全文获取类型
收费全文 | 2252篇 |
免费 | 114篇 |
国内免费 | 7篇 |
专业分类
化学 | 1497篇 |
晶体学 | 9篇 |
力学 | 55篇 |
数学 | 431篇 |
物理学 | 381篇 |
出版年
2023年 | 53篇 |
2022年 | 42篇 |
2021年 | 66篇 |
2020年 | 109篇 |
2019年 | 89篇 |
2018年 | 28篇 |
2017年 | 54篇 |
2016年 | 106篇 |
2015年 | 86篇 |
2014年 | 92篇 |
2013年 | 96篇 |
2012年 | 134篇 |
2011年 | 150篇 |
2010年 | 77篇 |
2009年 | 57篇 |
2008年 | 116篇 |
2007年 | 92篇 |
2006年 | 93篇 |
2005年 | 78篇 |
2004年 | 57篇 |
2003年 | 49篇 |
2002年 | 53篇 |
2001年 | 21篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1992年 | 8篇 |
1989年 | 9篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1970年 | 8篇 |
1968年 | 10篇 |
1967年 | 8篇 |
1934年 | 11篇 |
1933年 | 8篇 |
1930年 | 8篇 |
1905年 | 7篇 |
1881年 | 9篇 |
排序方式: 共有2373条查询结果,搜索用时 15 毫秒
31.
This paper discusses stationary rotordynamics of synchronous electric machinery, considering different load cases. The model comprises the electrical operation in a rigid network and in an isolated condition. The mechanical part is modelled as a Laval Rotor (Jeffcott Rotor) with a noncircular shaft, accounting for both static- and dynamic rotor eccentricities. The results show, that the machine's electrical operation may influence the occurence of mechanical vibrations significantly and therefore demonstrate the importance of analysing the electromechanical interaction. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
32.
33.
Prof. Xuefeng Wang Prof. Lester Andrews Dipl.Chem. Felix Brosi Dr. Sebastian Riedel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1397-1409
The reactions of laser‐ablated Au, Ag, and Cu atoms with F2 in excess argon and neon gave new absorptions in the M? F stretching region of their IR spectra, which were assigned to metal‐fluoride species. For gold, a Ng? AuF bond was identified in mixed neon/argon samples. However, this bonding was much weaker with AgF and CuF. Molecules MF2 and MF3 (M=Au, Ag, Cu) were identified from the isotopic distribution of the Cu and Ag atoms, comparison of the frequencies for three metal fluorides, and theoretical frequency calculations. The AuF5 molecule was characterized by its strongest stretching mode and theoretical frequency calculations. Additional evidence was observed for the formation of the Au2F6 molecule. 相似文献
34.
Dipl.‐Chem. Steffen Styra Dr. Sandra González‐Gallardo Dr. Felix Armbruster Dr. Pascual Oña‐Burgos Dipl.‐Chem. Eric Moos Dr. Matthias Vonderach Priv.‐Doz. Dr. Patrick Weis Priv.‐Doz. Dr. Oliver Hampe Dipl.‐Chem. Anneken Grün Dipl.‐Chem. Yvonne Schmitt Prof. Dr. Markus Gerhards Dipl.‐Chem. Fabian Menges Dipl.‐Chem. Maximilian Gaffga Prof. Dr. Gereon Niedner‐Schatteburg Prof. Dr. Frank Breher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8436-8446
A series of bimetallic silyl halido cuprates consisting of the new tripodal silicon‐based metalloligand [κ3N‐Si(3,5‐Me2pz)3Mo(CO)3]? is presented (pz=pyrazolyl). This metalloligand is straightforwardly accessible by reacting the ambidentate ligand tris(3,5‐dimethylpyrazolyl)silanide ({Si(3,5‐Me2pz)3}?) with [Mo(CO)3(η6‐toluene)]. The compound features a fac‐coordinated tripodal chelating ligand and an outward pointing, “free” pyramidal silyl donor, which is easily accessible for a secondary coordination to other metal centers. Several bimetallic silyl halido cuprates of the general formula [CuX{μ‐κ1Si:κ3N‐Si(3,5‐Me2pz)3Mo(CO)3}]? (X=Cl, Br, I) have been synthesized. The electronic and structural properties of these complexes were probed in detail by X‐ray diffraction analysis, electrospray mass spectrometry, infrared‐induced multiphoton dissociation studies, cyclic voltammetry, spectroelectrochemistry, gas‐phase photoelectron spectroscopy, as well as UV/Vis and fluorescence spectroscopy. The heterobimetallic complexes contain linear two‐coordinate copper(I) entities with the shortest silicon–copper distances reported so far. Oxidation of the anionic complexes in methylene chloride and acetonitrile solutions at ${E{{0\hfill \atop 1/2\hfill}}}$ =?0.60 and ?0.44 V (vs. ferrocene/ferrocenium (Fc/Fc+)), respectively, shows substantial reversibility. Based on various results obtained from different characterization methods, as well as density functional theory calculations, these oxidation events were attributed to the Mo0/MoI redox couple. 相似文献
35.
36.
