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991.
Omaezallene from Red Alga Laurencia sp.: Structure Elucidation,Total Synthesis,and Antifouling Activity
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Dr. Taiki Umezawa Yuko Oguri Dr. Hiroshi Matsuura Shohei Yamazaki Masahiro Suzuki Erina Yoshimura Dr. Takeshi Furuta Dr. Yasuyuki Nogata Dr. Yukihiko Serisawa Dr. Kazuyo Matsuyama‐Serisawa Dr. Tsuyoshi Abe Prof. Dr. Fuyuhiko Matsuda Dr. Minoru Suzuki Dr. Tatsufumi Okino 《Angewandte Chemie (International ed. in English)》2014,53(15):3909-3912
Natural antifouling products have been the subject of considerable attention. We screened marine algae for antifouling activity and discovered omaezallenes, the new bromoallene‐containing natural products isolated from the red alga Laurencia sp. Described is the isolation, structure elucidation, and total syntheses of omaezallenes. The relative and absolute configurations of natural omaezallenes were unambiguously established through total synthesis. The antifouling activities and ecotoxicity of omaezallenes were also evaluated. 相似文献
992.
Plasmon‐Induced Ammonia Synthesis through Nitrogen Photofixation with Visible Light Irradiation
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Dr. Tomoya Oshikiri Prof. Kosei Ueno Prof. Hiroaki Misawa 《Angewandte Chemie (International ed. in English)》2014,53(37):9802-9805
We have successfully developed a plasmon‐induced technique for ammonia synthesis that responds to visible light through a strontium titanate (SrTiO3) photoelectrode loaded with gold (Au) nanoparticles. The photoelectrochemical reaction cell was divided into two chambers to separate the oxidized (anodic side) and reduced (cathodic side) products. To promote NH3 formation, a chemical bias was applied by regulating the pH value of these compartments, and ethanol was added to the anodic chamber as a sacrificial donor. The quantity of NH3 formed at the ruthenium surface, which was used as a co‐catalyst for SrTiO3, increases linearly as a function of time under irradiation with visible light at wavelengths longer than 550 nm. The NH3 formation action spectrum approximately corresponds to the plasmon resonance spectrum. We deduced that plasmon‐induced charge separation at the Au/SrTiO3 interface promotes oxidation at the anodic chamber and subsequent nitrogen reduction on the cathodic side. 相似文献
993.
Highly Efficient Chiral Resolution of dl‐Arginine by Cocrystal Formation Followed by Recrystallization under Preferential‐Enrichment Conditions
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Dr. Sekai Iwama Kazunori Kuyama Yuko Mori Dr. Kochunnoonny Manoj Dr. Rajesh G. Gonnade Dr. Katsuaki Suzuki Dr. Colan E. Hughes P. Andrew Williams Prof. Kenneth D. M. Harris Dr. Stéphane Veesler Dr. Hiroki Takahashi Prof. Hirohito Tsue Prof. Rui Tamura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10343-10350
An excellent chiral symmetry‐breaking spontaneous enantiomeric resolution phenomenon, denoted preferential enrichment, was observed on recrystallization of the 1:1 cocrystal of dl ‐arginine and fumaric acid, which is classified as a racemic compound crystal with a high eutectic ee value (>95 %), under non‐equilibrium crystallization conditions. On the basis of temperature‐controlled video microscopy and in situ time‐resolved solid‐state 13C NMR spectroscopic studies on the crystallization process, a new mechanism of phase transition that can induce preferential enrichment is proposed. 相似文献
994.
