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261.
262.
Masato Matsugi Misaki Suganuma Shoko Yoshida Shohei Hasebe Yoko Kunda Kotaro Hagihara Sayaka Oka 《Tetrahedron letters》2008,49(46):6573-6574
A convenient methodology for the separation of a fluorous by-product using fluorous chemistry is described. A Mukaiyama coupling reagent bearing a medium fluorous tag, between 40% and 60% fluorine by weight, can be effectively separated from non-fluorous components by increasing the water content of the crude reaction mixture and subsequent filtration. Additional fluorous solid phase extraction is not necessary. 相似文献
263.
Dr. Weifan Wang Fiona Hanindita Yusei Tanaka Kotaro Ochiai Dr. Hiroyasu Sato Dr. Yongxin Li Prof. Dr. Takuma Yasuda Prof. Dr. Shingo Ito 《Angewandte Chemie (International ed. in English)》2023,62(8):e202218176
Sulfur-embedded polycyclic aromatic compounds have been used as building blocks for numerous organic semiconductors over the past few decades. While the success is based on thiophene-containing compounds, aromatic compounds that contain thiepine, a sulfur-containing seven-membered-ring arene, has been less well investigated. Here we report the synthesis and properties of π-extended pyrrole-fused heteropine compounds such as thiepine and oxepine. A π-extended pyrrole-fused thiepine exhibited a “pitched π-stacking” structure in the crystal, and exhibited a high charge carrier mobility of up to 1.0 cm2 V−1 s−1 in single-crystal field-effect transistors. 相似文献
264.
Transparent thermoplastic polymers that exhibit no birefringence are ideal for optical components such as optical films for liquid crystal displays and various lenses. Copolymerization of a positive birefringent monomer with a negative monomer is an effective technique for obtaining low birefringent polymers, especially zero‐photoelastic birefringence polymers that exhibit no photoelastic birefringence even during elastic deformation. We prepared four types of trifluoromethyl‐substituted polystyrenes. By substituting hydrogens at the ortho or meta positions of the benzene ring of polystyrene, we demonstrated that poly(2‐(trifluoromethyl)styrene), poly(3‐(trifluoromethyl)styrene), and poly(3,5‐bis(trifluoromethyl)styrene) had negative photoelastic coefficients. However, poly(4‐(trifluoromethyl)styrene) had a positive photoelastic coefficient similar to that of polystyrene. Based on these results, we synthesized a zero‐photoelastic birefringence polymer of poly(2‐(trifluoromethyl)styrene‐co‐4‐(trifluoromethyl)styrene) (55/45 wt.) exhibiting no photoelastic birefringence in elastic deformation, in which the positive photoelastic birefringence of the poly(4‐(trifluoromethyl)styrene) unit was compensated for by the negative photoelastic birefringence of the poly(2‐(trifluoromethyl)styrene) unit. The discovery of polymers having negative photoelastic coefficients is valuable for the design and synthesis of zero‐photoelastic birefringence polymers. The four types of trifluoromethyl‐substituted polystyrenes are promising optical materials because they have high transparency (transmittance > 89–92% for 27–34‐µm thickness films) in the visible and near‐infrared regions and a high decomposition temperature of approximately 400°C. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
265.
Bifacial Base‐Pairing Behaviors of 5‐Hydroxyuracil DNA Bases through Hydrogen Bonding and Metal Coordination
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Dr. Yusuke Takezawa Kotaro Nishiyama Dr. Tsukasa Mashima Prof. Dr. Masato Katahira Prof. Dr. Mitsuhiko Shionoya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14713-14716
A novel bifacial ligand‐bearing nucleobase, 5‐hydroxyuracil ( UOH ), which forms both a hydrogen‐bonded base pair ( UOH –A) and a metal‐mediated base pair ( UOH –M– UOH ) has been developed. The UOH –M– UOH base pairs were quantitatively formed in the presence of lanthanide ions such as GdIII when UOH – UOH pairs were consecutively incorporated into DNA duplexes. This result established metal‐assisted duplex stabilization as well as DNA‐templated assembly of lanthanide ions. Notably, a duplex possessing UOH –A base pairs was destabilized by addition of GdIII ions. This observation suggests that the hybridization behaviors of the UOH ‐containing DNA strands are altered by metal complexation. Thus, the UOH nucleobase with a bifacial base‐pairing property holds great promise as a component for metal‐responsive DNA materials. 相似文献
266.
