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51.
In this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm × 15 mm × 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 °C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO·Al2O3 precipitation observed along the frit–refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO·Al2O3 precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite. 相似文献
52.
It is quite common to see that classical periodic or Poisson packet traffic models are used for evaluating the performance of wireless sensor networks (WSNs). However, these models may not be appropriate for modeling the data traffic resulting from a particular application. Furthermore, they may be overestimating the performance of a WSN. In this paper, we show the significance of using a realistic and application-specific packet traffic model by comparing the performance of a well-known WSN protocol under the Surveillance WSN packet traffic model (SPTM), as well as under periodic and binomial traffic models. A packet traffic framework specific to surveillance applications is proposed which is then used for deriving SPTM analytically. In order to be adaptable and flexible, SPTM incorporates a probabilistic and parametric sensor detection model. Simulation results show that to employ an application-specific packet traffic model has significant impact on the performance evaluation of the WSN and ordinary traffic models may overestimate the capacity of the WSN. 相似文献
53.
54.
Aydin UNAL Kutay TASDEMIR Sema OYMAK Mustafa DURAN Ismail KOCYIGIT Fatih OGUZ Bulent TOKGOZ Murat Hayri SIPAHIOGLU Cengiz UTAS Oktay OYMAK 《Hemodialysis international. International Symposium on Home Hemodialysis》2010,14(4):398-402
The aim of this prospective study was to evaluate long‐term effects of arteriovenous fistula (AVF) on the development of pulmonary arterial hypertension (PAH) and the relationship between blood flow rate of AVF and pulmonary artery pressure (PAP) in the patients with end‐stage renal disease (ESRD). This prospective study was performed in 20 patients with ESRD. Before an AVF was surgically created for hemodialysis, the patients were evaluated by echocardiography. Then, an AVF was surgically created in all patients. After mean 23.50 ± 2.25 months, the second evaluation was performed by echocardiography. Also, the blood flow rate of AVF was measured at the second echocardiographic evaluation. Pulmonary arterial hypertension was defined as a systolic PAP above 35 mmHg at rest. Mean age of 20 patients with ESRD was 55.05 ± 13.64 years; 11 of 20 patients were males. Pulmonary arterial hypertension was detected in 6 (30%) patients before AVF creation and in 4 (20%) patients after AVF creation. Systolic PAP value was meaningfully lower after AVF creation than before AVF creation (29.95 ± 10.26 mmHg vs. 35.35 ± 7.86 mmHg, respectively, P: 0.047). However, there was no significant difference between 2 time periods in terms of presence of PAH (P>0.05). Pulmonary artery pressure did not correlate with blood flow rate of AVF and duration after AVF creation (P>0.05). In hemodialysis patients, a surgically created AVF has no significant effect on the development of PAH within a long‐term period. Similarly, blood flow rate of AVF also did not affect remarkably systolic PAP within the long‐term period. 相似文献
55.
Two donor‐acceptor systems, 4,7‐di‐2‐thienyl‐2,1,3‐benzoselenadiazole (TSeT) and 4,7‐di‐2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl‐2,1,3‐benzoselenadiazole (ESeE) are synthesized and electropolymerized to give polymers PTSeT and PESeE, respectively. One of the polymers, PTSeT, is blue‐green in the neutral state and soluble, exhibiting a deep‐red emission color. The other, PESeE, is the first 2,1,3‐benzoselenadiazole‐based neutral state green polymer with a narrow bandgap (1.04 eV). Furthermore, PESeE has superior and durable n‐ and p‐doping processes. Beyond the stability and the robustness, both of the polymer films exhibit multi‐electrochromic behavior. 相似文献
56.
57.
Ozan Gürbüz Duygu Göçmen Fatih Dagˇdelen Murat Gürsoy Sami Aydin İsmet Şahin Levent Büyükuysal Mehmet Usta 《Food chemistry》2007,100(2):518-525
Concentrations of trans-resveratrol, catechin and epicatechin were analyzed in musts and wines produced from seven red and four white grape cultivars from various wine growing regions of Turkey. Phenolics were quantified using an HPLC method optimized for the separation of wine phenolics. Wine samples contained higher phenolics levels than the corresponding musts. With the exception of Semillion, white wines and musts contained lower concentrations of phenolics than red wines and musts. However, the white cultivar Semillion had the highest concentrations of catechin and epicatechin among all wine and must samples. Semillion wine catechin and epicatechin were 13.7 and 11.8 mg/L, respectively. The highest level of trans-resveratrol among the white cultivars was found in Narince wine (1.93 mg/L). Within the red wine and must cultivars, Bo?azkere, Öküzgozü, and Cabernet contained the highest concentrations of flavan-3-ols and trans-resveratrol. Catechin was the major phenolic in all wines and most musts. Epicatechin was the major phenolic in 6 of the 11 must samples, but none of the wine samples. trans-Resveratrol was generally found in lowest concentrations in both wines and musts. 相似文献
58.
