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991.
This study made use of poly(ethylene glycol) (PEG) samples of different molecular weights, which were reacted with a diisocyanate ester, and an anion center for the synthesis of polyurethane (PU), which was then mixed with chitosan to form a polymer adsorbent. It was tested for the determination of its adsorption toward acidic dyestuffs under various conditions. Our results showed that under all the tested conditions, the blended polymer adsorbent possessed a better adsorbing ability than chitosan by itself, and the degree of adsorption varied positively as the adsorbent concentration, ambient temperature, and contact time increased. Furthermore, the addition of PU remarkably increased the adsorption efficiency, whereas PEG with a greater molecular weight yielded a better adsorption performance. As for the dyestuffs, the red one surpassed the others in adsorption efficiency. Finally, a 5 mg/mL concentration of the adsorbent solution, a temperature of 45°C, and a contact time of 15 min gave fairly good adsorption results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3991–3998, 2004 相似文献
992.
Cheng-Ping Chiu Laming-Chang Shih Jong-Hwei Wei 《Polymer Engineering and Science》1991,31(19):1417-1425
This paper presents the development of a nonlinear mathematical model for the study of the mold filling process in an injection molding machine. The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics. The mold filling process can be approximated by the transient phenomenon of the non-Newtonian fluids flowing through a closed conduit. The comparison between the experimental results and the theoretical simulation indicate that the nonlinear model is a reasonable representation of the mold filling dynamics when the acrylonitrile-butadiene-styrene (ABS) is injected into a disk shape mold. The actuation system dynamics of an injection molding machine are also investigated. The results indicate that the nonlinear model can also adequately predict the transient behavior of the actuation system. 相似文献
993.
This paper outlines the results of an experimental program aimed at established the best formation parameters for dynamic Zr (IV) — PAA membranes formed on porous ceramic supports. The membrane formation parameters investigated are the pressure, the circulation velocity, the Zr (IV) concentration, and the PAA concentration. The formation pressure was allowed to vary between 200 psig (1.4 MPa) to 800 psig (5.4 MPa), the circulation velocity from 6 fps (1.8 m/s) to 24 fps (7.3 m/s), the Zr (IV) concentration from 10-4M to 9 × 10-4M, and the PAA concentration from 50 ppm to 250 ppm.Twenty statistically designed experiments were conducted to evaluate the effect of these four parameters on the flux and rejection of the resulting membrane at the end of the formation procedure. The results were used in a multiple linear regression computer program named BMD-PIR which develops the measured values with an accuracy of +_ 2 percent. Using these models, it is possible to form a membrane with a given value of flux or rejection within their ranges.For the range of variables used in this study, the maximum membrane rejection was 91% corresponding to a flux of 10 gpd/ft2(1.7 cm/hr) for 0.05 M NaCl and 800 psi (5.4 MPa). High rejection was obtained by increasing the membrane formation pressure and by increasing the PAA concentration. High flux can be achieved by increasing the formation pressure, by increasing the Zr (IV) concentration up to 9.0 × 10-4M -, and by increasing the circulation velocity. 相似文献
994.
The influences of nitric acid oxidation on the surface properties and the adsorption capacity of single-walled carbon nanotubes (SWCNTs) were investigated in this work. To eliminate the size effects on the adsorption capacity, o-xylene and p-xylene were used as model adsorbates. It was found that purification of the SWCNTs by nitric acid significantly increased the internal surface area as well as the micropore volume of the SWCNTs, and introduced oxygen-containing surface groups. The adsorption capacities of the SWCNTs for o-xylene and p-xylene were mainly influenced by the positions of the methyl groups on the xylene molecules and the presence of oxygen-containing groups on the surface of the SWCNTs. Results also indicated that purification greatly changes the adsorption of o-xylene by the SWCNTs. This could be attributed to the dispersive attractions and the electrostatic repulsions between o-xylene molecules and the surface of the purified SWCNTs, which are introduced by the oxygen-containing surface groups. When compared to the as-grown and the purified SWCNTs, activated carbon had a greater adsorption capacity because of its large specific surface area and the absence of oxygen-containing surface groups. However, when the adsorption capacity was calculated based on surface area, the as-grown SWCNTs had a greater adsorption capacity than did the activated carbons because the micropore size of the activated carbon is mainly smaller than the size of a xylene molecule. 相似文献
995.
Information technology personnel are often ill prepared to react in a positive fashion to the aggressive communications from their customers, the users. Being able to regulate the emotions spiked by aggressive customer behavior is important to the long term health and retention of IT employees. Surface acting responses, the ability to display false emotions to mask strong emotions, is common, but not better for the long term health of the individual or organization. Deep acting responses, where emotional responses are modified to encourage expected behavior, are the better response and can be promoted with an organizational climate of support. A model derived from emotion response theory demonstrates these relationships hold for IT employees, who tend to be more introverted than most employees and often react differently to aggressive communication from customers. The model is verified with a sample of IT employees in Taiwan companies. Organizations should provide a climate of support for IT personnel and train them on how to respond appropriately to customer aggression through emotion regulation strategies in a direction that promotes better relationships. 相似文献
996.
