全文获取类型
收费全文 | 438篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
化学 | 303篇 |
晶体学 | 5篇 |
力学 | 7篇 |
数学 | 56篇 |
物理学 | 82篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 18篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 21篇 |
2012年 | 28篇 |
2011年 | 34篇 |
2010年 | 9篇 |
2009年 | 15篇 |
2008年 | 29篇 |
2007年 | 25篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 26篇 |
2003年 | 21篇 |
2002年 | 25篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1967年 | 3篇 |
1964年 | 1篇 |
排序方式: 共有453条查询结果,搜索用时 0 毫秒
101.
Kaname Kanai Kouki Akaike Kiichirou Koyasu Kentaro Sakai Toshio Nishi Yasunori Kamizuru Tatsuhiko Nishi Yukio Ouchi Kazuhiko Seki 《Applied Physics A: Materials Science & Processing》2009,95(1):309-313
The unoccupied π
* states of the solid film of electron accepting organic molecules, 7,7,8,8-tetracyanoquinodimethane (TCNQ), fluorinated TCNQ
derivatives, 11,11,12,12-tetracyanonaphtho-2,6-quinodimethane (TNAP), C60, and 6,6-phenyl-C61-butyric acid methyl ester (PCBM) have been studied by inverse photoemission spectroscopy. The assignment of the π
* affinity levels of these typical electron accepting molecules provides the basic information for the organic electronics
and the new electronic functional molecular design. The comparison with density functional theory calculations enables understanding
how the electron affinity evolves in terms of molecular orbitals. The correlation between the film morphology and the irradiation
damage on the TCNQ derivative samples by electron impact during the inverse photoemission measurements is also discussed. 相似文献
102.
Yasunori Ohba Chika Watanabe Shigeaki Nakazawa Seigo Yamauchi 《Applied magnetic resonance》2010,37(1-4):781-794
We reported determination of the loaded quality factor (Q) of highly overcoupled (dielectric, loop-gap, and cavity) resonators used in time-domain electron paramagnetic resonance. We introduced a microwave absorber into resonators and achieved critical-coupling. Due to the deep “Q-dip” of critical-coupling, we can easily determine the loaded Q as low as 10. The loaded Q of resonators with and without the microwave absorber was examined under various overcoupling conditions. We found that the radiation Q (Q r) can be calculated from the loaded Q of the resonator that contains the microwave absorber. We proposed a simple model that represents the loaded Q of the overcoupled resonator in terms of two parameters, Q 0 and Q r. Q 0 is the effective unloaded Q of the resonator determined for the critically coupled resonator without the microwave absorber and is independent of a degree of coupling. The model can be applied to overcoupling in which the coupling parameter (Q 0/Q r) is in the range of 1 to ca. 20. 相似文献
103.
Yasunori Iwai Akihiro Hiroki Masao Tamada Kanetsugu Isobe Toshihiko Yamanishi 《Radiation Physics and Chemistry》2010,79(1):46-51
The cation-exchange Nafion N117 membranes swelling in electrolyte solution were irradiated with γ-rays or electron beams at various doses up to 1500 kGy in the temperature range from room temperature to 343 K to obtain detailed information on the effect of ion-exchange on the radiation deterioration in mechanical properties and ion-exchange capacity. Considerable deterioration in mechanical properties was observed when the Nafion membranes swelling in electrolyte solution were irradiated. A reason is the promotion of degradation with oxygen molecules produced by the irradiation of electrolyte solution. The concentration of electrolyte solution influenced strongly the radiation deterioration in mechanical properties. Keeping the concentration of metal ions to be negligible is important when electrolyzed highly radioactive solution in the light of the durability of polyperfluorosulfonic acid (PFSA) membrane. A sort of cation in electrolyte solution negligibly influenced radiation deterioration in mechanical properties. A sort of anion in electrolyte solution had negligible effect on radiation deterioration in mechanical properties and ion-exchange capacity. The discrepancy in the radiation deterioration in mechanical properties of Nafion membranes swelling in NaCl solution was observed between the specimens irradiated with γ-rays and electron beams. This discrepancy can be explained from the low diffusivity of oxygen from bulk into the membrane. 相似文献
104.
Three new dimeric benzofuran derivatives, ligulacephalins A (1), B (2) and C (3), were isolated from the roots of Ligularia stenocephala MATSUM. ET KOIDZ. (Compositae) together with three known compounds, 5,6-dimethoxy-2-isopropenylbenzofuran (4), euparin (5) and (R)-(-)-hydroxytremetone (6). The structures of the new compounds were determined by spectroscopic evidence. The chiral HPLC analysis demonstrated that 1-3 occurred as a racemate. The absolute configurations of each enantiomer from 1-3 were elucidated on the basis of circular dichroism (CD) data. 相似文献
105.
The mechanism of second H2O formation in fully reduced cytochrome c oxidase is examined by sequential additions of one electron and two protons to a [Fe(IV)O, Cu(II)] compound II, which is the final intermediate of first H2O formation. It is found that the addition of one electron induces the concerted proton–electron transfer from the CuB to FeO moieties with no energy barriers. The H2O molecule coordinating to the Cu atom is a key molecule for the proton transfer from the CuB moiety to the FeO and/or Fe–OH moieties. It is also found from the results in previous and the present works that one can realize the reduction process of dioxygen by fully reduced cytochrome c oxidase. 相似文献
106.
