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   386篇
  免费   24篇
电工技术   4篇
化学工业   146篇
金属工艺   14篇
机械仪表   23篇
建筑科学   6篇
能源动力   26篇
轻工业   39篇
无线电   67篇
一般工业技术   42篇
冶金工业   12篇
原子能技术   6篇
自动化技术   25篇
  2022年   3篇
  2021年   8篇
  2020年   9篇
  2019年   3篇
  2018年   8篇
  2017年   7篇
  2016年   19篇
  2015年   11篇
  2014年   14篇
  2013年   27篇
  2012年   22篇
  2011年   20篇
  2010年   21篇
  2009年   17篇
  2008年   20篇
  2007年   10篇
  2006年   13篇
  2005年   9篇
  2004年   17篇
  2003年   32篇
  2002年   30篇
  2001年   11篇
  2000年   13篇
  1999年   14篇
  1998年   9篇
  1997年   6篇
  1996年   8篇
  1995年   4篇
  1994年   8篇
  1993年   6篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1983年   1篇
排序方式: 共有410条查询结果,搜索用时 15 毫秒
41.
The activation and degranulation of immune cells play a pivotal role in allergic inflammation, a pathological condition that includes anaphylaxis, pruritus, and allergic march-related diseases. In this study, trifuhalol A, a phlorotannin isolated from Agarum cribrosum, inhibited the degranulation of immune cells and the biosynthesis of IL-33 and IgE in differentiated B cells and keratinocytes, respectively. Additionally, trifuhalol A suppressed the IL-33 and IgE-mediated activation of RBL-2H3 cells through the regulation of the TAK1 and MK2 pathways. Hence, the effect of trifuhalol A on allergic inflammation was evaluated using a Compound 48/80-induced systemic anaphylaxis mouse model and a house dust mite (HDM)-induced atopic dermatitis (AD) mouse model. Trifuhalol A alleviated anaphylactic death and pruritus, which appeared as an early-phase reaction to allergic inflammation in the Compound 48/80-induced systemic anaphylaxis model. In addition, trifuhalol A improved symptoms such as itching, edema, erythema, and hyperkeratinization in HDM-induced AD mice as a late-phase reaction. Moreover, the expression of IL-33 and thymic stromal lymphopoietin, inflammatory cytokines secreted from activated keratinocytes, was significantly reduced by trifuhalol A administration, resulting in the reduced infiltration of immune cells into the skin and a reduction in the blood levels of IgE and IL-4. In summarizing the above results, these results confirm that trifuhalol A is a potential therapeutic candidate for the regulation of allergic inflammation.  相似文献   
42.
This work determined the characteristics of β-carotene produced from Rhodosporidium sp. isolated from citrus fruits, and an effective extraction method was established. To extract β-carotene from the isolated Rhodosporidium sp., the cell walls were destroyed using dimethyl sulfoxide (DMSO) solution with and without the use of glass beads and a sonicator. Extracted β-carotene was identified by high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) with a β-carotene standard. The yields of β-carotene extracted in DMSO, DMSO and glass beads, and DMSO with a sonicator were 3.371, 5.112, and 3.301 μg/mL, respectively. Isolated β-carotene was relatively heat stable, with 80% of the viable molecules remaining at 80°C.  相似文献   
43.
Catalytic destruction has been applied to control polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/Fs) emissions from different facilities. The cost of carbon-based catalysts is considerably lower than that of the metal oxide or zeolite-based catalysts used in the selective catalytic reduction (SCR) system. In this study, destruction and adsorption efficiencies of PCDD/Fs achieved with Cu/C and Fe/C catalysts from flue gas streams of a metal smelting plant (MSP) and a large-scale municipal waste incinerator (MWI), respectively, are evaluated via the pilot-scale catalytic reactor system (PCRS). The results indicate that Cu and Fe catalysts supported on carbon surface are capable of decomposing and adsorbing PCDD/ Fs from gas streams. In the testing sources of MSP and MWI, the PCDD/F removal efficiencies achieved with Cu/C catalyst at 250 degrees C reach 96%, however, the destruction efficiencies are negative (-1,390% and -112%, respectively) due to significant PCDD/F formation on catalyst promoted by copper. In addition, Fe/C catalyst is of higher removal and destruction efficiencies compared with Cu/C catalyst in both testing sources. The removal efficiencies of PCDD/Fs achieved with Fe/C catalyst are 97 and 94% for MSP and MWI, respectively, whereas the destruction efficiencies are both higher than 70%. Decrease of PCDD/F destruction efficiency and increase of adsorption efficiency with increasing chlorination of dioxin congeners is also observed in the test via three-layer Fe/C catalyst. Furthermore, the mass of 2,3,7,8-PCDD/Fs retained on catalyst decreases on the order of first to third layer of catalyst. Each gram Fe/C catalyst in first layer adsorbs 10.9, 6.91, and 3.04 ng 2,3,7,8-PCDD/Fs in 100 min testing duration as the operating temperature is controlled at 150, 200, and 250 degrees C, respectively.  相似文献   
44.
45.
