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991.
以硝酸镍、硼酸和柠檬酸为原料,采用溶胶凝胶法于150 ℃形成咖啡色干凝胶,再于750 ℃焙烧得到硼酸镍纳米棒。采用XRD、SEM、TEM和FTIR对产物结构和形貌进行表征。结果表明产物为分布均匀的Ni3(BO3)2纳米棒,纳米棒的长度受硝酸镍和硼酸的物质的量之比影响,硼酸用量越大,长度越大。当nNi3(BO3)2∶nN3BO3=1∶3时,纳米棒直径为200~300 nm,长度为2~3 μm。对硼酸镍纳米棒的生长机理进行了探讨, 结果表明, 柠檬酸与镍离子反应产生网状结构的配合物,促使镍源均匀地分散在网格间,为硼酸镍纳米棒的生成提供有利的反应空间。 相似文献
992.
Dr. Pei‐Pei Yang 《无机化学与普通化学杂志》2011,637(9):1234-1237
A homometallic lanthanide tetranuclear cluster, namely [Yb4(pdmH)2(pdm)4 (PhCO2)2(PhCO2H)2(H2O)2] · PhCO2H · 0.25MeOH ( 1 ) (pdmH2 = pyridine‐2,6‐dimethanol) was prepared and structurally characterized. Single‐crystal X‐ray analysis revealed that complex 1 has a tetranuclear core with a zigzag arrangement. Magnetic properties of complex 1 were also investigated. 相似文献
993.
994.
The aim of this paper is to apply a perturbation approach to deal with Fenchel- Lagrange duality based on weak efficiency to a constrained vector optimization problem. Under the stability criterion, some relationships between the solutions of primal problem and the Fenchel-Lagrange duality are discussed. Moreover, under the same condition, two saddle-points theorems are proved. 相似文献
995.
In fully three-dimensional (3D) positron emission tomography (PET) imaging, the scatter fraction (SF) is about 40%-60%, which may degrade the imaging quality severely. Scatter correction is important for high quality image reconstruction. Model-based scatter correction has been proved to be accurate and available in clinical PET. However, it does not correct the scatter from out of the field of view (OFOV) and multiple scatters. In this study, we demonstrate the radial and axial distribution of scatters from OFOV when the source is located in different radial positions. In order to apply the above conclusions to different PET systems, we characterize the scatters from OFOV as a function of the ratio of the scanner diameter to the length of the axial field of view (AFOV) by modeling several typical whole-body and micro PET systems. The proportions of true events (S0-0), single scatter of one photon (S1-0) , single scatter of both photons (S1-1) , double scatter of one photon (S2-0) and multiple scatter (Sm) are also calculated and compared. Here the 3D-PET Monte Carlo simulations are performed with the Geant4 Application for Tomography Emission (GATE). In summary, the scatters from OFOV tend to be recorded on the lines of response (LOR) far away from the source. They have a much more serious impact on whole-body PET than micro PET depending on the ratio of scanner diameter to the length of AFOV. In whole-body PET, twice scatters including single scatter of both photons (S1-1) and double scatter of one photon (S2-0) add up to about 12% so that twice scatter correction must be taken into account to acquire a high quality reconstruction image. 相似文献
996.
Natural zeolite supported Fe3+-TiO2 photocatalysts were synthesized for the sake of improving the recovery and photocatalytic efficiency of TiO2. The as-prepared materials were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). Methyl orange was used to estimate the photocatalytic activity of the samples. The results showed that zeolite inhibited the growth of TiO2 crystallite sizes. The Fe3+ concentration played an important role on the microstructure and photocatalytic activity of the samples. The iron ions could diffuse into TiO2 lattice to the form Fe-O-Ti bond and gave TiO2 the capacity to absorb light at lower energy levels. The photocatalytic activity of the samples could be enhanced as appropriate dosages of Fe3+ were doped. 相似文献
997.
a-axis- and c-axis-oriented YBa2Cu3O7−δ (YBCO) films were epitaxially grown on (1 0 0) LaAlO3 substrates by laser chemical vapor deposition. The preferred orientation in the YBCO film changed from the a-axis to the c-axis with increasing laser powers from 77 to 158 W (the deposition temperatures from 951 to 1087 K). The a-axis-oriented YBCO film showed in-plane epitaxial growth of YBCO [0 0 1]//LAO [0 0 1], and the c-axis-oriented YBCO film showed that of YBCO [0 1 0]//LAO [0 0 1]. A c-axis-oriented YBCO film with a high critical temperature of 90 K was prepared at a deposition rate of 90 μm h−1, about 2-1000 times higher than that of metalorganic chemical vapor deposition. 相似文献
998.
999.
1000.
We theoretically study the plasmon mode spectrum of a multilayer structure consisting of a periodic gold nanowire array and
a spatially separated thin silver film with periodic slits. Results show that the plasmon mode spectrum of the multilayer
structure depends sensitively on the relative lateral displacement of the Au nanowire array with respect to the textured silver
film. This is due to the interaction between the localized surface plasmon (LSP) of the nanowire array and the plasmon modes,
including the horizontal LSP and the antisymmetric short-range surface plasmon polariton (SPP), of the textured thin silver
film. The strong coupling between the LSP and the antisymmetric short-range SPP results in a redshifted plasmon resonance
with a significantly narrow linewidth and a large electromagnetic field enhancement. Moreover, the lateral displacement also
has a great influence on the spacer layer controlled dipole-surface interaction. Therefore, this relative lateral displacement
provides an efficient way to tune the optical properties of the multilayer structure, and this kind of highly tunable nanostructure
can be used as a tunable plasmonic filter or a substrate for LSPs sensor. 相似文献