C.-H. Lin C.-H. Lee J.-H. Chao C.-Y. Kuo Y.-C. Cheng W.-N. Huang H.-W. Chang Y.-M. Huang M.-K. Shih 《Catalysis Letters》2004,98(1):61-66
TiO2 nanotubes promoted with Pt metal were prepared and tested to be the photocatalytic dehydrogenation catalyst in neat ethanol for producing H2 gas (C2H5OHC3CHO +H2). It was found that the ability to produce H2, the liquid phase product distribution and the catlyst stability of these promoted nano catalysts all depended on the Pt loading and catalyst preparation procedure. These Pt/TiO2 catalysts with TiO2 nanotubes washed with diluted H2SO4 solution produced 1, 2-diethoxy ethane (acetal) as the major liquid phase product, while over those washed with diluted HCl solution or H2O, acetaldehyde was the major liquid phase product. 相似文献
997.
Mixed-Mode Fracture Toughness of Ceramic Materials 总被引:6,自引:0,他引:6
S. Suresh C. F. Shih A. Morrone N. P. O'Dowd 《Journal of the American Ceramic Society》1990,73(5):1257-1267
An experimental technique whereby pure mode I, mode II, and combined mode I-mode II fracture toughness values of ceramic materials can be determined using four-point bend specimens containing sharp, through-thickness precracks is discussed. In this method, notched and fatigue-precracked specimens of brittle solids are subjected to combined mode I-mode II and pure mode II fracture under asymmetric four-point bend loading and to pure mode I under symmetric bend loading. A detailed finite element analysis of the test specimen is performed to obtain stress intensity factor calibrations for a wide range of loading states. The effectiveness of this method to provide reproducible combined mode I-mode II fracture toughness values is demonstrated with experimental results obtained for a polycrystalline Al2 O3 . Multiaxial fracture mechanics of the Al2 O3 ceramic in combined modes I, II, and III are also described in conjunction with the recent experimental study of Suresh and Tschegg (1987). While the mode II fracture toughness of the alumina ceramic is comparable to the mode I fracture toughness K Ic , the mode III fracture initiation toughness is 2.3 times higher than K Ic . The predictions of fracture toughness and crack path based on various mixed-mode fracture theories are critically examined in the context of experimental observations, and possible effects of fracture abrasion on the apparent mixed-mode fracture resistance are highlighted. The significance and implications of the experimental methods used in this study are evaluated in the light of available techniques for multiaxial fracture testing of brittle solids. 相似文献
998.
999.
Yen-Huai Lin Yu-Tai Shih Michael Mu Huo Teng 《International journal of molecular sciences》2021,22(10)
Osteosarcopenia, the coexistence of bone and muscle loss, is common in older adults, but its definition lacks international consensus. This cross-sectional study (n = 1199 post-menopausal women) aimed to determine the association between osteosarcopenia and fragility fractures and to investigate the impact of the definition of the “osteo” component. Bone mineral density and bone microarchitecture were measured by dual-energy X-ray absorptiometry and the trabecular bone score (TBS), respectively. The “osteo” component of osteosarcopenia was classified as osteoporosis (T-score ≤ −2.5 SD), osteopenia/osteoporosis (T-score < −1 SD), and high-fracture-risk osteopenia (−2.5 SD < T-score < −1 SD)/osteoporosis (T-score ≤ −2.5 SD). The Fracture Risk Assessment Tool was used to identify high-fracture-risk osteopenia. Altogether, 30.3%, 32.2%, 14.4%, and 23.1% of participants had osteosarcopenia, osteoporosis alone, sarcopenia alone, and neither condition, respectively. The odds ratios between osteosarcopenia and fragility fractures were 3.70 (95% CI: 1.94–7.04) for osteosarcopenia, 2.48 (95% CI: 1.30–4.71) for osteoporosis alone, and 1.87 (95% CI: 0.84–4.14) for sarcopenia alone. Women with osteosarcopenia also had lower TBS, indicating worse bone microarchitecture. In conclusion, women with osteosarcopenia were more likely to have previously sustained a fracture compared to those without osteosarcopenia, with sarcopenia alone, and with osteoporosis alone. The relationship between osteosarcopenia and fracture risk may be best identified when considering high-fracture-risk osteopenia and osteoporosis. 相似文献
1000.
Yu‐Shih Weng Shau‐Feng Chang Ming‐Cheng Shih Shih‐Heng Tseng Chih‐Huang Lai 《Advanced materials (Deerfield Beach, Fla.)》2017,29(36)
The considerable advances that have been made in the development of organotypic cultures have failed to overcome the challenges of expressing tissue‐specific functions and complexities, especially for organs that require multitasking and complex biological processes, such as the liver. Primary liver cells are ideal biological building blocks for functional organotypic reconstruction, but are limited by their rapid loss of physiological integrity in vitro. Here the concept of lattice growth used in material science is applied to develop a tissue incubator, which provides physiological cues and controls the 3D assembly of primary cells. The cues include a biological growing template, spatial coculture, biomimetic radial flow, and circulation in a scaffold‐free condition. The feasibility of recapitulating a multiscale physiological structural hierarchy, complex drug clearance, and zonal physiology from the cell to tissue level in long‐term cultured liver‐on‐a‐chip is demonstrated. These methods are promising for future applications in pharmacodynamics and personal medicine. 相似文献