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941.
He Huang Yanxiu Li Yu Tong En‐Ping Yao Maximilian W. Feil Alexander F. Richter Markus Dblinger Andrey L. Rogach Jochen Feldmann Lakshminarayana Polavarapu 《Angewandte Chemie (International ed. in English)》2019,58(46):16558-16562
The growing demand for perovskite nanocrystals (NCs) for various applications has stimulated the development of facile synthetic methods. Perovskite NCs have often been synthesized by either ligand‐assisted reprecipitation (LARP) at room temperature or by hot‐injection at high temperatures and inert atmosphere. However, the use of polar solvents in LARP affects their stability. Herein, we report on the spontaneous crystallization of perovskite NCs in nonpolar organic media at ambient conditions by simple mixing of precursor–ligand complexes without application of any external stimuli. The shape of the NCs can be controlled from nanocubes to nanoplatelets by varying the ratio of monovalent (e.g. formamidinium+ (FA+) and Cs+) to divalent (Pb2+) cation–ligand complexes. The precursor–ligand complexes are stable for months, and thus perovskite NCs can be readily prepared prior to use. Moreover, we show that this versatile synthetic process is scalable and generally applicable for perovskite NCs of different compositions. 相似文献
942.
Ingeborg Csöregh Mátyás Czugler Edwin Weber Jochen Ahrendt 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(3):309-322
The crystal structures of the inclusion compounds oftrans-9,10-dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid host (1) with formic acid (1a), acetic acid (1b), and propionic acid (1c) as guests, and of the coordinatoclathrate of the 1,1-binaphthyl-2,2-dicarboxylic acid host (2) with acetic acid as guest (2b) have been studied by single crystal X-ray diffraction. These studies show that inclusion of small carboxylic acids by carboxylic acid hosts like1 and2 results in formation of isolated, hydrogen-bonded guest dimers. Additional H-bond contacts between host and guest carboxylic groups are only formed in cases1a and2b. The dimeric acidic guest units are sitting in the cavities of the host or host-guest framework and have no other interactions than those of a weak Van der Waals' type with the neighbouring molecules. Crystal data:1·formic acid (1:2): triclinic (P),a = 11.6769(6),b = 9.4067(4),c = 9.0020(4) Å,a = 81.522(4), = 100.310(6), = 104.208(6)°,Z = 2,R = 0.048 for 2392 reflections;1·acetic acid (1:1): monoclinic (P21/n),a = 9.717(2),b = 14.462(2),c = 13.038(3)Å, = 104.27(1)°,Z=4,R=0.046 for 3042 observations;1·propionic acid (1:1): monoclinic (P21/n),a = 9.897(4),b = 14.671(7),c = 13.284(7) Å, = 105.92(6)°,Z = 4,R = 0.056 for 2302 reflections;2·acetic acid (2:3): triclinic (P),a = 12.746(1),b = 17.781(2),c = 11.010(1) Å, = 105.606(4), = 112.992(8), = 81.175(6)°,Z = 2,R = 0.067 for 4375 observations. 相似文献
943.
The interaction of ethylene carbonate (EC) with Si surfaces is studied by density functional theory. The results show a strong structure sensitivity in the adsorption of EC on Si surfaces. While the adsorbed EC molecule readily decomposes on the Li/Si(111) surface, it does not dissociate on the Li/Si(100) and Li/Si(110) surfaces. On Si(111), the O atom at the top of EC is detached from the EC molecule and binds to the Li adatom, forming Li?O molecules. The mechanism of EC decomposition is the transfer of 2.4 electrons from the surface to the EC molecule, as well as the formation of a covalent bond between the Li adatom and the EC molecule. This result shows that in lithium‐ion batteries with Si anodes, dissociation of the solvent and formation of a solid electrolyte interphase layer start as soon as the Li atoms cover the anode surface. 相似文献
944.
Enhanced Fibril Fragmentation of N‐Terminally Truncated and Pyroglutamyl‐Modified Aβ Peptides 下载免费PDF全文
Melanie Wulff Monika Baumann Anka Thümmler Dr. Jay K. Yadav Liesa Heinrich Uwe Knüpfer Dagmar Schlenzig Dr. Angelika Schierhorn Dr. Jens‐Ulrich Rahfeld Dr. Uwe Horn Prof. Dr. Jochen Balbach Prof. Dr. Hans‐Ulrich Demuth Prof. Dr. Marcus Fändrich 《Angewandte Chemie (International ed. in English)》2016,55(16):5081-5084
N‐terminal truncation and pyroglutamyl (pE) formation are naturally occurring chemical modifications of the Aβ peptide in Alzheimer's disease. We show herein that these two modifications significantly reduce the fibril length and the transition midpoint of thermal unfolding of the fibrils, but they do not substantially perturb the fibrillary peptide conformation. This observation implies that the N terminus of the unmodified peptide protects Aβ fibrils against mechanical stress and fragmentation and explains the high propensity of pE‐modified peptides to form small and particularly toxic aggregates. 相似文献
945.