Smart structures and their applications on active vibration control: Studies in the Department of Aerospace Engineering, METU 总被引:1,自引:0,他引:1
Melin Sahin Fatih Mutlu Karadal Yavuz Yaman Omer Faruk Kircali Volkan Nalbantoglu Fatma Demet Ulker Tarkan Caliskan 《Journal of Electroceramics》2008,20(3-4):167-174
This work presents the theoretical and experimental studies conducted in Aerospace Engineering Department of Middle East Technical
University on smart structures with particular attention given to the structural modelling characteristics and active suppression
of in-vacuo vibrations. The smart structures considered in these analyses are finite and flat aluminium cantilever beam-like
(called as smart beam) and plate-like (called as smart fin) structures with surface bonded lead–zirconate–titanate patches.
Finite element models of smart beam and smart fin are obtained. Then the experimental studies regarding open loop behaviour
of the structures are performed by using strain gauges and laser displacement sensor to determine the system models. Further
studies are carried out to obtain H
∞ and μ-synthesis controllers which are intended to be used in the suppression of free and forced vibrations of the smart structures.
It is observed that satisfactory attenuation levels are achieved and robust performance of the systems in the presence of
uncertainties is ensured. In that respect a comparative study involving H
∞ and sliding mode controls is also conducted. Recently, the studies involving aerodynamic loading are also gathering pace. 相似文献
59.
Determination of biogenic amines in sucuk 总被引:1,自引:0,他引:1
Hüseyin Gencelep Güzin Kaban Muhammet rfan Aksu Fatih
z Mükerrem Kaya 《Food Control》2008,19(9):868-872
The biogenic amines content of sucuk (Turkish dry fermented sausage) were determined on 30 samples obtained from retail markets and butchers in Turkey. Also, pH and aw values, microbiological properties, and NPN levels of these samples were analyzed. The most important biogenic amines were tyramine (range 2.4–676 mg/kg), followed by putrescine varied from not detected to 364 mg/kg. Histamine content was under 50 mg/kg in 80% of the samples while it was over 100 mg/kg in only one sample. Tryptamine was detected in 16 of 30 samples in the range of 1.2–82.3 mg/kg.
Lactic acid bacteria, Micrococcus/Staphylococcus and Enterobacteriaceae counts of samples varied from 2.84 to 8.85 log cfu/g, <2.00 to 6.74 log cfu/g, and <2.00 to 5.04 log cfu/g, respectively. pH values were varied between 4.53 and 6.29 while water activity (aw) were measured to be between 0.761 and 0.960. NPN values were determined to be between 1.47% and 4.10%. Generally, total amine content was high in samples that had high NPN levels. 相似文献
60.
Mürüvvet Yurdako Mehmet Akay Yaln Tonbul Fatih Ok Kadir Yurdako 《Microporous and mesoporous materials》2008,111(1-3):211-218
Four pillared bentonites (Cr-PILB, Cr(acac)3-PILB, Fe-PILB and Fe(acac)3-PILB were prepared and characterized by X-ray diffraction (XRD), nitrogen sorption measurements and thermogravimetric (TG) analysis. The surface acidities of the samples and their structures were also investigated in the gas phase adsorption data of pyridine by the aid of FT-IR spectroscopic techniques. The XRD data and FT-IR spectra of the samples reflected mainly the structure of bentonite. The nitrogen adsorption–desorption isotherms of the samples were Type II shaped and showed in general mesoporous structures with pore openings of 4 nm. Two steps mass losses were observed in the TGA thermograms of B, Cr-PILB and Fe-PILB, while three steps mass losses were detected in the case of Cr(acac)3-PILB and Fe(acac)3-PILB. IR study by the adsorption of pyridine on the samples showed both Lewis and Brönsted acid sites on their surfaces. 相似文献