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931.
Iakov S. Fomenko Medhanie Afewerki Marko I. Gongola Eugene S. Vasilyev Lidia S. Shulpina Nikolay S. Ikonnikov Georgiy B. Shulpin Denis G. Samsonenko Vadim V. Yanshole Vladimir A. Nadolinny Alexander N. Lavrov Alexey V. Tkachev Artem L. Gushchin 《Molecules (Basel, Switzerland)》2022,27(13)
The reactions of CuX2 (X = Cl, Br) with dipinodiazafluorenes yielded four new complexes [CuX2L1]2 (X = Cl (1), Br (2), L1 = (1R,3R,8R,10R)-2,2,9,9-Tetramethyl-3,4,7,8,9,10-hexahydro-1H-1,3:8,10-dimethanocyclopenta [1,2-b:5,4-b’]diquinolin-12(2H)-one) and [(CuX2)2L2]n (X = Cl (3), Br (4), L2 = (1R,3R,8R,10R,1’R,3’R,8’R,10’R)-2,2,2’,2’,9,9,9’,9’-Octamethyl-1,1’,2,2’,3,3’,4,4’,7,7’,8,8’,9,9’,10,10’-hexadecahydro-1,3:1’,3’:8,10:8’,10’-tetramethano-12,12’-bi(cyclopenta [1,2-b:5,4-b’]diquinolinylidene). The complexes were characterized by IR and EPR spectroscopy, HR-ESI-MS and elemental analysis. The crystal structures of compounds 1, 2 and 4 were determined by X-ray diffraction (XRD) analysis. Complexes 1–2 have a monomeric structure, while complex 4 has a polymeric structure due to additional coordinating N,N sites in L2. All complexes contain a binuclear fragment {Cu2(μ-X)2×2} (X = Cl, Br) in their structures. Each copper atom has a distorted square-pyramidal coordination environment formed by two nitrogen atoms and three halogen atoms. The Cu-Nax distance is elongated compared to Cu-Neq. The EPR spectra of compounds 1–4 in CH3CN confirm their paramagnetic nature due to the d9 electronic configuration of the copper(II) ion. The magnetic properties of all compounds were studied by the method of static magnetic susceptibility. For complexes 1 and 2, the effective magnetic moments are µeff ≈ 1.87 and 1.83 µB (per each Cu2+ ion), respectively, in the temperature range 50–300 K, which are close to the theoretical spin value (1.73 µB). Ferromagnetic exchange interactions between Cu(II) ions inside {Cu2(μ-X)2X2} (X = Cl, Br) dimers (J/kB ≈ 25 and 31 K for 1 and 2, respectively) or between dimers (θ′ ≈ 0.30 and 0.47 K for 1 and 2, respectively) were found at low temperatures. For compounds 3 and 4, the magnetic susceptibility is well described by the Curie–Weiss law in the temperature range 1.77–300 K with µeff ≈ 1.72 and 1.70 µB for 3 and 4, respectively, and weak antiferromagnetic interactions (θ ≈ −0.4 K for 3 and −0.65 K for 4). Complexes 1–4 exhibit high catalytic activity in the oxidation of alkanes and alcohols with peroxides. The maximum yield of cyclohexane oxidation products reached 50% (complex 3). Based on the data on the study of regio- and bond-selectivity, it was concluded that hydroxyl radicals play a decisive role in the oxidation reaction. The initial products in reactions with alkanes are alkyl hydroperoxides. 相似文献
932.
Ibuprofen is a non-steroidal anti-inflammatory drug possessing analgesic and antipyretic activity. Electron paramagnetic resonance (EPR) spectroscopy could be applied to study its interaction with biological membranes and proteins if its spin-labeled analogs were synthesized. Here, a simple sequence of ibuprofen transformations—nitration, esterification, reduction, Sandmeyer reaction, Sonogashira cross-coupling, oxidation and saponification—was developed to attain this goal. The synthesis resulted in spin-labeled ibuprofen (ibuprofen-SL) in which the spin label TEMPOL is attached to the benzene ring. EPR spectra confirmed interaction of ibuprofen-SL with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers. Using 2H electron spin echo envelope modulation (ESEEM) spectroscopy, ibuprofen-SL was found to be embedded into the hydrophobic bilayer interior. 相似文献
933.
