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141.
Moubaraki B Leita BA Halder GJ Batten SR Jensen P Smith JP Cashion JD Kepert CJ Létard JF Murray KS 《Dalton transactions (Cambridge, England : 2003)》2007,(39):4413-4426
A range of bis-facial tridentate chelate complexes of type [Fe((R-pz)(3)CH)((3,5-Me(2)pz)(3)CH)](BF(4))(2) has been characterised that contain two different tris-pyrazolylmethane ligands, with variations in R being H (complex crystallised as polymorphs and ) and 4-Me (), as well as R = H with a CH(2)OH arm off the methane carbon (). A tris(pyridyl)methane analogue is also described (). The tris(3,5-dimethylpyrazolyl)methane co-ligand (3,5-Me(2)pz), and the BF(4)(-) counterion, are constant throughout. The spin-crossover properties of these Fe(ii) d(6) compounds have been probed in detail by variable temperature magnetic, M?ssbauer spectral and crystallographic methods. The effects of distortions from octahedral symmetry around the Fe(ii) centres, of crystal solvate molecules (1.5 MeCN in and 2 MeCN in ) and of supramolecular/crystal packing, are discussed. In the case of , subtle twisting of pyrazole rings occurs, as a function of temperature, that has a greater effect upon the relative positions of the Fe(ii) chelate molecules in polymorph than in polymorph ; this is thought to drive the cooperativity differences observed in the magnetism of the polymorphs. Comparisons are also made between to and their homoleptic, parent [Fe(L)(2)] (2+) materials. The complexes were screened for the LIESST (light induced excited spin state trapping) effect by measurements of diffuse absorption spectra on the surface of powder samples, at different temperatures. One example, , showed a 2-step thermal spin crossover transition and it was probed in detail for its photomagnetic features. The T(LIESST) and T(1/2) values for did not obey an empirical relationship, T(LIESST) = 150 - 0.3T(1/2) followed by many Fe(ii)(N-donor)(6) crossover compounds of the bis-tridentate (meridional) type, and possible reasons for this are discussed. 相似文献
142.
Pavan Kumar Pingali Sukanya Halder Debasish Mukherjee Sankar Basu Rahul Banerjee Devapriya Choudhury Dhananjay Bhattacharyya 《Journal of computer-aided molecular design》2014,28(8):851-867
RNA contains different secondary structural motifs like pseudo-helices, hairpin loops, internal loops, etc. in addition to anti-parallel double helices and random coils. The secondary structures are mainly stabilized by base-pairing and stacking interactions between the planar aromatic bases. The hydrogen bonding strength and geometries of base pairs are characterized by six intra-base pair parameters. Similarly, stacking can be represented by six local doublet parameters. These dinucleotide step parameters can describe the quality of stacking between Watson–Crick base pairs very effectively. However, it is quite difficult to understand the stacking pattern for dinucleotides consisting of non canonical base pairs from these parameters. Stacking interaction is a manifestation of the interaction between two aromatic bases or base pairs and thus can be estimated best by the overlap area between the planar aromatic moieties. We have calculated base pair overlap between two consecutive base pairs as the buried van der Waals surface between them. In general, overlap values show normal distribution for the Watson–Crick base pairs in most double helices within a range from 45 to 50 Å2 irrespective of base sequence. The dinucleotide steps with non-canonical base pairs also are seen to have high overlap value, although their twist and few other parameters are rather unusual. We have analyzed hairpin loops of different length, bulges within double helical structures and pseudo-continuous helices using our algorithm. The overlap area analyses indicate good stacking between few looped out bases especially in GNRA tetraloop, which was difficult to quantitatively characterise from analysis of the base pair or dinucleotide step parameters. This parameter is also seen to be capable to distinguish pseudo-continuous helices from kinked helix junctions. 相似文献
143.
Heinz-Richard Halder 《Archiv der Mathematik》1971,22(1):302-303
Ohne Zusammenfassung 相似文献
144.
145.
