全文获取类型
收费全文 | 277篇 |
免费 | 10篇 |
专业分类
化学 | 211篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 6篇 |
物理学 | 62篇 |
出版年
2023年 | 9篇 |
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2014年 | 3篇 |
2013年 | 14篇 |
2012年 | 13篇 |
2011年 | 24篇 |
2010年 | 14篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 14篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1966年 | 4篇 |
1965年 | 8篇 |
1963年 | 2篇 |
排序方式: 共有287条查询结果,搜索用时 15 毫秒
161.
Organic structure-directing agents (OSDAs) are often employed for synthesis of zeolites with desired frameworks. A priori prediction of such OSDAs has mainly relied on the interaction energies between OSDAs and zeolite frameworks, without cost considerations. For practical purposes, the cost of OSDAs becomes a critical issue. Therefore, the development of a computational de novo prediction methodology that can speed up the trial-and-error cycle in the search for less expensive OSDAs is desired. This study utilized a nature-inspired ant colony optimization method to predict physicochemically and/or economically preferable OSDAs, while also taking molecular similarity and heuristics of zeolite synthesis into consideration. The prediction results included experimentally known OSDAs, candidates having structures closely related to known OSDAs, and novel ones, suggesting the applicability of this approach.Inspired by the exploratory methods of ant colonies, adaptive optimization was employed to explore the chemical space for organic molecules that guide zeolite crystallization, giving both physicochemically and economically promising molecules. 相似文献
162.
Koki Matsumoto Dr. Masaru Kato Prof. Ichizo Yagi Siqi Xie Prof. Kiyotaka Asakura Prof. Shin-ichiro Noro Prof. Norimitsu Tohnai Dr. Stéphane Campidelli Prof. Takashi Hayashi Prof. Akira Onoda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(5):e202103545
Fe/N/C single-atom catalysts containing Fe−Nx sites prepared by pyrolysis are promising cathode materials for fuel cells and metal-air batteries due to their high oxygen reduction reaction (ORR) activities. We have developed iron complexes containing N2- or N3-chelating coordination structures with preorganized aromatic rings in a 1,12-diazatriphenylene framework tethering bromo substituents as precursors to precisely construct Fe−N4 sites in an Fe/N/C catalyst. One-step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe−N4 sites without iron aggregates. X-ray absorption spectroscopy (XAS) and electrochemical measurements revealed that the iron complex with N3-coordination is more effectively converted to Fe−N4 sites catalyzing ORR with a TOF value of 0.21 e site−1 s−1 at 0.8 V vs. RHE. This indicates that the formation of Fe−N4 sites is controlled by precise tuning of the chemical structure of the iron complex precursor. 相似文献
163.
Tatsuro Tominaga Koki Fukuda Dr. Kazutaka Koga Dr. Makoto Fukudome Prof. Dr. De-Qi Yuan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202103940
Miniature models of acyl-transfer systems in cells, which were composed by replacing the protein, coenzyme, and substrate with CD, functional group, and CD, respectively, and combining them all together in one, displayed definite role-sharing and exact cooperation of the functional groups and hydrophobic cavity, and thus enabled the regio-specific reaction. 相似文献
164.
Tadaaki Horii Toshinobu Shinnai Kazuhiko Tsuchiya Takeshi Mori Masashi Kijima 《Journal of polymer science. Part A, Polymer chemistry》2012,50(21):4557-4562
Carbazole and fluorene‐based random and alternating copolycondensates were synthesized to develop high‐performance blue light‐emitting polymers by improving electron injection ability of poly(N‐aryl‐2,7‐carbazole)s that showed intense blue electroluminescence (EL) with good hole‐injection and ‐transport ability. These copolycondensates absorbed light energy at about λmax = 390 nm in CHCl3 and 400 nm in film state, and fluoresced at about λmax = 417 nm in CHCl3 and 430 nm in the thin film state. Energy gaps between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of them were about 2.9 eV, and the energy levels of LUMO situated lower than that of corresponding polycarbazole. Polymer light‐emitting diode devices having configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate)/polymer/CsF/Al using the copolycondensates, poly(N‐arylcarbazole‐2,7‐diyl), and poly(9,9‐dialkylfluorene‐2,7‐diyl), emitted bluish EL at operating voltages lower than 7 V. The device embedded the random copolycondensate showed notably higher performance with maximum luminance of 31,200 cd m?2 at 11.0 V, and the current efficiencies observed under operating voltages lower than 7 V were higher than those of the other devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
165.
Soichiro Nagase Koki Miyama Akikazu Matsumoto 《Journal of polymer science. Part A, Polymer chemistry》2019,57(14):1569-1579
N‐substituted maleimides polymerize in the presence of a radical initiator to give polymers with excellent thermal stabilities and transparency. In this study, we synthesized various maleimide copolymers with styrenes and acrylic monomers to control their thermal and mechanical properties by the introduction of bulky substituents and intermolecular hydrogen bonding. Three‐component copolymers of N‐(2‐ethylhexyl)maleimide in combination with styrene, α‐methylstyrene (MSt), or 1‐methylenebenzocyclopentane (BC5) as the styrene derivatives, and n‐butyl acrylate, 2‐hydroxyethyl acrylate, 4‐hydroxybutyl acrylate, or acrylic acid as the acrylic monomers were prepared by radical copolymerization. These copolymers were revealed to exhibit excellent heat resistance by thermogravimetric analysis. Glass transition temperatures increased by the introduction of bulky MSt and BC5 repeating units. The mechanical properties of the copolymer films were improved by the introduction of intermolecular hydrogen bonding. Optical properties, such as transmittance, refractive index, Abbe number, and birefringence, were determined for the copolymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1569–1579 相似文献
166.
