全文获取类型
收费全文 | 1109篇 |
免费 | 78篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 308篇 |
金属工艺 | 14篇 |
机械仪表 | 34篇 |
建筑科学 | 25篇 |
矿业工程 | 2篇 |
能源动力 | 32篇 |
轻工业 | 303篇 |
水利工程 | 7篇 |
石油天然气 | 8篇 |
无线电 | 91篇 |
一般工业技术 | 133篇 |
冶金工业 | 91篇 |
原子能技术 | 4篇 |
自动化技术 | 116篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 42篇 |
2021年 | 71篇 |
2020年 | 46篇 |
2019年 | 56篇 |
2018年 | 43篇 |
2017年 | 57篇 |
2016年 | 55篇 |
2015年 | 36篇 |
2014年 | 55篇 |
2013年 | 86篇 |
2012年 | 64篇 |
2011年 | 87篇 |
2010年 | 62篇 |
2009年 | 55篇 |
2008年 | 54篇 |
2007年 | 35篇 |
2006年 | 31篇 |
2005年 | 33篇 |
2004年 | 28篇 |
2003年 | 20篇 |
2002年 | 15篇 |
2001年 | 17篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 26篇 |
1997年 | 20篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1975年 | 1篇 |
排序方式: 共有1188条查询结果,搜索用时 15 毫秒
71.
A Gougoux P Vinay M Cardoso M Duplain G Lemieux 《Canadian Metallurgical Quarterly》1982,243(3):F227-F234
Studies were performed to determine whether ammoniagenesis could adapt instantaneously to acidosis in the dog kidney. Following acute respiratory acidosis, renal glutamine extraction rose acutely in dogs with stable renal blood flow but did not change when the renal blood flow fell by more than 25%. Acute hypercapnia immediately increased renal ammonia production in both groups of dogs. The rate of both glutamine extraction and ammonia production in acutely hypercapnic dogs without hemodynamic changes was comparable to the rates observed in dogs with chronic metabolic acidosis. Furthermore, the renal metabolite profile observed in acute hypercapnia was similar to the pattern described in chronic metabolic acidosis, i.e., a marked fall in renal glutamate and alpha-ketoglutarate concentrations and a fivefold increase in malate and oxaloacetate concentrations. In the liver and muscle, acute hypercapnia induced no significant change in glutamine concentration but glutamate and alpha-ketoglutarate concentrations decreased. Our findings demonstrate that the dog kidney can adapt immediately to acidosis but that hemodynamic change may mask this adaptation. 相似文献
72.
Semantic Web developers have adopted OWL to represent knowledge. OWL, or a language with similar theoretical foundations, will lead the way in the semantic exploration of the Web. Currently, Web-based standards are the preferred way to represent knowledge. Furthermore, respondents mainly use ontologies to allow both humans and computers to understand knowledge and domain models. Web 3.0 can bring a new breed of spectacular applications compared to Web 2.0. with the same magnitude that separates Web 2.0 from Web 1.0. 相似文献
73.
Leonardo B. Trindade José Ernesto A. Nadalon Antǒnio C. F. Vilela Marco T. M. B. Vilhena Rodrigo B. Soares 《国际钢铁研究》2007,78(9):708-713
To investigate the inclusion removal in billets cast under electromagnetic stirring (EMS) influence, a numerical model has been developed to compute the magnetic field, the Lorentz force, the steel flow velocities, and the particle transport within the liquid pool. The electromagnetic field was described by the Maxwell equations and the finite element method was applied using a commercial package. The turbulent fluid flow was described by the Navier‐Stokes equation and by the Reynolds Stress model and the finite volume method was applied using another numerical package. The time average of the Lorentz force was calculated in each element center and this value was applied as a body force in the Navier‐Stokes equation. The magnetic flux density profile was compared with the data obtained in the stirrer of the steel plant. The particle transport model includes the drag force, the buoyancy force and the random walk model, to include the turbulence effects on the particle trajectory. The inclusion removal was calculated and analysed in function of casting speed and stirring current for one size section of mold. The inclusions considered in the calculations have a fixed density and four values of diameter. The numerical results of the electromagnetic model are in agreement with the experimental measurements. A good relationship between the electromagnetic model and the fluid flow model could be shown. An interesting effect is the break of the rotation motion due to the EMS by the jet from the nozzle. The fraction of inclusions removed by the top surface of the mold was improved due to the EMS. 相似文献
74.
