全文获取类型
收费全文 | 782篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
化学 | 679篇 |
晶体学 | 9篇 |
力学 | 7篇 |
数学 | 39篇 |
物理学 | 70篇 |
出版年
2023年 | 5篇 |
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 16篇 |
2014年 | 23篇 |
2013年 | 49篇 |
2012年 | 40篇 |
2011年 | 46篇 |
2010年 | 29篇 |
2009年 | 25篇 |
2008年 | 44篇 |
2007年 | 42篇 |
2006年 | 38篇 |
2005年 | 37篇 |
2004年 | 29篇 |
2003年 | 36篇 |
2002年 | 34篇 |
2001年 | 22篇 |
2000年 | 24篇 |
1999年 | 19篇 |
1998年 | 21篇 |
1997年 | 9篇 |
1996年 | 18篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1983年 | 5篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1970年 | 4篇 |
1968年 | 8篇 |
1967年 | 2篇 |
排序方式: 共有804条查询结果,搜索用时 15 毫秒
1.
Frequency dependence of ac conductivity from 1 to 105 Hz and time series of the conductivity at 2 kHz were measured along c-axis of thulium nitrate crystal, Tm(NO3)36H2O at temperatures from 203.15 to 293.15 K. The meta-stability was observed. The frequency spectra of the conductivity were similar to those in disorder system. Aging effect was observed. Non-periodic instability (burst) was found. Non-linear dynamical property was characterized by 1/f noise spectrum, limit cycle in return map and dependence of correlation exponent on embedding dimension. 相似文献
2.
Md. Nur Alam Per B. Zetterlund Masayoshi Okubo 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4995-5004
Bimolecular termination in nitroxide‐mediated radical polymerization in miniemulsion has been investigated through the heating of a polystyrene–2,2,6,6‐tetramethylpiperidinyl‐1‐oxy macroinitiator and its 4‐hydroxy‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy analogue in an aqueous toluene dispersion with sodium dodecyl benzenesulfonate as a surfactant at 125 °C. The level of bimolecular termination by combination, evaluated from the high‐molecular‐weight shoulder, was higher in miniemulsion than in solution and increased with decreasing particle size. Quantitative analysis revealed that these results cannot be rationalized solely by nitroxide partitioning to the aqueous phase. The results are explained by an interface effect, by which nitroxide is adsorbed or located at the aqueous–organic interface. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4995–5004, 2007 相似文献
3.
Takuji Sato 《Proceedings of the American Mathematical Society》2003,131(9):2903-2909
We obtain a non-Kähler almost Hermitian manifold of constant holomorphic sectional curvature by changing the almost complex structure in a Kähler manifold of constant holomorphic sectional curvature.
4.
Takuji Hirose Kumiko Naito Megumi Nakahara Hiroaki Shitara Yoshio Aoki Hiroyuki Nohira Bruce W. Baldwin 《Journal of inclusion phenomena and macrocyclic chemistry》2002,43(1-2):87-93
Two Kemp's acid diamides were synthesized and applied to chiral amine recognition using 1H NMR analysis. One derivative based on 1-(1-naphthyl)ethylamine had good chiral recognition of six amines and was useful to determine the optical purity for three amines, i.e., methylbenzylamine, 1-(1-naphthyl)ethylamine and 1- henylpropylamine,however, the cyclohexylethylamine derivative showed little discrimination for the amines studied. Together with the results for alkylamines, it was shown that aromatic structure was important for aromatic shielding anisotropy and –– interactions between host and guest. The structure of the 1-(1-naphthyl)ethylamine derivative in solution was also considered based on 1H NMR data and computer simulation. 相似文献
5.
Influence of shell strength on shape transformation of micron-sized,monodisperse, hollow polymer particles 总被引:1,自引:0,他引:1
Micron-sized, monodisperse, non-spherical polymer particles with "rugby ball" and "red blood corpuscle"-like shapes were produced by seeded polymerization of the dispersion of (divinylbenzene/vinylbiphenyl/xylene)-swollen polystyrene particles prepared by utilizing the dynamic swelling method which the authors proposed in 1991. Their non-spherical shapes were based on buckling of the shell of the resultant hollow particles. In this article, the reversible shape transformation of the hollow composite polymer particle between spherical and such non-spherical shapes was studied in detail by controlling the shell strength. A part of the shell was buckled by external pressure which was caused by evaporation of xylene from the hollow when the shell had the tensile modulus below the critical value calculated from the pressure-buckling relationship of a spherical shell proposed by Uemura. The plasticization of the shell by a good solvent was one of key factors for the shape transformation. 相似文献
6.
