首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   313篇
  免费   9篇
  国内免费   4篇
化学   205篇
晶体学   4篇
力学   7篇
数学   42篇
物理学   68篇
  2024年   1篇
  2023年   3篇
  2022年   13篇
  2021年   14篇
  2020年   13篇
  2019年   26篇
  2018年   16篇
  2017年   15篇
  2016年   16篇
  2015年   9篇
  2014年   27篇
  2013年   39篇
  2012年   17篇
  2011年   25篇
  2010年   25篇
  2009年   10篇
  2008年   14篇
  2007年   10篇
  2006年   6篇
  2005年   5篇
  2004年   7篇
  2003年   3篇
  2002年   2篇
  2001年   1篇
  2000年   3篇
  1999年   2篇
  1994年   1篇
  1985年   2篇
  1984年   1篇
排序方式: 共有326条查询结果,搜索用时 46 毫秒
111.
In this paper, a particle swarm optimization algorithm (PSO) is presented to solve the permutation flowshop sequencing problem (PFSP) with the objectives of minimizing makespan and the total flowtime of jobs. For this purpose, a heuristic rule called the smallest position value (SPV) borrowed from the random key representation of Bean [J.C. Bean, Genetic algorithm and random keys for sequencing and optimization, ORSA Journal of Computing 6(2) (1994) 154–160] was developed to enable the continuous particle swarm optimization algorithm to be applied to all classes of sequencing problems. In addition, a very efficient local search, called variable neighborhood search (VNS), was embedded in the PSO algorithm to solve the well known benchmark suites in the literature. The PSO algorithm was applied to both the 90 benchmark instances provided by Taillard [E. Taillard, Benchmarks for basic scheduling problems, European Journal of Operational Research, 64 (1993) 278–285], and the 14,000 random, narrow random and structured benchmark instances provided by Watson et al. [J.P. Watson, L. Barbulescu, L.D. Whitley, A.E. Howe, Contrasting structured and random permutation flowshop scheduling problems: Search space topology and algorithm performance, ORSA Journal of Computing 14(2) (2002) 98–123]. For makespan criterion, the solution quality was evaluated according to the best known solutions provided either by Taillard, or Watson et al. The total flowtime criterion was evaluated with the best known solutions provided by Liu and Reeves [J. Liu, C.R. Reeves, Constructive and composite heuristic solutions to the P∥∑Ci scheduling problem, European Journal of Operational Research 132 (2001) 439–452], and Rajendran and Ziegler [C. Rajendran, H. Ziegler, Ant-colony algorithms for permutation flowshop scheduling to minimize makespan/total flowtime of jobs, European Journal of Operational Research, 155(2) (2004) 426–438]. For the total flowtime criterion, 57 out of the 90 best known solutions reported by Liu and Reeves, and Rajendran and Ziegler were improved whereas for the makespan criterion, 195 out of the 800 best known solutions for the random and narrow random problems reported by Watson et al. were improved by the VNS version of the PSO algorithm.  相似文献   
112.
113.
A new polymer,poly(imino isophthaloyl imino(2,4,8,10-tetraoksoaspiro[5,5]undekan-3,9-dipropylene)) [poly(IPIT)]was synthesized by an interfacial polycondensation reaction.The characterization of poly(IPIT)was conducted by using FT-IR,~(13)C-NMR,TG and DTA techniques.The kinetics of the thermal degradation of poly(IPIT)was investigated by thermogravimetric analysis at different heating rates.TG curves showed that the thermal decomposition of poly(IPIT) occurred in three stages.The apparent activation ener...  相似文献   
114.
A new vicinal dioxime ligand containing azo and thione chromophores, namely 1,3-bis[4-(phenyldiazenyl)phenyl]-2-thiooxaimidazoline-4,5-dione dioxime (bppH2), was synthesized by the reaction of cyanogen di-N-oxide with N,N′-bis(4-phenylazophenyl) thiourea in dichloromethane solution at −10 °C. Mononuclear complexes of bppH2 with nickel(II), cobalt(II), and copper(II) were synthesized. The complexes, [Ni(bppH)2], [Cu(bppH)2], and [Co(bppH)2] were characterized by several techniques using elemental analyses, conductivity measurements, FT-IR, and electronic spectral studies. The data suggest that the ligand coordinates through the N,N atoms, as do most vic-dioximes. The molar conductivities in DMF solution indicate nonelectrolytic nature for the complexes. Antimicrobial activities of the ligand and its metal complexes were estimated for five bacteria, namely Klebsiella pneumoniae, Micrococcus luteus, Mycobacterium smegmatis, Enterobacter cloaca and Bacillus megaterium and three fungi, namely Candida albicans, Kluyveromyces marxianus, and Rhodotorula rubra.  相似文献   
115.
