全文获取类型
收费全文 | 668篇 |
免费 | 20篇 |
国内免费 | 9篇 |
专业分类
化学 | 354篇 |
晶体学 | 1篇 |
力学 | 18篇 |
数学 | 58篇 |
物理学 | 266篇 |
出版年
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 19篇 |
2019年 | 12篇 |
2018年 | 13篇 |
2017年 | 4篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 13篇 |
2013年 | 40篇 |
2012年 | 35篇 |
2011年 | 34篇 |
2010年 | 16篇 |
2009年 | 30篇 |
2008年 | 30篇 |
2007年 | 34篇 |
2006年 | 21篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 18篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 19篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1971年 | 3篇 |
1958年 | 3篇 |
1935年 | 2篇 |
排序方式: 共有697条查询结果,搜索用时 15 毫秒
71.
Siew Leng Lim Yiliang LiuJing Li En-Tang KangChong Kim Ong 《Applied Surface Science》2011,257(15):6612-6617
Transparent TiO2 nanotube arrays of micrometer lengths were prepared by anodization of titanium thin film RF sputtered on indium tin oxide (ITO) which was coated on glass substrate. The sputtering process took place at elevated temperature of 500 °C. The structures of the films were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD) while the optical properties of the films were investigated using UV-visible spectroscopy. Two types of electrolytes were used in this work: an aqueous mixture of acetic acid and HF solution and a mixture of NH4F and water dissolved in ethylene glycol. The concentration of NH4F, voltage and the thickness of the sputtered titanium film were varied to study their effect on the formation of TiO2 nanotube arrays. It is demonstrated in this work that the nanoporous layer is formed on top of the ordered array of TiO2 nanotubes. Furthermore, the optical transmittance of TiO2 nanotubes annealed at 450 °C is much lower than the non annealed TiO2 nanotubes in the visible wavelength region. 相似文献
72.
The voltage power spectrum of NbSe3 has been studied in the upper charge-density wave (CDW) state where only one CDW exists. In the non-Ohmic regime sharp spikes appear in the spectrum. The frequency of these spikes increases monotonically with current as in the lower CDW state. We study the “fine structure” of the spectrum and find evidence for “frequency pulling” between the modes. A linear coupled-mode treatment is used to model this effect. There is also evidence of heterodyning of an intrinsic (current independent) 2MHz mode. We briefly discuss these phenomena in terms of Fröhlich sliding conductivity. Difficulties with the simple two-fluid model as well as models based on solid state turbulence are pointed out. 相似文献
73.
Cinabro D Henderson S Liu T Saulnier M Wilson R Yamamoto H Bergfeld T Eisenstein BI Gollin G Ong B Palmer M Selen M Thaler JJ Sadoff AJ Ammar R Ball S Baringer P Bean A Besson D Coppage D Copty N Davis R Hancock N Kelly M Kwak N Lam H Kubota Y Lattery M Nelson JK Patton S Perticone D Poling R Savinov V Schrenk S Wang R Alam MS Kim IJ Nemati B O'Neill JJ Severini H Sun CR Zoeller MM Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y 《Physical review letters》1994,72(10):1406-1410
74.
The FTIR spectrum of the nu6 band of H13COOH has been collected at a resolution of 0.004 cm-1 in the frequency range of 1030-1160 cm-1. The nu6 band was analyzed to be an A-B hybrid band and perturbed by the nearby nu8 band through a-, and b-Coriolis coupling terms. Using a Watson's A-reduced Hamiltonian in the Ir representation, with the inclusion of a- and b-Coriolis resonances, a total of 3004 IR transitions of nu6 have been analyzed to provide rovibrational constants for the v6 = 1 state with a standard deviation of 0.00047 cm-1. The nu6 band was found to be centered at 1095.40365 +/- 0.00003 cm-1. Copyright 1999 Academic Press. 相似文献
75.
M.L. Foo Q. Huang Wei-Li Lee I.S. Hagemann N.P. Ong 《Journal of solid state chemistry》2006,179(2):563-572
The synthesis, structure, and physical properties of five R-type Ru ferrites with chemical formula BaMRu5O11 (M=Li and Cu) and BaM′2Ru4O11 (M′=Mn, Fe and Co) are reported. All the ferrites crystallize in space group P63/mmc and consist of layers of edge sharing octahedra interconnected by pairs of face sharing octahedra and isolated trigonal bipyramids. For M=Li and Cu, the ferrites are paramagnetic metals with the M atoms found on the trigonal bipyramid sites exclusively. For M′=Mn, Fe and Co, the ferrites are soft ferromagnetic metals. For M′=Mn, the Mn atoms are mixed randomly with Ru atoms on different sites. The magnetic structure for BaMn2Ru4O11 is reported. 相似文献
76.
