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361.
Frontispiece: Formation and High Reactivity of the anti‐Dioxo Form of High‐Spin μ‐Oxodioxodiiron(IV) as the Active Species That Cleaves Strong C−H Bonds 下载免费PDF全文
362.
Formation and High Reactivity of the anti‐Dioxo Form of High‐Spin μ‐Oxodioxodiiron(IV) as the Active Species That Cleaves Strong C−H Bonds 下载免费PDF全文
Prof. Dr. Masahito Kodera Shin Ishiga Tomokazu Tsuji Katsutoshi Sakurai Prof. Dr. Yutaka Hitomi Dr. Yoshihito Shiota Dr. P. K. Sajith Prof. Dr. Kazunari Yoshizawa Dr. Kaoru Mieda Prof. Dr. Takashi Ogura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5924-5936
Recently, it was shown that μ‐oxo‐μ‐peroxodiiron(III) is converted to high‐spin μ‐oxodioxodiiron(IV) through O?O bond scission. Herein, the formation and high reactivity of the anti‐dioxo form of high‐spin μ‐oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic‐absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ‐oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluene<ethylbenzene≈cumene<trans‐β‐methylstyrene. The rate constants increased proportionally to the substrate concentration at low substrate concentration. At high substrate concentration, however, the rate constants converge to the same value regardless of the kind of substrate. This is explained by a two‐step mechanism in which anti‐μ‐oxodioxodiiron(IV) is formed by syn‐to‐anti transformation of the syn‐dioxo form and reacts with substrates as the oxidant. The anti‐dioxo form is 620 times more reactive in the C?H bond cleavage of ethylbenzene than the most reactive diiron system reported so far. The KIE for the reaction with toluene/[D8]toluene is 95 at ?30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H2O2. 相似文献
363.
Yasufumi Takahashi Yu Kobayashi Ziqian Wang Yoshikazu Ito Masato Ota Hiroki Ida Akichika Kumatani Keisuke Miyazawa Takeshi Fujita Hitoshi Shiku Yuri E. Korchev Yasumitsu Miyata Takeshi Fukuma Mingwei Chen Tomokazu Matsue 《Angewandte Chemie (International ed. in English)》2020,59(9):3601-3608
High‐resolution scanning electrochemical cell microscopy (SECCM) is used to image and quantitatively analyze the hydrogen evolution reaction (HER) catalytically active sites of 1H‐MoS2 nanosheets, MoS2, and WS2 heteronanosheets. Using a 20 nm radius nanopipette and hopping mode scanning, the resolution of SECCM was beyond the optical microscopy limit and visualized a small triangular MoS2 nanosheet with a side length of ca. 130 nm. The electrochemical cell provides local cyclic voltammograms with a nanoscale spatial resolution for visualizing HER active sites as electrochemical images. The HER activity difference of edge, terrace, and heterojunction of MoS2 and WS2 were revealed. The SECCM imaging directly visualized the relationship of HER activity and number of MoS2 nanosheet layers and unveiled the heterogeneous aging state of MoS2 nanosheets. SECCM can be used for improving local HER activities by producing sulfur vacancies using electrochemical reaction at the selected region. 相似文献
364.