Flow Intensity Parameter in Pier Scour Experiments 总被引:1,自引:0,他引:1
Gonzalo Simarro Luis Teixeira António H. Cardoso 《Canadian Metallurgical Quarterly》2007,133(11):1261-1264
Technical note discusses a detailed approach to dimensional analysis for the bridge pier scour phenomenon and the introduction of flow intensity. It demonstrates the dependence of critical upstream velocity on the rest of the parameters describing the process and its implications on dimensional analysis. Assuming that the viscous effects are negligible in the local scour phenomenon, it is concluded that the flow intensity of the approaching undisturbed flow is not an adequate parameter to describe the process in usual laboratory conditions. A new proposal is established. 相似文献
75.
Nonhydrolytic sol-gel synthesis and characterization of YAG 总被引:1,自引:0,他引:1
Eduardo José Nassar Paula Fabiana dos Santos Pereira Evelisy Cristina de Oliveira Nassor Lilian Rodrigues Ávila Katia Jorge Ciuffi Paulo Sergio Calefi 《Journal of Materials Science》2007,42(7):2244-2249
Yttrium–aluminum oxides are interesting compounds, which are widely used as hosts for lasers and phosphors due to their stable
physical and chemical properties. The manufacture of YAG has been investigated thoroughly. YAG powders are traditionally synthesized
through the reaction of aluminum and yttrium powders at high temperatures. The work reported here involved an investigation
into the preparation of YAG by a nonhydrolytic sol-gel route and the influence of heating time at low temperatures to obtain
YAG from inorganic precursors (yttrium and aluminum chloride). AlCl3, YCl3 and ethanol were reflux reacted under an argon atmosphere. Europium III chloride was added as a structural probe. The powder
was treated at 800 °C for 1, 2, 4, 8 and 16 h. The YAG structure was analyzed by X-ray diffraction (XRD), nuclear magnetic
resonance (NMR), thermal analysis (TA) and photoluminescence (PL). The XRD revealed only peaks corresponding to the YAG phase.
PL data showed that the YAG phase was formed in 2 min with samples pretreated at 50 °C. For the samples pretreated at 800 °C,
the YAG phase appeared in 30 s. The excitation spectra presented a maximum of 394 nm corresponding to the 5L6 level, while the emission spectra of Eu III ions showed characteristic transition bands arising from the 5D0 → 7F
J
(J = 1, 2, 3, 4) manifolds at maximum excitation. The magnetic dipole 5D0 → 7F1 transition exhibited greater intensity than the electric dipole 5D0 → 7F2 transition. This methodology proved efficient for obtaining YAG phase. 相似文献
76.
Nadia Segura Roberta Claro da Silva Fabiana A. Schäfer de M. Soares Luiz Antonio Gioielli Iván Jachmanián 《Journal of the American Oil Chemists' Society》2011,88(12):1945-1954
Although beef tallow (BT) has been considered a hard low-trans fat convenient to be used in several bakery applications, it has some undesirable characteristics like fatty acid composition,
crystallization behavior, graininess formation and poor plastic range. This work studied the modification of BT by blending
at different percentages with high oleic sunflower oil (HOSFO) followed by the enzyme-catalyzed interesterification of the
blends. The reduction in the solid fat content achieved by the simple blending was enhanced by the interesterification process,
as a result of the increase in the concentration of the diunsaturated monosaturated type triacylglycerols. Interesterification
strongly impacted too on the crystallization behavior of the blends, since products showed more homogeneous and regular crystals
than the starting mixture. Results show that lipase catalyzed interesterification of BT with HOSFO offers a useful tool for
the design of fats with adjustable physicochemical properties, improved with respect to that of the starting fats. 相似文献
77.