Inside Cover: Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: A Potential Tetraradicaloid Hydrocarbon (Angew. Chem. Int. Ed. 7/2015)
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267.
Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from cottonseed oil and valeric acid in batch culture of Ralstonia sp. strain JC-64 总被引:1,自引:0,他引:1
Cunjiang Song Lixing Zhao Shin Ono Choichiro Shimasaki Masami Inoue 《Applied biochemistry and biotechnology》2001,94(2):169-178
A Ralstonia sp. strain JC-64 that is capable of accumulating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P[3HB-co-3HV]) from cottonseed oil and valeric acid was isolated. By using a high limiting-nitrogen (HLN) mineral medium as the medium
for the second stage of the fermentation process and by adding the two carbon sources at different times, a range of copolymers
with 12–62 mol% of 3HV were produced from a series of HLN mineral mediums containing different compositions of cottonseed
oil and valeric acid by Ralstonia sp. JC-64. The melting temperature (T
m
) of polyhydroxybutyrate from cottonseed oil was 174°C and that of P(3HB-co-3HV) with the highest 3HV-mol fraction (62%) was 81°C. 相似文献
268.
Dr. Kotaro Tateno Prof. Kosuke Ono Prof. Hidetoshi Kawai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15765-15771
Helical structures were constructed by using π-spacer-bridged dimers of dibenzopyrrolo[1,2-a][1,8]naphthyridine, which has a highly fluorescent L-shaped π-extended skeleton. Three dimers with biphenylene (dimer 1 ), phenanthrene (dimer 2 ), and m-phenylene (dimer 3 ) spacers, as well as a fixed-helical dimer 4 where two quinolone rings were covalently cross-linked, were designed and prepared. 1H NMR and ROESY spectra revealed that dimers 1 and 2 adopted helical forms in solution, whereas dimer 3 did not. The helical conformation of 1 was strengthened by addition of either polar or nonpolar solvents to the chloroform solution, which suggested that π–π stacking was the main contributor to the stabilization of the helical structure. All of the dimers, including fixed-helical dimer 4 , emitted fluorescence with high quantum yields (ϕ=0.79–0.86). 相似文献
269.
Pd-Fe nanoparticles as electrocatalysts for oxygen reduction 总被引:1,自引:0,他引:1
We have synthesized new electrocatalysts for the O2 reduction reaction that does not contain Pt. They consist of carbon-supported Pd-Fe alloys and have very high oxygen reduction. The nanoparticles with a Pd:Fe molar ratio of 3:1 (Pd3Fe/C) show a higher mass activity than that of commercial Pt/C. The surface-specific activity of the Pd-Fe alloys is related to the Pd-Pd bond distance: the shorter the bond distance, the higher the activity. This new class of electrocatalysts promises to alleviate some major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance. 相似文献
270.
Kotaro Satoh Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2000,38(15):2728-2733
Aqueous sulfonic acids (HOSO2R; R = CH3, Ph‐p‐CH3, and Ph‐p‐NO2), coupled with a water‐tolerant Lewis acid, ytterbium triflate [Yb(OTf)3; OTf = OSO2CF3], initiate the cationic suspension polymerization of p‐methoxystyrene (pMOS) in heterogeneous aqueous media. They induce controlled polymerization of pMOS at 30 °C, and the molecular weights of the polymers (weight‐average molecular weight/number‐average molecular weight ∼ 1.7) increase with conversion. These suspension polymerizations are initiated by the entry of sulfonic acid from the aqueous phase into the organic phase and proceed via reversible activation of the sulfonyl terminus by the Lewis acid. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2728–2733, 2000 相似文献