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1.
Greenhouse gases emitted into the atmosphere by burning of fossil fuels cause global warming. One option is obtaining biodiesel. Nannochloropsis oculata was cultured under different light intensities and reactors at 25°C for 21 days with f/2 medium to assess their effects on cell density, lipid, and fatty acids (FAs). N. oculata improved cell density on fed-batch glass tubular reactor (7 L) at 200 μmol E m−2 s−1, yielding 3.5 × 108 cells ml−1, followed by fed-batch Erlenmeyer flask (1 L) at 650 μmol E m−2 s−1 with 1.7 × 108 cells ml−1. The highest total lipid contents (% g lipid × g dry biomass−1) were 44.4 ± 0.8% for the reactor (1 L) at 650 μmol E m−2 s−1 and 35.2 ± 0.2% for the tubular reactor (7 L) at 200 μmol E m−2 s−1, until twice as high compared with the control culture (Erlenmeyer flask 1 L, 80 μmol E m−2 s−1) with 21.2 ± 1%. Comparing the total lipid content at 200 μmol E m−2 s−1, tubular reactor (7 L) and reactor 1 L achieved 35.2 ± 0.2% and 28.3 ± 1%, respectively, indicating the effect of shape reactor. The FAs were affected by high light intensity, decreasing SFAs to 2.5%, and increased monounsaturated fatty acids + polyunsaturated fatty acids to 2.5%. PUFAs (20:5n-3) and (20:4n-3) were affected by reactor shape, decreasing by half in the tubular reactor. In the best culture, fed-batch tubular reactor (7 L) at 200 μmol E m−2 s−1 contains major FAs (16:0; 38.06 ± 0.16%), (16:1n-7; 30.74 ± 0.58%), and (18:1n-9; 17.15 ± 0.91%).  相似文献   
2.
Volume of fluid (VOF) method with its Piecewise Linear Interface Calculation (PLIC) reconstruction algorithm is one of the most popular approaches in numerical simulation of interfacial flows with a wide range of applications in different areas. In an effort to evaluate the similarity of the PLIC-generated planes in comparison with the exact interface, a point-cloud, based on the polygon centers of PLIC planes is extracted, which later is used to form a triangular grid that represents the estimated interface. The main objective of this article is to evaluate the interface geometrical properties based on the extracted triangular grid of the interface. The methods presented in this article, characterized by a higher spatially convergence ratio, are compared with the commonly used methods. The proposed methods are tested for two 3-dimensional general test cases, where an evident improvement is seen in calculation accuracy and spatial convergence of the errors of interface normal vector and curvature.  相似文献   
3.

Probabilistic topic modeling algorithms like Latent Dirichlet Allocation (LDA) have become powerful tools for the analysis of large collections of documents (such as papers, projects, or funding applications) in science, technology an innovation (STI) policy design and monitoring. However, selecting an appropriate and stable topic model for a specific application (by adjusting the hyperparameters of the algorithm) is not a trivial problem. Common validation metrics like coherence or perplexity, which are focused on the quality of topics, are not a good fit in applications where the quality of the document similarity relations inferred from the topic model is especially relevant. Relying on graph analysis techniques, the aim of our work is to state a new methodology for the selection of hyperparameters which is specifically oriented to optimize the similarity metrics emanating from the topic model. In order to do this, we propose two graph metrics: the first measures the variability of the similarity graphs that result from different runs of the algorithm for a fixed value of the hyperparameters, while the second metric measures the alignment between the graph derived from the LDA model and another obtained using metadata available for the corresponding corpus. Through experiments on various corpora related to STI, it is shown that the proposed metrics provide relevant indicators to select the number of topics and build persistent topic models that are consistent with the metadata. Their use, which can be extended to other topic models beyond LDA, could facilitate the systematic adoption of this kind of techniques in STI policy analysis and design.

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Journal of Materials Science: Materials in Electronics - In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from...  相似文献   
6.
