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21.
The heat of combustion of two distinctly synthesized stoichiometric tantalum-tungsten oxide energetic composites was investigated by bomb calorimetry. One composite was synthesized using a sol-gel (SG) derived method in which micrometric-scale tantalum is immobilized in a tungsten oxide three-dimensional nanostructured network structure. The second energetic composite was made from the mixing of micrometric-scale tantalum and commercially available (CA) nanometric tungsten oxide powders. The energetic composites were consolidated using the spark plasma sintering (SPS) technique under a 300 MPa pressure and at temperatures of 25, 400, and 500 °C. For samples consolidated at 25 °C, the density of the CA composite is 61.65 ± 1.07% in comparison to 56.41 ± 1.19% for the SG derived composite. In contrast, the resulting densities of the SG composite are higher than the CA composite for samples consolidated at 400 and 500 °C. The theoretical maximum density for the SG composite consolidated to 400 and 500 °C are 81.30 ± 0.58% and 84.42 ± 0.62%, respectively. The theoretical maximum density of the CA composite consolidated to 400 and 500 °C are 74.54 ± 0.80% and 77.90 ± 0.79%, respectively. X-ray diffraction analyses showed an increase of pre-reaction of the constituents with an increase in the consolidation temperature. The increase in pre-reaction results in lower stored energy content for samples consolidated to 400 and 500 °C in comparison to samples consolidated at 25 °C. 相似文献
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Antonio De León‐Rodríguez Enrique Galindo Octavio T. Ramírez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2010,85(7):950-956
BACKGROUND: A laboratory scale one‐compartment scale‐down system (1‐CSDS), used to generate dissolved oxygen tension (DOT) gradients was designed and characterized. The system consists of a 1.5‐L stirred‐tank bioreactor coupled to an automatic DOT controller that changes the oxygen partial pressure in the inlet gas through a feedback proportional–integral–derivative algorithm, while maintaining the hydrodynamic conditions constant. Oscillatory control of DOT was achieved by employing time‐dependent square wave or sinusoidal setpoints. RESULTS: The 1‐CSDS can be modeled as a first‐order dynamic system, but showing a permanent lag between the system response and the setpoint. The 1‐CSDS had a faster response rate for generating oscillating DOT when a square wave setpoint was used rather than a sinusoidal setpoint. The 1‐CSDS generated symmetric DOT oscillations at periods above of 100 s. CONCLUSION: The 1‐CSDS is suited to investigate the responses of microorganisms and cells, of biotechnological importance, to oscillatory DOT conditions. It was found that the response of the 1‐CSDS was limited by the kLa. Copyright © 2010 Society of Chemical Industry 相似文献
24.
Edgar Ramirez-Jaramillo Carlos Lira-Galeana Octavio Manero Brito 《Petroleum Science and Technology》2001,19(5):587-608
A liquid-solid compositional model that uses an equation of state has been developed to predict the phenomenon of wax deposition in model oil wells. Numerical solutions to the conservation equations for Newtonian-to-non-Newtonian flow regimes show temperature, radial mass flux and wax deposition profiles as a function of time and position in the pipe, using realistic pressure and temperature profiles of a model well. Such rheologic regime changes are dictated by thermodynamic arguments. 相似文献
25.
F. J. Gil J. A. Picas J. M. Manero A. Forn J. A. Planell 《Journal of Alloys and Compounds》1997,260(1-2):147-152
In the present work, experimental research on grain growth kinetics at different temperatures and times of heat treatment for titanium and Ti---0.2Pd in the and β phases has been carried out. The grain size parameters were obtained by the image analysis technique. The aim of the present study was to quantify the progress of grain growth and the corresponding activation energy for and β titanium, and to determine the effect of Palladium. By means of EDS microanalysis, it has been observed that the effect of a higher concentration of palladium on the grain growth is to decrease the growth exponent for the Ti-0.2Pd alloy. The activation energies differ a lot between the two phases and β for Ti and Ti-0.2Pd. This difference might be due to the different crystal structures. 相似文献
26.
N‐oxide polymers possess strong zwitterionic character, high solubility in water, and high chelating properties with various cations. In this work, N‐oxide polymers were synthesized following various routes and their solution properties were determined. Molecular properties of the polymers (molecular weight, square root of the mean‐squared radius, and virial coefficients) were related to their chain expansion in solution by determining the intrinsic viscosity as a function of pH. Viscosity results were correlated with the flocculation ability of the polymers for suspending solids removal. These polymers exhibit dramatic conformation changes as the solution pH is varied, especially at low pH values. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2693–2700, 2002 相似文献
27.
The effect of grain size on the martensitic transformation in Ni42Ti shape memory alloy has been studied. The kinetics of
grain growth has been evaluated and the influence of different grain sizes on the transformation temperatures and the thermodynamic
magnitudes has been reported. Image analysis and flow calorimetry techniques have been used. The study shows that grain boundaries
favour the martensitic transformation and at the same time obstruct retransformation. Enthalpy and entropy variations are
independent of grain size, but elastic energy decreases with the grain size. 相似文献
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29.
Javier Octavio Morales Jason Thomas McConville 《Drug development and industrial pharmacy》2014,40(5):577-578
During the past years, buccal drug delivery has attracted the attention of researchers looking for alternative delivery routes of administration. As an alternative to oral drug delivery, the buccal mucosal route avoids the passage through the acidic gastric environment, intestinal and bacterial enzymatic activity, absorption issues associated with the intestinal epithelium (e.g. P-glycoprotein efflux), and the first pass metabolism of the liver. Therefore, the buccal route could be a good delivery route for macromolecules and other drugs not compatible with the gastrointestinal tract environment. This “Buccal Drug Delivery” special edition of Drug Development and Industrial Pharmacy aims to bring together a range of different aspects relevant to the growing field of buccal drug delivery. The special edition includes thorough reviews of the literature, as well as original research articles touching on most prominent features related to buccal drug delivery systems, such as the move toward the use of nanotechnology in different ways to facilitate buccal drug delivery with the potential to prompt future product developments. 相似文献
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