全文获取类型
收费全文 | 290篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
化学 | 217篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 5篇 |
物理学 | 80篇 |
出版年
2023年 | 4篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 16篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 18篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 22篇 |
2007年 | 15篇 |
2006年 | 14篇 |
2005年 | 6篇 |
2004年 | 13篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 12篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1964年 | 3篇 |
1963年 | 3篇 |
排序方式: 共有306条查询结果,搜索用时 15 毫秒
281.
A polystyrene‐cross‐linking tricyclohexylphosphine (PS‐TCP) was synthesized through radical emulsion polymerization of 4‐tert‐butylstyrene as a monomer and tris(trans‐4‐styrylcyclohexyl)phosphine as a threefold cross‐linker. The PS‐TCP showed enhanced ligand performance compared to the corresponding polystyrene‐triphenylphosphine hybrid PS‐TPP and tricyclohexylphosphine in Pd‐catalyzed Suzuki–Miyaura and Buchwald–Hartwig reactions of aryl chlorides. 相似文献
282.
It is well known that the MIC–Kepler problem, an extension of the three-dimensional Kepler problems, admits the same dynamical and symmetry groups as the Kepler problem. This paper aims to study dynamical and symmetry groups of the SU(2) Kepler problem, where the SU(2) Kepler problem is defined to be the dynamical system reduced from the eight-dimensional conformal Kepler problem through an SU(2) symmetry and turns out to be an extension of the five-dimensional Kepler problem. It is shown that the SU(2) Kepler problem admits a dynamical group SO*(8) and that the phase space of the SU(2) Kepler problem is symplectomorphic with a co-adjoint orbit of SO*(8), on which the Kirillov–Kostant–Souriau form is defined. It is further shown that the subgroups, SU(4), SU*(4), and Sp(2)×SR5, of SO*(8) provide the symmetry groups, SU(4)/Z2SO(6), SU*(4)/Z2SO0(1,5), and (Sp(2)×SR5)/Z2SO(5)×SR5, of the SU(2) Kepler problem with negative, positive, and zero energies, respectively, where ×S denotes a semi-direct product. Furthermore, constants of motion for the SU(2) Kepler problem are found together with their Poisson brackets. The symmetry Lie algebra formed by constants of motion is shown to be isomorphic with so(6)su(4), so(1,5)su*(4), or so(5)SR5sp(2)SR5, depending on whether the energy is negative, positive, or zero, where S denotes a semi-direct sum. These Lie algebras are subalgebras of so*(8)so(2,6). 相似文献
283.
Iwai Y Kita K Matsushita Y Yamauchi A Kihara M 《Chemical & pharmaceutical bulletin》2002,50(3):441-443
The new coupling reaction of phenacylamines with silylstannane and lithium diisopropylamide (LDA) is reported. The treatment of a phenacylamine iodide 1 with (trimethylsilyl)tributylstannane (Me3SiSnBu3) and cesium fluoride (CsF) gave a dimerization product 2 having no iodine atom. Reaction of 1 with LDA afforded a dimerization product 3 with an iodine atom. The products 2 and 3 were separated to the meso and racemic isomers, respectively. 相似文献
284.
Shinji Takeoka Hiroyuki Ohno Hidetaka Iwai Eishun Tsuchida 《Journal of polymer science. Part A, Polymer chemistry》1990,28(4):717-730
Small and large unilamellar liposomes composed of 1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine (DODPC) are prepared by sonication and extrusion, respectively. They are polymerized with water-insoluble radical initiator, azobis(isobutyronitrile) (AIBN) which can selectively polymerize diene groups in 1-acyl chains of the lipids. Polymerized liposomes are freeze-dried to obtain the polymerized liposome powder. There are two methods to redisperse lyophilized liposomes into water. The extrusion is an effective method to disperse them because the energy at extrusion is necessary only for redispersion, whereas the excess energy at sonication gives damage on liposome structure. There is no difference in stability between polymerized liposomes before and after redispersion with extrusion. DODPC polymers, obtained from free radical-initiated polymerization with AIBN, are linear and have polymerizable diene groups in 2-acyl chains. The liposome powder is therefore soluble in organic solvents. Reconstruction of polymerized liposomes is performed with lipid polymers having low or high molecular weight. The lipid polymers having high molecular weight provide stable large unilamellar liposomes by ethanol injection, but unstable small unilamellar liposomes are formed by sonication. The liposomes reconstructed from lipid polymers having low molecular weight are unstable regardless of their size. After reconstruction of liposomes selectively polymerized by AIBN, diene groups in 2-acyl chains are polymerized by water-soluble radical initiator or UV-irradiation to yield highly crosslinked structure. Their stability is improved remarkably by this postpolymerization. 相似文献
285.
Iwai H Fang-Yen C Popescu G Wax A Badizadegan K Dasari RR Feld MS 《Optics letters》2004,29(20):2399-2401
We describe a quantitative phase-imaging interferometer in which phase shifting and noise cancellation are performed by an active feedback loop using a reference laser. Depth gating via low-coherence light allows phase measurement from weakly reflecting biological samples. We demonstrate phase images from a test structure and living cells. 相似文献
286.
Uchiyama S Kawai N de Silva AP Iwai K 《Journal of the American Chemical Society》2004,126(10):3032-3033
We illustrate a general polymeric design of fluorescent logic gates, for example, AND, using temperature and pH as inputs. 相似文献
287.
A bi-directional fiber ring laser with a semiconductor optical amplifier has been developed in which a frequency difference between the counter-propagating oscillations is controlled by an introduced birefringent medium. With the material which causes the retardation change by a physical phenomenon to be measured, the laser in this study is applicable to a novel fiber sensor of which the sensing signal is obtained in a frequency domain. 相似文献
288.
Iwai S Ono M Maeda A Matsuzaki H Kishida H Okamoto H Tokura Y 《Physical review letters》2003,91(5):057401
We demonstrate the ultrafast photoinduced Mott transition from a charge transfer insulator to a metal in a halogen-bridged Ni-chain compound by pump-probe reflection spectroscopy. Upon the irradiation of a 130-femtosecond laser pulse, the spectral weight of the gap transition is transferred to the inner-gap region. When the photoexcitation density exceeds 0.1/Ni site, the Drude-like high-reflection band appears in the infrared region, signaling the formation of a metallic state. The photogeneration of the metallic state and the subsequent recovery to the original gapped state occur within a few picoseconds. 相似文献
289.
This paper investigates, experimentally, the dynamic properties of triply-scattered speckled speckles and their application to the velocity measurement of a moving diffuse object, which is behind a transparent diffuse screen. The comparison between triply-scattered speckled speckles and singly-scattered normal speckles shows that the triply-scattered speckle pattern has a high degree of randomness in the spatial domain and that its time-varying intensity fluctuations have a rate 72 times that of the normal speckle case in the temporal domain. Consequently, a velocimeter using the triply-scattered speckles can measure the object velocity with a greatly reduced measuring time than when using normal speckles. 相似文献
290.