全文获取类型
收费全文 | 2988篇 |
免费 | 81篇 |
国内免费 | 14篇 |
专业分类
化学 | 2083篇 |
晶体学 | 26篇 |
力学 | 43篇 |
数学 | 198篇 |
物理学 | 733篇 |
出版年
2022年 | 18篇 |
2021年 | 23篇 |
2020年 | 36篇 |
2019年 | 31篇 |
2018年 | 27篇 |
2017年 | 29篇 |
2016年 | 58篇 |
2015年 | 40篇 |
2014年 | 65篇 |
2013年 | 124篇 |
2012年 | 143篇 |
2011年 | 160篇 |
2010年 | 77篇 |
2009年 | 86篇 |
2008年 | 162篇 |
2007年 | 169篇 |
2006年 | 170篇 |
2005年 | 154篇 |
2004年 | 115篇 |
2003年 | 110篇 |
2002年 | 109篇 |
2001年 | 80篇 |
2000年 | 69篇 |
1999年 | 59篇 |
1998年 | 35篇 |
1997年 | 31篇 |
1996年 | 33篇 |
1995年 | 33篇 |
1994年 | 28篇 |
1993年 | 35篇 |
1992年 | 55篇 |
1991年 | 52篇 |
1990年 | 34篇 |
1989年 | 36篇 |
1988年 | 43篇 |
1987年 | 37篇 |
1986年 | 36篇 |
1985年 | 57篇 |
1984年 | 42篇 |
1983年 | 35篇 |
1982年 | 34篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 32篇 |
1978年 | 22篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1975年 | 19篇 |
1974年 | 19篇 |
1973年 | 22篇 |
排序方式: 共有3083条查询结果,搜索用时 31 毫秒
891.
K. Okuma T. Fujisaki Y. Nakazawa K. Saito M. Oguni 《Journal of Thermal Analysis and Calorimetry》2005,81(3):587-590
Summary We have performed low-temperature heat capacity measurements on pellet samples of (DMe-DCNQI)2M (M=Li, Ag) which is known to show spin-Peierls transitions at 51 and 86 K, respectively. A linearly temperature-dependent term in the low-temperature heat capacity has been observed for both the samples: It is attributable to the spin-wave excitations induced by the inhomogeneous pressure effects produced in the pellet forming process. Although the temperature dependences of the magnetic susceptibility in both materials are almost the same, the coefficient of T-linear term of the Ag salt becomes three times larger that that of the Li salt. The peculiar electronic state originating from the competition of the spin-Peierls mechanism and the Coulomb repulsion is suggested. 相似文献
892.
Jun Terao Kazushi Torii Koyu Saito Nobuaki Kambe Akio Baba Noboru Sonoda 《Angewandte Chemie (International ed. in English)》1998,37(19):2653-2656
Vinylsilanes and/or allylsilanes are formed upon silylation of terminal alkenes with R3′SiCl in the presence of a Grignard reagent and a catalytic amount of [Cp2ZrCl2] [Eq. (a)]. The reaction also proceeds under mild conditions when silylsulfides (X=SPh), silylselenides (X=SePh), and silyltellurides (X=TePh) are used in place of chlorosilanes (X=Cl). R″=alkyl, aryl, alkylsilyl; R′=Me, Et, nPr; R=CH2R″, aryl, H. 相似文献
893.
Hiroshi Saito Xiangdong Wu J. Milton Harris Allan S. Hoffman 《Macromolecular rapid communications》1997,18(7):547-550
Graft copolymers of poly(ethylene glycol) (PEG) on a chitosan backbone (PEG-g-chitosan) have been synthesized and their aqueous solution properties were investigated. At pH 6.5 the graft copolymers are 100% soluble, while chitosan phase separates from solution at those conditions. These interesting graft copolymers may be especially suitable as carriers for delivery of anionic drugs, such as proteins, glycosaminoglycans, and DNA plasmids or oligonucleotides. 相似文献
894.
Tetsumi Tanabe Evgeni B. Starikov Koji Noda Manabu Saito 《Chemical physics letters》2006,430(4-6):380-385
Electron-cation collisions have been studied for various protonated deoxyoligonucleotide monocations, using an electrostatic storage ring equipped with a merged-electron-beam device. Resonant neutral-particle emissions have been observed at a collision energy of about 4.5 eV for some of them. The resonance parameters depend on DNA base composition and sequence, and the resonances occur only in oligonucleotide monocations with base stacking. The resonance widths increase with oligonucleotide length, but saturate at trimers. Quantum-chemical estimations performed here help explain these results. 相似文献
895.
