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131.
Aderemi R. Oki Jesus Sanchez Robert J. Morgan Lena Ngai 《Transition Metal Chemistry》1996,21(1):43-48
Summary CuII and NiII coordination compounds with N,N,N,N-tetrakis[(2-benzimidazolyl)methyl]-1,2-cyclohexanediamine (CDTB) have been prepared and characterized. The crystal structure of [Cu(CDTB)](ClO4)2 has been determined. The geometry around the Cu atom is highly irregular and can best be described as a cis-distorted octahedron, with four short CuN bond distances of 1.988(3) Å and 2.028(3) Å, and two very long CuN bond lengths of 2.543(4) A. The cis NCuN chelate angles in the complex range from 68.8(2) for N(1)CuN(1) to 141.03° for N(4)CuN(1). The cyclic voltammogram of the complex shows a fully reversible one-electron redox wave at E
1/2 = 0.162V versus standard calomel electrode, corresponding to the CuI/II redox couple. The structure of [Ni(CDTB)](NO3)2 ·EtOH has also been determined. The geometry around the Ni atom in this compound can be described as distorted octahedral, with N(4), N(4), N(1), N(1) as the ligating atoms in the basal plane, with cis chelate angles ranging from 79.37(10) to 120.9(2)° with the trans N(2)NiN(2) angle at 175.1(2)°. The structural differences in these two compounds are undoubtedly electronic rather than steric. 相似文献
132.
Inga Respondek Lena Bressel Peter Saalfrank Holger Kmpf Andreas Grohmann 《Chemical physics》2008,347(1-3):514-522
Two novel spin crossover (SCO) compounds, namely [Fe(INMe)(pyN4)]Br2, and [Fe(IMMe)(pyN4)](OTf)2, where pyN4 = 2,6-Bis(1′,3′-diamino-2′methyl-prop-2′yl)pyridine, INMe = isonicotinic acid methyl ester, IMMe = N-methyl-imidazole, and OTf = triflate, are characterized here both from experimental and theoretical viewpoints. In particular, we apply various density functionals and basis sets to obtain optimized geometries for low- (LS) and high-spin (HS) states, vibrational spectra, LS–HS splittings, and temperature-dependent UV/vis spectra. While geometries and spectra are in good agreement with experimental data, the well-known spin pairing problem makes it difficult to compute accurate LS–HS splitting energies and enthalpies. Based on TD–DFT calculations, the capacity of the compounds for use as reversibly photo-switchable molecules is discussed. 相似文献
133.
The retention behavior of a monoclonal antibody has been characterized on a weak cation exchanger, Fractogel EMD COO(-)(s). This new generation of resin materials comprise of a higher mechanical strength compared to softer gel-type matrices while maintaining elevated capacities, resulting in higher productivity and longer lifetimes. These parameters are extremely important when working with large bio-molecules such as proteins, and in particular monoclonal antibodies. In the first part of this work a parameter estimation strategy is presented to fully characterize the retention behavior of a single monoclonal antibody and determine suitable model parameters. Literature correlations were used for the estimation of mass transfer rates. The transport limiting parameter, pore diffusion, was regressed experimentally. Various methods for the adsorption isotherm determination have been applied, their combinations resulting in little experimental effort and accurate predictions of elution profiles. The process has been modelled with a complete pore diffusion model and the agreement between experimental and predicted profiles is good in general. However, a very marked sensitivity to changes in the effective pore diffusion coefficient has been observed. A correlation describing the effect of the separation conditions on the diffusion rate is therefore needed in order to have a fully predictive mathematical model. 相似文献
134.
Photoinduced Palladium‐Catalyzed Negishi Cross‐Couplings Enabled by the Visible‐Light Absorption of Palladium–Zinc Complexes
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Irini Abdiaj Dr. Lena Huck José Miguel Mateo Prof. Dr. Antonio de la Hoz Dr. M. Victoria Gomez Prof. Dr. Angel Díaz‐Ortiz Dr. Jesús Alcázar 《Angewandte Chemie (International ed. in English)》2018,57(40):13231-13236
A visible‐light‐induced Negishi cross‐coupling is enabled by the activation of a Pd0–Zn complex. With this photocatalytic method, the scope of deactivated aryl halides that can be employed in the Negishi coupling was significantly expanded. NMR experiments conducted in the presence and absence of light confirmed that the formation of the palladium–zinc complex is key for accelerating the oxidative addition step. 相似文献
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136.
Degradation mechanisms of polyfluorene‐based organic semiconductor lasers under ambient and oxygen‐free conditions
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Philipp Brenner Lena‐Maria Fleig Xin Liu Alexander Welle Stefan Bräse Uli Lemmer 《Journal of Polymer Science.Polymer Physics》2015,53(15):1029-1034
In this communication we investigate the degradation mechanisms of different highly fluorescent polyfluorenes for applications as active organic semiconductor material in laser devices. Using various analytical methods, like Ultraviolet‐Visible (UV‐Vis) absorption spectroscopy, Fourier‐transform infrared spectroscopy (FT‐IR) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), we investigate photo‐induced degradation mechanisms. It is shown that the photo‐oxidation rate decreases with an increasing number of benzothiadiazole units within the conjugated polymer. Photooxidation is much more distinct for poly[9,9‐dioctylfluorenyl‐2,7‐diyl] (PFO) than for poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐alt‐co‐(1,4‐benzo‐{2,1′,3}‐thiadiazole)] (F8BT). The influence of the photooxidation on the lifetime of the organic laser devices is not as profound as previously assumed, since the laser shuts down before any evidence of photo‐oxidation in F8BT manifests. We observe that the solubility of the material is different at various degradation levels and we consider chain scission of excited bonds and cross‐linking as dominant degradation factors. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1029–1034 相似文献
137.
Investigation of a Lithium–Halogen Exchange Flow Process for the Preparation of Boronates by Using a Cryo‐Flow Reactor
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Dr. James A. Newby Lena Huck Dr. D. Wayne Blaylock Dr. Paul M. Witt Prof. Steven V. Ley Dr. Duncan L. Browne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):263-271
Conducting low‐temperature organometallic reactions under continuous flow conditions offers the potential to more accurately control exotherms and thus provide more reproducible and scalable processes. Herein, progress towards this goal with regards to the lithium–halogen exchange/borylation reaction is reported. In addition to improving the scope of substrates available on a research scale, methods to improve reaction profiles and expedite purification of the products are also described. On moving to a continuous system, thermocouple measurements have been used to track exotherms and provide a level of safety for continuous processing of organometallic reagents. The use of an in‐line continuous liquid–liquid separation device to circumvent labour intensive downstream off‐line processing is also reported. 相似文献
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140.
Dr. Marian Olaru Artem Schröder Dr. Lena Albers Daniel Duvinage Dr. Stefan Mebs Prof. Dr. Jens Beckmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9861-9865
Efforts to prepare an elusive donor-free phosphenium ion, [R2P]+, led us to synthesize functionalized fluorophosphonium cations of the type [R2P(F)X]+ (X=SiEt3, H, F), which were obtained from the related neutral fluorophosphines R2PF and R2PF3 upon protonation and reaction with solvated [Et3Si]+ ions (R=2,6-Mes2C6H3). The hypothetical reductive elimination of [R2P(F)SiEt3]+ and [R2P(F)H]+ affording [R2P]+, Et3SiF and HF, respectively, was calculated to be endothermic by 40.1 and 190.6 kJ mol−1. 相似文献