Sign Reversal of a Large Circularly Polarized Luminescence Signal by the Twisting Motion of a Bidentate Ligand
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Dr. Junpei Yuasa Hiroshi Ueno Prof. Dr. Tsuyoshi Kawai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8621-8627
This work demonstrates sign reversal of large circularly polarized luminescence (CPL) signal based on the hinge‐like twisting motion of a bidentate ligand, 3,3‐bis(diphenylphosphoryl)‐2,2‐bipyridine (BIPYPO), in a cis–trans isomerization of chiral europium(III) complexes. X‐ray diffraction analysis revealed that twisting motion of BIPYPO provides s‐cis and s‐trans geometries of a chiral EuIII complex containing either tris[3‐(trifluoromethylhydroxymethylene)‐(+)‐camphorate] (D ‐ 1 ) or tris[3‐(heptafluoropropylhydroxymethylene)‐(+)‐camphorate] (D ‐ 2 ). The s‐cis EuIII complexes show eight‐coordinate geometry around the EuIII ion, in which the chelate between the phosphoryl oxygen and the EuIII ion forces the s‐cis geometry of BIPYPO. In contrast, the phosphorus–nitrogen interaction provides a conformational lock for the s‐trans geometry of the BIPYPO ligand, inducing a quasi‐seven‐coordinate EuIII complex. The difference in coordination geometry causes the sign change of the CPL signals between the s‐cis and s‐trans isomers, whereby the s‐cis and s‐trans isomers of EuIII complexes exhibit the positive and negative CPL signals, respectively, for the 5D0→7F1 transition. The proportion of the s‐trans‐D ‐ 1 against s‐cis‐D ‐ 1 increases upon changing the solvent from [D3]acetonitrile to [D6]acetone, inducing a sign change of the CPL signals. The complexes D ‐ 1 and D ‐ 2 show a biexponential decay with two different lifetimes, suggesting two emitting species, that is, the s‐cis and s‐trans isomers of EuIII complexes. In both cases, the proportions of the longer lifetime components (τ1) decrease and instead the shorter lifetime components (τ2) increase upon changing the solvent from [D3]acetonitrile to [D6]acetone. 相似文献
995.
Acid‐Promoted Chemoselective Introduction of Amide Functionality onto Aromatic Compounds Mediated by an Isocyanate Cation Generated from Carbamate
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Akinari Sumita Hiroaki Kurouchi Prof. Dr. Yuko Otani Prof. Dr. Tomohiko Ohwada 《化学:亚洲杂志》2014,9(10):2995-3004
Carbamates have been used as precursors of isocyanates, but heating in the presence of strong acids is required because cleavage of the C? O bond in carbamates is energy‐demanding even in acid media. Direct amidation of aromatic compounds by isocyanate cations generated at room temperature from carbamoyl salicylates in trifluoromethanesulfonic acid (TfOH) was examined. Carbamates with ortho‐salicylate as an ether group (carbamoyl salicylates) showed dramatically accelerated O? C bond dissociation in TfOH, which resulted in facile generation of the isocyanate cation. These chemoselective intermolecular aromatic amidation reactions proceeded even at room temperature and showed good compatibility with other electrophilic functionalities and high discrimination between N‐monosubstituted carbamate and N,N‐disubstituted carbamate. The reaction rates of secondary and tertiary amide formation were markedly different, and this difference was utilized to achieve successive (tandem) amidation reactions of molecules with an N‐monosubstituted carbamate and an N,N‐disubstituted carbamate with two kinds of aromatic compounds. 相似文献
996.
Masahiro Muraoka Mamoru Ohta Yuko Mizutani Mashio Takezawa Ayuri Matsumoto Yohji Nakatsuji 《Journal of inclusion phenomena and macrocyclic chemistry》2014,78(1-4):137-144
A new type of cryptand-based pseudorotaxane was prepared, utilizing a novel cryptand incorporating two aromatic rings as a wheel component, combined with various bipyridinium salts as the axle component. These pseudorotaxanes exhibited charge-transfer absorption at approximately 380 nm due to π-electron interactions between the cryptand and the bipyridinium salt. Upon addition of one equivalent of sodium ion to the pseudorotaxane, this absorption was observed to disappear as a result of displacement of the bipyridinium salt by the sodium. 相似文献
997.
