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1.
This paper proposes two constructive heuristics for the well-known single-level uncapacitated dynamic lot-sizing problem. The proposed heuristics, called net least period cost (nLPC) and nLPC(i), are developed by modifying the average period cost concept from Silver and Meal's heuristic, commonly known as least period cost (LPC). An improved tie-breaking stopping rule and a locally optimal decision rule are proposed in the second heuristic to enhance performance. We test the effectiveness of the proposed heuristics by using 20 benchmarking test problems frequently used in the literature. Furthermore, we perform a large-scale simulation study involving three factors, 50 experimental conditions, and 100?000 randomly generated problems to evaluate the proposed heuristics against LPC and six other well-known constructive heuristics in the literature. The simulation results show that both nLPC and nLPC(i) produce average holding and setup costs lower than or equal to those of LPC in every one of the 50 experimental conditions. The proposed heuristics also outperform each of the six other heuristics evaluated in all experimental conditions, without an increase in computational requirements. Lastly, considering that both nLPC and nLPC(i) are fairly simple for practitioners to understand and that lot-sizing heuristics have been commonly used in practice, there should be a very good chance for practical applications of the proposed heuristics. 相似文献
2.
Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson H Bintinger DL Bobbink GJ Bolognese TS Bross AD Buchanan CD Buijs A Cain MP Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Eisner AM Enomoto R Erné FC Fujii T Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG Linde FL Lindsey CS Loken SC Lu A Lu X 《Physical review letters》1986,57(8):945-948
3.
Nicolaou KC Baran PS Zhong YL Barluenga S Hunt KW Kranich R Vega JA 《Journal of the American Chemical Society》2002,124(10):2233-2244
The discovery and development of the o-iodoxybenzoic acid (IBX) reaction with certain unsaturated N-aryl amides (anilides) to form heterocycles are described. The application of the method to the synthesis of delta-lactams, cyclic urethanes, hydroxy amines, and amino sugars among other important building blocks and intermediates is detailed. In addition to the generality and scope of this cyclization reaction, this article describes a number of mechanistic investigations suggesting a single electron transfer from the anilide functionality to IBX and implicating a radical-based mechanism for the reaction. 相似文献
4.
Mathis B. Hodge 《Tetrahedron》2004,60(42):9397-9403
The addition of chlorotitanium enolates of N-acetyl isopropyl thiazolidine-2-thione to aldehydes was investigated. The stereoselectivity of the aldol products was controlled by the number of equivalents of base added. The syn aldol product was obtained preferentially when 2 equiv of Lewis acid and 1 equiv of base were employed. The anti aldol product was obtained preferentially when 1 equiv of Lewis acid and 2 equiv of base were employed for unsaturated aldehydes. Unexpected results were found with hindered aldehydes when 2 equiv of base were employed. 相似文献
5.
6.
The coupling of subcritical water separation with flame ionization detection (FID) in the split mode has been investigated in this study. In order to keep the FID system stable during subcritical water separation, a Tee union was connected between the separation column and the FID system to split the water flow. The ratio of the water flow to the FID system over the flow-rate to a waste bottle varied depending on the dimension of capillary tubings and the total water flow-rate used. Separations of several carbohydrates, carboxylic acids, and amino acids were performed on commercially available columns using a laboratory-made subcritical water chromatography-FID system. The FID system was very stable in this split mode even at total flow-rate as high as 1.24 ml/min. The linear dynamic range was up to three orders of magnitude and the limit of detection (LOD) ranged from 38 to 111 ng (306-925 ng/microl injected) with split ratios of approximately 1:10 to approximately 1:17 (FID/waste bottle) for several analytes studied. However, the LOD can be significantly lowered by adjusting the dimensions of the restrictors to allow a higher percentage of the total flow to the FID system. 相似文献
7.
Kotel'nikov A. I. Ortega J. M. Medvedev E. S. Psikha B. L. Garcia D. Mathis P. 《Russian Journal of Electrochemistry》2002,38(1):77-87
The electron transfer from the heme of cytochrome c to the bacteriochlorophill dimer in reaction centers of photosynthetic purple bacteria Rps. sulfoviridis is studied by laser flash photolysis at 40–296 K in conditions where one, two, or three cytochrome hemes are chemically reduced. In the model used for the electron transfer kinetics, the protein relaxation is described with a temperature-independent oscillatory coordinate and a temperature-dependent diffusion coordinate, with the protein dielectric relaxation times widely distributed along the diffusion coordinate. It is found that all the protein complexes can be divided into proteins with fast (k
et = 107 to 10–4 s–1) and slow (k
et 100 s–1) electron transfer. These populations presumably differ by the protonation state of the functional group. The contribution of the oscillatory and diffusion coordinates alters, which severely affects k
et. Parameters V
ab, G, , 0, and for these reactions are determined. 相似文献
8.
Abstract— Phototransformation at 2°C of the red-absorbing form of phytochrome (Pr) to the far-redabsorbing form (Pfr) was studied with both undegraded oat ( Avena sativa L., cv. Garry) and undergraded pea Pisum sativum L., cv. Alaska) phytochrome. Phototransformation was initiated by a 15-ns laser pulse with maximum emission near 600 nm and output power of 30 mJ. The first resolvable transformation intermediate exhibited relative to Pr a maximum absorbance increase near 700 nm and was fully present at the earliest time measured, which was 60 ns after the flash. This intermediate absorbance decayed by two reactions for oat phytochrome (half-lives of 11 and 140 μs assuming parallel reactions) and by three for pea phytochrome (half-lives of 14, 280 and 1600 μs assuming parallel reactions). The kinetics of the slowest reaction for pea phytochrome, however, might be somewhat distorted by an instrument artifact. The appearance of the far-red-absorbing phytochrome, as monitored by absorbance increase at 720 nm, occurred by at least two reactions for both oat (half-lives of 47 and 250 ms assuming parallel reactions) and pea (half-lives of 170 and 770 ms assuming parallel reactions) phytochrome. The possibility of slower reactions was not tested. Assays for possible proteolysis of the phytochrome samples studied here indicated that the presence of degraded phytochrome could not account for the observed multiphasic kinetics except possibly for one phase of the triphasic intermediate decay seen with pea phytochrome. 相似文献
9.
Corrigendum: Triazole‐Tailored Guanosine Dinucleosides as Biomimetic Ion Channels to Modulate Transmembrane Potential
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10.