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1.
Buckling of sandwich wide columns 总被引:2,自引:0,他引:2
The paper deals with the theoretical prediction of buckling loads for sandwich columns with metallic and laminated facings and foam or honeycomb core. The loading is a uniform axial compression, applied statically (very slowly) and suddenly with constant magnitude and infinite duration (step loading). The effect of length and boundary conditions is assessed and results are presented for the following cases: for a cantilever column, a simply supported column and a clamped column, for several lengths. Several fiber materials are used in the laminated facings. Two types of core were examined: alloy-foam or hexagonal glass/phenolic honeycomb. The facings are Boron/Epoxy, Graphite/Epoxy and Kevlar/Epoxy laminates with 0° orientation with respect to the column axis and a metallic one made out of aluminum. These various materials are employed to provide comparative data that can be used in design. Results, for the static case are generated by computer codes as well as by the use of closed form theoretical solutions. For the dynamic case, results are generated by the DYNA3D code. 相似文献
2.
3.
N. Sh. Lebedeva R. S. Kumeev G. A. Al’per E. V. Parfenyuk A. S. Vashurin T. V. Tararykina 《Journal of solution chemistry》2007,36(6):793-801
For the first time the interactions between zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine (Zn(4—O—CO—C6H4—OC11H23)Pc) and 1,4-diazabicyclo[2.2.2]octane (DABCO) in o-xylene and chloroform have been studied by calorimetric titration and NMR and electron absorption spectroscopic methods.
It has been found that in o-xylene at concentrations of Zn(4—O—CO—C6H4—OC11H23)Pc higher than 6×10−4 mol⋅L−1
π–π dimers species are formed (λ
max= 685 nm). Additions of DABCO to the solution up to mole ratio 1 : 8 (Zn(4—O—CO—C6H4—OC11H23)Pc : DABCO) lead to a shift of the aggregation equilibrium towards monomer species due to formation of monoligand axial complexes.
Further increasing the DABCO concentration results in formation of Zn(4—O—CO—C6H4—OC11H23)Pc—DABCO—Zn(4—O—CO—C6H4—OC11H23)Pc sandwich dimers (λ
max= 675 nm). 相似文献
4.
γ-[SiW10O36]8-夹心型稀土元素单取代多酸化合物的合成与表征 总被引:2,自引:0,他引:2
利用缺位填充法合成了12个γ-[SiW10O36]8-夹心型稀土元素单取代多酸化合物K13[Ln(SiW10O36)2]·nH2O(Ln=La3+,Ce3+,Pr3+,Nd3+,Sm3+,Eu3+,Gd3+,Tb3+,Dy3+,Ho3+,Er3+,Yb3+).通过元素分析确定其组成,由红外光谱、紫外-可见吸收光谱、循环伏安及室温磁化率测定结果确认稀土离子与γ-[SiW10O36]8-相配位;183WNMR及荧光光谱结果则表明,稀土离子处于2个γ-[SiW10O36]8-构成的八配位环境中,标题化合物具有夹心型D2d对称性结构. 相似文献
5.
The organo-iron mediated activation of arene in the sandwich complexes [FeCp(η6-arene)][PF6] is shown to produce 1 → 3 connectivity at benzylic positions that was utilized for dendrimer syntheses. This mini-review of the work carried out in the authors’ laboratory summarizes this principle and its applications with emphasis on recent significant improvements in the CpFe+-mediated reactions, recyclability of the CpFe+ group, mechanistic features and examples of efficient and useful functionalization reactions. 相似文献
6.
Emilio Carrizosa Horst W. Hamacher Rolf Klein Stefan Nickel 《Journal of Global Optimization》2000,18(2):195-210
It is well-known that some of the classical location problems with polyhedral gauges can be solved in polynomial time by finding a finite dominating set, i.e. a finite set of candidates guaranteed to contain at least one optimal location.In this paper it is first established that this result holds for a much larger class of problems than currently considered in the literature. The model for which this result can be proven includes, for instance, location problems with attraction and repulsion, and location-allocation problems.Next, it is shown that the approximation of general gauges by polyhedral ones in the objective function of our general model can be analyzed with regard to the subsequent error in the optimal objective value. For the approximation problem two different approaches are described, the sandwich procedure and the greedy algorithm. Both of these approaches lead - for fixed - to polynomial approximation algorithms with accuracy for solving the general model considered in this paper. 相似文献
7.