Anuj Krishna N. Vijayan B. Riscob B. S. Gour D. Haranath J. Philip S. Verma M. S. Jayalakshmy G. Bhagavannarayana S. K. Halder 《Applied Physics A: Materials Science & Processing》2014,114(4):1257-1265
A potential semiorganic nonlinear optical material, L-alanine cadmium chloride monohydrate has been successfully synthesised and single crystals have been grown by slow evaporation solution growth technique at room temperature by using double distilled water as the solvent. The lattice dimensions of the grown crystal have been analysed by adopting powder X-ray diffraction technique and found that it crystallised in monoclinic system with space group C2. The crystalline perfection of the as-grown crystal has been assessed by high resolution X-ray diffraction and X-ray topography techniques and observed that the quality of the grown specimen is reasonably good. Its optical properties were examined by UV–Vis and photoluminescence techniques and found that there is no absorption in the entire visible range. Its functional groups were identified from FT-Raman and observed that there is no incorporation of other impurities during crystallisation. Its relative second harmonic generation efficiency has been tested with different particle size by Kurtz powder technique and found that within the coherence length the title compound is phase matchable. Its various thermal properties like thermal conductivity, specific heat, thermal effusivity, etc. have been evaluated by photopyroelectric technique and compared with other organic and inorganic materials. To confirm its piezoelectric response, its piezoelectric charge coefficient was measured using piezometer and found low. Its optical homogeneity as well as birefringence measurement of the grown specimen has been carried out by interferometric technique. The surface defects of the grown LACCM single crystal were analysed with etching at room temperature using water as an etchant. 相似文献
146.
147.
The performance of Maximum a posteriori (MAP) estimation is studied analytically for binary symmetric multi-channel Hidden Markov processes. We reduce the estimation problem to a 1D Ising spin model and define order parameters that correspond to different characteristics of the MAP-estimated sequence. The solution to the MAP estimation problem has different operational regimes separated by first order phase transitions. The transition points for L-channel system with identical noise levels, are uniquely determined by L being odd or even, irrespective of the actual number of channels. We demonstrate that for lower noise intensities, the number of solutions is uniquely determined for odd L, whereas for even L there are exponentially many solutions. We also develop a semi analytical approach to calculate the estimation error without resorting to brute force simulations. Finally, we examine the tradeoff between a system with single low-noise channel and one with multiple noisy channels. 相似文献
148.
Heinz-Richard Halder 《Journal of Geometry》1974,5(2):147-157
In this paper we get necessary conditions for the existence of (k,n)-arcs K with the following property: Each point of K is incident with exactly m lines intersecting K in exactly m points. We prove that the set of tangent lines of such arcs forms an arc of the same type in the dual plane. Moreover we determine an upper bound for k for the existence of m-regular (k,n)-arcs. 相似文献
149.
S. Halder P. Gerber T. Schneller R. Waser 《Applied Physics A: Materials Science & Processing》2005,81(1):11-13
The electromechanical properties of thin films of barium titanate zirconate were studied with the help of a double-beam interferometer. Thin films of barium titanate zirconate (Ba(Ti1-xZrx)O3) of various compositions (x=0, 0.03, 0.05, 0.07, 0.1, 0.2, 0.3 and 0.4) were deposited by chemical solution deposition on Pt/TiO2/SiO2/Si substrates. The thin films show a strain of around 0.05 (at 200 kV/cm) for the unsubstituted BaTiO3 thin films. For higher Zr substitutions up to 5% the strain increases slightly and subsequently falls to 0.01 at 200 kV/cm for even higher Zr content. The d33 values were found to vary between 30 pm/V and 10 pm/V for 0x0.4. PACS 77.65.-j; 77.55.+f; 77.84.Dy 相似文献
150.
Ultrastable Imine‐Based Covalent Organic Frameworks for Sulfuric Acid Recovery: An Effect of Interlayer Hydrogen Bonding
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Arjun Halder Suvendu Karak Dr. Matthew Addicoat Saibal Bera Dr. Amit Chakraborty Shebeeb H. Kunjattu Dr. Pradip Pachfule Prof. Dr. Thomas Heine Prof. Dr. Rahul Banerjee 《Angewandte Chemie (International ed. in English)》2018,57(20):5797-5802
A rapid and scalable synthesis of six new imine‐linked highly porous and crystalline COFs is presented that feature exceptionally high chemical stability in harsh environments including conc. H2SO4 (18 m ), conc. HCl (12 m ), and NaOH (9 m ). This is because of the presence of strong interlayer C?H???N hydrogen bonding among the individual layers, which provides significant steric hindrance and a hydrophobic environment around the imine (?C=N?) bonds, thus preventing their hydrolysis in such an abrasive environment. These COFs were further converted into porous, crystalline, self‐standing, and crack‐free COF membranes (COFMs) with extremely high chemical stability for their potential applications for sulfuric acid recovery. The as‐synthesized COFMs exhibit unprecedented permeance for acetonitrile (280 Lm?2 h?1 bar?1) and acetone (260 Lm?2 h?1 bar?1). 相似文献