全文获取类型
收费全文 | 582篇 |
免费 | 41篇 |
国内免费 | 1篇 |
专业分类
化学 | 458篇 |
晶体学 | 15篇 |
力学 | 3篇 |
数学 | 32篇 |
物理学 | 116篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 20篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 24篇 |
2013年 | 41篇 |
2012年 | 60篇 |
2011年 | 62篇 |
2010年 | 32篇 |
2009年 | 29篇 |
2008年 | 34篇 |
2007年 | 32篇 |
2006年 | 26篇 |
2005年 | 22篇 |
2004年 | 22篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有624条查询结果,搜索用时 31 毫秒
101.
102.
Takaaki Shirai Shunsuke Satou Morihiro Saito Jun Kuwano Hidenobu Shiroishi 《Solid State Ionics》2009,180(6-8):569-574
The proton conducting 0.9MO2·0.05In2O3·1.3P2O5 (MTi, Sn, Zr) electrolytes based on a core-shell structure were synthesized by a ball milling method. The core-shell type electrolytes showed the proton conductivities ranging from a higher value than those of Nafion membranes to 10? 5 Scm? 1 at intermediate temperatures of 150–200 °C, depending on the heat-treatment conditions. The samples with high conductivity were proved to adopt a core-shell structure by SEM observation, powder XRD analysis and 31P MAS-NMR measurements. 相似文献
103.
Chiral phosphine oxide successfully catalyzed the direct aldol-type reactions of cyclohexanone derivatives and benzaldehyde derivatives in high stereoselectivities. The reaction mechanism involves the in situ formation of trichlorosilyl enol ethers. The present reaction could be extended to the cross-aldol reactions between two aldehydes. 相似文献
104.
The Ni-catalyzed [3+2+2] cocyclization between ethyl cyclopropylideneacetate (1) and 1,3-diynes afforded cycloheptadiene derivatives. The three-component reaction of 1, 1,3-diynes, and alkynes proceeded with good yield and high selectivity. Scope of the substrates was studied, and the origin of chemo- and regioselectivity of the reaction is discussed. 相似文献
105.
Isamu Shiina Takashi Katoh Shunsuke Nagai Minako Hashizume 《Chemical record (New York, N.Y.)》2009,9(6):305-320
Various intermediates for the synthesis of erythronolide A, an aglycon of erythromycin A, are prepared from the corresponding seco‐acids using 2‐methyl‐6‐nitrobenzoic anhydride (MNBA) in the presence of 4‐(dimethylamino)pyridine (DMAP) with or without triethylamine. The efficiency of the MNBA lactonization is assessed by studying this method and comparing the results with those of the other established macrocyclization protocols. It has been finally concluded that (i) the conformationally appropriate substrate for the monomeric cyclization gave the desired lactone in excellent yield under mild reaction conditions in the presence of MNBA and DMAP, (ii) the highly‐strained substrate for the cyclization also afforded the monomeric lactone in relatively good yield at 100°C in toluene, and (iii) the seco‐acid having stable linear conformation, which preferred dimerizing more than forming the monomeric lactone, provided the corresponding diolide in high yield with the constant ratio of the monomer to dimeric lactone (approximately 1/5). © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 305–320; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.200900017 相似文献
106.
Shunsuke Murai Ryosuke Hattori Tomohiko Matoba Koji Fujita Katsuhisa Tanaka 《Journal of Non》2011,357(11-13):2259-2263
Wavelength-selective enhancement of optical birefringence has been observed in a tellurite glass containing silver nanoparticles (Ag NPs) induced via thermal poling. The birefringence appears as an optical rotation of linearly polarized light; a large optical rotation is observed at around the wavelength of localized surface plasmon resonance (LSPR) of Ag NPs. The optic axis is oriented along the electric field applied during the thermal poling, suggesting that birefringence induced in the glass matrix through the thermal poling is drastically enhanced by the NPs at around the LSPR. Because of the birefringence of the matrix, the wavelength of LSPR shifts depending on the polarization state of the incident light, which in turn induces the polarization dependence of the real part of the refractive index via the Kramers–Kronig relation. 相似文献
107.
Jing R Guang Y Huidan Z Guorong C Tanaka K Fujita K Murai S Tsujiie Y 《Optics letters》2006,31(23):3492-3494
Second-harmonic generation in 60GeS(2)-20Ga(2)S(3)-20KBr chalcohalide glass was investigated by the thermal poling method. A large second-order nonlinear susceptibility, as high as 7.0 pm/V, was obtained in a poled sample by Maker fringe analysis. We believe this to be the first time that a clear second-harmonic wave was observed in chalcohalide glasses containing large amount of alkali ions (6.25 at. %). Such observation is of great potential use in all optical waveguide devices. 相似文献
108.
Shunsuke Kurioka David R. Dowling 《International Journal of Computational Fluid Dynamics》2013,27(3):233-243
Three-dimensional dynamic gas–liquid flow simulations that accurately track the phase interface are numerically challenging. This article presents a numerical study of the performance of the level-set phase–interface tracking method when combined with extremely high order (7th to 11th) weighted essentially non-oscillatory (WENO) advection schemes for gas–liquid free surface flows. Comparisons between simulation results and prior benchmark results suggest that such a combination of methods can be satisfactorily applied to the level-set and Navier-Stokes equations for free surface flow simulations when volume conservation is enforced at every time step, and minor numerical oscillations are suppressed through use of an artificial viscosity term. In particular, simulations of solid body rotation, the unsteady flow following an ideal dam break, tank sloshing, and the rise of a single bubble all agree with analytical or experimental results to within ± 3.12% when the level-set method is combined with an 11th order WENO scheme. Furthermore, use of an 11th order WENO advection scheme actually has a computational cost advantage because, for the same accuracy, it can be used on a coarser grid when compared with a more-common second-order advection scheme; computational savings of up to 87% are possible. 相似文献
109.
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110.
A synthetic method of azaspirocyclohexadienones has been developed through copper-catalyzed aerobic spirocyclization of biaryl-N-H-imines prepared by the reaction of biarylcarbonitriles and Grignard reagents. 相似文献