We report the effects of the Sr2+ and Ni2+ co-doping of BiFeO3 on the crystal structure and multiferroic properties of Bi1?xSrxFe1-yNiyO3 (x?=?0.05, 0.0?≤?y?≤?0.10, and Δy?=?0.05) that is synthesized using assisted high-energy ball milling. The mixtures of Bi2O3, Fe2O3, SrO and NiO were milled for 5?h, pressed at 900?MPa, and sintered at 800?°C in order to obtain cylindrical test pieces. X-ray diffraction and Rietveld refinement elucidated the effects of Sr2+ and Ni2+ on the crystal structure. Co-doping with SrNi in suitable proportions stabilizes rhombohedral BiFeO3. High contents of Ni2+ promote the precipitation of secondary phases in the forms of NiFe2O4 and Bi25FeO40. The magnetic behavior was examined by means of vibrating sample magnetometry. The results showed a change in the magnetic order from antiferromagnetic for the undoped sample to the ferromagnetic order for the co-doped samples. This change is attributed to the modulations in the magnetic moment due to crystal structure distortions. All samples show high relative permittivity values, which were enhanced by doping with Sr2+. Ni2+ cations increase the dielectric dissipation factor; this enhancement is related to their interactions with cations of a different oxidation state, such as Fe3+, Fe2+, Ni2+, Bi3+ and Sr2+ in the crystal structure of BiFeO3. The magnetoelectric coupling that was evaluated using magnetodielectric measurements was above 4% at 1?kHz for the higher applied magnetic field of 18?kOe.  相似文献   
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Heterocyclic compounds are well known for their biological activity and coordination properties. Some heterocyclic compounds have been employed in the stabilization against coalescence of metallic nanoparticles in colloidal solutions, for example, tetrazole, triazole, and pyrazole. The aim of this work is to design new polyelectrolytes with heterocyclic pendant groups useful as reducing agents of Au3+ and as stabilizing agents for the synthesis of colloidal Au nanoparticles. Thus, polyelectrolytes with thiosemicarbazone and 1,3,4-thiadiazole pendant groups were used as reducing agents of Au3+ ions and stabilizing agents of Au nanoparticles. The voltammetry study of the polyelectrolytes showed that one with thiosemicarbazone pendant groups is the better reducing agent than polyelectrolytes with heterocyclic pendant groups. The polyelectrolytes can control the growth of the nanoparticles, obtaining structures with an average size of 9 nm. In this study, it was concluded that the nature of the heterocyclic group does not have an effect on the shape of nanoparticles and quasi-spherical nanoparticles were obtained with all polyelectrolytes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47790.  相似文献   
9.
Pure and Mn-doped lithium tantalate nanofibers, with Mn concentrations of 1%, 2.5%, and 5%, were synthesized by the electrospinning method. The morphology, microstructure, and crystal structure of as-spun and annealed composite nanofibers were characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Raman spectroscopy has shown to be a powerful tool to detect either local variations or changes of the whole structure. Position and width of one Raman line can be used as markers of a structural change. Some vibrational modes are especially associated with the site of Li or Ta ions and so, they can be affected by the introduction of dopant ions. Any damages or local changes in the microstructure can be detected by a line broadening. With the use of Raman spectroscopy, the sites where Mn ions enter the doped structures were established by recording the shift and broadening of peaks in Mn-doped structures with respect to pure lithium tantalate. Thus it was proven that Mn ions enter the Li sites for low Mn concentration and, on the other hand, for higher concentrations, the dopant substitutes Li and Ta sites. First-principles calculations were performed within the density functional theory, including lattice-dynamic calculations of the phonon modes at the zone center (Γ point), for the pure structure, to find the irreducible representation of the modes.  相似文献   
10.
A series of symmetrical dialkyl methanesulfonate amphiphiles [DiC n CHSO 3 ] m M (n = 6, 7, 8) with different counter cations (Mm+ = H+, Li+, Na+, K+, Cu2+, Zn2+, Mg2+, Ca2+, Sc3+) were synthesized in five steps. Their solubility and critical micelle concentration (CMC) in water were determined highlighting a huge effect of the chain length and the nature of the cation. The hydrophilic–lipophilic balance of the surfactants were assessed with the phase inversion temperature (PIT)-slope method based on the deviation from the PIT of the reference C10E4/n-octane/0.01 M NaCl(aq) emulsion through addition of increasing amounts of the dialkyl methanesulfonates. The hydrophilicity of the surfactants was thus ranked in terms of dPIT/dxsulfonate. A “cation” scan with the [DiC 6 CHSO 3 ] m M /benzene/water systems at fw = 0.5 was finally performed confirming the hydrophilicity ranking obtained with the PIT-slope method. It revealed that the [DiC 6 CHSO 3 ] 2 Mg behaves as a “Balanced Surfactant” able to form spontaneously a three-phase microemulsion system (Winsor III) just in the presence of water and oil, in the same way as the catalytic surfactant dimethyldioctylammonium molybdate, which has the same PIT-slope.  相似文献   
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