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111.
Alvarez-Arenas T.E.G. Gomez I.G. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(4):772-778
Propagation of ultrasounds through open-cell polymeric foams is studied using air-coupled ultrasound and Fourier spectral analysis (both phase and magnitude) in the frequency range 0.1 to 6 MHz. A detailed micrographic study is first performed to determine struts dimensions and cell geometry, hence, a unit cell model to describe these foams is proposed. Ultrasound phase velocity and transmission loss were then measured. Variation of these magnitudes with the frequency follows the shape of a sigmoid growth. This behavior of the phase velocity can be explained by introducing an apparent tortuosity with a relaxation-like behavior, which can be explained by considering a probabilistic tortuous walk, as it has recently been performed for other kind of foams. However and unlike in previous studies, the present one shows the whole transition of this sigmoid growth for all studied foams. This is achieved by a precise selection of the foam samples and by the fabrication of new air-coupled transducers that enlarge the experimental working frequency range to lower frequencies. The study of the measured sigmoid growth is used to determine the probability function, required by the probabilistic tortuous walk model, which best describes the variation of the apparent tortuosity. 相似文献
112.
Tamara Carolina; Timberlake William; Leffel Joseph 《Canadian Metallurgical Quarterly》2010,124(3):302
In two experiments we investigated the extent to which rats (Rattus norvegicus) use an egocentric trajectory and landmarks to locate a goal. In Experiment 1 we trained groups to locate the hidden platform in a water maze with either 1 of 3 or 3 of 3 predictive landmarks, and with either a random or fixed egocentric trajectory. A choice test revealed that regardless of the landmark configuration, rats relied on a directional, egocentric trajectory, when it was available, to locate the platform. In Experiment 2 we found that adding four predictive landmarks following training with a constant egocentric trajectory did not alter rats' initial attention to the trajectory. We conclude that the presence of nonpredictive landmarks in a predictive array did not affect the use of landmarks. With a blocking design, rats used initially an egocentric path, then landmarks. These results add to the notion that animals use available spatial cues sequentially. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
113.
Isabel Comino Ana Real Maria de Lourdes Moreno Raquel Montes Ángel Cebolla Carolina Sousa 《Journal of the science of food and agriculture》2013,93(4):933-943
BACKGROUND: Cereals used for beer manufacturing contain gluten, which is immunotoxic for celiac patients. The gluten remaining after processes of malting and brewing is mostly hydrolyzed, which makes practical evaluation of the immunotoxicity of the gluten pools challenging. RESULTS: We analyzed the presence of gluten peptides equivalent to the major immunotoxic protease‐resistant gliadin 33‐mer in 100 Belgium beers, using monoclonal antibodies (G12/A1). Immunochromatographic strips and enzyme‐linked immonosorbent assay G12/A1 methods estimated at least 20 ppm gluten equivalents in 90 beers and gluten‐free in 10 beers. The G12/A1 reactivity of beer high‐performance liquid chromatographic fractions correlated to the presence of T‐cell‐reactive epitopes identified by peptide sequencing. CONCLUSION: The determination of equivalent gliadin 33‐mer epitopes in beers has been shown to be practical, specific, and sensitive for the measurement of potential immunotoxicity for celiac patients. Copyright © 2012 Society of Chemical Industry 相似文献
114.
Zeynep Yilmazer Hitit Carolina Zampol Lazaro Patrick C. Hallenbeck 《International Journal of Hydrogen Energy》2017,42(10):6578-6589
Both dark and photo-fermentation can be used for biological hydrogen production; either performed separately, in two-stage systems, or in co-culture. A single stage process is less laborious and costly; however, the two types of microorganisms have different nutritional requirements requiring optimization of culture conditions. Here a response surface methodology (RSM) with a Box-Behnken design was used to optimize microorganism ratio and substrate and buffer concentrations, and to evaluate their interactive effects for maximization of hydrogen yield. Clostridium butyricum and Rhodopseudomonas palustris were grown on a potato starch/glucose base medium at 30 °C under continuous illumination (40 W m?2 light intensity). The highest hydrogen yield, 6.4 ± 1.3 mol H2/mol glucose, was obtained with a substrate concentration of 15 g/L, buffer concentration of 50 mM, and microorganism ratio of 3. The observed strong interaction between buffer and substrate concentration is most likely due to the need to optimize the pH for co-cultures. 相似文献
115.