Peter Fechner Oliver Bleher Melanie Ewald Kathrin Freudenberger Dominik Furin Urs Hilbig Felix Kolarov Katrin Krieg Lothar Leidner Goran Markovic Günther Proll Florian Pröll Sabrina Rau Johannes Riedt Barbara Schwarz Patricia Weber Julia Widmaier 《Analytical and bioanalytical chemistry》2014,406(17):4033-4051
This review is focused on methods for detecting small molecules and, in particular, the characterisation of their interaction with natural proteins (e.g. receptors, ion channels). Because there are intrinsic advantages to using label-free methods over labelled methods (e.g. fluorescence, radioactivity), this review only covers label-free techniques. We briefly discuss available techniques and their advantages and disadvantages, especially as related to investigating the interaction between small molecules and proteins. The reviewed techniques include well-known and widely used standard analytical methods (e.g. HPLC-MS, NMR, calorimetry, and X-ray diffraction), newer and more specialised analytical methods (e.g. biosensors), biological systems (e.g. cell lines and animal models), and in-silico approaches. 相似文献
37.
Michael Hengge Paul Hänsch Daniel Ehjeij Frank S. Benneckendorf Jan Freudenberg Uwe H. F. Bunz Klaus Müllen Emil J. W. List-Kratochvil Felix Hermerschmidt 《Journal of polymer science. Part A, Polymer chemistry》2022,60(12):1878-1886
An increasing number of organic light-emitting diodes (OLEDs) is nowadays based on the use of polymers as the emissive material. For this material class in particular, solution-processing of the OLEDs has gained traction in both research and industry. However, in order to access multilayer material systems, orthogonal solvents must be used to prevent dissolution of previously prepared layers. The use of crosslinkers can facilitate this production method by reducing the number of orthogonal solvents needed since insoluble networks are generated. In this work, a novel bisazide crosslinker is employed to insolubilize Super Yellow, a polyphenylene-vinylene emitter. This allows the use of an additional poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine electron blocking layer (EBL) from the same solvent. Devices including the blocking layer show improved efficacies compared to reference devices without the additional EBL, while also maintaining the emission spectrum. Using the upscalable technique of doctor blading, OLEDs were fabricated which showed a particularly noticeable effect of the blocking layer with a nearly twofold increase in luminance and a 56% increase in current efficacy. 相似文献
38.
Felix Duensing Elisabeth Gruber Paul Martini Marcelo Goulart Michael Gatchell Bilal Rasul Olof Echt Fabio Zappa Masoomeh Mahmoodi-Darian Paul Scheier 《Molecules (Basel, Switzerland)》2021,26(12)
Complexes of atomic gold with a variety of ligands have been formed by passing helium nanodroplets (HNDs) through two pickup cells containing gold vapor and the vapor of another dopant, namely a rare gas, a diatomic molecule (H2, N2, O2, I2, P2), or various polyatomic molecules (H2O, CO2, SF6, C6H6, adamantane, imidazole, dicyclopentadiene, and fullerene). The doped HNDs were irradiated by electrons; ensuing cations were identified in a high-resolution mass spectrometer. Anions were detected for benzene, dicyclopentadiene, and fullerene. For most ligands L, the abundance distribution of AuLn+ versus size n displays a remarkable enhancement at n = 2. The propensity towards bis-ligand formation is attributed to the formation of covalent bonds in Au+L2 which adopt a dumbbell structure, L-Au+-L, as previously found for L = Xe and C60. Another interesting observation is the effect of gold on the degree of ionization-induced intramolecular fragmentation. For most systems gold enhances the fragmentation, i.e., intramolecular fragmentation in AuLn+ is larger than in pure Ln+. Hydrogen, on the other hand, behaves differently, as intramolecular fragmentation in Au(H2)n+ is weaker than in pure (H2)n+ by an order of magnitude. 相似文献
39.
Lukas Martin Müller-Wirtz Daniel Kiefer Sven Ruffing Timo Brausch Tobias Hüppe Daniel I. Sessler Thomas Volk Tobias Fink Sascha Kreuer Felix Maurer 《Molecules (Basel, Switzerland)》2021,26(11)
Exhaled aliphatic aldehydes were proposed as non-invasive biomarkers to detect increased lipid peroxidation in various diseases. As a prelude to clinical application of the multicapillary column–ion mobility spectrometry for the evaluation of aldehyde exhalation, we, therefore: (1) identified the most abundant volatile aliphatic aldehydes originating from in vitro oxidation of various polyunsaturated fatty acids; (2) evaluated emittance of aldehydes from plastic parts of the breathing circuit; (3) conducted a pilot study for in vivo quantification of exhaled aldehydes in mechanically ventilated patients. Pentanal, hexanal, heptanal, and nonanal were quantifiable in the headspace of oxidizing polyunsaturated fatty acids, with pentanal and hexanal predominating. Plastic parts of the breathing circuit emitted hexanal, octanal, nonanal, and decanal, whereby nonanal and decanal were ubiquitous and pentanal or heptanal not being detected. Only pentanal was quantifiable in breath of mechanically ventilated surgical patients with a mean exhaled concentration of 13 ± 5 ppb. An explorative analysis suggested that pentanal exhalation is associated with mechanical power—a measure for the invasiveness of mechanical ventilation. In conclusion, exhaled pentanal is a promising non-invasive biomarker for lipid peroxidation inducing pathologies, and should be evaluated in future clinical studies, particularly for detection of lung injury. 相似文献
40.
The long-time behavior of transport coefficients in a model for spatially heterogeneous media in two and three dimensions is investigated by molecular dynamics simulations. The behavior of the velocity autocorrelation function is rationalized in terms of a competition of the critical relaxation due to the underlying percolation transition and the hydrodynamic power-law anomalies. In two dimensions and in the absence of a diffusive mode, another power-law anomaly due to trapping is found with an exponent -3 instead of -2. Further, the logarithmic divergence of the Burnett coefficient is corroborated in the dilute limit; at finite density, however, it is dominated by stronger divergences. 相似文献