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41.
This work concentrates on the structural optimization of a class of non-linear systems with deterministic structural parameters subject to stochastic excitation. The optimization problem is formulated as the minimization of an objective function subject to constraints on the response level. The stochastic response is characterized by its first two statistical moments, which are computed by a statistical equivalent linearization technique. The implicit structural optimization problem is replaced by a sequence of explicit sub-optimization problems. The sub-problems are constructed by using a conservative first-order approximation of the objective and constraint functions. The applicability of the proposed design process is demonstrated in three numerical examples where the methodology is applied to systems with nonlinearity of hardening and hysteretic type. The effects of the nonlinearity on the general performance of the final designs are discussed. At the same time, some engineering implications of the results obtained in this work are addressed. 相似文献
42.
Intrinsically Zirconium‐89 Labeled Gd2O2S:Eu Nanoprobes for In Vivo Positron Emission Tomography and Gamma‐Ray‐Induced Radioluminescence Imaging 下载免费PDF全文
43.
Facile Preparation of Multifunctional WS2/WOx Nanodots for Chelator‐Free 89Zr‐Labeling and In Vivo PET Imaging 下载免费PDF全文
Liang Cheng Anyanee Kamkaew Sida Shen Hector F. Valdovinos Haiyan Sun Reinier Hernandez Shreya Goel Teng Liu Cyrus R. Thompson Todd E. Barnhart Zhuang Liu Weibo Cai 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(41):5750-5758
While position emission tomography (PET) is an important molecular imaging technique for both preclinical research and clinical disease diagnosis/prognosis, chelator‐free radiolabeling has emerged as a promising alternative approach to label biomolecules or nanoprobes in a facile way. Herein, starting from bottom‐up synthesized WS2 nanoflakes, this study fabricates a unique type of WS2/WOx nanodots, which can function as inherent hard oxygen donor for stable radiolabeling with Zirconium‐89 isotope (89Zr). Upon simply mixing, 89Zr can be anchored on the surface of polyethylene glycol (PEG) modified WS2/WOx (WS2/WOx‐PEG) nanodots via a chelator‐free method with surprisingly high labeling yield and great stability. A higher degree of oxidation in the WS2/WOx‐PEG sample (WS2/WOx (0.4)) produces more electron pairs, which would be beneficial for chelator‐free labeling of 89Zr with higher yields, suggesting the importance of surface chemistry and particle composition to the efficiency of chelator‐free radiolabeling. Such 89Zr‐WS2/WOx (0.4)‐PEG nanodots are found to be an excellent PET contrast agent for in vivo imaging of tumors upon intravenous administration, or mapping of draining lymph nodes after local injection. 相似文献
44.
Hector M. Henao Colin Nexhip David P. George-Kennedy P.C. Hayes E. Jak 《Metallurgical and Materials Transactions B》2010,41(4):767-779
Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all
are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational
temperature. Optimal control of the slag chemistry in the copper smelting, therefore, is essential for high recovery and productivity;
this, in turn, requires detailed knowledge of the slag phase equilibria. The present work provides new phase equilibrium experimental
data in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 system at oxygen partial pressure of 10−8 atm within the range of temperatures and compositions directly relevant to copper smelting. For the range of conditions relevant
to the Kennecott Utah Copper (South Magna, UT) smelting furnace, it was confirmed experimentally that increasing concentrations
of MgO or CaO resulted in significant decreases of the tridymite liquidus temperature and in changes in the position of the
tridymite liquidus in the direction of higher silica concentration; in contrast, the spinel liquidus temperatures increase
significantly with the increase of MgO or CaO. Olivine and clinopyroxene precipitates appeared at high MgO concentrations
in the liquid slag. The liquidus temperature in the spinel primary phase field was expressed as a linear function of 1/(wt
pctFe/wt pctSiO2), wt pctCaO, wt pctMgO, and wt pctAl2O3. The positions of each of the liquidus points (wt pctFe)/(wt pctSiO2) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO,
and wt pctAl2O3. 相似文献
45.
This work presents conditions for hexavalent and trivalent chromium removal from aqueous solutions using natural, protonated and thermally treated Ectodermis of Opuntia. A removal of 77% of Cr(VI) and 99% of Cr(III) can be achieved. The sorbent material is characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, infrared spectroscopy, thermogravimetric analysis, before and after the contact with the chromium containing aqueous media. The results obtained from the characterization techniques indicate that the metal ion remains on the surface of the sorbent material. The percentage removal is found to depend on the initial chromium concentration and pH. The Cr(VI) and Cr(III) uptake process is maximum at pH 4, using 0.1g of sorbent per liter of aqueous solution. The natural Ectodermis of Opuntia showed a chromium adsorption capacity that was adequately described by the Langmuir adsorption isotherm. Finally, an actual mine drainage sample that contained Cd, Cr, Cu, Fe Zn, Ni and Pb was tested under optimal conditions for chromium removal and Ectodermis of Opuntia was found to be a suitable sorbent material. The use of this waste material for the treatment of metal-containing aqueous solutions as well as mine drainage is effective and economical. 相似文献
46.
