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排序方式: 共有592条查询结果,搜索用时 15 毫秒
451.
Dr. Christa Grogger Dr. Michaela Flock Madeleine Heurix Ana Torvisco Dr. Andreas W. Kyri Prof. Dr. Harald Stueger 《欧洲无机化学杂志》2023,26(25):e202300243
Imidazole-2-thiones have attracted considerable interest in the past as materials for potential applications in the pharmaceutical and chemical industries. Herein, the synthesis of a series of backbone silylated 1,3-dialkylimidazol-2-thiones is reported. The developed synthesis protocol involves the silylation of N,N-dimethylimidazol-2-thione 1 followed by the addition of organochlorosilanes RnSiCl4–n (R=Me, Ph; n=0–4) and enabled the synthesis of the C-silylated derivatives with monocyclic, silyl-bridged or fused tricyclic structures. Reactivity studies performed with N,N-dimethyl-4,5-bistrimethylsilylimidazole-2-thione as a model substance showed surprisingly stable silicon-vinyl bonds and reactivity patterns closely related to those observed for the unsilylated species 1 . Combined UV-spectroscopic and computational studies revealed only minor impact of the silyl substituents on the electronic structure of the imidazol-2-thione ring. 相似文献
452.
Renáta Šelešovská Lenka Janíková Michaela Štěpánková Jaromíra Chýlková 《Chemical Papers》2017,71(3):679-688
Voltammetric behavior of the antineoplastic drug 5-fluorouracil is for the first time studied on polished copper solid amalgam electrode. It was proved that the presence of the copper in the electrode material is advantageous for the determination of 5-fluorouracil, and one well-developed cathodic signal belonging to the reduction of the absorbed complex of 5-fluorouracil–Cu(II) was found as suitable for its precise determination. The highest response was recorded in Britton–Robinson buffer of pH 8 and excellent results like repeatability of measurements and determination as well or limit of detection (1.2 × 10?9 mol L?1) were reached. Moreover, the proposed method was successfully applied to the analysis of pharmaceutical sample with excellent recovery (97.0–100.9%). 相似文献
453.
454.
Lubomír Prokeš Michaela Vašinová Galiová Simona Hušková Tomáš Vaculovič Aleš Hrdlička Andrew Zed Mason Hector Neff Antonín Přichystal Viktor Kanický 《Chemical Papers》2015,69(6):761-778
The provenance of obsidian artefacts and raw materials was studied by the multivariate statistical analysis of forty-five samples using elemental composition data obtained by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). One ICP-MS instrument equipped with a quadrupole mass filter and the other based on a time-of-flight analyser were coupled to the same type of laser ablation device (Nd:YAG 213 nm), thereby affording a comparison of the different mass spectrometers in terms of precision and verification of the consistency of the results. The influence of surface roughness (polished raw material vs artefact) and microinhomogeneity on the LA-ICP-MS signal was studied under the optimised working conditions of the laser ablation device. Principal component analysis, correspondence analysis, independent component analysis, multi-dimensional scaling, Sammon mapping and fuzzy cluster analysis were applied and compared in order to reveal statistically significant compositional differences between particular geological sites and to disclose the provenance of the raw materials used in manufacture of the artefacts. Twenty-seven artefacts and eighteen raw material samples from natural resources in the Czech Republic, Slovakia, Italy, Greece, Syria, Iraq, Turkey, Mexico and Nicaragua were examined with special attention focused on samples from Moravia (Czech Republic) and some Near East sites (Tell Arbid, Tell Asmar). The Carpathian origin of the obsidian artefacts was investigated in the Moravian samples using the Pb, Rb and U contents. The Near East samples were classified according to their Sr, Ba, Zr and REE contents as per-alkaline obsidians (Bingöl A/Nemrut Da?) originating from Southeast Anatolia. 相似文献
455.
