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141.
The time scale of proton transfer between H(2)O and OH adsorbed on a Pt(111) surface was determined by a combination of laser-induced thermal desorption (LITD) and microscale x-ray photoelectron spectroscopy (micro-XPS). The patterned distribution OH+H(2)O/H(2)O/OH + H(2)O was initially prepared on the Pt(111) surface by the LITD method and the time evolution of the spatial distribution of H(2)O and OH was observed by the micro-XPS technique. From quantitative analyses based on a diffusion equation, we found two proton-transfer pathways with different time scales of 5.2+/-0.9 ns and 48+/-12 ns at 140 K, which were attributed to direct proton transfer to the neighbor site and H(3)O(+)-mediated transfer to the next-nearest site, respectively. 相似文献
142.
Narumasa Saito Jun Takaya Nobuharu Iwasawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):10103-10107
Iridium complexes having a pincer‐type gallylene ligand were successfully synthesized utilizing bis(phosphino)terpyridine as an efficient scaffold for the Ir?GaI bond. The stabilization of the gallylene moiety by the pincer‐type structure enabled various reactions at Ir with keeping the gallylene ligand intact, leading to unique structures and reactivities of PGaIP?Ir complexes. 相似文献
143.
Iwasawa H Yamakawa K Saitoh T Inaba J Katsufuji T Higashiguchi M Shimada K Namatame H Taniguchi M 《Physical review letters》2006,96(6):067203
We present the electronic structure of Sr(1-(x+y))La(x+y)Ti(1-x)Cr(x)O3 investigated by high-resolution photoemission spectroscopy. In the vicinity of the Fermi level, it was found that the electronic structure was composed of a Cr 3d local state with the t(2g)3 configuration and a Ti 3d itinerant state. The energy levels of these Cr and Ti 3d states are well interpreted by the difference of the charge-transfer energy of both ions. The spectral weight of the Cr 3d state is completely proportional to the spin concentration x irrespective of the carrier concentration y, indicating that the spin density can be controlled by x as desired. In contrast, the spectral weight of the Ti 3d state is not proportional to y, depending on the amount of Cr doping. 相似文献
144.
Shankha S. Acharyya Shilpi Ghosh Yusuke Yoshida Takuma Kaneko Takehiko Sasaki Yasuhiro Iwasawa 《Chemical record (New York, N.Y.)》2019,19(9):2069-2081
Catalytic benzene C?H activation toward selective phenol synthesis with O2 remains a stimulating challenge to be tackled. Phenol is currently produced industrially by the three‐steps cumene process in liquid phase, which is energy‐intensive and not environmentally friendly. Hence, there is a strong demand for an alternative gas‐phase single‐path reaction process. This account documents the pivotal confined single metal ion site platform with a sufficiently large coordination sphere in β zeolite pores, which promotes the unprecedented catalysis for the selective benzene hydroxylation with O2 under coexisting NH3 by the new inter‐ligand concerted mechanism. Among alkali and alkaline‐earth metal ions and transition and precious metal ions, single Cs+ and Rb+ sites with ion diameters >0.300 nm in the β pores exhibited good performances for the direct phenol synthesis in a gas‐phase single‐path reaction process. The single Cs+ and Rb+ sites that possess neither significant Lewis acidic?basic property nor redox property, cannot activate benzene, O2, and NH3, respectively, whereas when they coadsorbed together, the reaction of the inter‐coadsorbates on the single alkali‐metal ion site proceeds concertedly (the inter‐ligand concerted mechanism), bringing about the benzene C?H activation toward phenol synthesis. The NH3‐driven benzene C?H activation with O2 was compared to the switchover of the reaction pathways from the deep oxidation to selective oxidation of benzene by coexisting NH3 on Pt6 metallic cluster/β and Ni4O4 oxide cluster/β. The NH3‐driven selective oxidation mechanism observed with the Cs+/β and Rb+/β differs from the traditional redox catalysis (Mars‐van Krevelen) mechanism, simple Langmuir‐Hinshelwood mechanism, and acid?base catalysis mechanism involving clearly defined interaction modes. The present catalysis concept opens a new way for catalytic selective oxidation processes involving direct phenol synthesis. 相似文献
145.
Tomoya Uruga Mizuki Tada Oki Sekizawa Yasumasa Takagi Toshihiko Yokoyama Yasuhiro Iwasawa 《Chemical record (New York, N.Y.)》2019,19(7):1444-1456
We designed and constructed a beamline BL36XU at the 8 GeV synchrotron radiation facility SPring‐8 to provide information required for the development of next‐generation polymer electrolyte fuel cells (PEFCs) by clarifying the dynamic aspects of structures and electronic states of cathode catalysts under PEFC operating conditions and in the deterioration processes by accelerated durability test protcols. To investigate the mechanism and degradation process for the cathode electrocatalysis in practical PEFCs, we developed advanced time‐ and spatially‐resolved in‐situ/operando X‐ray absorption fine structure measurement systems and complementary analytical systems (X‐ray emission spectroscopy (XES), X‐ray diffraction (XRD), X‐ray computer tomography (CT) and hard X‐ray photoelectron spectroscopy (HAXPES)) and combined them to develop multi‐analytical systems at BL36XU. Multi‐analytical systems are very powerful for observing spatial‐temporal features of the transient processes occurring in complex systems such as PEFCs. This account describes the design, performance, and research results of the BL36XU and multi‐analytical in‐situ/operando systems. 相似文献
146.
A lithium enolate of menthyl acetate added to PMP-imines, in the presence of an equimolar amount of lithium diisopropylamide, affords the Mannich-type addition products in high stereoselectivity. [reaction--see text] 相似文献
147.
148.
Isobe H Sugiyama S Fukui Ki Iwasawa Y Nakamura E 《Angewandte Chemie (International ed. in English)》2001,40(18):3364-3367
149.
150.
The growth of Pt nanoparticles from the metal-organic precursor [MeCpPtMe3: (methylcyclopentadienyl) trimethyl platinum] on TiO2(110) was studied by scanning tunneling microscopy. 2D-like Pt particles on the surface were formed in a self-limiting growth mode. The inner structure of the particles was resolved as unique tetramerlike bright spots. A mechanism for the self-limiting growth of Pt particles is proposed. 相似文献