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A more realistic model, requiring a few parameters to explain the interactions among distant neighbours and valid for various crystallographic structures, is developed to study phonon dispersion in the bulk fcc metals. The model free from usual fitting procedure is employed to obtain phonon-dispersion in the bulk of fcc strontium crystal which has attracted scant attention so far. The computed results showing good agreement with the recent experimental results lend reliability and credibility to the theory. 相似文献
94.
Two types of the non-pair forces, one from the Born-Mayer and other from the Morse potential, are derived to discuss the response of the electrons in heavy alkali metals, i.e. rubidium and caesium. These potentials are added to the two-body potential of Morse to account for the ion-ion interactions as well. The potentials so obtained are employed to predict the phonon dispersion relations in the bcc metals, which are also compared with the recent precise neutron scattering data. 相似文献
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96.
The Wacker-type oxidation is an important procedure catalyzed by palladium complexes. A mild and general method for the preparation of β-substituted-δ-oxosulfoxides from the corresponding β-substituted-γ,δ-unsaturated sulfoxides is described. The products are versatile synthetic intermediates for the preparation of syn- and anti-1,3-diol and 1,3-aminoalcohol derivatives. 相似文献
97.
Electroactive tetraarylbenzo[1,2- b:4,5- b']difuran (BDF) and model diarylbenzofuran derivatives are synthesized and their structures are established by X-ray crystallography. Isolation and X-ray crystallographic characterization of the robust cation-radical salts of BDF derivatives confirm that a single charge in the BDFs is stabilized largely by the benzodifuran and coplanar alpha-aryl groups lying on the longitudinal axis. These findings suggest that the linear arrays of BDFs may allow the construction of molecular wires suitable for long-range electron transport. 相似文献
98.
Badiadka Narayana Hemmige S. Yathirajan Ravindranath S. Rathore Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(9):664-669
4‐Antipyrine [4‐amino‐1,5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one] and its derivatives exhibit a range of biological activities, including analgesic, antibacterial and anti‐inflammatory, and new examples are always of potential interest and value. 2‐(4‐Chlorophenyl)‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamide, C19H18ClN3O2, (I), crystallizes with Z′ = 2 in the space group P, whereas its positional isomer 2‐(2‐chlorophenyl)‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamide, (II), crystallizes with Z′ = 1 in the space group C2/c; the molecules of (II) are disordered over two sets of atomic sites having occupancies of 0.6020 (18) and 0.3980 (18). The two independent molecules of (I) adopt different molecular conformations, as do the two disorder components in (II), where the 2‐chlorophenyl substituents adopt different orientations. The molecules of (I) are linked by a combination of N—H…O and C—H…O hydrogen bonds to form centrosymmetric four‐molecule aggregates, while those of (II) are linked by the same types of hydrogen bonds forming sheets. The related compound N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)‐2‐(3‐methoxyphenyl)acetamide, C20H21N3O3, (III), is isomorphous with (I) but not strictly isostructural; again the two independent molecules adopt different molecular conformations, and the molecules are linked by N—H…O and C—H…O hydrogen bonds to form ribbons. Comparisons are made with some related structures, indicating that a hydrogen‐bonded R22(10) ring is the common structural motif. 相似文献
99.
Chebny VJ Banerjee M Rathore R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(22):6508-6513
We have designed and synthesized a polymer-supported material in which a versatile fluorene-p-xylene-based receptor is woven onto the backbone of polystyrene. This polymer-supported receptor adopts a pi-prismand-like conformation through a simple C--C bond rotation that results in the quantitative binding of a single silver cation per receptor site with a remarkable efficiency that exceeds the binding abilities of the well-known tris[2.2.2]-p-cyclophane (or pi prismand) by at least a factor of 100. More importantly, the binding event can be readily monitored by 1H NMR spectroscopy, as well as by a more sensitive emission spectroscopic technique in which the quenching of fluorescence of the receptor moiety is quantitatively related to the binding of silver cations. 相似文献
100.
Convergent synthetic routes for the preparation of hitherto unknown fluorene-p-xylene oligomers (containing up to 10 fluorene moieties) from readily available starting materials are described. The conformationally adaptable monomeric receptor (which is made of a pair of fluorene and one p-xylene ring, i.e., Z1) undergoes a simple C-C bond rotation in the presence of silver cations to produce a pi-prismand-like receptor which binds a single silver cation with remarkable efficiency (i.e., K approximately 15,000 M(-1)). The data on 1H NMR spectroscopic titrations with Ag+ together with the density functional theory and AM1 calculations allows us to establish that various oligomers of Z1 (i.e., Z2-Z9) also undergo ready folding into the structures that contain multiple pi-prismand-like receptor sites in the presence of silver cations. The multiple cavities in Z3-Z9 accommodate a single silver cation per cavity with efficiency similar to that of Z1. 相似文献