首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   129篇
  免费   23篇
化学工业   63篇
金属工艺   1篇
机械仪表   7篇
能源动力   2篇
轻工业   24篇
水利工程   1篇
无线电   2篇
一般工业技术   11篇
冶金工业   5篇
原子能技术   5篇
自动化技术   31篇
  2023年   2篇
  2022年   11篇
  2021年   11篇
  2020年   2篇
  2019年   6篇
  2018年   9篇
  2017年   7篇
  2016年   10篇
  2015年   10篇
  2014年   10篇
  2013年   9篇
  2012年   6篇
  2011年   13篇
  2010年   8篇
  2009年   8篇
  2008年   6篇
  2007年   4篇
  2006年   5篇
  2005年   1篇
  2004年   4篇
  2003年   2篇
  2002年   2篇
  2000年   3篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
排序方式: 共有152条查询结果,搜索用时 15 毫秒
41.
The electron cyclotron heating and current drive complex on the DIII-D tokamak presently comprises six gyrotrons injecting rf power from the low field side at 110 GHz, the 2f ce resonance at the center of the vacuum chamber. Typical injected rf power is 600–650 kW per gyrotron. The launched rf can be directed over ±20° toroidally to create both co- and counter-current drive and scanned over 40° poloidally to permit the injected rf beams to intersect, and be absorbed at, the second harmonic resonance anywhere in the tokamak upper half plane. The elliptical polarization is controlled so that the desired extraordinary or ordinary modes are excited for any injection geometry. The maximum injected energy on a single plasma shot has been 16.6 MJ for six gyrotrons injecting a total of 3.4 MW for 5 seconds.  相似文献   
42.
This paper investigates the manufacture of milk-based beverages by application of several Kombucha starters. Local Kombucha culture was grown up on three substrates: sweetened black and green tea, and topinambur. Their concentrates were obtained by vacuum-evaporation and amounts of 10% and 15% (v/v) were applied to milk (2.2% fat). The traditional yoghurt starter (B3) was applied for producing control samples. All fermentations were stopped when the pH reached 4.4. Fermentation curves were registered, linear for yoghurt and sigmoidal for Kombucha. Two times faster process was achieved with yoghurt starter. Influence of inoculum concentration on the rate of fermentation was insignificant. Viscosities were higher for Kombucha beverages at lower speeds of spindle, but lower at higher speeds of spindle. Very high sensory scores were achieved for all beverages, after production and after 5-days’ storage.  相似文献   
43.
Cat allergy is a major trigger factor for respiratory reactions (asthma and rhinitis) in patients with immunoglobulin E (IgE) sensitization. In this study, we used a comprehensive panel of purified cat allergen molecules (rFel d 1, nFel d 2, rFel d 3, rFel d 4, rFel d 7, and rFel d 8) that were obtained by recombinant expression in Escherichia coli or by purification as natural proteins to study possible associations with different phenotypes of cat allergy (i.e., rhinitis, conjunctivitis, asthma, and dermatitis) by analyzing molecular IgE recognition profiles in a representative cohort of clinically well-characterized adult cat allergic subjects (n = 84). IgE levels specific to each of the allergen molecules and to natural cat allergen extract were quantified by ImmunoCAP measurements. Cumulative IgE levels specific to the cat allergen molecules correlated significantly with IgE levels specific to the cat allergen extract, indicating that the panel of allergen molecules resembled IgE epitopes of the natural allergen source. rFel d 1 represented the major cat allergen, which was recognized by 97.2% of cat allergic patients; however, rFel d 3, rFel d 4, and rFel d 7 each showed IgE reactivity in more than 50% of cat allergic patients, indicating the importance of additional allergens in cat allergy. Patients with cat-related skin symptoms showed a trend toward higher IgE levels and/or frequencies of sensitization to each of the tested allergen molecules compared with patients suffering only from rhinitis or asthma, while there were no such differences between patients with rhinitis and asthma. The IgE levels specific to allergen molecules, the IgE levels specific to cat allergen extract, and the IgE levels specific to rFel d 1 were significantly higher in patients with four different symptoms compared with patients with 1–2 symptoms. This difference was more pronounced for the sum of IgE levels specific to the allergen molecules and to cat extract than for IgE levels specific for rFel d 1 alone. Our study indicates that, in addition to rFel d 1, rFel d 3, rFel d 4, and rFel d 7 must be considered as important cat allergens. Furthermore, the cumulative sum of IgE levels specific to cat allergen molecules seems to be a biomarker for identifying patients with complex phenotypes of cat allergy. These findings are important for the diagnosis of IgE sensitization to cats and for the design of allergen-specific immunotherapies for the treatment and prevention of cat allergy.  相似文献   
44.