Using the Riesz basis approach, we study a sandwich beam that is composed of an outer stiff layer and a compliant middle layer.
The dynamic behavior and analyticity of the system are obtained based on a detailed spectral analysis and Riesz basis generation.
As a consequence, the analyticity of the solution and the exponential stability of the system are concluded.
This work was supported by the National Natural Science Foundation of China, Program for New Century Excellent Talents in
the Universities of China and by the National Research Foundation of South Africa. 相似文献
8.
R. Sritharan 《Discrete Mathematics》2008,308(12):2581-2588
Golumbic, Kaplan, and Shamir [Graph sandwich problems, J. Algorithms 19 (1995) 449-473], in their paper on graph sandwich problems published in 1995, left the status of the sandwich problems for strongly chordal graphs and chordal bipartite graphs open. It was recently shown [C.M.H. de Figueiredo, L. Faria, S. Klein, R. Sritharan, On the complexity of the sandwich problems for strongly chordal graphs and chordal bipartite graphs, Theoret. Comput. Sci., accepted for publication] that the sandwich problem for strongly chordal graphs is NP-complete. We show that given graph G with a proper vertex coloring c, determining whether there is a supergraph of G that is chordal bipartite and also is properly colored by c is NP-complete. This implies that the sandwich problem for chordal bipartite graphs is also NP-complete. 相似文献
9.
Priyadarshi Satpati 《Journal of organometallic chemistry》2008,693(7):1159-1165
We find sandwiched metal dimers CB5H6M-MCB5H6 (M = Si, Ge, Sn) which are minima in the potential energy surface with a characteristic M-M single bond. The NBO analysis and the M-M distances (Å) (2.3, 2.44 and 2.81 for M = Si, Ge, Sn) indicate substantial M-M bonding. Formal generation of CB5H6M-MCB5H6 has been studied theoretically. Consecutive substitution of two boron atoms in B7H−27 by M (Si, Ge, Sn) and carbon, respectively followed by dehydrogenation may lead to our desired CB5H6M-MCB5H6. We find that the slip distorted geometry is preferred for MCB5H7 and its dehydrogenated dimer CB5H6M-MCB5H6. The slip-distortion of M-M bond in CB5H6M-MCB5H6 is more than the slip distortion of M-H bond in MCB5H7. Molecular orbital analysis has been done to understand the slip distortion. Larger M-M bending (CB5H6M-MCB5H6) in comparison with M-H bending (MCB5H7) is suspected to be encouraged by stabilization of one of the M-M π bonding MO’s. Preference of M to occupy the apex of pentagonal skeleton of MCB5H7 over its icosahedral analogue MCB10H11 has been observed. 相似文献
10.
以丙烯酰胺(AM)和N-乙烯基咪唑(NVI)为双功能单体,借助"三明治"结构有效控制前驱液的填充,制备了可特异性识别Cu~(2+)的反蛋白石结构光子晶体水凝胶膜(PCHs).该PCHs具有相互贯通的三维有序大孔结构,可在Cu~(2+)缓冲溶液中快速响应,产生特征的布拉格(Bragg)衍射峰.随着Cu~(2+)浓度的增大(0~10-4mol/L),PCHs的Bragg衍射峰位移66 nm,并伴随着明显的颜色变化(由棕红色逐渐变为黄绿色).此外,PCHs在混合金属盐溶液中仍能实现对Cu~(2+)的特异性识别.PCHs对Cu~(2+)的特异识别性、快速响应及自表达的特点为Cu~(2+)现场快速检测提供了可能. 相似文献