Zeng F  Rohde CB  Yanik MF 《Lab on a chip》2008,8(5):653-656
Techniques for stable, rapid and repeatable small-animal immobilization are necessary for high-throughput in vivo genetic/drug screens using cellular and sub-cellular features in multi-cellular organisms. We demonstrate a method for non-invasive and high-throughput on-chip immobilization of physiologically active C. elegans without the use of anesthesia or cooling, but with comparable stability even for the most demanding purposes. We show observation and manipulation of sub-cellular features in immobilized animals using two-photon microscopy and femtosecond-laser microsurgery.  相似文献   
116.
117.
A pair of Latin squares, A and B, of order n, is said to be pseudo-orthogonal if each symbol in A is paired with every symbol in B precisely once, except for one symbol with which it is paired twice and one symbol with which it is not paired at all. A set of t Latin squares, of order n, are said to be mutually pseudo-orthogonal if they are pairwise pseudo-orthogonal. A special class of pseudo-orthogonal Latin squares are the mutually nearly orthogonal Latin squares (MNOLS) first discussed in 2002, with general constructions given in 2007. In this paper we develop row complete MNOLS from difference covering arrays. We will use this connection to settle the spectrum question for sets of 3 mutually pseudo-orthogonal Latin squares of even order, for all but the order 146.  相似文献   
118.
New Pt(0) nanoparticles were easily and reproducibly prepared by the simultaneous reduction method using 1-butylamine (BA) and tributylamine (TBA) for the first time as capturing ligands at room temperature. X-ray diffraction, X-ray photoelectron microscopy and transmission electron microscopy measurements verify the formation of well-dispersed Pt(0) nanoparticles [~3.63 and ~3.98 nm for catalysts prepared using BA (catalyst I) and TBA (catalyst II), respectively] on an activated carbon surface. The catalytic performances of these nanoparticles in terms of activity, isolability and reusability were investigated for both alcohol oxidation and the dehydrocoupling of dimethylamine-borane (DMAB). These nanoparticles were shown to be as active and reusable heterogeneous catalysts even at room temperature. The prepared catalysts can catalyze the dehydrogenation of DMAB with one of the highest known activities at room temperature and also C1–C3 alcohol oxidation with very high electrochemical activities.  相似文献   
119.
Addressed herein, monodisperse Vulcan carbon supported Pt nanoparticles (Mw-Pt NPs@VC) have been reproducibly synthesized using the microwave assisted method and their application for methylene blue (MB) removal from aqueous solutions was investigated through the adsorption mechanism. The prepared nanomaterials were characterized by X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. All results show that highly crystalline and colloidally stable nanoparticles have been formed and Mw-Pt NPs@VC were found to be one of the the most active catalyst. The results showed that the Mw-Pt NPs@VC nanoparticles had remarkable MB adsorption capacity of 271.15 mg/g. The equilibrium for MB adsorption was attained in ~55 min. Moreover, Mw-Pt NPs@VC is a reusable and promising material for MB removal since it preserves 95.6 % of its initial efficiency after six successive cycles of adsorption–desorption.  相似文献   
120.
Surface modification of clay materials has become an important issue to improve the efficiency of the adsorbent. The adsorption capacity of the clay material can be increased by thermal or chemical modifications. In this study, plasma technology was applied for the surface modification of sepiolite to improve the removal of malachite green from contaminated water. This study is novel in preparing and examining the effectiveness of sepiolite in adsorption of malachite green from contaminated water. To achieve the aim, plasma application time, CO2, N2, or Ar plasma gases effect and pH were investigated with respect to the adsorption capacity of MG. The surface properties of raw and plasma treated sepiolite were investigated with SEM, FTIR, BET surface area and XRD measurements. The monolayer adsorption capacity was found to be 143 mg/g.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号