Spatially Resolved Quantification of Gadolinium(III)‐Based Magnetic Resonance Agents in Tissue by MALDI Imaging Mass Spectrometry after In Vivo MRI 下载免费PDF全文
Dr. Michaela Aichler Katharina Huber Dr. Franz Schilling Dr. Fabian Lohöfer Dr. Katja Kosanke Dr. Reinhard Meier Prof.Dr. Ernst J. Rummeny Prof. Dr. Axel Walch Dr. Moritz Wildgruber 《Angewandte Chemie (International ed. in English)》2015,54(14):4279-4283
Gadolinium(III)‐based contrast agents improve the sensitivity and specificity of magnetic resonance imaging (MRI), especially when targeted contrast agents are applied. Because of nonlinear correlation between the contrast agent concentration in tissue and the MRI signal obtained in vivo, quantification of certain biological or pathophysiological processes by MRI remains a challenge. Up to now, no technology has been able to provide a spatially resolved quantification of MRI agents directly within the tissue, which would allow a more precise verification of in vivo imaging results. MALDI imaging mass spectrometry for spatially resolved in situ quantification of gadolinium(III) agents, in correlation to in vivo MRI, were evaluated. Enhanced kinetics of Gadofluorine M were determined dynamically over time in a mouse model of myocardial infarction. MALDI imaging was able to corroborate the in vivo imaging MRI signals and enabled in situ quantification of the gadolinium probe with high spatial resolution. 相似文献
456.
Elizabeth A. German Jonathan E. Ross Dr. Peter C. Knipe Michaela F. Don Dr. Sam Thompson Prof. Dr. Andrew D. Hamilton 《Angewandte Chemie (International ed. in English)》2015,54(9):2649-2652
Many therapeutically relevant protein–protein interactions contain hot‐spot regions on secondary structural elements, which contribute disproportionately to binding enthalpy. Mimicry of such α‐helical regions has met with considerable success, however the analogous approach for the β‐strand has received less attention. Presented herein is a foldamer for strand mimicry in which dipolar repulsion is a central determinant of conformation. Computation as well as solution‐ and solid‐phase data are consistent with an ensemble weighted almost exclusively in favor of the desired conformation. 相似文献
457.
Douglas H. McQueen Karl-Michael Jäger Michaela Paligová 《Macromolecular Symposia》2005,221(1):217-226
Local variations in filler particle concentration and/or shape and orientation in static filler/polymer composites are modelled as distributions of percolation thresholds. The concentration variations can be due to insufficient mixing, formation of semicrystalline voids during cooling from the melt, shrinkage during polymer curing, flow during physical compression or the like. Irregular filler shapes, especially elongated shapes, reduce the percolation threshold; thus natural variations in the shapes and orientations of filler particle aggregates lead to locally varying percolation thresholds. A distribution of percolation thresholds leads to an apparent percolation threshold based on the conductivity below the mean percolation threshold. For filler concentrations above the apparent percolation threshold the dielectric constant continues to increase before reaching a lowered peak value at the mean percolation threshold and then decreasing. Own experimental results on EBA /carbon black composites support the theory. 相似文献
458.
Michaela Weiskircher Heike Niemeyer Frank Deters Roland Storm 《Nachrichten aus der Chemie》1996,44(10):1027-1028
459.
460.
Jens Hartung Michaela Schwarz Ingrid Svoboda Hartmut Fuess 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):o682-o684
The geometry of racemic methyl 2‐(4‐methyl‐2‐thioxo‐2,3‐dihydrothiazol‐3‐yloxy)propanoate, C8H11NO3S2, (I), is characterized by a distorted heterocyclic five‐membered ring and an enantiomorphic N‐alkoxy substituent, which is inclined at an angle of −68.8° to the thiazolethione plane in (M)‐(I). The unit cell consists of a 1:1 ratio of R,P‐ and S,M‐configured molecules of (I). The combination of a P configuration at the N—O axis and an R configuration at the asymmetric propanoate Cβ atom on one side, and an S,M configuration on the other side, is considered to originate from steric interactions. The largest substituent at the asymmetric propanoate Cβ atom, i.e. the methoxycarbonyl group, resides above the methyl substituent; the medium‐sized propanoate γ‐methyl substituent points in the opposite direction with respect to the N—O bond, whereas the H atom is located above the C=S double bond of the thiazolethione subunit. 相似文献