全文获取类型
收费全文 | 128篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 80篇 |
力学 | 4篇 |
数学 | 26篇 |
物理学 | 29篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 12篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 14篇 |
2013年 | 8篇 |
2012年 | 10篇 |
2011年 | 13篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 3篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2001年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1984年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有139条查询结果,搜索用时 46 毫秒
31.
Aleksi Kurkela 《Nuclear Physics A》2009,820(1-4):159c
It is expected that incorporating the center symmetry in the conventional dimensionally reduced effective theory for high-temperature SU(Nc) Yang-Mills theory, EQCD, will considerably extend its applicability towards the deconfinement transition. The construction of such a center-symmetric effective theory for the case of two colors is reviewed and lattice simulation results are presented. The simulations demonstrate that unlike EQCD, the new center-symmetric theory undergoes a second order confining phase transition in complete analogy with the full theory. 相似文献
32.
Danijela Klemenčič Brigita Tomšič Franci Kovač Barbara Simončič 《Cellulose (London, England)》2012,19(5):1715-1729
Functional antimicrobial cotton fibres were prepared in a novel two-step procedure utilising the pad-dry-cure method to apply an inorganic–organic hybrid sol–gel precursor (reactive binder, RB) followed by the in situ synthesis of AgCl particles on the RB-treated fibres. The morphology and surface composition of the modified cotton fibres were investigated by scanning electron microscopy imaging and X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy spectral analyses. The bulk concentration of Ag on the cotton fibres was determined by inductively coupled plasma mass spectroscopy, and the antimicrobial activity against the bacteria Escherichia coli and Staphylococcus aureus was estimated according to the ISO 20645:2004 (E) and AATCC 100-1999 methods. The results showed that this application process yields the following important benefits: (1) the presence of the RB silica matrix increased the fibres’ capacity for adsorbing AgCl particles compared with the same fibres without RB; (2) the in situ synthesis enabled a simple and environmentally friendly preparation of AgCl particles from AgNO3 and their embedment into the fibres; (3) the AgCl particles were bound to the RB silica matrix by physical forces, which allowed for their controlled release from the fibres; (4) the capacity of the RB-modified cotton samples to hold embedded AgCl particles was sufficient to provide a 100 % bacterial reduction even after 10 repeated washing cycles; and (5) the chemical modification of the cotton fibres did not significantly change their whiteness, wettability or softness. 相似文献
33.
Simo Huotari Tuomas Pylkkänen J. Aleksi Soininen Joshua J. Kas Keijo Hämäläinen Giulio Monaco 《Journal of synchrotron radiation》2012,19(1):106-113
X‐ray Raman scattering (XRS) provides a bulk‐sensitive method of measuring the extended X‐ray absorption fine structure (EXAFS) of soft X‐ray absorption edges. Accurate measurements and data analysis procedures for the determination of XRS‐EXAFS of polycrystalline diamond are described. The contributions of various angular‐momentum components beyond the dipole limit to the atomic background and the EXAFS oscillations are incorporated using self‐consistent real‐space multiple‐scattering calculations. The properly extracted XRS‐EXAFS oscillations are in good agreement with calculations and earlier soft X‐ray EXAFS results. It is shown, however, that under certain conditions multiple‐scattering contributions to XRS‐EXAFS deviate from those in standard EXAFS, leading to noticeable changes in the real‐space signal at higher momentum transfers owing to non‐dipole contributions. These results pave the way for the accurate application of XRS‐EXAFS to previously inaccessible light‐element systems. 相似文献
34.
Danijela Ili?Ivan Damljanovi? Mirjana Vuki?evi?Volker Kahlenberg Gerhard LausNiko S. Radulovi? Rastko D. Vuki?evi? 《Tetrahedron letters》2012,53(45):6018-6021
The reaction of 1-ferrocenyl-3-thiabutan-1-one with methyl iodide in acetonitrile at room temperature gave dimethyl(2-oxo-2-ferrocenylethyl)sulfonium iodide, which was characterized by spectral data (1H NMR, 13C NMR, IR) and X-ray crystallographic analysis. This salt reacted with a base (sodium hydride) in acetonitrile yielding a stabilized ylide—dimethylsulfonium ferrocenoylmethylide, which was in turn, submitted to reactions with seven conjugated enones. The obtained results showed that this methodology is potentially a new and useful approach to ferrocene-containing cyclopropanes. 相似文献
35.
Esa Hyytiä Aleksi PenttinenSamuli Aalto 《European Journal of Operational Research》2012,217(2):357-370
We consider the dispatching problem in a size- and state-aware multi-queue system with Poisson arrivals and queue-specific job sizes. By size- and state-awareness, we mean that the dispatcher knows the size of an arriving job and the remaining service times of the jobs in each queue. By queue-specific job sizes, we mean that the time to process a job may depend on the chosen server. We focus on minimizing the mean sojourn time (i.e., response time) by an MDP approach. First we derive the so-called size-aware relative values of states with respect to the sojourn time in an M/G/1 queue operating under FIFO, LIFO, SPT or SRPT disciplines. For FIFO and LIFO, the size-aware relative values turn out to be insensitive to the form of the job size distribution. The relative values are then exploited in developing efficient dispatching rules in the spirit of the first policy iteration. 相似文献
36.
