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91.
Eusebio Duarte Cabrera Panpan Zhang Wei‐Ching Liao Ying‐Chieh Yen Jiangfeng Yu Jose Castro L. James Lee 《Polymer Engineering and Science》2015,55(6):1374-1381
High strength light weight parts are critical for the development of new technologies, particularly electronic devices, such as laptop computers, smart phones, and tablet devices. Injection molded plastics and composites are excellent choices for mass producing such parts. As the part thickness decreases from traditional injection molding (>2 mm thickness) to thin wall molding (~1 mm thickness), and lastly, to ultra‐thin wall molding (<0.5 mm thickness), avoiding incomplete filling (short shots) becomes more challenging. Even though, methods exist today for molding thin‐wall plastic parts (i.e., fast heating/fast cooling injection molding), they require multiple steps resulting in a noncost efficient process. In this article, we demonstrate the technical feasibility of using graphene coating to facilitate flow, by promoting slip at the mold walls. We evaluate the influence of coated and uncoated mold inserts on fiber orientation. We present experimental results using un‐reinforced polypropylene and a 40% by weight carbon fiber reinforced polycarbonate/acrylonitrile butadiene styrene. POLYM. ENG. SCI., 55:1374–1381, 2015. © 2015 Society of Plastics Engineers 相似文献
92.
Nitrogen budget for fescue pastures fertilized with broiler litter in Major Land Resource Areas of the southeastern US 总被引:1,自引:0,他引:1
Samuel B. Marshall Michael D. Mullen Miguel L. Cabrera C. Wesley Wood Lois C. Braun Elizabeth A. Guertal 《Nutrient Cycling in Agroecosystems》2001,59(1):75-83
The southeast US produces a tremendous number of broiler chickens (Gallus gallus), which in turn produce massive quantities of litter (manure and bedding materials). In the Southeast, litter is most often disposed of via land application to pastures, however, the ultimate fate of much of the applied nitrogen (N) is not known. We have constructed N budgets for three sites across the southeastern U.S. in an effort to determine how much of the applied N is useful for plant production and how much is left to be absorbed by the environment. Study sites were located in the Coastal Plain (Alabama), Piedmont (Georgia), and Cumberland Plateau (Tennessee) Major Land Resource Areas (MLRA) of the southeastern US. Litter was applied in the Spring of two consecutive years at a rate to supply 70 kg of available N ha–1. The total amount of N applied ranged from 103 to 252 kg N ha–1 depending on site and year. Nitrogen fluxes monitored in this study were broiler litter N, ammonia (NH3) volatilization, denitrification, plant uptake, and leaching. Plant uptake represented the largest flux of applied N, averaging 43% of applied N. Losses due to NH3 volatilization and denitrification combined were only 6% of applied N on average. Loss of N due to NO3-N leaching appeared to be significant only at the Coastal Plain site where NO3-N concentrations in the groundwater peaked at 38 mg N l–1. We believe the majority of excess N shown in these budgets is likely accounted for by leaching losses and soil accumulation. Regardless of these assumptions and low gaseous losses, it is apparent that on average, 57% of applied N is destined for a fate other than plant uptake. The results of this study indicate that land-application of broiler litter at currently recommended rates has the potential for negative impacts on the environment of the southeastern U.S. in the long-term. 相似文献
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95.
Eusebio Duarte Cabrera Rachmat Mulyana Jose M. Castro L. James Lee Yong Min 《应用聚合物科学杂志》2013,127(5):3760-3767
In this article, a novel approach to decrease cycle time without compromising part dimensional stability developed in our group is compared with the use of supercritical nitrogen in injection molding. In this new approach, water is pre‐pressurized into the polymer pellets containing water carrier particles such as activated carbon (AC), thus no molding equipment modifications are required. Because of its high porosity, AC can trap water inside the particle, thus improving water compatibility with hydrophobic polymers for less water loss during handling and in the barrel during injection molding. After mixing, the polymer with the water carrier, the pellets are batch pressurized with water at a controlled temperature and pressure. The water containing pellets are then fed into the hopper of the injection molding machine. Parts with similar densities were molded and mechanical properties and warpage for both processes compared. It was found that the warpage and mechanical properties of the method presented here are comparable with the use of supercritical nitrogen, which is used in microcellular injection molding. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
96.