934.
Masoud Farhadi‐Khouzani Daniel M. Chevrier Prof. Dr. Peng Zhang Prof. Dr. Niklas Hedin Dr. Denis Gebauer 《Angewandte Chemie (International ed. in English)》2016,55(28):8117-8120
Temperature and pH value can affect the short‐range order of proto‐structured and additive‐free amorphous calcium carbonates (ACCs). Whereas a distinct change occurs in proto‐vaterite (pv) ACC above 45 °C at pH 9.80, proto‐calcite (pc) ACC (pH 8.75) is unaffected within the investigated range of temperatures (7–65 °C). IR and NMR spectroscopic studies together with EXAFS analysis showed that the temperature‐induced change is related to the formation of proto‐aragonite (pa) ACC. The data strongly suggest that the binding of water molecules induces dipole moments across the carbonate ions in pa‐ACC as in aragonite, where the dipole moments are due to the symmetry of the crystal structure. Altogether, a (pseudo‐)phase diagram of the CaCO3 polyamorphism in which water plays a key role can be formulated based on variables of state, such as the temperature, and solution parameters, such as the pH value. 相似文献
935.
A macroscopic nonlocal theory of sound propagation in homogeneous rigid-framed porous media permeated with a viscothermal fluid has been recently proposed in this journal. It accounts for the first time for the full temporal and spatial dispersion effects, independently of the nature of the microgeometry. In this paper this new Maxwellian theory is validated in the case of sound propagation in cylindrical circular tubes, by showing that it matches exactly the long-known direct Kirchhoff–Langevin’s solutions. 相似文献
936.
Rychkov Vladimir N. Semenishchev Vladimir S. Kirillov Evgeny V. Kirillov Sergey V. Ryabukhina Viktoria G. Smyshlyaev Denis V. Bunkov Grigory M. Botalov Maxim S. 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(1):203-213
Journal of Radioanalytical and Nuclear Chemistry - The paper deals with two rare earth elements (REE) concentrates recovered from uranium leach liquors after sorption separation of uranium.... 相似文献
937.
Some interesting variants of walking droplet based discrete dynamical bifurcations arising from diffeomorphisms are analyzed in detail. A notable feature of these new bifurcations is that, like Smale horseshoes, they can be represented by simple geometric paradigms, which markedly simplify their analysis. The two-dimensional diffeomorphisms that produce these bifurcations are called sigma maps or double sigma maps for reasons that are made manifest in this investigation. Several examples are presented along with their dynamical simulations. 相似文献
938.
939.
Denis Ivnitski Moran Amit Ohad Silberbush Yoav Atsmon‐Raz Jayanta Nanda Rivka Cohen‐Luria Yifat Miller Gonen Ashkenasy Nurit Ashkenasy 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(34):10142-10146
Peptide fibril nanostructures have been advocated as components of future biotechnology and nanotechnology devices. However, the ability to exploit the fibril functionality for applications, such as catalysis or electron transfer, depends on the formation of well‐defined architectures. Fibrils made of peptides substituted with aromatic groups are described presenting efficient electron delocalization. Peptide self‐assembly under various conditions produced polymorphic fibril products presenting distinctly different conductivities. This process is driven by a collective set of hydrogen bonding, electrostatic, and π‐stacking interactions, and as a result it can be directed towards formation of a distinct polymorph by using the medium to enhance specific interactions rather than the others. This method facilitates the detailed characterization of different polymorphs, and allows specific conditions to be established that lead to the polymorph with the highest conductivity. 相似文献
940.