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371.
A method for testing water/oil emulsion droplet membranes selectively has been demonstrated. The method uses electric fields
to induce attraction, membrane thinning and coalescence between aqueous droplets deposited in an oil continuum. The coalescence
process is monitored visually by the use of videomicroscopy. A set of model oils containing indigenous surfactants (asphaltenes)
from a crude oil has been studied, and the effects of asphaltene concentration, oil phase aromaticity, aging of oils and interfacial
exposure time have been investigated. The strength of the field at the point of coalescence is defined as the critical parameter
describing membrane strength. In the current experiments a.c. fields were used and droplet sizes were of the order of 500–600 μm.
Received: 8 October 1998 Accepted in revised form: 11 January 1999 相似文献
372.
Petra Stoll Christian Nther Inke Jeß Wolfgang Bensch 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(9):e368-e369
The reaction of Cs2S3, Ta and S yields single crystals of the new caesium tantalum chalcogenide hexacaesium tetratantalum docosasulfide, Cs6Ta4S22, which is isotypic with Rb6Ta4S22 and the niobium compounds A6Nb4S22 (A = Rb, Cs). The structure consists of discrete [Ta4S22]6? anions and Cs+ cations. 相似文献
373.
The new compounds K6Nb4S22 and K6Ta4S22 ( I ) have been synthesised by the reaction of NbS2 or Ta metal in a K2S3 flux. Using TaS2 as educt a second modification of K6Ta4S22 ( II ) is obtained. K6Nb4S22 and K6Ta4S22 (form I ) crystallise in the monoclinic space group C2/c with a = 35.634 (2)Å, b = 7.8448 (4)Å, c = 12.1505 (5)Å, β = 100.853 (5)°, V = 3335.8 (3)Å3, and Z = 4 for K6Nb4S22 and a = 35.563 (7) Å, b = 7.836 (2)Å, c = 12.139 (2)Å, β = 100.56 (3)°, V = 3325.5 (2)Å3, and Z = 4 for K6Ta4S22 ( I ). The second modification K6Ta4S22 (form II ) crystallises in the monoclinic space group P21/c with a = 7.5835 (6)Å, b = 8.7115 (5)Å, c = 24.421 (2)Å, β = 98.733 (9)°, V = 1594.6 (2)Å3, and Z = 2. The structures consist of [M4S22]6— anions composed of two M2S11 sub‐units which are linked into M4S22 units via terminal sulfur ligands. The anions are well separated by the K+ cations. Differences between the structures of the title compounds and those with the heavier alkali cations Rb+ and Cs+ are caused by the different arrangement of the [M4S22]6— anions around the cations and the different S2—/S22— binding modes. The thermal behaviour of both modifications was investigated using differential scanning calorimetry (DSC). From these investigations there is no hint for a polymorphic transition between the two forms. After heating crystals of form II above the melting point and cooling the melt to room temperature a crystalline powder of form I can be isolated. 相似文献
374.
375.
The new heteroleptic chromium complex [Ph4P][Cr(en)(S5)2] has been synthesised under mild solvothermal conditions by the reaction of chromium trichloride, sulfur, and tetraphenylphosphoniumbromide in a solution of ethylendiamine ( en ) in water. The crystal structure consists of isolated tetraphenylphosphonium cations and [Cr(en)(S5)2]– anions. The Cr3+ cations are in an octahedral coordination of two bidentate S52– polysulfide anions and one bidentate en ligand. The N atoms of the en ligand and the terminal S atoms of the S52– anions bonded to the Cr3+ ions are in a cis-position. The six-membered CrS5 rings are in a chair conformation. The three dimensional arrangement of the cations and anions is achieved via intermolecular hydrogen bonds. Investigations with differential thermal analysis (DTA) combined with thermogravimetry (TG) show a stepwise decomposition. In the first step the en ligand is removed completely followed by the emission of a part of the tetraphenylphosphonium cations and the sulfur atoms in the second step. The temperature dependence of the magnetic susceptibility exhibits a Curie-Weiss behaviour with an effective magnetic moment typical for a Cr3+ (d3) ion and a value for the Weiss constant of 1.3(2) K. Fourier transform infrared spectroscopy (FTIR) was also performed to characterise the optical properties. 相似文献
376.
The elongation method proposed by Imamura serves as a theoretical model for polymerization processes. It can now be used together with larger basis sets, Hartree–Fock and density functional methods from the Gaussian 94 package with direct self‐consistent field (SCF). This allows electronic structure calculation of elongating clusters with an efficiency superior to full cluster calculations and a precision superior to previous versions of our elongation method. Performance and accuracy compared with full cluster calculations on a regular polymer using the BLYP/6‐31G(d, p) method. Interaction energies of water and hydrogen fluoride polymers of increasing length are compared between HF, BLYP methods and 4‐31G, 6‐31G(d, p) basis sets: Diffuse and polarization functions have a large influence on the interaction energy on both polymers. Local density of states are calculated for different cluster lengths. They are in good agreement with full cluster calculations. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 35–47, 1999 相似文献
377.
Hans Bock Zdenek Havlas Delia Hess Christian Nther 《Angewandte Chemie (International ed. in English)》1998,37(4):502-504
Quite unexpectedly, all three electrons are taken up by the same anthryl moiety when 9,9′-bianthryl is reduced with an excess of sodium metal. Thanks to the “right” ligand/solvent mixture the first radical trianion salt (depicted on the right) could be isolated. It is a contact-ion quadruple of bianthryl in which all three Na+ counterions coordinate to the same half of the hydrocarbon molecule. 相似文献
378.
379.
Timm M. Reichenau Felix Steinke Dr. Michael T. Wharmby Prof. Dr. Christian Näther Dr. Tobias A. Engesser Prof. Dr. Norbert Stock 《Angewandte Chemie (International ed. in English)》2023,62(26):e202303561
A concept for obtaining isoreticular compounds with tri- instead of tetravalent metal cations using highly acidic reaction conditions was developed and successfully applied in a high throughput study using N,N′-piperazinebis(methylenephosphonic acid) (H4PMP), that resulted in the discovery of a new porous aluminium phosphonate denoted CAU-60⋅6 HCl. The high-throughput study was subsequently extended to other trivalent metal ions. Al-CAU-60⋅6 HCl demonstrates reversible desorption of HCl (18.3 wt % loading) with three distinct compositions observed with zero, four or six HCl molecules per formula unit. Structural changes were followed in detail by powder X-ray diffraction, EDX analysis as well as IR spectroscopy. Rapid desorption of HCl in water within minutes and subsequent adsorption from the gas phase and from aqueous solution are shown. Furthermore, it is possible to adsorb HBr into the guest free Al-CAU-60 framework, demonstrating the high stability of this compound. 相似文献