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41.
A steady state thermoelastic mixed boundary value problem for an isotropic thick plate is considered in this paper. The faces
of an external circular crack situated in the mid-plane of the plate are opened up by the application of temperature while
the bounding surface of the plate are maintained at a constant zero temperature. Solution valid for large values of the ratio
of the plate thickness to the diameter of the crack has been obtained. Expressions for various quantities of physical interest
are derived by finding iterative solutions of the equations and the results are shown graphically. 相似文献
42.
An axisymmetric steady-state thermoelastic problem of an infinite isotropic medium containing an annular crack is considered.
The faces of the crack are exposed to prescribed temperature distribution. The normal components of stress and displacement
on the crack plane and the stress-intensity factors at the boundaries of the crack are expressed in power series in terms
of the ratio between the radii of the inner and outer boundaries. These are illustrated graphically. 相似文献
43.
The nuclear response function of a nucleus has been computed in the Fermi Gas model when another nucleus collides with it. A simple relation has been derived for the frictional co-efficient for the later stages of the nucleus-nucleus collision. The results agree quite well with phenomenology and microscopic derivations of the frictional co-efficient. 相似文献
44.
Indranil Bhattacharyya Sanjib Ganguly Bikash Kumar Panda Animesh Chakravorty 《Journal of Chemical Sciences》2008,120(1):87-93
The reaction of [RhCl2(HPhL)(PhL)] with MII(ClO4)2·6H2O in presence of alkali has furnished trinuclear [RhCl2(PhL)2]2M(H2O)2·H2O (HPhL is phenylazobenzaldoxime; M = Mn, Co, Ni). A similar reaction with MI(PPh3)2NO3 yielded binuclear [RhCl2(PhL)2]M(PPh3)2 (M = Cu, Ag). In these molecules the oximato group acts as a bridge between RhIII (bonded at N) and MII or MI (bonded at O). In structurally characterized [RhIIICl2(PhL)2]2Mn(H2O)2.H2O the centrosymmetric distorted octahedral MnO6 coordination sphere is spanned by four oximato oxygen atoms and two water molecules lying in trans position. In the lattice the neighbouring molecules are held together by H2O⋯H2O⋯H2O hydrogen bonds generating infinite zigzag chains. The manganese atoms lie parallel to the C-axis, the shortest Mn...Mn distance
being 7.992 ?. Magnetic exchange interactions if any are small as seen in room temperature magnetic moments. The manganese
system displays a strong EPR signal near g = 2.00. In the complex [RhCl2(PhL)2]Cu(PPh3)2 the copper atom is coordinated to two oximato oxygen atoms and the two phosphorus atoms in a distorted tetrahedral geometry.
The softness of the phosphine ligand is believed to sustain the stable coordination of hard oximato oxygen to soft CuI. The coordination sphere of the RhIII atom in both the complexes is uniformly trans-RhN4Cl2. 相似文献
45.
NMR spectroscopic discrimination of optical enantiomers is most often carried out using (2)H and (13)C spectra of chiral molecules aligned in a chiral liquid crystalline solvent. The use of proton NMR for such a purpose is severely hindered due to the spectral complexity and the significant loss of resolution arising from numerous short- and long-distance couplings and the indistinguishable overlap of spectra from both R and S enantiomers. The determination of all the spectral parameters by the analyses of such intricate NMR spectra poses challenges, such as, unraveling of the resonances for each enantiomer, spectral resolution, and simplification of the multiplet pattern. The present study exploits the spin state selection achieved by the two-dimensional (1)H NMR correlation of selectively excited isolated coupled spins (Soft-COSY) of the molecules to overcome these problems. The experiment provides the relative signs and magnitudes of all of the proton-proton couplings, which are otherwise not possible to determine from the broad and featureless one-dimensional (1)H spectra. The utilization of the method for quantification of enantiomeric excess has been demonstrated. The studies on different chiral molecules, each having a chiral center, whose spectral complexity increases with the increasing number of interacting spins, and the advantages and limitations of the method over SERF and DQ-SERF experiments have been reported in this work. 相似文献
46.