Seven new compounds were isolated from the roots of Ligularia dentata, including five bisabolane‐type sesquiterpenoids (bisabolane=1‐(1,5‐dimethylhexyl)‐4‐methylcyclohexane), namely (8β,10α)‐8‐(angeloyloxy)‐5,10‐epoxybisabola‐1,3,5,7(14)‐tetraene‐2,4,11‐triol ( 1 ), (8β,10α)‐8‐(angeloyloxy)‐5,10‐epoxythiazolo[5,4‐a]bisabola‐1,3,5,7(14)‐tetraene‐4,11‐diol ( 2 ), (1α,2α,3β,5α,6β)‐1,5,8‐tris(angeloyloxy)‐10,11‐epoxy‐2,3‐dihydroxybisabol‐7(14)‐en‐4‐one ( 3 ), (1α,2α,3β,5α,6β)‐2,5,8‐tris(angeloyloxy)‐10,11‐epoxy‐1,3‐dihydroxybisabol‐7(14)‐en‐4‐one ( 4 ), and (1α,2β,3β,5α,6β)‐1,8‐bis(angeloyloxy)‐2,3‐epoxy‐5,10‐dihydroxy‐11‐methoxybisabol‐7(14)‐en‐4‐one ( 5 ) (angeloyloxy=[(2Z)‐2‐methyl‐1‐oxobut‐2‐enyl]oxy), and two lactone derivatives, (2α,3β,5α)‐2‐(acetyloxy)‐9‐methoxy‐5‐(methoxycarbonyl)‐2,3‐dimethylheptano‐5‐lactone ( 6 ), and (2β,4β)‐2‐ethyl‐5‐hydroxy‐5‐(methoxycarbonyl)‐4,5‐dimethylpentano‐4‐lactone ( 7 ) (α/β denote relative configurations), together with (2E,4R,5S)‐2‐ethylidene‐5‐(methoxycarbonyl)‐4‐methylhexano‐5‐lactone ( 8 ), a known synthetic compound. Compound 2 is the first sesquiterpenoid derivative containing the uncommon benzothiazole moiety. The structures of 1 – 8 were established by spectroscopic methods, especially 2D‐NMR and MS analyses. 相似文献
107.
Application of integrated computer simulation approach to solid surfaces and interfaces 总被引:2,自引:0,他引:2
Abhijit Chatterjee Momoji Kubo Kazuo Teraishi Hiromitsu Takaba Yasunori Oumi Akira Miyamoto 《Catalysis Surveys from Japan》1998,2(2):133-153
The atomistic understanding of the structure, reactivity, and electronic properties of solid surfaces and interfaces are essential for the design of novel catalysts and electronics/photonics devices which have high-performance and unexplored properties. Computational chemistry is expected not only to rationalize the experimental results but also to predict new features. We have applied integrated computer simulation methods including quantum chemistry, periodic density functional theory, molecular dynamics, embedded atom method, and atomic force microscopy simulation to various topics related to solid surfaces and interfaces. In the present paper, we reviewed our recent activities on supported metal catalysts, metal clusters, atomic force microscopy simulation, high-temperature superconductors, tribology, Si semiconductor and V2O5 catalysts. Our activities also involve the generation of a lot of new computer simulation codes. We emphasize that the integrated computer simulation system provides not only methods for scientific studies but also a key technology for industrial innovations in research and development. 相似文献
108.
Chang CJ Nolan EM Jaworski J Okamoto K Hayashi Y Sheng M Lippard SJ 《Inorganic chemistry》2004,43(21):6774-6779
The synthesis of a difluorofluorescein monocarboxaldehyde platform and its use for preparing ZP8, a new member of the Zinpyr family of neuronal Zn(2+) sensors, are described. By combining an aniline photoinduced electron transfer (PET) switch and an electron-withdrawing fluorescein scaffold, ZP8 displays reduced background fluorescence and improved dynamic range compared to previous ZP probes. The bright sensor undergoes an 11-fold increase in fluorescence intensity upon Zn(2+) complexation (Phi = 0.03-0.35) with high selectivity over cellular concentrations of Ca(2+) and Mg(2+). In addition, sensors in the ZP family have been utilized for optical imaging in biological samples using two-photon microscopy (TPM). The cell-permeable ZP3 probe is capable of identifying natural pools of labile Zn(2+) within the mossy fiber synapses of live hippocampal slices using TPM, establishing the application of this technique for monitoring endogenous Zn(2+) stores. 相似文献
109.
Steven A. Markgraf Yasunori Furukawa Masayoshi Sato 《Journal of Crystal Growth》1994,140(3-4):343-348
We report on the top-seeded solution growth of LiB3O5 from an excess B2O3 solution. Parameters investigated include the Li2O/B2O3 ratio, rotation rate, pulling rate, cooling rate, and seed direction. With careful control of the above parameters, we have grown clear crystals of 25 × 30 × 20 mm in size. Selected nonlinear optical properties of these crystals are reported. Observations concerning the occurrence of unstable growth (inclusions, hopper growth) are discussed, and methods to eliminate the unstable growth are suggested. 相似文献
110.
Shizuo Tokito Hiromitsu Tanaka Koji Noda Akane Okada Yasunori Taga 《Macromolecular Symposia》1998,125(1):181-188
Novel hole and electron transporting materials have been synthesized to improve the thermal stability of organic electroluminescent (EL) devices. Molecular structures of such hole and electron transporting materials were designed based on triphenylamine (TPA) and oxadiazole (OXD) moieties, respectively. It has been found that the resulting materials have high glass transition temperatures (Tg) over 100°C and the vacuum-deposited thin films are significantly thermally stable. For the two-layer EL devices using the novel hole transporting materials and the typical emitting material, tris(8-quinolinolato) aluminum, the thermal stability has been clearly seen to depend on the Tg of the hole transporting material; excellent thermal stability was achieved. For the three-layer EL device using the novel electron transporting material, good emission efficiency and good stability were achieved. The electron transporting materials have been also applied to the polymeric system with polyvinylcarbazole matrix. 相似文献