Michael Pascoe-Chalke Javier Gomez Victor Rangel Miguel Lopez-Guerrero 《Wireless Networks》2010,16(3):743-757
In this paper, we present a model that estimates the time duration of routes formed by several intermediate nodes in mobile
multi-hop ad-hoc networks. First, we analyze a 3-node route, where only the intermediate node is in movement while source
and destination nodes remain static. From this case, we show how route duration is affected by the initial position of the
intermediate node and the size of the region where it is located. We also consider a second case where all nodes of 3-node
routes are mobile. Based on extensive analysis of these routes, we determine the PDF of route duration under two different
mobility models. This PDF can be determined by either analytical or statistical methods. The main contribution of this paper
is that the time duration of a route formed by N intermediate nodes can be accurately computed by considering the minimum route duration of a set of N routes of 3 nodes each. Simulation work was conducted using the NS-2 network simulator to verify the accuracy of the proposed
model and to compare it with other proposals found in the literature. We show that our model is in better agreement with simulation
results as compared with other models. Results from this work can be used to compute overhead signaling during route-maintenance
of unicast and multicast routing protocols for mobile ad-hoc networks. Similarly, because route duration decreases with route
length, this study can be used to scale the network size up/down. 相似文献
116.
117.
Natalia A. Castillo Alejandra de Moreno de LeBlanc Carolina Maldonado Galdeano Gabriela Perdigón 《Food research international (Ottawa, Ont.)》2012,45(2):831-841
Salmonella produces infections of different nature and severity depending of many factors including the Salmonella serovar involved, strain virulence, infective dose, host animal species, age and immune status of the host. The treatments against Salmonella infections rely on supportive and antibiotic therapy to eliminate the pathogen, but the development of resistance by Salmonella to the antimicrobials most commonly used limits its efficacy. Other disadvantages of antibiotic treatments are that they can lead to acute diarrhea (antimicrobials normally induce an imbalance of intestinal bacterial flora) and may produce chronic toxicity. Considering this undesired consequences of antibiotics and because at the present there are no effective oral vaccines which protect against salmonellosis, scientists have been searching for alternative methods to control enteric infections. In the present review, probiotics are proposed as an attractive possibility to attend this concern. Probiotic are live microorganisms, which when administered in adequate amounts confer a health benefit on the host. In vitro and in vivo studies showed the effectiveness of probiotic administration in the prevention or in the treatment against Salmonella infection. There are several mechanisms by which probiotic strains might exert their effects. They include non immune mechanisms (stabilization of the gut mucosal barrier, competition for adhesion, secretion of antimicrobial substances, etc.) and the modulation of the mucosal and systemic immune responses. These mechanisms are species and/or strain specific. There are also evidences that in some cases, a mix of probiotic strains can be more useful than each strain alone against this infection. In addition, the presence of one or more probiotic strains in a fermented product can improve the beneficial properties of the probiotic strains involved. It was also reviewed the security of probiotics administration after Salmonella infection in healthy host and in immunosuppressed or babies hosts. Although, the major part of the researches were performed in animal models through in vivo assays or by in vitro studies using human cell lines, some studies carried out in humans to verify the probiotic effects were also addressed in the present review. Nevertheless, is of critical importance to perform more clinical trials in humans to validate the results obtained with each specific probiotic strain or probiotic product. 相似文献
118.
Julian Salas Marina Alvarez Gabriel Gomez Janer Veras 《Building Research & Information》2013,41(6):367-376
In a previous issue the Instituto Eduardo Torroja in Spain described the development of lightweight panels made from ordinary Portland cement and rice husk ash (RHA). This paper discusses the crucial effect of the curing régime on compressive strength with temperatures maintained at 30C and relative humidity at 80 percent. 相似文献
119.
120.
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