Enhancement of electronic excitation energy transfer in the colloidal crystals of colloidal silica suspensions doped with fluorescent dyes 总被引:1,自引:0,他引:1
Kiyoshi Shibata Hiroshi Kimura Akira Tsuchida Tsuneo Okubo 《Colloid and polymer science》2006,285(2):127-133
The efficiency of electronic excitation energy transfer from photo-excited rhodamine 110 (Rh110, energy donor) to rhodamine B (RhB, energy acceptor) in an exhaustively deionized colloidal silica suspension has been studied. This colloidal suspension shows Bragg reflection due to the formation of colloidal crystals and the Bragg-peak wavelength is controllable by the volume fraction of the silica spheres. When the Bragg-peak wavelength matches with the fluorescence band of Rh110, a depletion was observed in the Rh110 fluorescence spectrum. This means the fluorescence of Rh110 is partially trapped due to the Bragg reflection inside the crystal lattice. In the coexistence of RhB, the enhancement of RhB fluorescence intensity was observed. These facts clearly indicate the trapped photon energy of Rh110 is efficiently transferred to RhB within the colloidal crystals. The quantitative measurements showed that the enhancement of the transfer efficiency is 20% (or slightly more) in the present experimental conditions. 相似文献
7.
Production of submicron-size monodisperse polymer particles having aldehyde groups by seeded aldol condensation polymerization 总被引:2,自引:0,他引:2
Submicron-size monodisperse polystyrene/polyglutaraldehyde composite particles having aldehyde groups at the surfaces were produced by seeded aldol condensation polymerization of glutaraldehyde in the presence of polystyrene particles prepared by emulsifier-free emulsion polymerization. This technique is expected to be useful for the production of size-controlled polymer particles having aldehyde groups.Part CXXXVI of the series Studies on Suspension and Emulsion 相似文献
8.
Takeshi Ishijima Yoshiki Mizumori Kenji Kikuchi Atsushi Suzuki Takuji Okaya 《Colloid and polymer science》2005,283(7):799-804
Polymerization of vinyl acetate (VAc) in various fatty acids (carbon numbers 4–18) was carried out. Chain transfer constants to the acids were determined to be 20–35×10–4, from which the constant to a methylene group was obtained to be 0.73×10–4. Viscometry in aqueous solution of derived poly (vinyl alcohol) (PVA) showed the usual behavior in terms of Huggins constant obtained by the Schulz–Blaschkes equation for PVAs derived from fatty acid systems lower than hexadecanoic acid. PVA derived from octadecanoic acid system showed abnormality, indicating association of alkyl groups. Contact angles on surfaces of PVAs cast from aqueous solutions were measured. While those of PVA derived from lower acid systems were 62°, those of PVAs derived from higher aids were higher and increased to 92° with increase in carbon number to octadecanoic acid. Alkyl groups in the PVAs were estimated to appear on the surfaces. Surface tension of aqueous solution of the PVA derived from octadecanoic acid showed high surface activity, and depended on pH of the solution, indicating the presence and cleavage of lactone ring at the combined portion between PVA and the acid. 相似文献
9.
Phase separation in the formation of hollow particles by suspension polymerization for divinylbenzene/toluene droplets dissolving polystyrene 总被引:1,自引:0,他引:1
Phase-separation behavior within polymerizing divinylbenzene/toluene droplet dissolving polystyrenes (PS) was investigated to clarify the formation mechanism of the hollow polymer particles by suspension polymerization. No hollow particles were obtained at a low content of low-molecular-weight PS where phase separation occurred at high conversion. On the other hand, hollow particles were obtained at a high content of high-molecular-weight PS where phase separation occurred at low conversion. The phase separation in an early stage of the polymerization, which was promoted by the presence of PS and cross-links of polydivinylbenzene, was a key factor for the formation of the hollow structure. 相似文献
10.
Akira Okubo Hiroyuki Kawai Toshiro Matsunaga Tatsuji Chuman Sunao Yamazaki Shozo Toda 《Tetrahedron letters》1980,21(42):4095-4096
T1 gives a clue to assign cis- and trans-methyl carbons in 2-methyl-1-propenyl moiety. 相似文献