全文获取类型
收费全文 | 467篇 |
免费 | 28篇 |
国内免费 | 1篇 |
专业分类
化学 | 392篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 5篇 |
物理学 | 94篇 |
出版年
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 13篇 |
2014年 | 15篇 |
2013年 | 18篇 |
2012年 | 36篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 20篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 20篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1972年 | 8篇 |
1968年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有496条查询结果,搜索用时 15 毫秒
91.
A conceptual design of a high efficiency, high repetition-rated (rep-rated) pulsed power system for an electron-beam (e-beam)
pumped KrF laser driver for inertial fusion energy (IFE) is presented. The proposed pulsed power circuit incorporates linear
induction voltage adders to charge pulse forming lines for the generation of 900 kV, 260 ns e-beamsat several Hz. This rep-rated
power system meets the pulsed power requirements of the future IFE drivers that necessitate high amplifier efficiency as well
as high laser energy.
Received: 3 March 2000 / Published online: 16 June 2000 相似文献
92.
The chiral heterobimetallic complexes Li[Ln(η5 : η1-C5R41SiMe2NCH2CH2R2)2] (Ln = Y, Lu; C5R41 = C5Me4, C5H4, 3-C5H3 t Bu; R2 = OMe, NMe2; Me: methyl; tBu: tert-butyl) have been found to polymerize ϵ-caprolactone to give a polymer of high molecular weight (M̄n < 20 000) and moderate polydispersity (M̄w/M̄n < 2.0). Failure to observe a correlation between monomer/initiator ratio and molecular weight suggests a polymerization mechanism different from a pseudo-anionic mechanism. 相似文献
93.
Takashi Uemura Nobuyuki Okuda Hiroya Kirmura Yasuko Okuda Yoshinobu Ueba Tuguru Shirakawa 《先进技术聚合物》1997,8(7):437-442
Electroluminescent(EL) devices have been fabricated using four different polymers with different glass transition temperatures (Tg) dispersed with N,N′-bis-(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD) as a hole transport layer and tris(8-hydroxyquinoline) aluminum (Alq3) as an emitting layer. It was found that the higher the Tg of the polymer, the longer the lifetime of the device. From observations of TPD-doped polymer films with optical microscope and atomic force microscope, dispersing TPD in the polymers was found to suppress the crystallization that causes the roughness of the film surface. It was also observed that the higher the Tg of the host polymers, the more difficult TPD crystallization was. The property of the EL device with polyethersulfone (PES) dispersed with TPD was also investigated. The lifetime of EL device with the TPD doped PES film was improved more than five times at a current density below 10 mA/cm2 compared with the device with a conventional TPD hole transport layer. © 1997 John Wiley & Sons, Ltd. 相似文献
94.
N. Taguchi A. Iwase N. Maeda T. Kojima R. Taniguchi S. Okuda T. Akita T. Abe T. Kambara H. Ryuto F. Hori 《Radiation Physics and Chemistry》2009,78(12):1049-1053
Bimetallic Au–Pd nanoparticles were synthesized under high-energy irradiation fields (1.17 and 1.33 MeV γ-rays, 9 MeV electrons, and 1.6 GeV C ions) from solutions containing Au3+ and Pd2+ and cationic surfactant (sodium dodecyl sulfate). Particles synthesized by the irradiation were observed using conventional transmission electron microscope (TEM) and annular dark-field scanning transmission electron microscopy (ADF-STEM). The particles synthesized by γ-rays and C ion irradiation exhibit core–shell structure with a Au-core and a Pd-shell. The dependence of the size distribution of nanoparticles on the dose rate is discussed. 相似文献
95.
Thomas S. Dols Thomas P. Spaniol Jun Okuda 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(11):m443-m446
High‐quality crystals of two bis(phenolate)titanium complexes, namely dichlorido{4,4′‐dimethyl‐2,2′‐[cyclohexane‐1,2‐diylbis(sulfanediyl)]diphenolato}titanium(IV), [Ti(C20H22O2S2)Cl2], (I), and dichlorido{2,2′‐[cyclohexane‐1,2‐diylbis(sulfanediyl)]diphenolato}titanium(IV), [Ti(C18H18O2S2)Cl2], (II), were obtained by reactive crystallization. Depending on the solvent, compound (II) was obtained as unsolvated (IIa) or as the toluene hemisolvate, [Ti(C18H18O2S2)Cl2]·0.5C7H8, (IIb). These systems without bulky substituents on the aromatic phenolate rings serve as ideal model compounds for precatalysts. The excellent X‐ray diffraction data will help clarify the nature of the mismatched interactions between the soft S atoms within the ligand and the hard titanium center. Molecule (I) has crystallographic C2 symmetry. 相似文献
96.