Rui Yan Bikash Mishra Dr. Michael Traxler Dr. Jérôme Roeser Nicolas Chaoui Bidhan Kumbhakar Dr. Johannes Schmidt Prof. Shuang Li Prof. Arne Thomas Dr. Pradip Pachfule 《Angewandte Chemie (International ed. in English)》2023,62(32):e202302276
Lithium-sulphur (Li−S) batteries are a promising alternative power source, as they can provide a higher energy density than current lithium-ion batteries. Porous materials are often used as cathode materials as they can act as a host for sulphur in such batteries. Recently, covalent organic frameworks (COFs) have also been used, however they typically suffer from stability issues, resulting in limited and thus insufficient durability under practical conditions and applications. Herein, we report the synthesis of a crystalline and porous imine-linked triazine-based dimethoxybenzo-dithiophene functionalized COF (TTT-DMTD) incorporating high-density redox sites. The imine linkages were further post-synthetically transformed to yield a robust thiazole-linked COF (THZ-DMTD) by utilizing a sulphur-assisted chemical conversion method, while maintaining the crystallinity. As a synergistic effect of its high crystallinity, porosity and the presence of redox-active moieties, the thiazole-linked THZ-DMTD exhibited a high capacity and long-term stability (642 mAh g−1 at 1.0 C; 78.9 % capacity retention after 200 cycles) when applied as a cathode material in a Li−S battery. 相似文献
47.
Markad SD Xia S Snyder NL Surana B Morton MD Hadad CM Peczuh MW 《The Journal of organic chemistry》2008,73(16):6341-6354
The facial selectivity in the DMDO epoxidation of carbohydrate-based oxepines derived from glucose, galactose, and mannose has been determined by product analysis and density functional theory (DFT, B3LYP/6-31+G**//B3LYP/6-31G*) calculations. Oxepines 3 and 4, derived from d-galactose and d-mannose, largely favor alpha- over beta-epoxidation. The results reported here, along with selectivities in the DMDO-mediated epoxidation of d-xylose-based oxepine 1 and d-glucose-based oxepines 2 and 5 reported earlier, support a model in which electronic effects, guided by the stereochemistry of the oxygens on the oxepine ring, largely determine the stereoselectivity of epoxidation. Other contributing factors included conformational issues in the oxepine's transition state relative to the reactant, the asynchronicity in bond formation of the epoxide, and the overall steric bulk on the alpha- and beta-faces of the oxepine. Considered together, these factors should generally predict facial selectivity in the DMDO-epoxidation of cyclic enol ethers. 相似文献
48.
Baishya B Mavinkurve RG Suryaprakash N 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,185(2):221-229
The spectra of molecules oriented in liquid crystalline media are dominated by partially averaged dipolar couplings. In the 13C-1H HSQC, due to the inefficient hetero-nuclear dipolar decoupling in the indirect dimension, normally carried out by using a pi pulse, there is a considerable loss of resolution. Furthermore, in such strongly orienting media the 1H-1H and 13C-1H dipolar couplings leads to fast dephasing of transverse magnetization causing inefficient polarization transfer and hence the loss of sensitivity in the indirect dimension. In this study we have carried out 13C-1H HSQC experiment with efficient polarization transfer from 1H to 13C for molecules aligned in liquid crystalline media. The homonuclear dipolar decoupling using FFLG during the INEPT transfer delays and also during evolution period combined with the pi pulse heteronuclear decoupling in the t1 period has been applied. The studies showed a significant reduction in partially averaged dipolar couplings and thereby enhancement in the resolution and sensitivity in the indirect dimension. This has been demonstrated on pyridazine and pyrimidine oriented in the liquid crystal. The two closely resonating carbons in pyrimidine are better resolved in the present study compared to the earlier work [H.S. Vinay Deepak, Anu Joy, N. Suryaprakash, Determination of natural abundance 15N-1H and 13C-1H dipolar couplings of molecules in a strongly orienting media using two-dimensional inverse experiments, Magn. Reson. Chem. 44 (2006) 553-565]. 相似文献
49.
The classification system is very important for making decision and it has been attracted much attention of many researchers. Usually, the traditional classifiers are either domain specific or produce unsatisfactory results over classification problems with larger size and imbalanced data. Hence, genetic algorithms (GA) are recently being combined with traditional classifiers to find useful knowledge for making decision. Although, the main concerns of such GA-based system are the coverage of less search space and increase of computational cost with the growth of population. In this paper, a rule-based knowledge discovery model, combining C4.5 (a Decision Tree based rule inductive algorithm) and a new parallel genetic algorithm based on the idea of massive parallelism, is introduced. The prime goal of the model is to produce a compact set of informative rules from any kind of classification problem. More specifically, the proposed model receives a base method C4.5 to generate rules which are then refined by our proposed parallel GA. The strength of the developed system has been compared with pure C4.5 as well as the hybrid system (C4.5 + sequential genetic algorithm) on six real world benchmark data sets collected from UCI (University of California at Irvine) machine learning repository. Experiments on data sets validate the effectiveness of the new model. The presented results especially indicate that the model is powerful for volumetric data set. 相似文献
50.