全文获取类型
收费全文 | 85篇 |
免费 | 9篇 |
专业分类
化学 | 52篇 |
力学 | 1篇 |
数学 | 19篇 |
物理学 | 22篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 7篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 6篇 |
1973年 | 1篇 |
排序方式: 共有94条查询结果,搜索用时 0 毫秒
81.
Dini D Calvete MJ Hanack M Pong RG Flom SR Shirk JS 《The journal of physical chemistry. B》2006,110(25):12230-12239
The axially substituted complex chloro indium(III) 2-tetrabromo-3-tetra-(3,5-di-tert-butylphenyloxy)naphthalocyanine [Br4(tBu2PhO)4NcInCl (1); MW = 1996] has been synthesized for the first time, and its nonlinear transmission properties have been evaluated with the Z-scan technique in both open and closed aperture configurations at 532 nm for nanosecond pulsed radiation. The tetrabrominated complex 1 displayed a larger positive nonlinear absorption coefficient when compared to an analogous nonbrominated naphthalocyanine [(tBu2PhO)8NcInCl (2); MW = 2498]. The effect of the four Br atoms on the nonlinear optical behavior of 1 is evaluated, discussed, and compared with the nonlinear optical behavior of 2. It is shown that the bromination of the naphthalocyanine ring considerably improves the limiting properties of such a system when high-intensity radiations are produced by nanosecond laser pulses at 532 nm. 相似文献
82.
Guoyin Li Alfred Ka Chun Ma Ting Kei Pong 《Computational Optimization and Applications》2014,58(2):347-379
In this paper, we consider a least square semidefinite programming problem under ellipsoidal data uncertainty. We show that the robustification of this uncertain problem can be reformulated as a semidefinite linear programming problem with an additional second-order cone constraint. We then provide an explicit quantitative sensitivity analysis on how the solution under the robustification depends on the size/shape of the ellipsoidal data uncertainty set. Next, we prove that, under suitable constraint qualifications, the reformulation has zero duality gap with its dual problem, even when the primal problem itself is infeasible. The dual problem is equivalent to minimizing a smooth objective function over the Cartesian product of second-order cones and the Euclidean space, which is easy to project onto. Thus, we propose a simple variant of the spectral projected gradient method (Birgin et al. in SIAM J. Optim. 10:1196–1211, 2000) to solve the dual problem. While it is well-known that any accumulation point of the sequence generated from the algorithm is a dual optimal solution, we show in addition that the dual objective value along the sequence generated converges to a finite value if and only if the primal problem is feasible, again under suitable constraint qualifications. This latter fact leads to a simple certificate for primal infeasibility in situations when the primal feasible set lies in a known compact set. As an application, we consider robust correlation stress testing where data uncertainty arises due to untimely recording of portfolio holdings. In our computational experiments on this particular application, our algorithm performs reasonably well on medium-sized problems for real data when finding the optimal solution (if exists) or identifying primal infeasibility, and usually outperforms the standard interior-point solver SDPT3 in terms of CPU time. 相似文献
83.
We report the infrared spectrum of InCl3 in solid argon. The observed spectrum is consistent with a planar D3h structure for this molecule. 相似文献
84.
Photoemission from evaporated films of LiF were measured at photon energies of 10-27 eV. The photoelectron spectra exhibit features that can be identified as density-of-states structures in the valence and conduction bands of LiF. Regions of high density of states can be seen at ca. 3.3 and 7.8 eV above the vacuum level. The valence-band spectrum shows a doublet structure similar to the calculated density of states for the F?2p band of LiF. The base width of this structure is found to be 4.6 ± 0.3 eV. The photoelectron spectra for photon energies > 15 eV indicate that the highest occupied states of the F?2p band are located at 11.8 ± 0.3 eV below the vacuum level. The photoelectron spectra in the exciton region, however, show photo-emission from higher occupied states. 相似文献
85.
Glenn D. Prestwich Stephen G. Spanton Swee Hock Goh Yow Pong Tho 《Tetrahedron letters》1981,22(17):1563-1566
The structure of 3α, 9β, 13α-trihydroxy-1β, 8β-trinervita-11(12), 15(17)-diene was established by X-ray crystallography. The naturally-occuring tripropionate and dipropionate monoacetate were isolated from the Malaysian termite sp. 相似文献
86.
Travis Walton Wen Zhang Li Li Chun Pong Tam Jack W. Szostak 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):10926-10933
The emergence of the replication of RNA oligonucleotides was a critical step in the origin of life. An important model for the study of nonenzymatic template copying, which would be a key part of any such pathway, involves the reaction of ribonucleoside‐5′‐phosphorimidazolides with an RNA primer/template complex. The mechanism by which the primer becomes extended by one nucleotide was assumed to be a classical in‐line nucleophilic‐substitution reaction in which the 3′‐hydroxyl of the primer attacks the phosphate of the incoming activated monomer with displacement of the imidazole leaving group. Surprisingly, this simple model has turned out to be incorrect, and the dominant pathway has now been shown to involve the reaction of two activated nucleotides with each other to form a 5′–5′‐imidazolium bridged dinucleotide intermediate. Here we review the discovery of this unexpected intermediate, and the chemical, kinetic, and structural evidence for its role in template copying chemistry. 相似文献
87.
In many practical applications of conical diffusers, the flow is fed by an annular flow passage formed by a center body. Flow separation, which occurs if the center body ends abruptly, is undesirable because it degrades the diffuser performance. The present experiment utilizes magnetic resonance velocimetry to acquire three-component mean velocity measurements for a set of conical diffusers with an annular inlet. The results show strong coupling between the diffuser wall boundary layer development and the wake of the center body. Coanda blowing is used to mitigate the center body wake separation. The diffuser wall boundary layer is thick in the absence of the central separation bubble and separates when Coanda blowing is too strong. 相似文献
88.
Zofia Ciecierska-Tworek Shut Pong Van O.Hayes Griffith 《Journal of Molecular Structure》1973,16(1):139-148
An electron spin resonance study was performed on a dinitroxide, 4,4-dimethyl-3-oxyl-oxazolidme-2-spiro-4'-(2',2',6',6'-tetramethyl-1'-oxyl-piperidine) oriented in single crystals of the corresponding diamine. The electron-electron dipolar interaction between the two unpaired electrons gives rise to a doublet splitting, characterized by the zero field parameters D = ± 216 G and E = ±5G (both values ± 2 %). The anisotropy of the splitting was measured and is accounted for by a first order treatment of the dinitroxide spin Hamiltonian. 相似文献
89.
90.
White-electroluminescent device with horizontally patterned blue/yellow phosphor-layer structure 总被引:1,自引:0,他引:1
White-electroluminescent (EL) devices with stripe-patterned and square-patterned phosphor-layer structures are fabricated through a screen printing method: electrode/BaTiO3 insulator layer/patterned blue ZnS:Cu, Cl and yellow ZnS:Cu, Mn phosphor layer/ITO PET substrate. The luminous intensities of EL devices with stripe-patterned and square-patterned phosphor-layer structures are 33% and 23% higher than a conventional device with the phosphor-layer structure without any patterns using the phosphor blend. It can be explained in terms of the absorption of the emitted blue light of blue phosphor layer by the yellow-emitting phosphor layer. The EL device of our patterned phosphor-layer structure gives the possibility to enhance the luminance. 相似文献