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151.
A series of uranyl aryloxide complexes has been prepared via metathesis reactions between [UO(2)Cl(2)(THF)(2)](2) and di-ortho-substituted phenoxides. Reaction of 4 equiv of KO-2,6-(t)()Bu(2)C(6)H(3) with [UO(2)Cl(2)(THF)(2)](2) in THF produces the dark red uranyl compound, UO(2)(O-2,6-(t)()Bu(2)C(6)H(3))(2)(THF)(2).THF, 1. Single-crystal X-ray diffraction analysis of 1 reveals a monomer in which the uranium is coordinated in a pseudooctahedral fashion by two apical oxo groups, two cis-aryloxides, and two THF ligands. A similar product is prepared by reaction of KO-2,6-Ph(2)C(6)H(3) with [UO(2)Cl(2)(THF)(2)](2) in THF. Single-crystal X-ray diffraction analysis of this compound reveals it to be the trans-monomer UO(2)(O-2,6-Ph(2)C(6)H(3))(2)(THF)(2), 2. Dimeric structures result from the reactions of [UO(2)Cl(2)(THF)(2)](2) with less sterically imposing aryloxide salts, KO-2,6-Cl(2)C(6)H(3) or KO-2,6-Me(2)C(6)H(3). Single-crystal X-ray diffraction analyses of [UO(2)(O-2,6-Cl(2)C(6)H(3))(2)(THF)(2)](2), 3, and [UO(2)Cl(O-2,6-Me(2)C(6)H(3))(THF)(2)](2), 4, reveal similar structures in which each U atom is coordinated by seven ligands in a pseudopentagonal bipyramidal fashion. Coordinated to each uranium are two apical oxo groups and five equatorial ligands (3, one terminal phenoxide, two bridging phenoxides, and two nonadjacent terminal THF ligands; 4, one terminal chloride, two bridging phenoxides, and two nonadjacent terminal THF ligands). Apparently, the phenoxide ligand steric features exert a greater influence on the solid-state structures than the electronic properties of the substituents. Emission spectroscopy has been utilized to investigate the molecularity and electronic structure of these compounds. For example, luminescence spectra taken at liquid nitrogen temperature allow for a determination of the dependence of the molecular aggregation of 3 on the molecular concentration. Electronic and vibrational spectroscopic measurements have been analyzed to examine trends in emission energies and stretching frequencies. However, comparison of the data for compounds 1-4 reveals that the innate electron-donating capacity of phenoxide ligands is only subtly manifest in either the electronic or vibrational energy distributions within these molecules. 相似文献
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Hydrophobic polysulfone UF membranes were modified with UV irradiation and hydrophilicity increasing agents. The modifications were tested with 0.5% whey-protein solution and 0.05% lysozyme solution at pH 6 and with 0.05% bovine serum albumin solution at various pH values. UV irradiation increased flux and the hydrophilicity of the membranes. The flux increases obtained varied with pH and modification agents used and could be more than 400% compared to unmodified conditions without any loss in retention. The best retentions were obtained at pH values, where both the protein and the membrane had the same charge, and a strong electrostatic repulsion was obtained. The pores enlarged to fixed sizes, which depended on the sizes of the proteins and the range of double layer forces between proteins and membranes at different states of charge density. 相似文献
154.
At the interface between protein and double-stranded DNA, stair motifs simultaneously involve three different types of pairwise interactions: aromatic base stacking, hydrogen bonding, and cation-pi. The relative importance of these interactions is studied in the stair motif occurring in the 1TC3 crystal structure, which involves an arginine and two stacked guanines, by means of Hartree-Fock (HF) and M?ller-Plesset energy and free energy calculations, including vibrational, rotational, translational contributions, both in a vacuum and various solvents. The results obtained show an anti-cooperative tendency of the HF energy and vibrational free energy terms, and the cooperativity of the rotational, translational, and solvation free energies. Hence, the cooperativity of the stair motif interactions, in the context of protein-DNA recognition, can be viewed as arising from the environment. 相似文献
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Detoxification of VX and Other V‐Type Nerve Agents in Water at 37 °C and pH 7.4 by Substituted Sulfonatocalix[4]arenes 下载免费PDF全文
Dipl.‐Chem. Christian Schneider M. Sc. Anne Bierwisch Dr. Marianne Koller Prof. Dr. Franz Worek Prof. Dr. Stefan Kubik 《Angewandte Chemie (International ed. in English)》2016,55(41):12668-12672
Sulfonatocalix[4]arenes with an appended hydroxamic acid residue can detoxify VX and related V‐type neurotoxic organophosphonates with half‐lives down to 3 min in aqueous buffer at 37 °C and pH 7.4. The detoxification activity is attributed to the millimolar affinity of the calixarene moiety for the positively charged organophosphonates in combination with the correct arrangement of the hydroxamic acid group. The reaction involves phosphonylation of the hydroxamic acid followed by a Lossen rearrangement, thus rendering the mode of action stoichiometric rather than catalytic. Nevertheless, these calixarenes are currently the most efficient low‐molecular‐weight compounds for detoxifying persistent V‐type nerve agents under mild conditions. They thus represent lead structures for novel antidotes that allow treatment of poisonings by these highly toxic chemicals. 相似文献
157.
The anionic polymerization of caprolactam using small quantities of reactants was investigated as part of a project aimed at producing polyamide parts by additive manufacturing. Various methods were used to monitor the polymerization and crystallization processes. Drop on drop small‐scale polymerization was carried out on a hot surface and monitored by Fourier transform infrared, which showed that PA6 had been polymerized successfully. PA6 synthesis was carried out in a differential scanning calorimetry cell to monitor the exothermic and endothermic processes during polymerization, and the processes were also observed by hot stage microscopy. It was found that polymerization and crystallization occurred simultaneously at slow heating rates. The amount of crystallinity produced during polymerization decreased as the heating rate increased. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Prof. Dr. Sunney I. Chan Yu‐Jhang Lu Dr. Penumaka Nagababu Dr. Suman Maji Mu‐Cheng Hung Marianne M. Lee Prof. Dr. I‐Jui Hsu Pham Dinh Minh Jeff C.‐H. Lai Kok Yoah Ng Sridevi Ramalingam Prof. Dr. Steve S.‐F. Yu Prof. Dr. Michael K. Chan 《Angewandte Chemie (International ed. in English)》2013,52(13):3731-3735
160.
Karl J.J. Mayrhofer Josef C. Meier Sean J. Ashton Gustav K.H. Wiberg Florian Kraus Marianne Hanzlik Matthias Arenz 《Electrochemistry communications》2008,10(8):1144-1147
A newly developed methodology for examining fuel cell catalyst degradation is introduced. In contrast to the conventional, destructive TEM investigation procedure, this methodology enables the observation of corrosion processes of the same catalyst region repeatedly. In particular we demonstrate the impact of a potential cycling treatment on a carbon-supported platinum catalyst, and propose a new corrosion mechanism for fuel cell catalyst degradation. Under the applied harsh conditions, whole Pt particles detach from the support and dissolve into the electrolyte without re-deposition. 相似文献