The dynamics of diesel oil biodegradation were previously investigated at initial substrate concentrations of 1000 to 20,000 ppm using Gordonia nitida isolated from wastewater. Following the gas chromatogram profiles of diesel oil degradation, diesel oil with concentrations of up to 15,000 ppm was efficiently degraded by this strain. At a concentrations of 20,000 ppm, however, the degradation by this strain was not effective. The enhancement of the biodegradation of diesel oi1 (at 15,000 and 20,000 ppm) by a synthetic mycolic acid biosurfactant (at 9, 90 and 900 ppm) was also investigated. In G. nitida inoculated cultures, the degradation of diesel oil was enhanced by the biosurfactant. For comparison, diesel oil degradation in batch incubations was measured after the addition of rhamnolipid and other surfactants. Synthetic mycolic acid enhanced the degradation to a greater extent than any other surfactant tested. Additionally, it was demonstrated that the degradation-enhancing property of synthetic mycolic acid was similar to that of rhamnolipid and Tween 80.  相似文献   
46.
Previous gutting was applied to fresh kutum (Rutilus frissi kutum) to study the effects of cold smoking on the changes of rancidity and fatty acid (FA) content of the gutted and ungutted smoked kutum stored at room temperature (25 ± 2C) for 60 days. To do so, proximate (protein, ash, moisture and lipid), chemical (peroxide value [PV], thiobarbituric acid‐index [TBA‐i], total volatile basic nitrogen [TVB‐N] and FA profile) and pH analyses were carried out. The ungutting of kutum before smoking resulted in a higher degree of bacterial spoilage and oxidation during storage at room temperature, based on the results obtained from PV, TBA‐i, TVB‐N and FA content analyses. Moreover, pH as a critical factor on food spoilage showed a less decrease in smoked ungutted kutum during the 60‐day storage. It is concluded that the gutting of kutum before cold smoking is recommended as a pretreatment for storage at room temperature.  相似文献   
47.
Physical factors affecting the production of sisomicin byMicrornonospora inyoensis are presented. A sisomicin productivity was affected significantly by both the degree of aeration and the type of impeller used. In addition, the value of impeller tip speed was found to be an important factor in the sisomicin production. Therefore, scale-up on the basis of impeller tip speed was attempted and satisfactory results were obtained.  相似文献   
48.
The uncertainty associated with modeling and performance prediction of solar photovoltaic systems could be easily and efficiently solved by artificial intelligence techniques. During the past decade of 2009 to 2019, artificial neural network (ANN), fuzzy logic (FL), genetic algorithm (GA) and their hybrid models are found potential artificial intelligence tools for performance prediction and modeling of solar photovoltaic systems. In addition, during this decade there is no extensive review on applicability of ANN, FL, GA and their hybrid models for performance prediction and modeling of solar photovoltaic systems. Therefore, this article focuses on extensive review on design, modeling, maximum power point tracking, fault detection and output power/efficiency prediction of solar photovoltaic systems using artificial intelligence techniques of the ANN, FL, GA and their hybrid models. In addition, the selected articles on the solar radiation prediction using ANN, FL, GA and their hybrid models are also summarized. Total of 122 articles are reviewed and summarized in the present review for the period of 2009 to 2019 with 90 articles in the field of {ANN, FL, GA and their hybrid models} + solar photovoltaic systems and 32 articles in the field of {ANN, FL, GA and their hybrid models} + solar radiation. The review shows the suitability and reliability of ANN, FL, GA and hybrid models for accurate prediction of the solar radiation and the performance characteristics of solar photovoltaic systems. In addition, this review presents the guidance for the researchers and engineers in the field of solar photovoltaic systems to select the suitable prediction tool for enhancement of the performance characteristics of the solar photovoltaic systems and the utilization of the available solar radiation.  相似文献   
49.
Effect of nanoparticles on CHF enhancement in pool boiling of nano-fluids   总被引:1,自引:1,他引:1  
To investigate the characteristics of CHF (Critical Heat Flux) enhancement using nano-fluids, pool boiling CHF experiments of two water-based nano-fluids with titania and alumina nanoparticles were performed using electrically heated metal wires under atmospheric pressure. The results showed that the water-based nano-fluids significantly enhanced CHF compared to that of pure water. SEM (Scanning Electron Microscopy) observation subsequent to the pool boiling experiments revealed that a lot of nanoparticles were deposited on heating surface during pool boiling of nano-fluids. In order to investigate the role of the nanoparticle surface coating on CHF enhancement of nano-fluids, pool boiling CHF of pure water was measured using a nanoparticle-coated heater prepared by pool boiling of nano-fluids on a bare heater. It was found that pool boiling of pure water on the naonoparticle-coated heater sufficiently achieved the CHF enhancement of nano-fluids. It is supposed that CHF enhancement in pool boiling of nano-fluids is mainly caused by the nanoparticle coating of the heating surface.  相似文献   
50.
A novel salt-tolerant acid protease was produced from Aspergillus oryzae LK-101 (AOLK-101). The AOLK-101 protease was purified to homogeneity by ammonium sulfate precipitation, DEAE-Sephadex A-50 and Sephadex G-100 chromatographies in order. The specific activity and the purification ratio of the purified protease were 2,301 unit/mg and 11.6 fold, respectively, with 25 kDa of molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrpphoresis (SDS-PAGE). Its optimal pH and temperature were pH 6.5 and 50°C, respectively. This protease was relatively stable at pH 4.5–7.5, below 40°C, and up to 10% salt concentration. The protease was moderately inhibited by Ag2+ and Zn2+, and strongly by ethylenediamide tetraacetic acid (EDTA) and phenylmethysulfonyl fluoride (PMSF), but activated by Cu2+ and Mn2+. Therefore, the AOLK-101 protease was a serine protease based on the influence of metal ions and inhibitors. K m , V max , k cat , and k cat /K m values of AOLK-101 protease for hammastein milk casein were 1.04 mg/mL, 124.84 unit/L, 163.5/sec, and 3.9×106/m·sec, respectively.  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