Iron Alkynyl Helicenes: Redox‐Triggered Chiroptical Tuning in the IR and Near‐IR Spectral Regions and Suitable for Telecommunications Applications 下载免费PDF全文
Dr. Chengshuo Shen Dr. Goulc'hen Loas Dr. Monika Srebro‐Hooper Dr. Nicolas Vanthuyne Dr. Loïc Toupet Dr. Olivier Cador Dr. Frédéric Paul Prof. Juan T. López Navarrete Prof. Francisco J. Ramírez Dr. Belén Nieto‐Ortega Prof. Juan Casado Prof. Jochen Autschbach Prof. Marc Vallet Dr. Jeanne Crassous 《Angewandte Chemie (International ed. in English)》2016,55(28):8062-8066
The combination of a bis‐alkynyl‐helicene moiety with two iron centers leads to novel electroactive species displaying unprecedented redox‐triggered chiroptical switching. Upon oxidation, strong changes of vibrational modes (either local or extended coupled modes) are detected by vibrational circular dichroism and Raman optical activity. Remarkably, the sign of the optical rotation at 1.54 µm (that is, at wavelengths typically used for telecommunications) changes upon oxidation while the topology and stereochemistry of the helicene remain unchanged. 相似文献
946.
Ingo Schlachter Udo Hweler Waldemar Iwanek Mariusz Urbaniak Jochen Mattay 《Tetrahedron》1999,55(52):6776-14940
MD simulations using a combination of AMI and AMBER are performed to elucidate the origin of complexation between fullerenes and calix[n]arenes (n = 4,6,8). Only calix[6]arenes and calix[8]arenes are suitable for complex formation. By introducing benzyl substitutents on the upper rim of the calixarenes the interaction energy between host and guest is even improved. Analysis of the data also reveals a strong stabilization by t-butyl or benzyl substitutents beside π-π interactions between the arene units of the calixarene and fullerenes. The calculated data perfectly correlate with the experimentally observed equilibrium constants. 相似文献
947.
Jochen Ellermann Peter Gabold Christian Schelle Falk A. Knoch Matthias Moll Walter Bauer 《无机化学与普通化学杂志》1995,621(11):1832-1843
Chemistry of Polyfunctional Molecules. 118. Syntheses and Crystal Structures of Bicyclic Metallaphosphazenes with Four and Six Membered Rings Anhydrous MCl2 (M = Pt, Fe) react with LiN(PPh2)2 ( 1 ) in the molar ratio of 1:2 in boiling toluene within 25 hours under partially oxidative scrambling of the PNP chain in 1 yielding the bicyclic metallaphosphazenes 5 a, b . While compound 5 a can be isolated in substance, the intermediate 5 b proves to be highly reactive but can be stabilized in the presence of CO, forming the 18-valence-electron coordination compound as an isomeric trans( 6 a )/cis( 6 b ) mixture in the molar ratio of 99:1. Also treatment of anhydrous PtCl4 with four equivalents of 1 in boiling toluene during 60 hours yields 5 a . Alkylation of 5 a with CH3I leads to the formation of the ionic species [Pt2+{Ph2P? N(CH3)? PPh2}(Ph2P? N = PPh2 = N? PPh2?)]I? ( 9 ). The X-ray crystal structures of 5 a × 1 CH2Cl2 and 6 a reveal, that the metal centres have a planar P-coordination polyhedron in the solid state. In the complex 9 × 2,5 CH2Cl2 however the torsion angle between the P? Pt? P planes of the four and six membered rings shows to be 15°. The six membered metallacycles in 5 a × 1 CH2Cl2, 6 a and 9 × 2,5 CH2Cl2 differ in their geometrical arrangement. All the new compounds have also been characterized by their 1H, 31P{1H}, 13C{1H} NMR, IR, Raman and mass spectra. 相似文献
948.