Nobutaka Yoshimura Kazuhiro SaitoToru Saguchi Tomokazu FunatsuYoichi Araki Soichi AkataKoichi Tokuuye 《Magnetic resonance imaging》2013
Objective
The objective was to evaluate the usefulness of T1 mapping in distinguishing hepatic hemangiomas from metastatic tumors on gadoxetic-acid-enhanced magnetic resonance imaging.Methods
We examined 20 hemangiomas in 14 patients and 21 metastatic tumors in 11 patients. We performed T1 mapping using the double-flip angle method before and after the injection of gadoxetic acid. Quantitative evaluation was carried out using the pre- and post-contrast enhancement ratios (CERs), and qualitative evaluation was conducted to evaluate the added value of T1 mapping using receiver operating characteristics analysis.Results
The mean CERs of metastatic tumors at 70 s, 240 s and 20 min after the injection of gadoxetic acid were 1.54 (95% confidence interval: 1.37–1.71), 1.47 (1.34–1.6) and 1.30 (1.19–1.41); those of hemangiomas were 3.36 (2.41–4.31), 3.06 (2.44–3.68) and 2.20 (2.02–2.38), respectively. The mean CERs of hemangiomas were significantly higher than those of metastatic tumors (P< .05). When the mean CER cutoff value 20 min after the injection was set at 1.6, the diagnostic sensitivity of hepatic hemangiomas was 100%. There was no added value observed statistically in the qualitative evaluation of T1 mapping (P> .05).Conclusion
It is valuable to evaluate quantitatively T1 mapping 20 min after hepatobiliary phase acquisition in the case of difficulty in distinguishing hepatic hemangiomas from metastatic tumors qualitatively. 相似文献365.
Ban Xuan Dong Yoshihiro Honmou Hideaki Komiyama Shu Furumaki Tomokazu Iyoda Martin Vacha 《Macromolecular rapid communications》2013,34(6):492-497
Hybrid materials composed of phase‐separated block copolymer films and conjugated polymers of the phenylenevinylene family (PPV) are prepared. The PPV chains are embedded in vertical cylinders of nanometer diameter in the block‐copolymer films. The cylinders span continuously the whole film thickness of 70 nm. Incorporation of the PPV chains into the one‐dimensional cylinders leads to modified photoluminescence spectra and to large absorption anisotropy. The hybrid films show electroluminescence from the PPV chains in a simple light‐emitting device at minute doping concentrations, and also exhibit a factor of 19 increase in electron transport efficiency along the single PPV chains. 相似文献
366.
Masashi Harada Takahisa Suzuki Masayuki Ohya Daisuke Kawaguchi Atsushi Takano Yushu Matsushita Naoya Torikai 《Journal of Polymer Science.Polymer Physics》2005,43(12):1486-1494
Compositional profiles of bilayer films in the direction normal to the interfaces have been investigated by neutron reflectivity measurements and analyzed with mean field theory. The bilayer films were prepared with poly(4‐trimethylsilylstyrene) (PTMSS) and polyisoprene (PI), which constitute a miscible polymer pair and whose blends show phase separation at the lower critical solution temperature (LCST) by heating. Because we can accurately control the degree of polymerization of component polymers and can adjust the Flory–Huggins interaction parameter, χ, with the temperature, T, according to the relationship χ = 0.027–9.5/T, the phase behavior and the interfacial structure of PTMSS and PI are predictable by mean field theory. When the bilayer films of PTMSS and PI were set at 90 °C, which is a temperature below the LCST, diffusion at the interface was observed, and the original interface disappeared in several hours; this supports the idea that the polymer pair is miscible. No clear interfaces were identified below the LCST, whereas broad interfaces, compared with that of the strong segregation pairs, were observed above the LCST. The compositions of each layer are consistent with that of the coexisting phase in the polymer blends, and the interfacial widths agree well with the theoretical prediction considering the effect of capillary waves. In addition, all annealed films have a thin surface layer of PTMSS corresponding to surface segregation induced by the lower surface energy of PTMSS (with respect to that of PI). Thus, the interfacial profiles of PTMSS/PI bilayer films have been totally prospected in the framework of mean field theory. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1486–1494, 2005 相似文献
367.
The magnetic hyperfine splitting frequencies of90NbNi and93mMoNi in an external magnetic field of 0.2 T have been determined by the NMR-ON method to be 18.52(7) and23.73(10) MHz, respectively. With the assumption of Knight shift factorK=0 and with the knowng-factors, the hyperfine fields of90NbNi and93mMoNi were deduced asB
HF(90NbNi)=-4.118(16) T andB
HF(93mMoNi)=-3.491(33) T. The rather long spin-lattice relaxation time of 32(5) min was observed for90NbNi at an external magnetic field of 0.2T and8 mK. 相似文献
368.