Utilization of ramon seeds (Brosimum alicastrum swarts) as a new source material for thermoplastic starch production 下载免费PDF全文
Carlos Rolando Ríos‐Soberanis Raciel Javier Estrada‐León Víctor Manuel Moo‐Huchin María José Cabrera‐Sierra José Manuel Cervantes‐Uc Luis Arturo Bello‐Pérez Emilio Pérez‐Pacheco 《应用聚合物科学杂志》2016,133(47)
The development and characterization of biodegradable polymers deriving from renewable natural sources has attracted much attention. The aim of this work was to partially characterize a thermoplastic starch obtained from the starch of seeds from the ramon tree (TPS‐RS) as an option to substitute thermoplastic starch from corn (TPS‐CS), in some of its applications. At 55% of relative humidity (RH), TPS‐RS had higher tensile strength and deformation than TPS‐CS. X‐ray diffraction analysis showed similar values in residual crystallinity (percentage of crystallinity that remains after plasticization process) in both TPS. The SEM micrographs showed a few remnant granular structures in the TPS‐RS. The FTIR showed a greater intensity in band at 1016 cm?1 in the TPS‐CS and TPS‐RS in comparison with their corresponding native starch, indicating an increase in the amorphous region after plasticization. The TGA analysis showed greater thermal stability in TPS‐CS (340 °C) compared with TPS‐RS (327 °C). In addition, the glass transition temperature in both TPS was 24 °C. The results obtained represent a starting point to potentialize the use of TPS‐RS instead of TPS‐CS for the development of new biodegradable materials for practical applications in different areas. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44235. 相似文献
97.
Francisco A. Macías Ana M. Simonet Brigida D’Abrosca Claudia C. Maya Matías Reina Azucena González-Coloma Raimundo Cabrera Cristina Giménez Luis Villarroel 《Journal of chemical ecology》2009,35(1):39-49
The new bioactive sesquiterpenoid (3R,6E)-2,6,10-trimethyl-3-(3-p-hydroxyphenylpropanoyloxy)-dodeca-6,11-diene-2,10-diol, named megalanthine, was isolated from the resinous exudates of Heliotropium megalanthum. The degradation products of this compound were identified. Several plant-defensive properties (insecticidal, antifungal,
and phytotoxic) were evaluated after obtaining positive results in a preliminary etiolated wheat coleoptile bioassay. This
bioassay showed the need to have both the phenolic and sesquiterpene moieties of the natural product present to achieve a
biological effect. This result was confirmed in phytotoxicity bioassays. Megalanthine was ruled out as a significant plant–plant
defense agent because of its lack of stability. The positive results recorded in the antifungal and antifeedant tests suggest,
however, that this chemical is relevant in several ecological interactions involving H. megalanthum. 相似文献
98.
J. C. Álvarez Hostos A. D. Bencomo E. S. Puchi Cabrera I. M. Figueroa Poleo 《International Journal of Cast Metals Research》2018,31(1):47-55
The present work has been conducted in order to develop a novel solution for the heat transfer problem during the continuous casting of steel billets and blooms, by using the element-free Galerkin method under a pseudo-transient moving cross-section slice approach. The transport laws, non-linear aspects and boundary conditions of the initial value problem have been specified. A detailed explanation concerning the characteristics inherent to the application of the element-free Galerkin method to this problem has also been provided. The feasibility and suitability of this novel approach has been verified by comparison with the numerical techniques proposed and the results reported by other researchers as well as an analytical solution of a simple 1-D alloy solidification problem. The results have revealed that this technique could be used successfully in the pseudo transient moving cross-section solution of the heat transfer problem involved in the continuous casting of blooms and square billets. 相似文献
99.
Marcelo C. Murguía Laura M. Machuca María C. Lurá María I. Cabrera Ricardo J. Grau 《Journal of surfactants and detergents》2008,11(3):223-230
A series of new N-acetylated non-ionic and cationic gemini surfactants (3a–f) having dimeric structures derived from primary and tertiary amines with variably long tails (C8–C12–C18) were synthesized. In addition, N-acetylated monomeric analogues 6a and 6b were prepared and their antifungal potency and surface properties were also determined. Critical micelle concentration (CMC),
effectiveness of surface tension reduction (γCMC), surface excess concentration (Γ), and area per molecule at the interface (A) were also determined and the resulting values indicate that the cationic series is characterized by good surface-active
and self-aggregation properties. For the first time, all surfactants were tested to evaluate their antifungal properties using
the method for the broth macrodilution test (M27-A2, NCCLS). Four microbial strains were used to perform the study: Candida parapsilosis (ATCC 22019), C. albicans (ATCC 64548), and a wild-type strain of C. parasilosis and Saccharomyces cerevisiae (ATCC 9763). The antimicrobial activity was measured by yeast growth inhibition expressed as minimum inhibitory concentration
(MIC) values. Results were compared to those obtained for their monomeric analogues and for a commercially available reference
compound (Fluconazole). Gemini 3b, 3e and 3f were found to be the most potent compounds. The results show S. cerevisiae as the most sensitive strain. In contrast, the wild strain of C. parapsilosis was resistant.
相似文献
Ricardo J. Grau (Corresponding author)Email: |
100.