Maria de Araujo Flavio da Silva Emery 《Journal of heterocyclic chemistry》2015,52(2):518-521
α‐xiloidone is an interesting chromene that are structurally related to lapachones; in this work, we selectively synthesized α‐xiloidone from the reaction of lawsone 1 with 3,3‐chloro‐3‐methylbut‐1‐yne under copper/I2 catalysis via propargyl Claisen rearrangement. 相似文献
89.
Dr. Luca Pescatori Alice Boccia Dr. Flavio Ciesa Dr. Francesca Rossi Dr. Vincenzo Grillo Prof. Arturo Arduini Prof. Andrea Pochini Prof. Robertino Zanoni Dr. Andrea Secchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(36):11089-11099
A series of gold nanoparticles (AuNPs) stabilized by monodentate, bidentate, and tridentate thiolate calix[n]arene ligands 1 – 3 was prepared by using the Brust–Schiffrin two‐phase direct synthesis and characterized with NMR spectroscopy, elemental analysis, transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS). The experimental data show that the particular multidentate structure of calix[n]arene derivatives 2 and 3 introduces a control element in the preparation of the gold nanoparticles that allows, in the particular experimental conditions here reported, to obtain very small (≈1 nm) AuNPs. These are the first experimental findings that identify a role of ligand “denticity” in the determination of the nuclearity of nanoparticles. 相似文献
90.
Holm AH Ceccato M Donkers RL Fabris L Pace G Maran F 《Langmuir : the ACS journal of surfaces and colloids》2006,22(25):10584-10589
Phenylethanethiolate monolayer-protected Au38 and Au140 nanoclusters were modified by ligand place exchange with a series of thiolated peptides. The peptides were homooligomers based on the alpha-aminoisobutyiric acid unit. The effects of changing the peptide concentration and the peptide length in the capping monolayer were studied by differential pulse voltammetry. The results showed that the redox behavior of the nanoparticles can be affected very significantly by such modifications. For example, the first oxidation peak of Au38, a cluster displaying molecule-like behavior, could be shifted positively by as much as 0.7-0.8 V. Detectable redox shifts were noted even when one single oriented peptide was in the Au140 monolayer. These effects were attributed to the molecular dipole moments of the peptide ligands. 相似文献