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981.
Multifunctionalized tetrahydroindan derivatives with four stereocenters were constructed via two sequential Michael reactions between cyclic γ,δ-unsaturated-β-ketoester and nitroalkenes initiated with 0.5-2 mol % of cinchona alkaloid based bifunctional organocatalysts and then with 1 equiv of tetramethylguanidine for cyclization. The desired products could be obtained in high yields (up to 99% yield) with excellent enantioselectivities (95-99% ee) as well as diastereoselectivities (up to >99:1 dr) even on a gram scale. 相似文献
982.
New mesoporous organic?Cinorganic spheres were prepared by one step co-condensation of trialkoxysilylated camphorsulfonamide (CSA) and 1,2-bis(triethoxysilyl)ethane (BTSE) using octadecyltrimethylammonium chloride (C18TMACl) as template and ethanol as co-solvent in basic medium. The materials have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), nitrogen sorption measurement, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and elemental analysis (EA). Then the mesoporous organic?Cinorganic spheres were demonstrated to be novel packing materials for potential application in the normal-phase high performance liquid chromatography (HPLC). 相似文献
983.
First-principles studies on the efficient photoluminescent iridium(III) complexes with C^N═N ligands
The electronic structures and photophysical properties of several homoleptic iridium complexes IrL(3) with C^N═N ligands, including 1 (L = 3,6-diphenylpyridazine), 2 (L = 1,4-diphenylphthalazine), 3 (L = 3-phenyl-5H-indeno[1,2-c]pyridazine), and 4 (L = 3-phenylbenzo[h]cinnoline), are investigated using the density functional method. The comparison between the calculated results of the four complexes shows that the assumed complex 4 may possess higher photoluminescent quantum efficiency than complexes 1-3 and is the potential candidate to be an efficient green-emitting material. The photophysical properties of the assumed complex 3 can be comparable to that of experimentally found complex 1. For 1 and 3, the emission energies are nearly the same, consistent with their similar HOMO-LUMO energy gaps. Their emission characters are also similar and mainly dominated by one ligand. For 4 and the experimentally found complex 2, although they have similar HOMO-LUMO energy gaps, and their luminescent nature is nearly the same and dominated by the three ligands, the emission spectrum of 4 is blue-shifted as compared to that of 2. 相似文献
984.
Ab initio quantum mechanical/molecular mechanical method is combined with the polarized protein-specific charge to study the chemical reactions catalyzed by protein enzymes. Significant improvement in the accuracy and efficiency of free-energy simulation is demonstrated by calculating the free-energy profile of the primary proton transfer reaction in triosephosphate isomerase. Quantitative agreement with experimental results is achieved. Our simulation results indicate that electronic polarization makes important contribution to enzyme catalysis by lowering the energy barrier by as much as 3 kcal/mol. 相似文献
985.
We extended our previous calculation of the quantum rate dynamics for a model system of proton transfer (PT) reaction using the Liouville space hierarchical equations of motion method in this study. A rate promoting vibrational (RPV) mode that symmetrically coupled to the proton coordinate was included in the quantum dynamics calculations, in order to study the effect of enhanced tunneling by the proton donor-acceptor motion. Adding the RPV mode is observed to increase the PT rate and reduce the kinetic isotope effects. We also found that the PT dynamics is influenced by the dissipation of the RPV mode. Besides this extension, in the case without the RPV, we investigated whether the PT rate dynamics in the deep tunneling regime can reduce to an effective two-state spin-boson type of model and found that this is only possible at low reorganization energies. 相似文献
986.
Wang W Lian X Chen D Liu X Lin L Feng X 《Chemical communications (Cambridge, England)》2011,47(27):7821-7823
An efficient yttrium(III)-catalyzed highly enantioselective Friedel-Crafts alkylation of β-trichloro(trifluoro)methyl aryl enones is described. The reaction delivered a series of functionalized indoles with a chiral tertiary carbon center bearing a trichloro(trifluoro)methyl group in excellent results (up to 96% ee and 99% yield) under mild conditions. 相似文献
987.
Li Z Zhu H Xie D Wang K Cao A Wei J Li X Fan L Wu D 《Chemical communications (Cambridge, England)》2011,47(12):3520-3522
We report a fast (in 10-40 s) flame synthesis of high quality few-layered graphene/graphite films, offering the advantages of simplicity, high efficiency, energy saving, low cost and the ability to extend to continuous and mass production of graphene. 相似文献
988.
989.
The small scales associated with lab-on-a-chip technologies lend themselves well to capillarity-dominated phenomena. We demonstrate a new capillarity-dominated system where two adjoining ferrofluid droplets can behave as an electronically-controlled oscillator or switch by an appropriate balance of magnetic, capillary, and inertial forces. Their oscillatory motion can be exploited to displace a surrounding liquid (akin to an axial piston pump), forming electromagnetic "liquid pistons." Such ferrofluid pistons can pump a precise volume of liquid via finely tunable amplitudes (cf. pump stroke) or resonant frequencies (cf. pump speed) with no solid moving parts for long-term operation without wear in a small device. Furthermore, the rapid propagation of electromagnetic fields and the favorable scaling of capillary forces with size permit micron sized devices with very fast operating speeds (~kHz). The pumping dynamics and performance of these liquid pistons is explored, with experimental measurements showing good agreement with a spherical cap model. While these liquid pistons may find numerous applications in micro- and mesoscale fluidic devices (e.g., remotely activated drug delivery), here we demonstrate the use of these liquid pistons in capillarity-dominated systems for chip-level, fast-acting adaptive liquid lenses with nearly perfect spherical interfaces. 相似文献
990.