D. Mehandjiev E. Zhecheva B. R. Aleksi B. D. Aleksi B. Markovi S. Bogdanov 《Reaction Kinetics and Catalysis Letters》1991,43(1):7-12
Changes in composition and structure occurring in cobalt promoted and unpromoted Mo/Al2O3 catalysts during several subsequent cycles of activation and regeneration have been studied. Regeneration does not lead to the initial oxide form of the catalysts completely. The changes in the oxide catalyst composition increase with increasing number of activation-regeneration cycles.
, Mo/Al2O3 . . -.相似文献
37.
Silica Gel as a Promoter of Sequential Aza‐Michael/Michael Reactions of Amines and Propiolic Esters: Solvent‐ and Metal‐Free Synthesis of Polyfunctionalized Conjugated Dienes
下载免费PDF全文
![点击此处可从《化学:亚洲杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Jovana Aleksić Dr. Milovan Stojanović Prof. Dr. Marija Baranac‐Stojanović 《化学:亚洲杂志》2018,13(14):1811-1835
We present an efficient, simple, metal‐ and solvent‐free silica‐gel‐promoted synthesis of functionalized conjugated dienes by sequential aza‐Michael/Michael reactions by starting from commercially available primary amines and propiolic esters. The scope and usefulness of the method is demonstrated for 31 examples, including a range of propiolic esters, aliphatic amines, and differently substituted aromatic amines. For aliphatic amines, the products were obtained within 0.5 to 4 h in 52 to 85 % yield, compared with 3.5 to 22 h under classical solution‐phase synthesis, which proceeds with similar or lower yields. The method was found to be particularly useful for weakly nucleophilic aromatic amines, which provided products in 21 to 73 % yield over 2.5 to 9.5 h compared with yields of 0 to 49 % over 1 to 6 d under standard solution‐phase conditions, and for more hydrophobic esters that gave products in yields of 47 to 79 % over 1 to 3 h compared with 0 to 45 % over 4 to 114 h in solvent. 相似文献
38.
We analyze family of solutions to multidimensional scalar conservation law, with flux depending on the time and space explicitly,
regularized with vanishing diffusion and dispersion terms. Under a condition on the balance between diffusion and dispersion
parameters, we prove that the family of solutions is precompact in L1loc{L^1_{\rm loc}}. Our proof is based on the methodology developed in Sazhenkov (Sibirsk Math Zh 47(2):431–454, 2006), which is in turn based
on Panov’s extension (Panov and Yu in Mat Sb 185(2):87–106, 1994) of Tartar’s H-measures (Tartar in Proc R Soc Edinb Sect A 115(3–4):193–230, 1990), or Gerard’s micro-local defect measures (Gerard Commun
Partial Differ Equ 16(11):1761–1794, 1991). This is new approach for the diffusion–dispersion limit problems. Previous results
were restricted to scalar conservation laws with flux depending only on the state variable. 相似文献
39.
Ljiljana Pavlovi? Mirjana Lazi? Tatjana Aleksi? 《Discrete Applied Mathematics》2009,157(13):2938-2944
Let G be a graph and d(u) denote the degree of a vertex u in G. The zeroth-order general Randi? index 0Rα(G) of the graph G is defined as ∑u∈V(G)d(u)α, where the summation goes over all vertices of G and α is an arbitrary real number. In this paper we correct the proof of the main Theorem 3.5 of the paper by Hu et al. [Y. Hu, X. Li, Y. Shi, T. Xu, Connected (n,m)-graphs with minimum and maximum zeroth-order general Randi? index, Discrete Appl. Math. 155 (8) (2007) 1044-1054] and give a more general Theorem. We finally characterize 1 for α<0 the connected G(n,m)-graphs with maximum value 0Rα(G(n,m)), where G(n,m) is a simple connected graph with n vertices and m edges. 相似文献
40.
Solid phase extraction and HPLC determination of veterinary pharmaceuticals in wastewater 总被引:1,自引:0,他引:1
This work focuses on the application of SPE-HPLC analysis of important veterinary pharmaceuticals from different classes in highly complex wastewater matrix. The pharmaceutical investigated included three sulfonamides (sulfamethazine, sulfadiazine and sulfaguanidine), a sulfonamide synergist (trimethoprim), a tetracycline (oxytetracycline), a fluoroquinolone (enrofloxacine) and a β-lactame (penicillin G/procaine). The method involves pre-concentration and clean-up by solid phase extraction (SPE) using Oasis HLB extraction catridges. Final analysis of the selected pharmaceutical compounds was carried out by high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD). Recoveries were ranged from 68.3 to 97.9% with relative standard deviation below 8.4%. Only for sulfaguanidine low recovery was obtained. Limits of quantification were in the range 1.5-100 μg/L depending on pharmaceutical. The described method was applied to the determination of pharmaceuticals in wastewater samples from pharmaceutical industry. 相似文献