This study sought to evaluate the efficacy of passive ultrasonic irrigation (PUI) on removing the smear layer and debris from root dentin using scanning electron microscopy (SEM). Twenty‐five bovine incisors were manually prepared and divided into three groups according to the final irrigation protocol: EDTA, final irrigation with 12 mL of 17% EDTA for 3 minutes followed by 5 mL of 2.5% NaOCl; EDTA/PUI, final flush with 4 mL of 17% EDTA and PUI for 30 seconds. These procedures were repeated three times to standardize the volume of the irrigant. Control group, after preparation, the specimens were irrigated only with 17 mL of 2.5% NaOCl. The roots were fractured and analyzed using SEM. The intragroup analysis revealed that the EDTA/PUI protocol removed a higher amount of debris at the cervical third (P = 0.03). The intergroup analysis revealed that EDTA/PUI presented the lowest amount of debris at the cervical third (P = 0.007). Smear layer scores were higher in the control group compared with the EDTA and EDTA/PUI groups, but only at the cervical third (P = 0.02). None of the final irrigant protocols completely removed the smear layer and debris. EDTA/PUI only improved the removal of debris at the cervical third. Microsc. Res. Tech. 76:496–502, 2013. © 2013 Wiley Periodicals, Inc.  相似文献   
45.
This study evaluated dentin bond strength (BS) and nanoleakage of non‐ and pre‐etched dentin immediately (T0,), 7 days (T7), and 14 days (T14) after bleaching. Bovine incisors (150) were selected and half of them submitted to intrapulpal dentin etching (e). Non‐ and pre‐etched dentin were subjected to the following (n = 15): no bleaching/control (C); 35% carbamide peroxide (CP); 35% hydrogen peroxide (35% HP); 25% hydrogen peroxide (25% HP); and sodium perborate (SP). Bleaching agents were applied to the pulp chamber four times within a 72‐h interval. Afterwards, pulp chamber dentin was prepared for the BS test at different evaluation times (n = 5): T0, T7, and T14. Composite blocks were built on pulp chamber and sectioned in slices. Slices were reduced to an hour‐glass shape with a cross‐sectional area of 0.8 mm2 and submitted to microtensile BS test. Two additional specimens for each group were prepared for nanoleakage evaluation by transmission electron microscopy (TEM). Results were analyzed by ANOVA (two‐way) and Dunnett's test (p < .05). BS decreased immediately after intracoronal bleaching for both sound and pre‐etched dentin (p < .05). At T14, the BS of non‐etched bleached dentin increased for all groups, whereas the pre‐etched SPe group presented BS similar to the Ce. Nanoleakage within the hybrid layer was perceptible immediately after bleaching, although a decrease in nanoleakage was observed for all groups at T14. Adhesive restorations should be performed 7–14 days after bleaching, according to the bleaching agent used. Intracoronal bleaching should be performed preferably with sodium perborate if previous dentin etching is applied.  相似文献   
46.
Coastal wetland vegetation along the Great Lakes differs strongly with latitude, but most studies of Great Lakes wetland condition have attempted to exclude the effect of latitude to discern anthropogenic effects on condition. We developed an alternative approach that takes advantage of the strong relationship between latitude and coastal wetland floristic condition. Latitude was significantly correlated with 13 of 37 environmental variables tested, including growing degree days, agriculture, atmospheric deposition, nonpoint-source pollution, and soil texture, which suggests that latitude is a good proxy for several environmental drivers of vegetation. Using data from 64 wetlands along the U.S. coast of Lakes Huron, Michigan, Erie, and Ontario, we developed linear regressions between latitude and two measures of floristic condition, the Floristic Quality Index (FQI, adj. r2 = 0.437, p < 0.001) and the first axis scores from a non-metric multidimensional scaling of wetland plant cover (MDS1, adj. r2 = 0.501, p < 0.001). Departures from the central tendency of these regression models represented wetlands of better or worse condition than expected for their latitude. This approach provides a means to identify wetlands worthy of preservation, to establish vegetation targets for wetland restoration, and to forecast changes in floristic quality associated with future climate change.  相似文献   
47.
