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101.
Conrad Wagner Franka Kreis Dennis Popp Dr. Olaf Hübner Dr. Elisabeth Kaifer Prof. Hans-Jörg Himmel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(45):10336-10347
In this work, the change of reactivity induced by the introduction of two para-ethynyl substituents (CCSi(iPr)3 or CCH) to the organic electron-donor 1,2,4,5-tetrakis(tetramethylguanidino)-benzene is evaluated. The redox-properties and redox-state dependent fluorescence are evaluated, and dinuclear CuI and CuII complexes synthesized. The Lewis-acidic B(C6F5)3 substitutes the proton of the ethynyl −CCH groups to give new anionic −CCB(C6F5)3− substituents, leading eventually to a novel dianionic strong electron donor in its diprotonated form. Its two-electron oxidation with dioxygen in the presence of a copper catalyst yields the first redox-active guanidine that is neutral (instead of cationic) in its oxidized form. 相似文献
102.
When a polymer solution is cast on a flat substrate and the solvent is allowed to evaporate, dewetting might take place. Instead of a continuous film, the polymer forms micrometer-sized droplets. By controlling the solvent casting process with the help of a roller apparatus, the size and spacing of the polymer droplets can be adjusted. We investigated the effect of polymer concentration and roller speed on the pattern dimensions and found that higher concentrations lead to larger polymer droplets (from 1 to 11 microm), whereas faster roller speeds lead to a wider interdroplet spacing (from 4 to 130 microm). 相似文献
103.
Armin Presser Olaf Kunert Irmgard P?tschger 《Monatshefte für Chemie / Chemical Monthly》2006,26(1):365-374
Several improved approaches for the preparation of tetra-O-benzyl-α-D-glucopyranosyl bromide and tetra-O-pivaloyl-α-D-glucopyranosyl bromide are discussed. The importance of these compounds, which are useful glycosyl donors, was demonstrated
by successful preparation of cholesteryl glucopyranosides in an almost neutral medium without the formation of orthoesters.
In addition, accurate 1H and 13C NMR resonance assignments of the synthesized cholesteryl glycosides were performed by 2D NMR spectroscopy. 相似文献
104.
Xinghui Qi Dr. Sébastien Pillet Dr. Coen de Graaf Michał Magott Dr. El-Eulmi Bendeif Dr. Philippe Guionneau Dr. Mathieu Rouzières Dr. Valérie Marvaud Dr. Olaf Stefańczyk Dr. Dawid Pinkowicz Dr. Corine Mathonière 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3141-3145
The photoinduced properties of the octacoordinated complex K4MoIV(CN)8⋅2 H2O were studied by theoretical calculations, crystallography, and optical and magnetic measurements. The crystal structure recorded at 10 K after blue light irradiation reveals an heptacoordinated Mo(CN)7 species originating from the light-induced cleavage of one Mo−CN bond, concomitant with the photoinduced formation of a paramagnetic signal. When this complex is heated to 70 K, it returns to its original diamagnetic ground state, demonstrating full reversibility. The photomagnetic properties show a partial conversion into a triplet state possessing significant magnetic anisotropy, which is in agreement with theoretical studies. Inspired by these results, we isolated the new compound [K(crypt-222)]3[MoIV(CN)7]⋅3 CH3CN using a photochemical pathway, confirming that photodissociation leads to a stable heptacyanomolybdate(IV) species in solution. 相似文献
105.
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109.
Olaf Evers Erich Hdicke Gregor Ley 《Colloids and surfaces. A, Physicochemical and engineering aspects》1994,90(2-3):135-147
The self-consistent mean field model of Scheutjens and Fleer is used to model spherical aggregates of homopolymers and monomer—polymer particles in solution. For homopolymer aggregates we found that the chain ends are preferentially located at the exterior side of the polymer/solvent interface. The distribution of the end segments may be an important parameter in latex film formation. For monomer—polymer particles a “core-shell” structure is found with an extended core containing a monomer—polymer mixture and a thin shell a few nanometres thick strongly enriched with monomer. The monomer-enriched shell seems to function as a solvating envelope for the dangling chain ends. These results are compared with other simulations based on a single chain in a spherical-cavity model. 相似文献
110.
Axel Pramann Olaf Rienitz Detlef Schiel Bernd Güttler 《International journal of mass spectrometry》2011,299(2-3):78-86
The isotopic abundances and thus molar mass M(Si) of a silicon crystal material with natural isotopic abundances have been measured for the first time using multicollector-ICP-mass spectrometry (MC-ICP-MS) in combination with a novel concept of a modified isotope dilution mass spectrometry (IDMS)-method. This experimental work is the further development of part 1 of this series of papers. While part 1 describes the theoretical background and the mathematical derivation of the novel concept in detail, the measurements presented here serve to validate the novel concept and give experimental proof of its capability. Moreover, the also new method for the analytical calculation of calibration factors needed in the determination of absolute isotope amount ratios has been tested successfully. Silicon isotopic abundances have been measured directly from an aqueous alkaline matrix following a new sample preparation protocol developed within the framework of this study. A molar mass of M(Si) = 28.08548(13) g/mol with an associated relative uncertainty of urel = 4.6 × 10?6 (k = 1) has been measured. This is in excellent agreement with the current IUPAC value for the molar mass of natural silicon M(Sinat) = 28.08550(15) g/mol with urel = 5.3 × 10?6 (k = 1). An uncertainty budget according to the Guide to the Expression of Uncertainty in Measurement (GUM) was calculated to assess the presented results and to validate the novel concept with the help of experimental data. The development of a new experimental procedure is presented in detail and the contributions to the uncertainty are discussed in comparison to part 1 of this work. 相似文献