Adriana Gadioli Tarone Luiz Henrique Fasolin Fabiana de Assis Perrechil Míriam Dupas Hubinger Rosiane Lopes da Cunha 《Food and Bioproducts Processing》2013,91(2):111-120
Soy protein fractions rich in β-conglycinin (7S) or glycinin (11S) were freeze dried or spray dried at temperatures of 120, 150 or 180 °C. The fractions were characterized for their particle size distribution, sorption isotherms and by scanning differential calorimetry. The gelling capacity of the protein fractions was studied at pH values of 3 and 7 using oscillatory measurements, mechanical properties and water holding capacity. The rheological measurements showed that viscous modulus (G″) predominated at low temperatures and the elastic modulus (G′) at high temperatures. At pH 3, the G′–G″ crossover occurred at lower temperatures when compared to pH 7. This behaviour was more accentuated for the 11S fractions due to its capacity to form stronger gels. An increase of drying temperature led to a displacement of the gel point to higher temperatures and decreased the elasticity modulus or gelling capacity of protein fractions. These results were confirmed by the mechanical properties, since at higher temperatures the gels were more fragile and brittle, especially when formed at pH 7. 相似文献
78.
Denise Bevilaqua Heloisa A. Acciari Fabiana A. Arena Assis V. Benedetti Cecílio S. Fugivara Germano Tremiliosi Filho Oswaldo Garcia Júnior 《Minerals Engineering》2009,22(3):254-262
In this work, the monitoring of the bacterial and chemical dissolution of bornite was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS); the mineral surface was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The analysis of CV results allowed attributing the different peaks observed in both direct and reverse potential scanning to the oxidation of bornite to a secondary covellite and its reduction via different non stoichiometric copper sulphides intermediaries. EIS data for bornite were obtained in control medium up to 78 h of immersion, when a cellular suspension of A. ferrooxidans was added and the experiments continued up to a 192 h of test. The EIS response was different when bacteria were added in the beginning of the test or after some hours of immersion in acid solution. The experiments were performed in different cell configurations and a model of the electrode/electrolyte interface. The correspondent equivalent electrical circuit was used to fit impedance spectra for all studied conditions. A common equivalent circuit used for corrosion processes where anodic (degradation of the mineral) and cathodic (oxygen reduction) reactions occur in parallel, together film and biofilm formation was proposed. 相似文献
79.
Recently, one of us (O.L.M.) developed a theoretical approach to the energy transfer process between a ligand and a lanthanide ion in luminescent compounds. This approach takes into account the direct Coulomb interaction only. Here we present further calculations which also include the exchange Coulomb interaction (isotropic and anisotropic). The selection rules on the total angular momentum, J, of the lanthanide 4f states, derived from each interaction are different. They are in fact complementary. We discuss the case of energy transfer to the 5D1 manifold of the Eu3+ ion, which is forbidden when only the direct Coulomb interaction is considered but becomes allowed through the exchange interaction. In this case numerical estimates show that, depending on resonance conditions and the nature of the ligand donor state, the transfer rate may assume very high values. It is also emphasised that, according to the present approach, energy transfer to the 5D0 level of the Eu3+ ion is forbidden by both mechanisms, provided J-mixing between the 7F0 and 7F2 manifolds is neglected. 相似文献
80.
Fabiana A. Lobo Danielle Goveia Adriana P. de Oliveira Edenir R. Pereira-Filho Newton L. Dias Filho 《Fuel》2009,88(10):1907-1914
Experimental design was used as a tool to define the optimum pyrolysis and atomization temperatures for four analytes (Cu, Pb, Ni and Cd) in biodiesel samples. Two chemical modifiers (Pd + Mg and W) and two distinct sample preparation procedures (microemulsion and wet digestion in a focused microwave system) were also investigated. The pyrolysis and atomization temperatures were optimized using 24 factorial design for Cu, Pb, Ni and Cd, with 16 assays carried out for each analyte. The results for Cu and Pb indicated that variables of sample preparation for digestion by focused microwave was the most important one for both analytes. The pyrolysis and atomization temperatures applied were 1000 °C and 2200 °C for Cu and 500 °C and 2000 °C for Pb. None of the variables analyzed here were important for Ni, and the pyrolysis and atomization temperatures chosen for this element were 800 °C and 2300 °C. A different factorial design was used for Cd. The variables of medium and modifier were not important for this element, and the lowest temperatures, Tp-500 °C and Ta-1400 °C, were chosen based on this second design. The importance of factorial design in the simultaneous optimization of several variables studied by GFAAS was confirmed, for it involves fewer experiments and hence, lower costs, greater speed and higher efficiency. 相似文献