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991.
Otto Vogl 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1085-1113
Abstract A historical development of the polymerization of higher aldehydes is presented. It shows the development of the polymerization of the simplest example, formaldehyde, the very ancient and to some extent incorrect history of other aldehyde polymerizations, and actually starts with the full understanding of this field as of the early 1950s. Much of the early work is incoherent and inconsistent, not surprisingly because of the limited knowledge of polymer chemistry that was available at that time. This contribution tries to correlate the polymerization of formaldehyde, the higher aliphatic aldehydes, and the trihaloacetaldehydes within the framework of a comprehensive understanding of the field of polymer science. The extensive progress in the field of trihaloacetaldehyde polymerization has led to the development of cryotachensic polymerization, the concept of optical activity based on macromolecular asymmetry, ultimately the recognition of the importance of the study of oligomers of stereoregular polymers, and the very essence of the embryonic state of addition polymerization. 相似文献
992.
The electronic absorption spectra of charge-transfer complexes (CTC) of benzotriazole derivatives including 2(2H-hydroxyphenyl)2H-benzotriazole-containing copolymers with various electron acceptors were investigated. While no charge-transfer interaction was observed with weak acceptors, strong acceptors such as trinitrofluorenone and pyromellitic anhydride exhibited an absorption of the contact charge-transfer type with these donors. When the very strong acceptor tetracyanoethylene was used as acceptor, new peaks of a CTC type appeared at longer wavelengths. From the wavelengths of the absorption maxima and the equilibrium constants of the CTC, the electron-donating ability of several related (2(2-hydroxyphenyl)2H-benzotriazole derivatives was estimated as follows: 2(2-Hydroxy-5-methylphenyl)2H-benzotriazole > 2H-benzotriazole > 2(4-hydroxyphenyl)2H-benzotriazole > 2(2-acetoxy-5-methylphenyl)2H-benzotriazole > copolymers containing 2(2-hydroxyphenyl)2H-benzotriazole groups. 相似文献
993.
2,2,3,3-Tetramethyl-1,4-dibromobutane, when used as monomer for polymerization by Wurtz-type polycondensation, gave head-to-head polyisobutylene which is branched. Under similar conditions, 2, 5-dimethyl-2, 5-dibromohexane gave no polymer. Copolymerization of ethylene with tetramethylethylene under various conditions gave polyethylene of modest molecular weight with about 5% tetramethylene units in the polymer. 1,1,4, 4-Tetramethyl-1,3-butadiene (2,5-dimethylhexadiene-2,4) polymerized with BF3 initiator to high molecular weight trans- 1,4-poly-(1,1,4,4-tetrarnethylbutadiene-1,3). The polymer could not be hydrogenated with soluble hydrogenation catalysts and only partially by chemical reduction with diimide. Under forcing conditions, incorporation of portions of the decomposition products of the precursor of the diimide was observed. 相似文献
994.
The terpolymerization of acryionitrile, styrene, and pentabromophenyl acrylate in dimethylformamide solution was investigated. Experimental terpolymerization data agreed well with calculations using the Alfrey-Goldfinger equation. The relationship between monomer feed and terpolymer compositions are presented on triangular coordinate graphs, and the lines of unique and the lines of binary azeotropic composition were identified. No point of true ternary azeotropic composition was found but a “pseudoazeotropic” region was identified. The experimental results of the terpolymerization agreed well with the theoretical curves over a wide range of monomer composition up to high conversions. The influence of pentabromophenyl acrylate units on the thermal and flammability characteristics of the terpolymers are described. 相似文献
995.
Copolymerization of 2,3-dimethylmaleic anhydride and ethylene has been accomplished under ethylene pressure (up to 1000 psi) with AIBN as the initiator. The copolymers were obtained at relatively low yield and only of moderate molecular weight. The incorporation of 2,3-dimethylmaleic anhydride units into the copolymer is about 20 mol% at 1000 psi and is 33 mol% at 500 psi of ethylene pressure. Unlike maleic anhydride-ethylene copolymers, alternating 2,3-dimethylmaleic qnhydride-ethylene copolymers of reasonable molecular weight have not yet been prepared. 2,3-Dimethylmaleic anhydride-ethylene copolymers could be hydrolyzed to the polymeric acids and quantitatively esterified to the polymeric methyl esters. Both anhydride and ester copolymers have been characterized spectroscopically and by their thermal behavior. 相似文献
996.
