全文获取类型
收费全文 | 1081篇 |
免费 | 54篇 |
国内免费 | 2篇 |
专业分类
化学 | 773篇 |
晶体学 | 23篇 |
力学 | 12篇 |
数学 | 45篇 |
物理学 | 284篇 |
出版年
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 25篇 |
2017年 | 14篇 |
2016年 | 20篇 |
2015年 | 29篇 |
2014年 | 22篇 |
2013年 | 58篇 |
2012年 | 33篇 |
2011年 | 58篇 |
2010年 | 33篇 |
2009年 | 33篇 |
2008年 | 72篇 |
2007年 | 53篇 |
2006年 | 69篇 |
2005年 | 51篇 |
2004年 | 53篇 |
2003年 | 49篇 |
2002年 | 48篇 |
2001年 | 28篇 |
2000年 | 31篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 13篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 22篇 |
1992年 | 13篇 |
1991年 | 5篇 |
1990年 | 15篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有1137条查询结果,搜索用时 171 毫秒
41.
M. Yamanaka Y. Takeda S. Tanigawa A. Nishizawa N. Noda J. Fujita M. Takai M. Shimobayashi Y. Hayashi T. Koizumi K. Nagasaka S. Okajima Y. Tsunawaki A. Nagashima 《International Journal of Infrared and Millimeter Waves》1980,1(1):57-76
A twin optically-pumped far-infrared CH3OH laser has been constructed for use in plasma diagnostics. The antisymmetric doublet due to the Raman-type resonant two-photon transition is reproducibly observed at 118.8 m. With the 118.8-m line, it is obtained from the frequency separation of the anti-symmetric doublet that CH3OH absorption line center is 16±1 MHz higher than the pump 9.7-m P(36) CO2 laser line center. It is shown that the Raman-type resonant two-photon transition is useful in order to get several-MHz phase modulation for the far-infrared laser interferometer. Some preliminary performances of this twin laser for the modulated interferometer are described.This work was carried out under the collaborating research program at the Institute of Plasma Physics, Nagoya University, Nagoya 464, Japan. 相似文献
42.
Oku K Watanabe H Kubota M Fukuda S Kurimoto M Tsujisaka Y Komori M Inoue Y Sakurai M 《Journal of the American Chemical Society》2003,125(42):12739-12748
Trehalose is a disaccharide that attracts much attention as a stress protectant. In this study, we investigated the mechanism of the antioxidant function of trehalose. The spin-lattice relaxation times (T(1)) of (1)H and (13)C NMR spectra were measured to investigate the interaction between trehalose and unsaturated fatty acid (UFA). We selected several kinds of UFA that differ in the number of double bonds and in their configurations (cis or trans). Several other disaccharides (sucrose, maltose, neotrehalose, maltitol, and sorbitol) were also analyzed by NMR. The T(1) values for the (1)H and (13)C signals assigned to the olefin double bonds in UFA decrease with increasing concentration of trehalose and the changes reaches plateaus at integer ratios of trehalose to UFA. The characteristic T(1) change is observed only for the combination of trehalose and UFA with cis double bond(s). On the other hand, from the (13)C-T(1) measurements for trehalose, the T(1) values of the C-3 (C-3') and C-6' (C-6) are found to change remarkably by addition of UFA. (1)H[bond](1)H NOESY measurements provide direct evidence for complexation of trehalose with linoleic acid. These results indicate that one trehalose molecule stoichiometrically interacts with one cis-olefin double bond of UFA. Computer modeling study indicates that trehalose forms a stable complex with an olefin double bond through OH...pi and CH...O types of hydrogen bonding. Furthermore, a significant increase in the activation energy is found for hydrogen abstraction reaction from the methylene group located between the double bonds that are both interacting with the trehalose molecules. Therefore, trehalose has a significant depression effect on the oxidation of UFA through the weak interaction with the double bond(s). This is the first study to elucidate the antioxidant function of trehalose. 相似文献
43.
Inumaru K Kasahara T Yasui M Yamanaka S 《Chemical communications (Cambridge, England)》2005,(16):2131-2133
Well-crystallised TiO2 particles (P-25, 20-30 nm in diameter) were directly incorporated into surfactant-templated mesoporous silica particles (pore diameter: 2.7 nm), and the composite material with a high TiO2 content (60 wt%) showed molecular selective and enhanced photocatalysis for decomposition of 4-nonylphenol. 相似文献
44.
Kobayashi K Yamada Y Yamanaka M Sei Y Yamaguchi K 《Journal of the American Chemical Society》2004,126(43):13896-13897
Selective formation of a homo- or hetero-cavitand cage via metal-coordination, by using tetra(4-pyridyl)-cavitand (1), tetrakis(4-pyridylethynyl)-cavitand (2), or tetrakis(4-cyanophenyl)-cavitand (3) as deep cavitand ligands and Pd(dppp)(OTf)2 (4) as a connector, has been investigated by 1H NMR and CSI-MS. When the cavitand and 4 were mixed in CDCl3 in a 2:4 molar ratio, 1 gave a complicated mixture, whereas 2 or 3 formed a homo-cavitand cage {2(2).4[Pd(dppp)]}8+.8(TfO-) (5) or {2(3).4[Pd(dppp)]}8+.8(TfO-) (6), respectively, as a single species. In a 1:1:4 mixture of 2, 3, and 4, homo-cavitand cages 5 and 6 were observed in a 1:1 ratio. In marked contrast, a mixture of 1, 3, and 4 in a 1:1:4 ratio was exclusively self-assembled into a hetero-cavitand cage {1.3.4[Pd(dppp)]}8+.8(TfO-) (7). The selectivity for the self-assembly of the homo- or hetero-cavitand cage via metal coordination would arise from a combination of factors such as coordination ability and steric demand of cavitand ligands. 相似文献
45.