Zedda M Tuerk J Peil S Schmidt TC 《Rapid communications in mass spectrometry : RCM》2010,24(24):3531-3538
Within the scope of research of membrane degradation phenomena during fuel cell operation a reliable analytical procedure for the extraction, detection and quantification of possible membrane oxidation products has been developed. These oxidation products originate from the attack of hydroxyl or peroxyl radicals on the membrane polymer. Such radicals are formed in situ (during fuel cell operation) or ex situ (Fenton test as oxidative stress simulation). The analysis of membrane oxidation products was carried out by electrospray ionization tandem mass spectrometry. Five potential membrane oxidation products (4‐hydroxybenzoic acid (4‐HBA), 4‐hydroxybenzaldehyde (4‐HBAD), 4,4‐biphenol (4,4‐BP), 4‐hydroxybenzenesulfonate (4‐HBS), and 4,4‐sulfonylbiphenol (4,4‐SBP)) were selected based on the molecular structure of the sulfonated polyarylether membrane used. In conjunction with the development of a multiple reaction monitoring (MRM) method, the ionization and fragmentation of the selected compounds were investigated. For 4,4‐BP a molecular ion (M+?) was observed in the positive ionization mode and used for MRM method development. Reproducible extraction of the model compounds was achieved using a mixed‐mode sorbent material with both weak anion‐exchange and reversed‐phase retention properties. By using the developed analytical procedure, the identities of two membrane degradation products (4‐HBA and 4‐HBAD) were determined in situ and ex situ. In addition to the investigation of membrane degradation phenomena, the combination of extraction on a mixed‐mode sorbent material and tandem mass spectrometric detection is attractive for the analysis of aromatic sulfonic acids, phenolic acids and phenols. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
949.
The photoinduced oxidation of 1-naphthol to 1,4-naphthoquinone and of 5-hydroxy-1-naphthol to 5-hydroxy-1,4-naphthoquinone was studied by steady-state and time-resolved techniques. The direct photooxidation of naphthols in methanol or water takes place by reaction of the naphoxyl radical ((?)ONaph) with the superoxide ion radical (O(2)(?-)), the latter of which results from the reaction of the solvated electron with oxygen after photoionization. The sensitized oxidation takes place by energy transfer from the xanthene triplet state to oxygen. From the two oxygen atoms, which are consumed, one is incorporated into the naphthol molecule giving naphthoquinone and the second gives rise to water. The effects of eosin, erythrosin, and rose bengal in aqueous solution, pH, and the oxygen and naphthol concentrations were studied. The quantum yield of the photosensitized transformation was determined, which increases with the naphthol concentration and is largest at pH > 10. The quantum yield of oxygen uptake is similar. The pathway involving singlet molecular oxygen is suggested to operate for the three sensitizers. The alternative pathway via electron transfer from the naphthol to the xanthene triplet state and subsequent reaction of (?)ONaph with O(2)(?-), the latter of which is formed by scavenging of the xanthene radical anion by oxygen, does also contribute. 相似文献
950.
Bertolotti G Bersani D Lottici PP Alesiani M Malcherek T Schlüter J 《Analytical and bioanalytical chemistry》2012,402(4):1451-1457
Three bronze samples created by CNR-ISMN (National Research Council—Institute of Nanostructured Materials) to be similar to
Punic and Roman coins found in Tharros (OR, Sardinia, Italy) were studied to identify the corrosion products on their surfaces
and to evaluate the reliability of the reproduction process. Micro-Raman spectroscopy was chosen to investigate the corroded
surfaces because it is a non-destructive technique, it has high spatial resolution, and it gives the opportunity to discriminate
between polymorphs and to correlate colour and chemical composition. A significant amount of green copper hydroxychlorides
(Cu2(OH)3Cl) was detected on all the coins. Their discrimination by Raman spectroscopy was challenging because the literature on the
topic is currently confusing. Thus, it was necessary to determine the characteristic peaks of atacamite, clinoatacamite, and
the recently discovered anatacamite by acquiring Raman spectra of comparable natural mineral samples. Clinoatacamite, with
different degrees of order in its structure, was the major component identified on the three coins. The most widespread corrosion
product, besides hydroxychlorides, was the red copper oxide cuprite (Cu2O). Other corrosion products of the elements of the alloy (laurionite, plumbonacrite, zinc carbonate) and those resulting
from burial in the soil (anatase, calcite, hematite) were also found. This study shows that identification of corrosion products,
including discrimination of copper hydroxychlorides, could be accomplished by micro-Raman on valuable objects, for example
archaeological findings or works of art, avoiding any damage because of extraction of samples or the use of a destructive
analytical technique. 相似文献