Graphene sheets can be regarded as base structure of many carbon nanostructures, and atomic arrangements and variations in the atomic structure have a drastic impact on their unique properties. Using a single/double layer graphene model structure, we present a strategy to “see” single carbon atoms in 3-D. In high-resolution transmission electron microscopy, exit-wave images are essential to obtain and to understand 3-D atomic structure. Using electrons at 80 kV not only minimizes the knock-on damage, but also improves the detection sensitivity due to the higher scattering power of carbon at lower acceleration voltage of the electron. Using experiments and image simulations, positions of individual carbon atoms in a single/double layer structure in graphene have been identified. 相似文献
47.
The goal of this paper is to present work that demonstrates the application of probabilistic modeling to evaluate the long-term performance of fiber-reinforced polymer (FRP) rehabilitated piping components. The time-dependent reliability index is evaluated for a fully deteriorated piping component rehabilitated with FRP considering the demands of internal fluid pressure, external soil pressure, and traffic loading. Carbon FRP (CFRP) and glass FRP (GFRP) composites are compared and the influence of material deterioration, fiber volume fraction (FVF), and variation in thickness of the composite are assessed using a first order reliability method and compared to a steel pipe under similar loading. A CFRP rehabilitation scheme having a FVF greater than 40% would be needed to exceed the as-built reliability index of a steel pipe under time-dependent composite deterioration, while no practical GFRP FVF can achieve the performance of steel pipe in the presence of time-dependent composite deterioration. Variations in the coefficient of variation (COV) can adversely affect the safety of both FRP rehabilitation schemes where an increase in COV from 10 to 30% result in decreases in the reliability index by 39.4% for CFRP (40% FVF) and 39.7% for GFRP (40% FVF). 相似文献
48.
Hector Gomez Thomas J.R. Hughes Xesús Nogueira Victor M. Calo 《Computer Methods in Applied Mechanics and Engineering》2010,199(25-28):1828-1840
This paper is devoted to the numerical simulation of the Navier–Stokes–Korteweg equations, a phase-field model for water/water-vapor two-phase flows. We develop a numerical formulation based on isogeometric analysis that permits straightforward treatment of the higher-order partial–differential operator that represents capillarity. We introduce a new refinement methodology that desensitizes the numerical solution to the computational mesh and achieves mesh invariant solutions. Finally, we present several numerical examples in two and three dimensions that illustrate the effectiveness and robustness of our approach. 相似文献
49.
Luis Fortino Cisneros‐Sinencio Alejandro Diaz‐Sanchez Jaime Ramirez‐Angulo Hector Vazquez‐Leal 《IEEJ Transactions on Electrical and Electronic Engineering》2014,9(6):692-694
Multiple‐input floating‐gate transistor (FGMOS) circuit designers face a serious problem along the design process: the lack of a realistic simulation model. For this reason, a solution that properly predicts the initial voltage at the floating gates is presented in this paper. In order to assess the performance of the proposal, a comparison is made against a test circuit fabricated in a 0.5‐µm On‐Semiconductor CMOS process. Based on this comparison, the proposed model is shown to be a fundamental tool in the design of FGMOS circuits. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
50.
Laura R. Turcer Amanda R. Krause Hector F. Garces Lin Zhang Nitin P. Padture 《Journal of the European Ceramic Society》2018,38(11):3905-3913
The high-temperature (1500?°C) interactions of two promising dense, polycrystalline EBC ceramics, YAlO3 (YAP) and γ-Y2Si2O7, with a calcia-magnesia-aluminosilicate (CMAS) glass have been explored as part of a model study. Despite the fact that the optical basicities of both the EBC ceramics and the CMAS are similar, they both react with the CMAS. In the case of the Si-free YAlO3, the reaction zone is small and it comprises three regions of reaction-crystallization products, including Y-Ca-Si apatite solid-solution (ss) and Y3Al5O12 (YAG)(ss). In contrast, only Y-Ca-Si apatite(ss) forms in the case of Si-containing γ-Y2Si2O7, and the reaction zone is an order-of-magnitude thicker. These CMAS interactions are analyzed in detail, and are found to be strikingly different than those observed in Y-free EBC ceramics (β-Yb2Si2O7 and β-Sc2Si2O7) in the accompanying Part II paper. This is attributed to the presence of the Y in the YAlO3 and γ-Y2Si2O7 EBC ceramics. 相似文献