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1.
Carotenoids are an essential component of cashew and can be used in pharmaceuticals, cosmetics, natural pigment, food additives, among other applications. The present work focuses on optimizing and comparing conventional and ultrasound-assisted extraction methods. Every optimization step took place with a 1:1 (w:w) mixture of yellow and red cashew apples lyophilized and ground in a cryogenic mill. A Simplex-centroid design was applied for both methods, and the solvents acetone, methanol, ethanol, and petroleum ether were evaluated. After choosing the extractor solvent, a central composite design was applied to optimize the sample mass (59–201 mg) and extraction time (6–34 min). The optimum conditions for the extractor solvent were 38% acetone, 30% ethanol, and 32% petroleum ether for CE and a mixture of 44% acetone and 56% methanol for UAE. The best experimental conditions for UAE were a sonication time of 19 min and a sample mass of 153 mg, while the CE was 23 min and 136 mg. Comparing red and yellow cashews, red cashews showed a higher carotenoid content in both methodologies. The UAE methodology was ca. 21% faster, presented a more straightforward composition of extracting solution, showed an average yield of superior carotenoid content in all samples compared to CE. Therefore, UAE has demonstrated a simple, efficient, fast, low-cost adjustment methodology and a reliable alternative for other applications involving these bioactive compounds in the studied or similar matrix. 相似文献
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ABSTRACT In this paper, the radiation shielding parameters such as linear attenuation coefficients (LAC, µ), mass attenuation coefficients (MAC, µ/ρ), effective atomic numbers (Zeff), effective electron densities (Neff), half value of layers (HVL), mean free paths (MFP) and buildup factors (exposure (EBF) and energy absorption (EABF)) were investigated for cream (M1), pink (M2), white (M3), maroon (M4) and green (M5) marbles. Attenuation coefficients were measured in the energy region 31.18–661.66 keV photon energies. The values of Zeff and Neff were then calculated using these coefficients with logarithmic interpolation method, and HVLs and MFPs were calculated using the values of LAC of marble samples at the same photon energies. The experimental results were compared with the theoretical values obtained from WinXCom program, and good agreements were observed between the experimental and theoretical results. HVLs and MFPs of all marble samples were compared with those of some concretes, glasses and commercial radiation shielding glasses (SCHOTT Co.). The studied marbles were better radiation shielding materials than standard shielding concretes due to lower HVL and MFP values lower than the ordinary concrete. Finally, EBFs and EABFs of the marbles were calculated in the energy region 0.015–1?MeV up to penetration depths of 40 mfps by Geometric Progression method (G-P), and the results were discussed in terms of photon energies and chemical compositions of the marbles. 相似文献
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Nicolas Pauly 《Surface and interface analysis : SIA》2023,55(1):52-62
We calculated a local inverse inelastic mean free path (local-IIMFP) for electrons crossing a medium–medium interface, considering various incident electron energies, crossing angles and combinations of materials. We used an extension of a classical dielectric model developed by Li and co-workers for an electron crossing a surface (interface vacuum-medium). Moreover, the integration over the distance of the local-IIMFP allows to obtain the interface excitation parameter (or IEP) characterizing the change in excitation probability for an electron crossing an interface once caused by the presence of the interface in comparison with an electron for which only volume excitations are considered. We perform these calculations for angles between 0° and 80°, for electron energies between 500 and 2500 eV and for various pairs of materials, as Al/In for its academic interest or Au/Si and SiO2/Si for their technological importance. Small but not negligible variations of the local-IIMFP and the IEP were observed for metal–metal or metal–semiconductor interfaces, while quite significant variations are obtained when one of the materials is a insulator. 相似文献
5.
Development of models for prediction of the antioxidant activity of derivatives of natural compounds
Antioxidants are important for maintaining the appropriate balance between oxidizing and reducing species in the body and thus preventing oxidative stress. Many natural compounds are being screened for their possible antioxidant activity. It was found that a mushroom pigment Norbadione A, which is a pulvinic acid derivative, shows an antioxidant activity; the same was found for other pulvinic acid derivatives and structurally related coumarines. Based on the results of in vitro studies performed on these compounds as a part of this study quantitative structure–activity relationship (QSAR) predictive models were constructed using multiple linear regression, counter-propagation artificial neural networks and support vector regression (SVR). The models have been developed in accordance with current QSAR guidelines, including the assessment of the models applicability domains. A new approach for the graphical evaluation of the applicability domain for SVR models is suggested. The developed models show sufficient predictive abilities for the screening of virtual libraries for new potential antioxidants. 相似文献
6.
Qiang Yu Xiangjun Li Diansheng Liu Jianfeng Li 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):545-548
`Picket‐fence' porphyrin compounds are used in the investigation of interactions of hemes with dioxygen, carbon monoxide, nitric monoxide and imidazole ligands. (Cryptand‐222)potassium chlorido[meso‐tetra(α,α,α,α‐o‐pivalamidophenyl)porphyrinato]manganese tetrahydrofuran monosolvate (cryptand‐222 is 4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane), [K(C18H36N2O6)][Mn(C64H64N8O4)Cl]·C4H8O or [K(222)][Mn(TpivPP)Cl]·THF [systematic name for TpivPP: 5,10,15,20‐tetrakis(2‐tert‐butanamidophenyl)porphyrin], is a five‐coordinate high‐spin manganese(II) picket‐fence porphyrin complex. It crystallizes with a potassium cation chelated inside a cryptand‐222 molecule; the average K—O and K—N distances are 2.83 (4) and 2.995 (13) Å, respectively. All four protecting tert‐butyl pickets of the porphyrin are ordered. The porphyrin plane is nearly planar, as indicated by the atomic displacements and the dihedral angles between the mean planes of the pyrrole rings and the 24‐atom mean plane. The axial chloride ligand is located inside the molecular cavity on the hindered porphyrin side and the Mn—Cl bond is tilted slightly off the normal to the porphyrin plane by 3.68 (2)°. The out‐of‐plane displacement of the metal centre relative to the 24‐atom mean plane (Δ24) is 0.7013 (4) Å, indicating a noticeable porphyrin core doming. 相似文献
7.
Rafał Ślusarz Justyna Samaszko-Fiertek Barbara Dmochowska Janusz Madaj 《Journal of carbohydrate chemistry》2017,36(1):45-58
Computational investigations were performed to examine the effects of the addition of 2-acetamido-2-deoxy-β-D-galactopyranosylamine or 1-amino-1-deoxy-D-glucitol connected to the C-terminus of vancomycin with different linkers. The purpose of this modification was to find more effective vancomycin derivatives by providing alternative interactions between vancomycin moiety and the peptidoglycan precursor. Each prepared vancomycin–peptidoglycan complex was optimized and submitted to the molecular dynamics study and analysis. The analysis of overall root mean square deviation, changes in position and interactions involving modified part of vancomycin as well as cluster analysis were carried out. One of the proposed vancomycin analogues seems to be efficient vancomycin substitute. 相似文献
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In this paper, we prove that several different definitions of the Finsler-Laplacian are equivalent. Then we prove that any Berwald metric is affinely equivalent to its mean metric and give some upper or lower bound estimates for the first eigenvalue of the mean Laplacian on Berwald manifolds, which generalize some results in Riemannian geometry. 相似文献