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891.
Horvath AK 《The journal of physical chemistry. A》2007,111(5):890-896
The kinetics of the periodate-iodide reaction has a contradictory history dating back to almost a century. This reaction has been reinvestigated spectrophotometrically in the pH range 3.13-5.55 in both buffered (acetic acid/acetate) and unbuffered solution at T=25.0+/-0.1 degrees C with an I=0.5 M ionic strength. The spectra between 290 and 500 nm were recorded and the reaction was followed until at least 95% of one of the reactants was consumed. The stoichiometry has been found to be strongly dependent on pH, but the rate of the initial step is independent of pH within the pH range studied. An eight-step kinetic model is proposed with four fitted kinetic parameters to take all the important characteristics of the experimental curves into account. On the basis of the model, a perfect reconciliation of the previous contradictory results is presented. It is shown that the kinetic parameters obtained from the initial rate of formation of a product unavoidably leads to misinterpretation of the results in the case of a branching mechanism (and stoichiometry). 相似文献
892.
Fabrication of Nitrogen‐Doped Mesoporous‐Carbon‐Coated Palladium Nanoparticles: An Intriguing Electrocatalyst for Methanol and Formic Acid Oxidation 下载免费PDF全文
Chaiti Ray Soumen Dutta Ramkrishna Sahoo Anindita Roy Prof. Dr. Yuichi Negishi Prof. Dr. Tarasankar Pal 《化学:亚洲杂志》2016,11(10):1588-1596
Inspired by the attractive catalytic properties of palladium and the inert nature of carbon supports in catalysis, a concise and simple methodology for in situ nitrogen‐doped mesoporous‐carbon‐supported palladium nanoparticles (Pd/N‐C) has been developed by carbonizing a palladium dimethylglyoximate complex. The as‐synthesized Pd/N‐C has been exfoliated as a fuel cell catalyst by studying the electro‐oxidation of methanol and formic acid. The material synthesized at 400 °C,namely, Pd/N‐C‐400,exhibitssuperior mass activity and stability among catalysts synthesized under different carbonization temperaturesbetween300 and 500 °C. The unique 1D porous structure in Pd/N‐C‐400 helps better electron transport at the electrode surface, which eventually leads to about five times better catalytic activity and about two times higher stability than that of commercial Pd/C. Thus, our designed sacrificial metal–organic templatedirected pathway becomes a promising technique for Pd/N‐C synthesis with superior catalytic performances. 相似文献
893.
Dr. Matthieu Starck Dr. Robert Pal Prof. David Parker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):570-580
Four anionic europium complexes are described based on triazacyclononane tris‐carboxylate or phosphinate ligands. In each case, the three sensitising chromophores comprise a substituted aryl–alkynyl pyridine group, with complex brightness in water falling in the range 4 to 23 mM ?1 cm?1. para‐Substitution of the aryl ring with carboxymethyl groups gives complexes that are taken into cells, stain the lysosomes selectively and unexpectedly permit lifetime measurements of lysosomal pH. In contrast, the introduction of sulfonate groups inhibits cell uptake enabling the Eu complex to be used as an extracellular donor for FRET applications at the membrane surface. Using time‐gated FRET microscopy, the cell membrane structure was highlighted, in which Cell Mask Deep Red was used as a membrane‐ localized FRET acceptor. 相似文献
894.
Dr. Georgian Melinte Dr. Veselina Georgieva Dr. Marie‐Anne Springuel‐Huet Dr. Andreï Nossov Prof. Ovidiu Ersen Dr. Flavien Guenneau Prof. Antoine Gedeon Dr. Ana Palčić Dr. Krassimir N. Bozhilov Dr. Cuong Pham‐Huu Prof. Shilun Qiu Dr. Svetlana Mintova Dr. Valentin Valtchev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):1881-1881
895.