An electrochemical, cationic, surfactant-selective sensor based on multiwalled carbon nanotubes (MWCNT) functionalized with a sulfate group and the cetylpyridinium ion (MWCNT–OSO3CP+) as a sensing material was used for optimization of the formulation of a fabric softener. Potentiometric titrations were performed and response measurements were obtained using four cationic surfactants (CS) of technical grade and four CS of analytical grade. The slope closest to Nernstian was obtained for di-(tallow carboxyethyl) hydroxyethyl methylammonium methosulfate (MAS) (59.5 ± 1.1 mV/decade of activity in water and 57.5 ± 1.3 mV/decade of activity in CaCl2). When using CS as analytes in potentiometric titrations, the best accuracy (99.8%) was obtained when using MAS; therefore, it was chosen as the CS for the fabric softener formulation. Due to the better properties of fabric softeners with silicone in their formulations, four silicones at several concentration levels were used as potential additives. Based on the stability and viscosity of the system, the diquaternary polydimethylsiloxane (DPS) (w = 0.19%) was chosen for the fabric softener formulation. The pH did not significantly influence the potential when in the range of 3–8 or the recovery of potentiometric titrations when in the range of 3–7. The application profile of the CS was assessed through streaming potential measurements of reference fabrics in an electrokinetic analyzer. The obtained electrokinetic parameters indicated on lag in adsorption of model fabric softener (MFS) based on MAS (w = 9%), with the addition of silicone DPS (MFS 3), on cotton and polyester fabrics, but advantage in stability when compared with other MFS investigated.  相似文献   
48.
49.
Fixed prosthetic restorations may generate periodontal irritation by various and complex mechanisms especially in the presence of the microbial factor. In this regard, changes that compromise the functional value of the support structures of the teeth occur. Studies on patients wearing fixed denture show that those prosthetic structures facilitate plaque accumulation. Close supervision leads to prevention of periodontal diseases, through learning of a proper hygiene. Between the marginal periodontium and the prosthetic restoration, there must be a relation of ‘mutual protection’ or at least ‘mutual respect’. In this study, we tried to analyze the reaction of the periodontal tissue in contact with fixed prosthesis depending on the prosthetic material used. There were 102 fixed prostheses considered by this study that have generated reactions in the periodontal tissues with which came into contact. Thus, from the total number of 102 fixed dental prostheses, 75% were made from metal alloys based on copper, 18% from Cr–Ni alloys, 2% from Cr–Co alloys, 4% from gold alloys, and one from stainless steel. In 35% of the cases, the patients had multiple fixed dentures made from different types of dental alloys, cases in which the symptoms of the periodontal problems may be also linked to the phenomenon of oral galvanism. The histological study showed various morphological changes from one patient to another, depending on the intensity of the inflammatory and reparative response, the associated diseases (diabetes, dyslipidemia, cardiovascular diseases) and especially on the dental hygiene status. Fixed prosthesis, in the absence of a proper cervical adaptation and an adequate local hygiene, may act as an irritative thorn and may induce gingivitis and periodontitis phenomena.  相似文献   
50.
Pure thermoplastic polyurethane (TPU), polypropylene (PP), and TPU/PP blends with different weight ratios prepared in a twin‐screw extruder were investigated by dynamic mechanical analysis (DMA), the universal tester for mechanical investigation, and by wide‐angle X‐ray diffraction (WAXD). The addition of PP above 20 wt % to the TPU stepwise changed the ductility and Young's modulus, i.e., apparently a kind of ductile → brittle transition occurred between TPU/PP 80/20 and TPU/PP 60/40 blends. This fact and the result of analysis of WAXD curves indicated matrix → dispersed phase inversion in this concentration region. TPU melt enabled easier migration of the PP chains and prolonged crystallization of PP matrix during solidification process affecting thus crystallite size, orientation, and crystallinity. In accordance to this fact, DMA results indicated partial miscibility of PP with polyurethane in the TPU/PP blends due to the lack of interfacial interaction and adhesion between the nonpolar crystalline PP and polar TPU phases. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3980–3985, 2007  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号