Petradza M Thun R Abrams G Amidei D Baden AR Barklow T Boyarski A Boyer J Burchat PR Burke DL Butler F Dorfan JM Feldman GJ Gidal G Gladney L Gold MS Goldhaber G Haggerty J Jaros JA Kadyk JA Karlen D Lankford AJ Larsen RR LeClaire BW Levi ME Lockyer NS Lüth V Nelson ME Ong RA Perl ML Richter B Riles K Rowson PC Schaad T Schellman H Schmidke WB Sheldon PD Trilling GH Wood DR Yelton JM 《Physical review D: Particles and fields》1990,42(7):2171-2179
77.
Ong QK Lin XM Wei A 《The journal of physical chemistry. C, Nanomaterials and interfaces》2011,115(6):2665-2672
Core-shell Fe@Fe(3)O(4) nanoparticles exhibit substantial exchange bias at low temperatures, mediated by unidirectionally aligned moments at the core-shell interface. These spins are frozen into magnetic alignment with field cooling, and are depinned in a temperature-dependent manner. The population of such frozen spins has a direct impact on both coercivity (H(C)) and the exchange-bias field (H(E)), which are modulated by external physical parameters such as the strength of the applied cooling field and the cycling history of magnetic field sweeps (training effect). Aging of the core-shell nanoparticles under ambient conditions results in a gradual decrease in magnetization but overall retention of H(C) and H(E), as well as a large increase in the population of frozen spins. These changes are accompanied by a structural evolution from well-defined core-shell structures to particles containing multiple voids, attributable to the Kirkendall effect. Energy-filtered and high-resolution transmission electron microscopy both indicate further oxidation of the shell layer, but the Fe core is remarkably well preserved. The increase in frozen spin population with age is responsible for the overall retention of exchange bias, despite void formation and other oxidation-dependent changes. The exchange-bias field becomes negligible upon deliberate oxidation of Fe@Fe(3)O(4) nanoparticles into yolk-shell particles, with a nearly complete physical separation of core and shell. 相似文献
78.
Yaoyu Feng Say‐Leong Ong Jiangyong Hu Wun‐Jern Ng 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):m34-m35
Reaction of 1,10‐phenanthroline (phen) with iron trichloride in the presence of sodium nitrilotriacetate (NTA) resulted in the formation of red crystals of the title complex, [Fe(C6H6NO6)(C12H8N2)(H2O)]·H2O. The Fe atom has a distorted capped trigonal prismatic coordination comprised of one tetradentate NTA, one bidentate phen molecule and a water molecule. Intermolecular O—H?O hydrogen bonds link the molecules into infinite chains. The chains are crosslinked by hydrogen bonds involving the solvent water molecule, leading to an infinite ladder packing mode. 相似文献
79.
Ren C Maurizot V Zhao H Shen J Zhou F Ong WQ Du Z Zhang K Su H Zeng H 《Journal of the American Chemical Society》2011,133(35):13930-13933
Described in this study is a conceptually new class of five-fold-symmetric cavity-containing planar pentameric macrocycles with their interior decorated by five convergently aligned, properly spaced carbonyl oxygen atoms. These cation-binding oxygens enclose a hydrophilic lumen of 2.85 ? in radius and thus display high-affinity binding toward alkali metal cations, and possibly many other cations, too. Arising from their high-affinity recognition of metal ions, these planar macrocycles form cation- or ion-pair-induced one-dimensional columnar aggregates, and subsequently fascinating fibrillation results. 相似文献
80.
Mir MH Ong JX Kole GK Tan GK McGlinchey MJ Wu Y Vittal JJ 《Chemical communications (Cambridge, England)》2011,47(42):11633-11635
A pair of trans,trans-muconate ligands have been successfully aligned in two novel Au(I) macrocycles by design from phosphino metal precursors that undergo photochemical cycloaddition reactions quantitatively, resulting in the formation of cyclooctadiene derivatives. 相似文献