By using frontier‐molecular‐orbital and electrostatic (nucleophilic) interactions as well as relaxed potential‐energy surface scans, it is shown that the initial step in the oxygen‐atom transfer (OAT) reaction of [MoVIO2‐(S2C2Me2)SMe]?1 ( 1 ) and [MoVIO2‐{(S2C2(CN)2}2]2? ( 2 ) with HSO3? takes place by oxoanionic binding of the substrate to the MoVI center with the formation of a stable Michaelis complex. The gas‐phase and solvent‐corrected enthalpy profile with fully optimized minima and transition states for the OAT reaction of 1 and 2 with HSO3? showed the release of reaction energy for both complexes. The optimized geometries of 1 and 2 in the respective enzyme–substrate complexes showed a common feature with the participation of hydrogen bonding of the substrate with the axial (spectator) oxo group in the subsequent formation of the six‐membered MoO2HOS transition state. The enzyme–substrate complex of 2 shows heptacoordination as proposed earlier, although the trans (to axial oxo)‐Mo? S(dithiolene) bond is elongated to 2.948 Å. 相似文献
896.
Dr. Kuntal Pal Oliver B. Hemming Dr. Benjamin M. Day Dr. Thomas Pugh Prof. Dr. David J. Evans Prof. Dr. Richard A. Layfield 《Angewandte Chemie (International ed. in English)》2016,55(5):1690-1693
In the presence of stoichiometric or catalytic amounts of [M{N(SiMe3)2}2] (M=Fe, Co), N‐heterocyclic carbenes (NHCs) react with primary phosphines to give a series of carbene phosphinidenes of the type (NHC)?PAr. The formation of (IMe4)?PMes (Mes=mesityl) is also catalyzed by the phosphinidene‐bridged complex [(IMe4)2Fe(μ‐PMes)]2, which provides evidence for metal‐catalyzed phosphinidene transfer. 相似文献
897.
I. V. Tkachenko I. N. Tarabara I. V. Omel’chenko V. A. Pal’chikov 《Russian Journal of Organic Chemistry》2016,52(5):661-669
Study of isomerization of 5-endo-hydroxy-4-azatricyclo[5.2.1.02,6]dec-8-en-3-ones under the action of Lewis acids (MgBr2, AlCl3), CF3COOH, and NaH showed that the optimum catalyst of the process was trifluoroacetic acid. In reaction of 4-benzyl-5-endo-hydroxy-4-azatricyclo-[5.2.1.02,6]dec-8-en-3-one with anhydrous AlCl3 in benzene was unexpectedly isolated N-benzyl-3-(diphenylmethyl)bicyclo[2.2.1]hept-5-ene-2-carboxamide. A convenient method was developed for the preparation of 5-exo-alkoxy-4-alkyl(aryl)-4-azatricyclo[5.2.1.02,6]dec- 8-en-3-ones. 相似文献
898.
Š. Palágyi 《Journal of Radioanalytical and Nuclear Chemistry》1988,121(2):323-330
A study is presented on the use of isotopic and non-isotopic ion exchange in a heterogeneous liquid-liquid system for the separation of131I from water. The method is based on the reaction between radioiodide in the aqueous phase and trioctylmethylammonium iodide or chloride in the organic phase. The effect of some important experimental parameters on the separation efficiency is discussed. It has been found that under optimum conditions the method of isotopic ion exchange can be used for the radiochemical determination of iodine in water. 相似文献
899.
900.
Sea level muon spectra at large zenith angles derived from the latest JACEE primary nucleon spectrum
Summary Sea level muon energy spectra at large zenith angles have been derived from the latest JACEE primary spectrum using the Fermilab
Single-Arm Spectrometer data on charged-meson production. The role of increasing total cross-section on the final result for
the energy spectra has been investigated here with special emphasis. The inclusion of the rising total cross-section at cosmic
range of energies, it is seen, has come into much use in explaining the observed data at very high energies.
The autors of this paper have agreed not to receive the proofs for correction. 相似文献