896.
Ikuko Tsukamoto Madoka Saito Minako Yamane Kenji Kawata Yuji Kitamura Youji Kitamura Masaki Mifune Yutaka Saito Jun Haginaka 《Analytical sciences》2006,22(7):1035-1038
The effect of the central metal of columns packed with silica gels binding Ni(2+)- and Cu(2+)-phthalocyanine derivatives (Ni-and Cu-PCS(D)s) on the retention behavior of poly-aromatic-hydrocarbons (PAHs) thereof in a polar eluent was examined. The retention factors of PAHs on the Ni- and Cu-PCS(D)s in 80% methanol showed a good linear correlation. The Cu-PCS(D) column exhibited the pi-pi interactions for PAHs, while the Ni-PCS(D) column exhibited the pi-d interactions for PAHs in addition to the pi-pi interaction for PAHs. Further, an investigation of the retention behavior of anthracene derivatives having different substituents revealed that the Ni- and Cu-PCS(D) columns could recognize the differences of substituents only in a polar eluent. 相似文献
897.
Yasumitsu Matsuo Go Kumasaka Keiko Saito Seiichiro Ikehata 《Solid State Communications》2005,133(1):61-64
We have fabricated a fuel cell based on the DNA film (DNAFC) and examined its properties under various humidity conditions at room temperature. The open-circuit voltage of a DNAFC is generated by supplying H2 gas to the anode. The open-circuit voltage strongly depends on the humidity conditions, and in a DNA film, the optimum condition in which the open-circuit voltage attains a value as high as 0.55 V is achieved under the relative humidity condition of 55%. Furthermore, the cell voltage of the DNAFC decreases with an increase in current density, as observed in fuel cells such as proton exchange membrane fuel cell, solid oxide fuel cell, and several others. These results indicate that DNA film can be used as the fuel cell electrolyte under approximately 55% humidity condition. 相似文献
898.
The orientation behavior of polystyrene‐block‐hydrogenated polyisoprene‐block‐polystyrene (SEPS) with cylindrical microdomains of polystyrene (PS) dispersed in the rubbery segments was investigated by simultaneous measurements of stress and birefringence during uniaxial stretching. The stress increased sharply with strain below the yield strain and then it gradually increased. In contrast, the birefringence changed little below the yield strain, increased sharply with strain above the yield strain up to a strain of 0.5, and then gradually increased. The characteristic birefringence behavior is attributed to the form birefringence induced by the orientation and the parallel arrangement of the cylindrical microdomains associated with the orientation of the rubbery segments. The orientation function of the cylindrical microdomains f evaluated by analyzing the form birefringence agrees well with that obtained from the SAXS result. The f was almost zero below the yield strain and it increased sharply with strain up to a strain of 0.5 and then was constant above a strain of 0.5. These results suggest that the orientation of the cylindrical microdomains occur above the yield strain up to a strain of 0.5 and that the orientation does not increase above a strain of 0.5 in spite of the continuous orientation of the rubbery ethylene–propylene segments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 715–723, 2009 相似文献
899.
The international HypHI collaboration proposes to perform hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR in order to study neutron and proton rich hypernuclei and to measure directly hypernuclear magnetic moments for the first time.The project is divided into four phases.In the first Phase 0 experiment,the feasibility of precise hypernuclear spectroscopy with heavy ion beams will be demonstrated by observing π~- decay channels of ~e_ΛH,~4_ΛH and ~5_ΛHe with ~6Li projectiles at 2 AGeV impinging on a ~(12)C target.In the later Phases 1 through 3,studies of proton and neutron rich hypernuclei,direct measurements of hypernuclear magnetic moments and the spectroscopy of hypernuclei toward the nucleon drip-lines are planned. 相似文献
900.
Kunio Hiroi Fumiko Kato Takamasa Oguchi Shinya Saito Takanori Sone 《Tetrahedron letters》2008,49(22):3567-3569
α-Allenylcyclopropanedicarboxylates, for which a novel synthetic method has been devised by conjugate addition of a copper hydride (Stryker) reagent to α-cyclopropylpropargylic esters, have been newly found to be smoothly converted to methylenecyclopentene derivatives under mild reaction conditions by further treatment with the copper hydride reagent. The mechanistic pathway is discussed. 相似文献