The heat capacity of [Fe(2-pic)3]Cl2·C2H5OH Crystal (2-pic: 2-picolylamine) has been measured with an adiabatic calorimeter between 13 and 315 K. Two phase transitions centered at 114.04 and 122.21 K were observed. This finding accords with recent prediction of possible existence of two-step spin-conversion (H. Köppen et al., Chem. Phys. Lett., 91 (1982) 348). The total transition enthalpy and entropy amounted to ΔH = 6.14 kJ mol?1 and ΔS = 50.59 J K?1 mol?1. The transition entropy consists of the magnetic contribution (13.38 J K?1 mol?1), the orientational order-disorder phenomenon of the solvate ethanol molecule (8.97) and the change in the phonon system, in particular the change in stretching and deformation vibrations of the metal-ligand (28.24). 相似文献
46.
Chiaki Yamanaka Kazuhiko Hashimoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(23):4158-4166
New polyurethanes with lactone groups in the pendants and main chains were synthesized by the polyaddition of two kinds of L ‐gulonolactone‐derived diols (2,3‐O‐isopropylidene‐L ‐gulono‐1,4‐lactone and 5,6‐O‐isopropylidene‐L ‐gulono‐1,4‐lactone) with hexamethylene diisocyanate and methyl (S)‐2,6‐diisocyanatohexanoate and by the subsequent deprotection of isopropylidene groups. They were hydrolyzed more quickly than the polyurethane derived from methyl β‐D ‐glucofuranosidurono‐6,3‐lactone in a phosphate buffer solution, the pH value of which was 8.0, at 27 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4158–4166, 2002 相似文献
47.
Yamanaka N Kawano R Kubo W Kitamura T Wada Y Watanabe M Yanagida S 《Chemical communications (Cambridge, England)》2005,(6):740-742
Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazolium cations, resulting in high conductivity of the electrolyte. 相似文献
48.
Takashi Yokoyama Kazuhiro Ikemoto Takatsugu Kihara Kouhei Teramura Keisuke Uryu Kohji Shimizu Motoki Bitoh Kohji Matsuzaki Michio Zenki 《Journal of solution chemistry》2006,35(5):639-657
Coordination equilibrium constants (K
NiS) of some donor solvent molecules to 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecanenickel(II) ([Ni(Me4[12]aneN4)]2+) were determined in nitrobenzene (a noncoordinating bulk solvent). The first (K
NiS1) and second stepwise coordination equilibrium constants (K
NiS2) for 1,4,7,10-tetraazacyclododecanenickel(II) ([Ni([12]aneN4)]2+), 1,4,8,11-tetraazac yclotetradecane- nickel(II) ([Ni([14] aneN4)]2+), 1,4,8,11-tetrathiacyclotetra-decanenickel(II) ([Ni([14]aneS4)]2+) were also reinvestigated. The K
NiS values for [Ni(Me4[12]aneN4)]2+ were compared to those of [Ni([12]aneN4)]2+, (1R,4S, 8R,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecanenickel(II) (R,S,R,S-[Ni(Me4[14]aneN4)]2+), R,R,S,S-[Ni(Me4[14]aneN4)]2+, [Ni([14]aneN4)]2+, and [Ni([14]aneS4)]2+. Coordination of pyridine (Py), N,N,N′,N′-tetramethylurea (TMU), and N,N-dimethylacetamide (DMA) to [Ni(Me4[12]aneN4)]2+ was observed, although these donor solvent molecules did not coordinate to R,S,R,S-[Ni(Me4[14]aneN4)]2+. The K
NiS values for Py, TMU, and DMA are 7.9, 2.8, and 9.0 dm3⋅mol−1, respectively. Some hydrogen-bonding waters were coordinated to R,S,R,S-[Ni(Me4[14]aneN4)]2+, but such waters did not coordinate to [Ni(Me4[12] aneN4)]2+. Also, the K
NiS2 values were larger than the corresponding K
NiS1 values for [Ni([14]aneS4)]2+. Furthermore, the K
NiS1 values for [Ni([12]aneN4)]2+ were the largest among these nickel(II) complex cations. The K
NiS, K
NiS1, and K
NiS2 values are discussed in terms of properties of the donor solvents and steric strains of these nickel(II) complex cations. 相似文献
49.
50.
Papadimitriou V Barker A Briere RA Gibbons LK Makoff G Patterson JR Somalwar S Wah YW Winstein B Winston R Woods M Yamamoto H Swallow EC Bock GJ Coleman R Enagonio J Hsiung YB Ramberg E Stanfield K Tschirhart R Yamanaka T Gollin GD Karlsson M Okamitsu JK Debu P Peyaud B Turlay R Vallage B 《Physical review D: Particles and fields》1991,44(3):R573-R576