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101.
Tom Bettens Marvin Hoffmann Prof. Mercedes Alonso Em. Prof. Paul Geerlings Prof. Andreas Dreuw Prof. Frank De Proft 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3397-3406
A hitherto unexplored class of molecules for molecular force probe applications are expanded porphyrins. This work proves that mechanical force is an effective stimulus to trigger the interconversion between Hückel and Möbius topologies in [28]hexaphyrin, making these expanded porphyrins suitable to act as conformational mechanophores operating at mild (sub-1 nN ) force conditions. A straightforward approach based on distance matrices is proposed for the selection of pulling scenarios that promote either the planar Hückel topology or the three lowest lying Möbius topologies. This approach is supported by quantum mechanochemical calculations. Force distribution analyses reveal that [28]hexaphyrin selectively allocates the external mechanical energy to molecular regions that trigger Hückel–Möbius interconversions, explaining why certain pulling scenarios favor the Hückel two-sided topology and others favor Möbius single-sided topologies. The meso-substitution pattern on [28]hexaphyrin determines whether the energy difference between the different topologies can be overcome by mechanical activation. 相似文献
102.
Tuba Iftikhar Dr. Natalya V. Izarova Dr. Jan van Leusen Prof. Dr. Paul Kögerler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(33):8500-8508
The propensity of the new, phenylphosphonate-stabilized polyoxotungstate [(C6H5PVO)2P4W24O92]16− to act as a precursor for new 3d metal-functionalized polyanions has been investigated. Reactions with MnII and CuII induce the formation of the previously unknown polyoxotungstate archetype {P4W27}, isolated as salts of the polyanions [Na⊂{MnII(H2O)}{WO(H2O)}P4W26O98]13− ( 1 ) and [K⊂{CuII(H2O)}{W(OH)(H2O)}P4W27O99]14− ( 2 ), which were characterized in the solid state (single-crystal X-ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry). 相似文献
103.
104.
Yuen Cheong Tse Dr. Robert Hein Edward J. Mitchell Zongyao Zhang Prof. Paul D. Beer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(58):14550-14559
Anion receptors employing two distinct sensory mechanisms are rare. Herein, we report the first examples of halogen-bonding porphyrin BODIPY [2]rotaxanes capable of both fluorescent and redox electrochemical sensing of anions. 1H NMR, UV/visible and electrochemical studies revealed rotaxane axle triazole group coordination to the zinc(II) metalloporphyrin-containing macrocycle component, serves to preorganise the rotaxane binding cavity and dramatically enhances anion binding affinities. Mechanically bonded, integrated-axle BODIPY and macrocycle strapped metalloporphyrin motifs enable the anion recognition event to be sensed by the significant quenching of the BODIPY fluorophore and cathodic perturbations of the metalloporphyrin P/P+. redox couple. 相似文献
105.
Quentin Vanbellingen Paul Servin Anaïs Coinaud Sonia Mallet-Ladeira Rgis Laurent Anne-Marie Caminade 《Molecules (Basel, Switzerland)》2021,26(8)
Pyridine, pyridine imine, and bipyridine imine ligands functionalized by a phenol have been synthesized and characterized, in many cases by X-ray diffraction. Several of these N-, N,N-, and N,N,N,-ligands have been grafted onto the surface of phosphorhydrazone dendrimers, from generation 1 to generation 3. The complexation ability of these monomers and dendrimers towards palladium(II) has been assayed. The corresponding complexes have been either isolated or prepared in situ. In both cases, the monomeric and dendritic complexes have been tested as catalysts in Heck couplings and in Sonogashira couplings. In some cases, a positive dendritic effect has been observed, that is, an increase of the catalytic efficiency proportional to the dendrimer generation. 相似文献
106.
