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961.
Ramesh C. Sharma 《Optics Communications》2009,282(6):1183-1388
We present the experimental demonstration of a novel, efficient, and vibrational selective technique to prepare population in vibrational level v″ = 1 using the stimulated Raman pumping. Photoacoustic Raman signal has been studied in non-radiative transitions in the molecule H2 (v″ = 0) and (v″ = 1). The population fraction in the v″ = 1 level can be estimated by using combined photoacoustic Raman spectroscopy with stimulated Raman pumping for the first time. 相似文献
962.
963.
Carbon coatings were deposited by atmospheric plasma jet. Influence of the distance between the exit of the plasma gun and a substrate (consequently temperature of the substrate) on properties of the coatings was investigated. The coatings deposited near to the exit of the plasma gun are porous with columnar structure, moderate hardness (∼10 GPa), and the lowest hydrogen (∼7 at.%) concentration. The coatings deposited at the larger standoff distance (>5 mm) have higher hydrogen (≤25 at.%) content and graphite-like structure. Most of the hydrogen in all coatings is bonded to the sp3 carbon (70-60 at.%) and predominantly forms methylene compounds. Decrease of standoff distance yields lower concentration of sp3 CH3 compounds and relative increase of amount of hydrogenated sp2 rings. 相似文献
964.
Taksu Cheon 《Physics letters. A》2010,374(45):4585-4588
We show that it is possible to define shape-independent three-dimensional short-range quantum interactions in two-parameter form for non-spherical angular momentum channels through double rescaling of potential strength. Unlike the special case of l=0, where the zero-range limit of the system is renormalizable, the effective ranges diverge for l≠0 channels, and the system becomes trivial at zero-size limit. It is also shown that the two-parameter representation with finite interaction range is useful in analyzing phase shifts and describing resonances with accuracy in non-spherical scatterings. 相似文献
965.
966.
Clément Falaise Dr. May Nyman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14678-14687
For 11 years now, the structural diversity and aesthetic beauty of uranyl–peroxide capsules have fascinated researchers from the diverse fields of mineralogy, polyoxometalate chemistry, and nuclear fuel technologies. There is still much to be learned about the mechanisms of the self‐assembly process, and the role of solution parameters including pH, alkali template, temperature, time, and others. Here we have exploited the high solubility of the UO22+/H2O2/LiOH aqueous system to address the effect of the hydroxide concentration. Important techniques of this study are single‐crystal X‐ray diffraction, small‐angle X‐ray scattering, and Raman spectroscopy. Three key phases dominate the solution speciation as a function of time and the LiOH/UO22+ ratio: the uranyl–triperoxide monomer [UO2(O2)3]4?and the two capsules [(UO2)(O2)(OH)]2424?(U24) and [(UO2)(O2)1.5]2828?(U28). When the LiOH/U ratio is around three, U28 forms rapidly and this cluster can be isolated in high yield and purity. This result was most surprising and challenges the hypothesis that alkali templating is the most important determinant in the cluster geometry. Moreover, analogous experiments with KOH, NH4OH, and TEAOH (TEA=tetraethylammonium) also rapidly yield U28, which suggests that U28 is the kinetically favored species. Complete mapping of the pH–time phase space reveals only a narrow window of the U28 dominance, which is why it was previously overlooked as an important kinetic species in this chemical system, as well as others with different counterions. 相似文献
967.
Consider the problem of scattering of electromagnetic waves by a doubly periodic Lipschitz structure. The medium above the structure is assumed to be homogenous and lossless with a positive dielectric coefficient. Below the structure there is a perfect conductor with a partially coated dielectric boundary. We first establish the well‐posedness of the direct problem in a proper function space and then obtain a uniqueness result for the inverse problem by extending Isakov's method. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
968.
Surface-enhanced Raman scattering active substrates were prepared by the chemical assembly of Co, Ni and Ag nanoparticles on 3-aminopropyltriethoxysilane-functionalized Al surface. Poly(2-vinylpyridine) films were also deposited on the Al substrates by electrochemical polymerization in aqueous solution. Raman intensities were measured with respect to pyridine. Although silver has very desirable physical properties, good relative abundance, and low cost, gold nanoparticles have been widely favored because of their proved stability and ease of use. Unlike gold, silver is notorious for its susceptibility to oxidation (tarnishing), which has limited the development of important silver-based nanomaterials. However, the substrates with poly(2-vinylpyridine) films were exceptionally stable as they produced spectra that did not change even after much more than one year. 相似文献
969.
The Raman and the infrared wavenumbers in the Aurivillius structure BaBi2Ta2O9 (BBT) having space group I4/mmm (no. 139-D4h17) are investigated using normal coordinate analysis. The calculation of zone center phonons incorporates seven stretching and seven bending force constants. The Raman and the infrared frequencies for BBT have been assigned for the first time in I4/mmm phase. The calculated Raman and infrared wavenumbers are in very good agreement with the observed ones. The potential energy distributions (PED) are also investigated for each normal mode in BBT and the contributions of different force constants to various frequencies are determined. 相似文献
970.
An analytic expression of the two-frequency mutual coherence function (MCF) was derived for a two-dimensional random rough
surface. The scattered field was calculated by the Kirchhoff approximation, which is valid in the case that the radius of
curvature of the surface is much larger than the incident wave length. The scattering problem of narrowband pulse was investigated
to simplify the analytic expression of the two-frequency MCF. Numerical simulations show that the two-frequency MCF is greatly
dependent on the root-mean-square (RMS) height, while less dependent on the correlation length. The analytic solutions were
compared with the results of Monte Carlo simulation to assess the accuracy and computational efficiency.
Supported by the National Natural Science Foundation of China (Grant No. 60571058) and the National Defense Foundation of
China (Grant No. 51403020505DZ0111) 相似文献