Y. Ikada H. Iwata S. Nagaoka F. Horii M. Hatada 《Journal of Macromolecular Science: Physics》2013,52(2):191-210
Surface pressure-area isotherms for monolayers from graft copolymers with one branch (or four) and diblock copolymers were determined at air/aqueous medium interfaces. The dependence of surface pressure on area for poly(vinyl acetate) (PVAc)-polystyrene(PS) graft and block copolymers was identical to that of pure PVAc at the large areas, while a sharp increase in pressure appeared with further compression. The surface pressure of PVAc-PS graft copolymer at the air/0. 2 N NaOH interface decreased with time, but the critical area at which the surface pressure increased rapidly remained constant, regardless or hydrolysis time. When a poly(vinyl alcohol) (PVA)-PS graft or block copolymer was spread over water, the surface pressure originating from the PVA chain was too small to be observed, and merely that of the PS sequence appeared. It was concluded that the PS sequence was always present in the form of a tightly coiled sphere at the interfaces, whereas the PVAc sequence was spread as a monomolecular film on water but diffused into the alkaline substrate as a result of the hydrolysis to PVA. Thus the PVA-PS graft and block copolymers spread on water seem to be so oriented that the PVA chain “dissolved” in water is supported at the interface by the compact, monomolecular particle of PS on the surface. 相似文献
167.
Fujimori T Urita K Tománek D Ohba T Moriguchi I Endo M Kaneko K 《The Journal of chemical physics》2012,136(6):064505
We introduce a way to selectively probe local vibration modes at nanostructured asperities such as tips of carbon nanohorns. Our observations benefit from signal amplification in surface-enhanced Raman scattering (SERS) at sites near a silver surface. We observe nanohorn tip vibration modes in the range 200-500 cm(-1), which are obscured in regular Raman spectra. Ab initio density functional calculations assign modes in this frequency range to local vibrations at the nanohorn cap resembling the radial breathing mode of fullerenes. Careful interpretation of our SERS spectra indicates presence of caps with 5 or 6 pentagons, which are chemically the most active sites. Changes in the peak intensities and frequencies with time indicate that exposure to laser irradiation may cause structural rearrangements at the cap. 相似文献
168.
Starič M Aihara H Arinstein K Asner DM Aushev T Bakich AM Bay A Bhardwaj V Bhuyan B Bozek A Bračko M Browder TE Chen A Chen P Cheon BG Chilikin K Chistov R Cho IS Cho K Choi Y Doležal Z Drásal Z Eidelman S Fast JE Gaur V Gabyshev N Golob B Haba J Hayasaka K Horii Y Hoshi Y Hou WS Hsiung YB Iijima T Inami K Ishikawa A Itoh R Iwabuchi M Iwasaki Y Iwashita T Julius T Kang JH Kawasaki T Kiesling C Kim HJ Kim HO Kim JB Kim KT Kim MJ Kim YJ Kinoshita K Ko BR Kobayashi N Koblitz S Kodyš P Korpar S 《Physical review letters》2012,108(7):071801
We search for CP violation in Cabibbo-suppressed charged D meson decays by measuring the difference between the CP-violating asymmetries for the Cabibbo-suppressed decays D(±)→K(+)K(-)π(±) and the Cabibbo-favored decays D(s)(±)→K(+)K(-)π(±) in the K(+)K(-) mass region of the ? resonance. Using 955 fb(-1) of data collected with the Belle detector, we obtain A(CP)(D+→?π+)=(+0.51±0.28±0.05)%. The measurement improves the sensitivity of previous searches by more than a factor of 5. We find no evidence for direct CP violation. 相似文献
169.
Sato Y Yamamoto H Aihara H Asner DM Aulchenko V Aushev T Aziz T Bakich AM Bhardwaj V Bhuyan B Bischofberger M Bondar A Bozek A Bračko M Browder TE Chang P Chen P Cheon BG Chilikin K Chistov R Cho IS Cho K Choi SK Choi Y Dalseno J Doležal Z Drásal Z Eidelman S Epifanov D Fast JE Gaur V Gabyshev N Goh YM Golob B Haba J Hara T Hayasaka K Hayashii H Horii Y Hoshi Y Hou WS Hyun HJ Ishikawa A Itoh R Iwabuchi M Iwasaki Y Iwashita T Julius T Kapusta P Kawasaki T Kichimi H Kiesling C Kim HJ Kim HO 《Physical review letters》2012,108(17):171801
We report a measurement of the CP-violation parameter sin2φ1 at the Υ(5S) resonance using a new tagging method, called "B-π tagging." In Υ(5S) decays containing a neutral B meson, a charged B, and a charged pion, the neutral B is reconstructed in the J/ψK(S)(0) CP-eigenstate decay channel. The initial flavor of the neutral B meson at the moment of the Υ(5S) decay is opposite to that of the charged B and may thus be inferred from the charge of the pion without reconstructing the charged B. From the asymmetry between B-π(+) and B-π(-) tagged J/ψK(S)(0) yields, we determine sin2φ1=0.57±0.58(stat)±0.06(syst). The results are based on 121 fb(-1) of data recorded by the Belle detector at the KEKB e(+)e(-) collider. 相似文献
170.
Nonlinear Dynamics - Stochastic synchrony, also known as noise-induced synchronization that leads to phase coherence, arises when a set of uncoupled neurons synchronizes to a common white noise... 相似文献