Felix Duensing Elisabeth Gruber Paul Martini Marcelo Goulart Michael Gatchell Bilal Rasul Olof Echt Fabio Zappa Masoomeh Mahmoodi-Darian Paul Scheier 《Molecules (Basel, Switzerland)》2021,26(12)
Complexes of atomic gold with a variety of ligands have been formed by passing helium nanodroplets (HNDs) through two pickup cells containing gold vapor and the vapor of another dopant, namely a rare gas, a diatomic molecule (H2, N2, O2, I2, P2), or various polyatomic molecules (H2O, CO2, SF6, C6H6, adamantane, imidazole, dicyclopentadiene, and fullerene). The doped HNDs were irradiated by electrons; ensuing cations were identified in a high-resolution mass spectrometer. Anions were detected for benzene, dicyclopentadiene, and fullerene. For most ligands L, the abundance distribution of AuLn+ versus size n displays a remarkable enhancement at n = 2. The propensity towards bis-ligand formation is attributed to the formation of covalent bonds in Au+L2 which adopt a dumbbell structure, L-Au+-L, as previously found for L = Xe and C60. Another interesting observation is the effect of gold on the degree of ionization-induced intramolecular fragmentation. For most systems gold enhances the fragmentation, i.e., intramolecular fragmentation in AuLn+ is larger than in pure Ln+. Hydrogen, on the other hand, behaves differently, as intramolecular fragmentation in Au(H2)n+ is weaker than in pure (H2)n+ by an order of magnitude. 相似文献
107.
Maxence Paul Luke BridgestockMark Rehkämper Tina van DeFlierdtDominik Weiss 《Analytica chimica acta》2015
A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2 L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a 207Pb–204Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28 ± 21 pg (1sd) and typical Pb recoveries of 40–60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12 ± 4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700–1500 ppm and 1000–2000 ppm were achieved for 207Pb/206Pb, 208Pb/206Pb and 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor 204Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the 206Pb/204Pb ratios are well correlated with 207Pb/206Pb, underlining the significant improvement achieved in the measurement of the minor 204Pb isotope. 相似文献
108.
The misuse of insulin for performance enhancement in sport or as toxic agent has frequently been reported in the past. In contrast to synthetic insulin analogues, the administration of recombinant human insulin is hardly recognized by mass spectrometry. The present study was designed to uncover the misuse of recombinant human insulin for doping control purposes as well as for forensic applications. It is hypothesized that an altered metabolite profile of circulating insulin prevails after subcutaneous administration due to exposure of insulin to epidermal proteases. 相似文献
109.
Computational Studies on Intramolecular Cycloadditions of Azidoenynes and Azidobutenenitriles to Give 6H‐Pyrrolo[1,2‐c][1,2,3]triazoles and 5H‐Pyrrolo[1,2‐d]tetrazoles 下载免费PDF全文
Gérard Audran Paul Brémond Douniazad El Abed Sylvain R. A. Marque Didier Siri Maurice Santelli 《Helvetica chimica acta》2015,98(7):1018-1027
Energetics of intramolecular cycloadditions of azidoenynes and azidobutenenitriles to give 6H‐pyrrolo[1,2‐c][1,2,3]triazoles and 5H‐pyrrolo[1,2‐d]tetrazoles have been calculated at the B3LYP/6.311++G(3df,3pd) level of theory in ideal gas and in H2O as solvent. Stabilities of the corresponding anions, tautomers, and isomers are discussed. Transition states of the cyclization of parent compounds are determined at the same level of theory. 相似文献
110.
Holly V. Adcock Elli Chatzopoulou Paul W. Davies 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(51):15745-15749
Gold carbene reactivity patterns were accessed by ynamide insertion into a C(sp3) H bond. A substantial increase in molecular complexity occurred through the cascade polycyclization of N‐allyl ynamides to form fused nitrogen‐heterocycle scaffolds. Exquisite selectivity was observed despite several competing pathways in an efficient gold‐catalyzed synthesis of densely functionalized C(sp3)‐rich polycycles and a copper‐catalyzed synthesis of fused pyridine derivatives. The respective gold–keteniminium and ketenimine activation pathways have been explored through a structure–reactivity study, and isotopic labeling identified turnover‐limiting C H bond‐cleavage in both processes. 相似文献