Hakamata W Nakanishi I Masuda Y Shimizu T Higuchi H Nakamura Y Saito S Urano S Oku T Ozawa T Ikota N Miyata N Okuda H Fukuhara K 《Journal of the American Chemical Society》2006,128(20):6524-6525
Planar catechin analogues having various alkyl side chain lengths were synthesized, and their remarkable antioxidative abilities and alpha-glucosidase inhibitory activities are shown. 相似文献
97.
Hirofumi Okuda Shigeru Matsushima Hideshi Sugiura Kenji Yamada Shunsuke Hamada Yoshihiro Nishida Naoki Ishiguro 《Magnetic resonance imaging》2014
Objective
Equivalent cross-relaxation rate imaging (ECRI) is an MRI technique used to evaluate qualitative changes in protein-water interactions. We aimed to prospectively evaluate the utility of ECRI for classification of adipocytic tumors.Materials and Methods
Institutional Review Board approval was obtained and all patients provided informed consent. Study participants included 40 patients with adipocytic tumors who were diagnosed with lipomas (n = 22), atypical lipomatous tissue/well-differentiated liposarcoma (ALT/WDL; n = 9), myxoid/round cell liposarcoma (MyL; n = 6), and dedifferentiated liposarcoma (DDL; n = 3), and 20 control patients for whom subcutaneous fat in the buttock or thigh was analyzed.Results
Mean ECR values of lipomas, ALT/WDL, and subcutaneous fat were low, and those of MyL and DDL were high. Mean ECR values of MyL and DDL were significantly higher than those of ALT/WDL. The cut-off value was 5.1%. There was a positive correlation between ECR value, pathological grade, and cell density in adipocytic tumors.Conclusion
The ECR value positively correlates with pathological grade and cell density of adipocytic tumors. Our findings suggest that ECRI is a useful method for preoperative evaluation of adipocytic tumors. 相似文献98.
Ajiro H Beckerle K Okuda J Akashi M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(12):5372-5378
The stereoregular synthetic polymer isotactic polystyrene bearing partially sulfonated groups (SiPS) was used as a layer-by-layer assembled thin film for the first time. When a low molecular weight compound was employed as the pair for the alternative layer-by-layer (LbL) assembly, the frequency shift was very small using quartz crystal microbalance (QCM) analysis, whereas poly(vinylamine) (PVAm) formed an effective pair for the construction of LbL films with SiPS. When it was neutralized, SiPS was not assembled, probably due to the loss of effective polymer-polymer interactions. The ionic strength conditions revealed a slight difference of the assembly behavior on the isotactic polymer as compared to the atactic one. The assembled LbL film showed the same peaks over the range from 1141 to 1227 cm(-1) and 700 cm(-1) in the FT-IR/ATR spectra as the bulk complex of SiPS/PVAm, and the thickness on one side was calculated at 76 nm by QCM analysis. The surface roughness of the film was also observed by AFM. 相似文献
99.
Jun-ichi Horinaka Atsushi Okuda Ryosuke Yasuda Toshikazu Takigawa 《Colloid and polymer science》2012,290(17):1793-1797
Dynamic viscoelasticity measurements were carried out for concentrated solutions of linear d-glucans in BmimCl to examine the effect of the linkage between repeating units of glucose on the rheological properties. The values of molecular weight between entanglements (M e) were determined for four d-glucans: curdlan, pullulan, cellulose, and amylose. From the concentration dependence of M e, the value of M e in the molten state (M e,melt) for each d-glucan was estimated as a material constant. The order of M e,melt became cellulose?<?pullulan?<?curdlan?<?amylose, indicating that the linkage is actually influential in M e,melt for the linear d-glucans. The relationship between M e,melt and the molecular structure of the d-glucans were discussed assuming that the values of M e,melt for the d-glucans primarily reflect the chain stiffness such as the characteristic ratio C ∞ on the analogy of synthetic polymers. Although the trend was not so clear, it was shown that N unit is a decreasing function of C ∞ . 相似文献
100.
Miyamoto K Kimura A Kuroda K Okuda T Shimada K Namatame H Taniguchi M Donath M 《Physical review letters》2012,108(6):066808
The surface of W(110) exhibits a Dirac-cone-like state with d character within a spin-orbit-induced symmetry gap. As a function of the wave vector parallel to the surface, it shows a nearly massless energy dispersion and a pronounced spin polarization, which is antisymmetric with respect to the Brillouin zone center. In addition, the observed constant energy contours are strongly anisotropic for all energies. This discovery opens new pathways to the study of surface spin-density waves arising from a strong Fermi surface nesting as well as d-electron-based topological properties. 相似文献