Lining Sun Tao Liu Yannan Qiu Jinliang Liu Liyi Shi Otto S. Wolfbeis 《Mikrochimica acta》2014,181(7-8):775-781
We have developed a one-step method for the synthesis of mesoporous upconverting nanoparticles (MUCNs) of the type NaYF4:Yb,Er@mSiO2 in ammoniacal ethanol/water solution. The mesoporous silica is directly encapsulating the hydrophobic upconversion nanoparticles (UCNs) due to the presence of the template CTAB. Intense green emission (between 520 and 560 nm) and weaker red emission (between 630 and 670 nm) is observed upon 980-nm laser excitation. The MUCNs display low cytotoxicity (as revealed by an MTT test) and were successfully applied to label and image human nasopharyngeal epidermal carcinoma (KB) cells. Figure
A facile one-step method was proposed for direct formation of core-shell mesoporous silica coated upconverting nanoparticles (MUCNs), NaYF4:Yb,Er@mSiO2, in an ammonia and ethanol aqueous solution and the obtained MUCNs were successfully applied to bioimaging of living cells. 相似文献
997.
Sayed M. Saleh Reham Ali Thomas Hirsch Otto S. Wolfbeis 《Journal of nanoparticle research》2011,13(10):4603-4611
We demonstrate an affinity system based on the interaction of two types of nanoparticles. The first consists of upconverting
luminescent NaYF4:Yb,Er nanoparticles (UCNPs) with a size of 40–100 nm, absorbing light in the infrared and showing luminescence at 521, 543
and at 657 nm. The second consists of (red) gold nanoparticles (Au-NPs) with a size of about 50 nm and capable of absorbing
the green luminescence of the UCNPs. By labeling the UCNPs with avidin and the AuNPs with biotin we have established a model
system for a self referenced affinity system applicable to sensing in biological samples. In the presence of avidin-modified
UCNPs, the biotinylated Au-NPs can be detected in the range from 12 to 250 μg mL−1 by ratioing the intensity of the red (analyte-independent) emission to that of the green (analyte-dependent) emission band.
The nanoparticles were characterized in terms of size and composition using transmission electron microscopy, thermogravimetry,
and FTIR spectroscopy. 相似文献
998.
999.
Martin Andreas Robert George Marko Frstel Otto Dopfer 《Angewandte Chemie (International ed. in English)》2020,59(29):12098-12104
Diamondoid cations are reactive intermediates in their functionalization reactions in polar solution. Hydration is predicted to strongly activate their C?H bonds in initial proton abstraction reactions. To study the effects of microhydration on the properties of diamondoid cations, we characterize herein the prototypical monohydrated adamantane cation (C10H16+–H2O, Ad+–W) in its ground electronic state by infrared photodissociation spectroscopy in the CH and OH stretch ranges and dispersion‐corrected density functional theory (DFT) calculations. The water (W) ligand binds to the acidic CH group of Jahn–Teller distorted Ad+ via a strong CH???O ionic H‐bond supported by charge–dipole forces. Although W further enhances the acidity of this CH group along with a proton shift toward the solvent, the proton remains with Ad+ in the monohydrate. We infer essentially free internal W rotation from rotational fine structure of the ν3 band of W, resulting from weak angular anisotropy of the Ad+–W potential. 相似文献
1000.
Thermal decomposition study of HAuCl4·3H2O and AgNO3 as precursors for plasmonic metal nanoparticles
K. Otto I. Oja Acik M. Krunks K. Tõnsuaadu A. Mere 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1065-1072
Thermal decomposition of HAuCl4·3H2O and AgNO3, as precursors for Au and Ag nanoparticles, respectively, was monitored by coupled TG–DTA with TG/EGA–FTIR and EGA–MS techniques in a flowing 80 %Ar + 20 %O2 and Ar atmospheres in the temperature range of 30–600 °C. The intermediate and final products of thermal decomposition were analysed by ex situ XRD and FTIR techniques. The thermal degradation of HAuCl4·3H2O starts immediately after melting at 75 °C and takes place in three steps in the temperature range of 75–320 °C with total mass loss of 49.4 and 49.7 % in artificial air and Ar atmospheres, respectively. EGA by MS and FTIR revealed a simultaneous release of H2O and HCl in the temperature range of 75–235 °C. EGA by MS revealed a release of Cl2 at around 225 °C and in the interval of 250–320 °C. According to the XRD analysis, the main solid product in the end of the first decomposition step at 190 °C is AuCl3; in the end of the second decomposition step at 240 °C is AuCl and the final product at 320 °C is Au. The thermal decomposition of AgNO3 takes place in a single step in the temperature range of 360–515 °C with a total mass loss of 39.0 and 37.8 % in flowing artificial air and Ar atmospheres, respectively. According to EGA–MS and EGA–FTIR the main evolved gases are NO2, NO and O2. The final product of the thermal decomposition at 600 °C is Ag irrespective of the atmosphere. 相似文献