By using a narrow single electron spin resonance (ESR) line agent, triarylmethyl, tris(8-carboxy-2,2,6,6-tetrahydroxyethylbenzo[1,2-d:4,5-d′]
bis(1,3)dithiole-4-yl)methyl sodium salt (TAM OX063), pulsed longitudinally detected ESR (LODESR) measurements of a phantom
or the chest of a living mouse at the operating frequency of ca. 300 MHz were taken and the effective longitudinal relaxation
time (T
1*) was estimated for oximetry. Under irradiation of a pair of π-pulses with a variable interval between pulses (τ), in-phase
LODESR signal intensities were obtained from the phantoms containing TAM dissolved in a physiological saline solution at a
concentration of 1 mM and various concentrations of oxygen. TheT
1* of the phantom was calculated from the plotted curve of the LODESR signal intensity against τ. It was found that the reciprocal
ofT
1*, i.e., the longitudinal relaxation rate, increased with the concentration of oxygen. In vivo pulsed LODESR measurements of
the chest of living mice that had received a TAM injection via the intraperitoneal route were made. While the LODESR measurements
were being made, the mice in one group breathed normal air and those in another group breathed 100% oxygen. It was found that
the longitudinal relaxation rate of the mice breathing 100% oxygen was significantly greater than that of mice breathing normal
air, indicating that breathing 100% oxygen elevates the thoracic longitudinal relaxation rate. 相似文献
369.
Wataru Ueda Damian Vitry Tomokazu Kato Nobufumi Watanabe Yusuke Endo 《Research on Chemical Intermediates》2006,32(3):217-233
Mo-V-O-based complex metal oxide catalysts were synthesized hydrothermally for the first time, characterized structurally
and tested in the selective oxidation of propane to acrylic acid, and the results obtained were compared on the basis of catalyst
crystal structures in order to clarify key aspects of alkane selective oxidation over multifunctional metal oxide catalysts.
The catalysts tested were black solids of rod-shaped crystals, which had a layer structure in the direction of fiber axis
and various high dimensional arrangements of metal octahedra in the cross-section plane. A strong dependency on the octahedra
arrangements and a facet dependency were observed, and the roles of metal elements in the course of selective oxidation of
propane were clarified by comparing the catalytic performance of various Mo-V-O-based catalysts. We discuss the multi-functional
character derived from high dimensional structures of the catalysts and mechanism of the selective oxidation of propane. 相似文献
370.
Dynamic Chirality Control of tropos DPCB‐digold Skeleton by Chiral Binaphthyldicarboxylate 下载免费PDF全文
Prof. Dr. Shigekazu Ito Masaki Nanko Tomokazu Shinozaki Masafumi Kojima Dr. Kohsuke Aikawa Prof. Dr. Koichi Mikami 《化学:亚洲杂志》2016,11(6):823-827
The planar 3,4‐diphosphinidenecyclobutene (DPCB) can be remarkably twisted into a C2‐type helical structure by dual coordination of a AuCl moiety. A prompt chirality control of the twisted DPCB skeleton ligated by the digold units affords the enantiopure structure by exchanging the chloride ligands for chiral [1,1′‐binaphthalene]‐2,2′‐dicarboxylate. The chirality of the diaurated 2,2′‐bis(diphenylphosphanyl)‐1,1′‐biphenyl (BIPHEP) system can be controlled prior to that of DPCB. Mixing of a DPCB‐bis(chlorogold) complex with the chiral silver salt dynamically leads to a single diastereomer, which was characterized by the 31P NMR spectrum and the CD couplet patterns in the visible (DPCB) area. The absolute configuration of the singly induced helical structure was assigned by the theoretical CD spectra determined by TD‐DFT calculations. Intramolecular alkoxycyclization of hexa‐4,5‐dien‐1‐ol catalyzed by the asymmetric DPCB‐digold structure were also attempted. 相似文献