Mai Akakabe Keiko Kumagai Masayuki Tsuda Yuko Konishi Akira Tominaga Masashi Tsuda Eri Fukushi Jun Kawabata 《Tetrahedron letters》2014
A novel linear polyketide, amphirionin-5 (1), has been isolated from the cultivated algal cells of the benthic dinoflagellate Amphidinium sp. (strain KCA09053), and the structure was elucidated on the basis of detailed analyses of 1D and 2D NMR data. Amphirionin-5 (1) resulted in a 282% increase in the proliferation of murine bone-marrow derived stromal ST-2 cells and 320% increase in the proliferation of murine osteoblastic MC3T3-E1 cells. 相似文献
998.
Dioxomolybdenum(VI) and dioxotungsten(VI) complexes: efficient catalytic activity for crosslinking reaction in ethylene‐vinyl acetate copolymer/alkoxysilane composites
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Kenta Adachi Shoko Toyomura Yuko Miyakuni Suzuko Yamazaki Kensuke Honda Tomoyuki Hirano 《先进技术聚合物》2015,26(6):597-605
The catalytic performances of several bis(acetylacetonato)metal complexes [Cu(acac)2, Zn(acac)2, TiO(acac)2, VO(acac)2, MoO2(acac)2, and WO2(acac)2] were investigated for the crosslinking reaction via transesterifications in the ethylene‐vinyl acetate copolymer/tetraethoxysilane (EVA/TEOS) composite system by means of dynamic attenuated total reflectance Fourier transform infrared, solvent swelling, and solid‐state 29Si cross polarization/magic angle spinning nuclear magnetic resonance techniques. Results of the kinetic examination revealed that MoO2(acac)2 and WO2(acac)2 exhibited a higher catalytic activity than di‐n‐butyltin(IV) oxide, which is a catalyst most commonly used for the transesterification process in polymer system, but has a toxic effect on the environmental health. And furthermore, the crosslink density and final siloxane network structure of crosslinked EVA/TEOS composites are found to be greatly correlated with the catalyst used. On the basis of the SN2‐Si pathway, a plausible catalytic mechanism of MoO2(acac)2 and WO2(acac)2 was proposed for the crosslinking reaction via transesterifications of the vinyl acetate moieties in EVA backbone with the ethoxysilane groups in one TEOS molecule. The findings in this study may fill the blank in the high performance and environmentally friendly catalyst in the field of the crosslinking reactions in polymer system and provide useful clue for other transesterifications. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
999.
Development of a Sensitive Bioluminogenic Probe for Imaging Highly Reactive Oxygen Species in Living Rats
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Dr. Mako Kamiya Prof. Eiji Kobayashi Dr. Toru Komatsu Dr. Tasuku Ueno Dr. Takuya Terai Dr. Kenjiro Hanaoka Prof. Tetsuo Nagano Prof. Yasuteru Urano 《Angewandte Chemie (International ed. in English)》2015,54(49):14768-14771
A sensitive bioluminogenic probe for highly reactive oxygen species (hROS), SO3H‐APL, was developed based on the concept of dual control of bioluminescence emission by means of bioluminescent enzyme‐induced electron transfer (BioLeT) and modulation of cell‐membrane permeability. This probe enables non‐invasive visualization of physiologically relevant amounts of hROS generated deep inside the body of living rats for the first time. It is expected to serve as a practical analytical tool for investigating a wide range of biological functions of hROS in vivo. The design concept should be applicable to other in vivo bioluminogenic probes. 相似文献
1000.
Yuko Okuyama Yuki Watanabe Mitsuhiro Takeshita Eunsang Kwon 《Tetrahedron letters》2009,50(2):193-5137
4-Hydroxy-prolinamide alcohol with different noncoordination sites as a molecule showed excellent asymmetric catalytic activity in both the Michael reaction (up to 98% ee) and the direct aldol reaction (up to >99% ee), and the catalyzing reactions with high enantioselectivity are supported by a DFT theoretical study of their transition state. 相似文献