全文获取类型
收费全文 | 114篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 44篇 |
力学 | 2篇 |
数学 | 42篇 |
物理学 | 29篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 6篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 1篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有117条查询结果,搜索用时 31 毫秒
101.
Maria Stella de Castro Lobo Yasar A. Ozcan Angela C. M. da Silva Marcos P. Estellita Lins Roberto Fiszman 《Central European Journal of Operations Research》2010,18(2):141-152
This study evaluates the performance and productivity changes for the Brazilian Federal University Hospitals, considering
the years of 2003 and 2006, that is, before and after a 2004 financing reform. The analysis is based on the Malmquist index
approach. Results indicate that the financing reform provided improvement in the technical efficiency, although the technological
frontier has not presented a positive shift. This suggests that increased budgets were a good stimulus for efficiency but
the intended enhancement of the technology through the financing reform has not yet taken place. 相似文献
102.
Lins G. Paulus I. Pohl F. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(5):676-678
Dielectric recovery data were obtained for vacuum arcs between chromium copper butt contacts 30 mm in diameter and 2 mm apart. The 50-Hz arc current was forced to zero at its maximum of 200 A in about 1 μs. Following current zero, high-voltage pulses of a sufficient amplitude to always cause breakdown were applied to the gap. Gap recovery is characterized by the measured breakdown voltage as a function of time. Dielectric strength of the gap rises sharply within the first few microseconds after current zero, reaching its final value in about 10 μs. Neutral copper concentration in the center of the gap was measured by laser-induced fluorescence under conditions very similar to those of the recovery measurements. In contrast to the fast gap recovery, the copper vapor concentration does not change substantially during the first 100 μs from its value of 1.4×1018 m -3 near current zero. It is concluded that the neutral copper vapor concentration does not play a decisive role in gap recovery under these experimental conditions. This is corroborated by the fact that the mean free path for electron-impact ionization of copper atoms exceeds the gap length by four orders of magnitude 相似文献
103.
The classical Gauss code problem asks to characterize which cyclic sequences arise as the vertex sequence of the straight-ahead path of a 4-regular graph embedded in the plane This problem is generalized to certain 4 regular graphs in arbitrary surfacesA characterization is given for the existence of a 4-regular graph in a specified surface yielding the specified sequence This characterization is obtained using a generalization of Shank's left-right paths 相似文献
104.
Soares TA Hünenberger PH Kastenholz MA Kräutler V Lenz T Lins RD Oostenbrink C van Gunsteren WF 《Journal of computational chemistry》2005,26(7):725-737
Over the past decades, the GROMOS force field for biomolecular simulation has primarily been developed for performing molecular dynamics (MD) simulations of polypeptides and, to a lesser extent, sugars. When applied to DNA, the 43A1 and 45A3 parameter sets of the years 1996 and 2001 produced rather flexible double-helical structures, in which the Watson-Crick hydrogen-bonding content was more limited than expected. To improve on the currently available parameter sets, the nucleotide backbone torsional-angle parameters and the charge distribution of the nucleotide bases are reconsidered based on quantum-chemical data. The new 45A4 parameter set resulting from this refinement appears to perform well in terms of reproducing solution NMR data and canonical hydrogen bonding. The deviation between simulated and experimental observables is now of the same order of magnitude as the uncertainty in the experimental values themselves. 相似文献
105.
An instrumental neutron activation method for V, Mn and W in alloy steels with a 241 Am/Be isotopic neutron source is described. The samples were irradiated to induce the nuclear reactions 51V(n, γ) 52V, 55Mn(n, γ)56Mn, and 186W(n, γ)187W. The activities were measured with a NaI(TI) detector. Interferences on the measured photopeaks were shown to be negligible by measuring the half-lives of 62V, 56Mn and 187W.These thre elementes were determined in the range 1.5–12.9% in special steels; manganese in the range 0.5–1.6% was measured in cast irons. Calibration was done by comparison with results from wet chemistry and x-ray fluorescence spectrometry. The processing times for the vanadium, manganese and tungsten determinations were 11 min, 3 h and 26.3 h, respectively, but these were reduced greatly by intoruding a scheme wherein six samples were simultaneously irradiated and the 56Mn and 187W nuclides were measured sequentially for a series of 66 samples. The average processing time was reduced to 45 min for tungsten with a precision of 4.0% and accuracy of 3.4% and 22.8 min for manganese with a precision of 3.8% and accuracy of 3.1%. 相似文献
106.
M P Estellita Lins L Angulo-Meza A C Moreira Da Silva 《The Journal of the Operational Research Society》2004,55(10):1090-1101
The choice for radial projections of classic data envelopment analysis (DEA) models, resulting in a number of projections onto the Pareto-inefficient portion of the frontier, has been seen lately as a disadvantage in DEA. The search for a non-radial projection method resulted in developments such as preference structure models. These models consider a priori preference incorporation, using weights in the search for the most preferred efficient target, although presenting some implementation difficulties. In this paper, we propose a multi-objective approach that determines the bases for a posteriori preference incorporation, through individual projections of each variable (input or output) as an objective function, thus allowing one to obtain a target at every extreme-efficient point on the frontier. This multi-objective approach is shown to be equivalent to the preference structure models, yet presenting some advantages, such as the mapping of the possible weights, assigned to partial efficiencies of an observed unit, in order to reach a specific target. 相似文献
107.
This paper presents an approach using a recursive algorithm for packing (?, w)-rectangles into larger rectangular and L-shaped pieces. Such a problem has actual applications for non-guillotine cutting and pallet/container loading. Our motivation for developing the L-approach is based on the fact that it can solve difficult pallet loading instances. Indeed, it is able to solve all testing problems (more than 20 000 representatives of infinite equivalence classes of the literature), including the 18 hard instances unresolved by other heuristics. We conjecture that the L-approach always finds optimum packings of (?, w)-rectangles into rectangular pieces. Moreover, the approach may also be useful when dealing with cutting and packing problems involving L-shaped pieces. 相似文献
108.
Dedicated to René Thom with admiration. 相似文献
109.
Sóstenes Lins 《Geometriae Dedicata》1986,20(1):1-25
A painting in dimension n is an object induced by certain regular (n+1)-colored finite graphs. Some classes of paintings are shown to be plane universal models for closed n-manifolds. Ferri and Gagliardi's equivalence theorem (graph-theoretical counterpart for homeomorphisms) [5], and Ferri's strengthening of their result [3] are used to provide a surprisingly simple way to state the equivalence theorem: the restricted crystallization moves [3] become deletion and insertion of one edge in certain plane graphs. Various new properties of minimum 3-crystallizations are obtained in the framework of paintings. Two conjectures related to the recognition of the 3-sphere are included.This work was performed under the support of UFPE, FINEP and CNPq (contract no. 30.1103/80). 相似文献
110.
Eliane Gonçalves Gomes Marcos Pereira Estellita Lins 《Annals of Operations Research》2002,116(1-4):243-269
This paper presents an application of the integration between Geographical Information Systems (GIS) and Multi-Criteria Decision Analysis (MCDA) to aid spatial decisions. We present a hypothetical case study to illustrate the GIS–MCDA integration: the selection of the best municipal district of Rio de Janeiro State, Brazil, in relation to the quality of urban life. The best municipal district is the one that presents the closest characteristics to those considered ideal by the decision-maker. The approach adopted is the Multi-Objective Linear Programming (MOLP) and the chosen method is the Pareto Race. 相似文献