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91.
Higher-order beam models are used in this paper to carry out free vibration analysis of civil engineering structures. Refined kinematic fields are developed using the Carrera Unified Formulation (CUF), which allows for the implementation of any-order theory without the need for ad hoc formulations. The principle of virtual displacements in conjunction with the finite element method (FEM) is used to formulate stiffness and mass matrices in terms of fundamental nuclei. The nuclei depend neither on the adopted class of beam theory nor on the FEM approximation along the beam axis. This paper focuses on a particular class of CUF models that makes use of Lagrange polynomials to discretize cross-sectional displacement variables. This class of models are referred to as component-wise (CW) in recent works. According to the CW approach, each structural component (e.g. columns, walls, frame members, and floors) can be modeled by means of the same 1D formulation. A number of typical civil engineering structures (e.g. simple beams, arches, truss structures, and complete industrial and civil buildings) are analyzed and CW results are compared to classical beam theories (Euler–Bernoulli and Timoshenko), refined beam models based on Taylor-like expansions of the displacements on the cross-section, and classical solid/shell FEM solutions from the commercial code MSC Nastran. The results highlight the enhanced capabilities of the proposed formulation. It is in fact demonstrated that CW models are able to replicate 3D solid results with very low computational efforts. 相似文献
92.
Chung SJ Zheng S Odani T Beverina L Fu J Padilha LA Biesso A Hales JM Zhan X Schmidt K Ye A Zojer E Barlow S Hagan DJ Van Stryland EW Yi Y Shuai Z Pagani GA Brédas JL Perry JW Marder SR 《Journal of the American Chemical Society》2006,128(45):14444-14445
Extended bis(donor)-substituted squaraine chromophores exhibit very high two-photon cross-sections (as high as 33 000 GM) in the near-IR; these can be attributed to the combination of large transition dipoles with small detuning energies. The modulus of the third-order nonlinear optical susceptibility at 1.3 mum has been found to be 7.0 x 10-11 esu for one of these chromophores. 相似文献
93.
94.
95.
基于结构方程(SEM)理论,以2008年统计数据为样本对影响城市现代化的测量指标进行了一阶、二阶验证性因素分析,得到了结构方程模型.并以测量指标在因子上的负荷、路径系数为基础构建权重,建立了城市现代化水平综合评价模型.对我国重要城市(直辖市、主要省会城市)现代化水平程度进行了相对评价,得到较为满意的结果. 相似文献
96.
Abbotto A Bruni S Cariati F Pagani GA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,(8):1543-1552
The co-ordination geometry of the complexes M(bbtm)2 and M(bbom)2 (M: Co, Ni, Cu, Zn; bbtm, bis(2-benzothiazolyl)methanate; bbom, bis(2-benzoxazolyl)methanate) are discussed on the basis of their IR, Raman, resonance Raman, electronic and ESR spectra. Compounds of Ni, Co, Zn with both ligands and Cu(bbom)2 resulted to have a distorted tetrahedral geometry. The distortion towards a square planar geometry is more marked for the M(bbtm)2 series than for the M(bbom)2 one. It has been impossible to suggest a co-ordination geometry for Cu(bbtm)2, that probably has a polymeric structure. 相似文献
97.
Benzene equilibrium absorption curve by EPR rubber (50 wt % C3) was measured at 23°C. Benzene activity a1 was plotted against its volume fraction ?1. Benzene clustering function G11/v1 was calculated according to Zimm and the mechanism of formation of benzene clusters is discussed. It was found that clusters at very low benzene partial pressures are monomolecular and randomly distributed: at higher partial pressures, clusters increase in size. Flory-Rehner theory, giving activity α1 against ?1, was checked; predictions of cluster formation were made but there were some discrepancies with Zimm's conclusions. 相似文献
98.
Silvia Bradamante Silvana Colombo Giorgio A. Pagani Stefano Roelens 《Helvetica chimica acta》1981,64(2):568-571
Phenylglycine esters react with pyruvic acid to give α-methylsuccinic amides 9 instead of the expected Schiff bases 8 , analogously to p-anisidine but unlike aniline. 相似文献
99.
Silvia Bradamante Silvana Colombo Giorgio A. Pagani Stefano Roelens 《Helvetica chimica acta》1981,64(8):2524-2527
N-Substituted 9-fluorenimines 1 are easily prepared from primary amines or aminoesters and 9-fluorenimine: their conjugate carbanions 2 are formed by the action of alkoxides and are reprotonated to 1 or to the tautomeric 9-alkylidenamino-fluorenes 3 depending upon substituents. 相似文献
100.
Mario Paglialunga Paradisi Giampiero Pagani Zecchini Ines Torrini Gino Lucente 《Journal of heterocyclic chemistry》1990,27(6):1661-1664
The synthesis of linear dipeptides containing N-protected L-phenylalanine and (3R-cis)-tetrahydro-1,4-thiazine-3,5-dicarboxylic acid dialkyl diester residues is described. N-Deprotection of these dipeptides by hydrogenolysis on palladium afforded directly a mixture of cis and trans dioxopiperazines. The stereochemistry and the solution conformational properties of the cyclic dipeptides are determined. 相似文献