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Treatment of a meso‐diarylporphyrin with PhI(OAc)2 in the presence of BF3 ? OEt2 and propionic acid affords the corresponding porphyrinquinone in a high yield (91%). A novel quinone derived from meso‐meso β–β doubly‐fused diporphyrin was obtained as the sole byproduct (16% yield), which exhibits strong panchromatic absorption between 300 and 1000 nm. It has a low HOMO‐LUMO gap owing to expanded and low‐symmetry π‐planes. 相似文献
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Hidekazu Miyaji Haruka Komada Keisuke Goto Junko Fujimoto Naoaki Kiriyama James H.R. Tucker 《Tetrahedron letters》2018,59(43):3853-3857
A redox-active ferrocene-based heteroditopic receptor bearing a boronic acid (as a catechol recognition site) and a benzo-18-crown-6-ether unit (as an ammonium ion recognition site) was synthesized. A 1:1 ditopic complex with dopamine was evidenced by mass spectrometry and NMR spectroscopy. Cyclic voltammetry measurements on the receptor in the presence of a series of organic guest species demonstrated the successful electrochemical sensing of dopamine through a distinct change in the ferrocene-centred redox-couple upon complex formation. 相似文献
146.
Ruthenium(0)‐Catalyzed Cycloaddition of 1,2‐Diols,Ketols, or Diones via Alcohol‐Mediated Hydrogen Transfer 下载免费PDF全文
Hiroki Sato Dr. Ben W. H. Turnbull Dr. Keisuke Fukaya Prof. Michael J. Krische 《Angewandte Chemie (International ed. in English)》2018,57(12):3012-3021
Merging the characteristics of transfer hydrogenation and carbonyl addition, a broad new class of ruthenium(0)‐catalyzed cycloadditions has been developed. As discussed in this Minireview, fused or bridged bicyclic ring systems are accessible in a redox‐independent manner in C?C bond‐forming hydrogen transfer reactions of diols, α‐ketols, or 1,2‐diones with diverse unsaturated reactants. 相似文献
147.
Frontispiece: Entropy‐Driven Diastereoselectivity Improvement in the Paternò–Büchi Reaction of 1‐Naphthyl Aryl Ethenes with a Chiral Cyanobenzoate through Remote Alkylation 下载免费PDF全文
148.
Stable and Highly Efficient Electrochemical Production of Formic Acid from Carbon Dioxide Using Diamond Electrodes 下载免费PDF全文
Dr. Keisuke Natsui Hitomi Iwakawa Dr. Norihito Ikemiya Prof. Dr. Kazuya Nakata Prof. Dr. Yasuaki Einaga 《Angewandte Chemie (International ed. in English)》2018,57(10):2639-2643
High faradaic efficiencies can be achieved in the production of formic acid (HCOOH) by metal electrodes, such as Sn or Pb, in the electrochemical reduction of carbon dioxide (CO2). However, the stability and environmental load in using them are problematic. The electrochemical reduction of CO2 to HCOOH was investigated in a flow cell using boron‐doped diamond (BDD) electrodes. BDD electrodes have superior electrochemical properties to metal electrodes, and, moreover, are highly durable. The faradaic efficiency for the production of HCOOH was as high as 94.7 %. Furthermore, the selectivity for the production of HCOOH was more than 99 %. The rate of the production was increased to 473 μmol m?2 s?1 at a current density of 15 mA cm?2 with a faradaic efficiency of 61 %. The faradaic efficiency and the production rate are almost the same as or larger than those achieved using Sn and Pb electrodes. Furthermore, the stability of the BDD electrodes was confirmed by 24 h operation. 相似文献
149.
A Permselective CeOx Coating To Improve the Stability of Oxygen Evolution Electrocatalysts 下载免费PDF全文
Keisuke Obata Prof. Kazuhiro Takanabe 《Angewandte Chemie (International ed. in English)》2018,57(6):1616-1620
Highly active NiFeOx electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time owing to the loss of Fe species from the active sites into solution during catalysis. The anodic deposition of a CeOx layer prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeOx layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH? and O2 through while preventing the diffusion of redox ions through the layer to function as a selective O2‐evolving electrode. The use of such a permselective protective layer provides a new strategy for improving the durability of electrocatalysts. 相似文献
150.
Polymeric aluminosilicate gels with Al2O3/SiO2 molar ratios of 1.3/2, 2.5/2, 3/2 and 4.7/2 were prepared by gelling a mixture of tetraethoxysilane and ethyl acetoacetate aluminium diisopropoxide. Mullite, without any other crystalline phase, directly crystallizes from the gel matrix at about 1000 °C for all investigated samples. The Al2O3 or SiO2 crystalline phase can only be detected at relatively high temperatures accompanying the modification of mullite in the lattice structure. 27Al and 29Si MAS-NMR studies indicate that segregation of Al and Si atoms occurs in all samples below 900 °C in the amorphous state, regardless of the gel composition. However, the species of segregated units are very different and strongly dependent on the composition of the starting gels. This segregation may not cause the exothermic effect in differential thermal analysis examination, but it appears to be responsible for the composition change behavior of crystalline mullite with different heat treatment. 相似文献