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   153篇
  免费   19篇
化学工业   93篇
机械仪表   4篇
建筑科学   3篇
能源动力   3篇
轻工业   42篇
无线电   1篇
一般工业技术   16篇
冶金工业   4篇
自动化技术   6篇
  2024年   2篇
  2023年   1篇
  2022年   28篇
  2021年   39篇
  2020年   7篇
  2019年   7篇
  2018年   10篇
  2017年   5篇
  2016年   8篇
  2015年   6篇
  2014年   11篇
  2013年   7篇
  2012年   11篇
  2011年   10篇
  2010年   5篇
  2008年   3篇
  2007年   1篇
  2006年   6篇
  2001年   1篇
  1998年   1篇
  1987年   1篇
  1985年   1篇
  1983年   1篇
排序方式: 共有172条查询结果,搜索用时 31 毫秒
31.
Ni/La–Al2O3 and Ni/Ce–Al2O3 catalysts with a small amount of promoters intended for prereforming of LNG were characterized by XRF, N2 adsorption-desorption, XRD, H2 chemisorption, HRTEM and XPS. The catalytic activity was evaluated in methane steam reforming both in the kinetic and diffusion regime, at temperatures characteristic of pre-reforming. Carbonaceous deposit was analysed by TPO-MS method. The nature and location of the coke were studied by HRTEM.La or Ce addition into Ni–Al system causes the increase of the active surface area of Ni by enhancing its dispersion. Studies at kinetic regime have shown that the promoted catalysts have almost twice the activity than reference Ni–Al catalyst. This effect was not confirmed by measurements in the diffusion regime on whole catalyst tablets. Almost identical textural properties of catalysts and diffusive limitations related to them but not the catalytic properties of the material itself appeared to be crucial factors. The presence of La (but not Ce) causes a significant increase in resistance to coking.  相似文献   
32.
Psoriasis is a chronic, systemic inflammatory disease with a genetic background that involves almost 3% of the general population worldwide. Approximately, 70–90% of patients with psoriasis suffer from pruritus, an unpleasant sensation that provokes a desire to scratch. Despite the enormous progress in understanding the mechanisms that cause psoriasis, the pathogenesis of psoriasis-related pruritus still remains unclear. In order to improve patients’ quality of life, development of more effective and safer antipruritic therapies is necessary. In turn to make it possible, better understanding of complexed and multifactorial pathogenesis of this symptom is needed. In this article we have systematized the current knowledge about pruritus origin in psoriasis.  相似文献   
33.
Margarines and spreads contribute greatly to the intake of saturated and trans fats in the diet. Therefore, the objective of this work was to produce margarines using the oleogel technology and to verify the physical, thermal, oxidative, and sensorial properties of this product during six months of shelf life, comparing it with commercial margarine. When compared with commercial margarine, the oleogel margarine showed similar color results. Due to the different structural shape, the results of microstructure and the melting curve were differentiated, but this indicated a structure more resistant to temperature oscillations and an overall softer product. However, the sensorial difference between the samples was easily detected by the consumers, mainly with respect to the parameters of taste, texture, and overall impression. It was concluded that it is possible to produce margarines using the oleogel technology, which display good physical properties, similar shelf life, and improved nutritional characteristics.  相似文献   
34.
The stretch zone width (SZW) data for 15‐5PH steel CTOD specimens fractured at ?150°C to + 23°C temperature were measured based on focused images and 3D maps obtained by extended depth‐of‐field reconstruction from light microscopy (LM) image stacks. This LM‐based method, with a larger lateral resolution, seems to be as effective for quantitative analysis of SZW as scanning electron microscopy (SEM) or confocal scanning laser microscopy (CSLM), permitting to clearly identify stretch zone boundaries. Despite the worst sharpness of focused images, a robust linear correlation was established to fracture toughness (KC) and SZW data for the 15‐5PH steel tested specimens, measured at their center region. The method is an alternative to evaluate the boundaries of stretched zones, at a lower cost of implementation and training, since topographic data from elevation maps can be associated with reconstructed image, which summarizes the original contrast and brightness information. Finally, the extended depth‐of‐field method is presented here as a valuable tool for failure analysis, as a cheaper alternative to investigate rough surfaces or fracture, compared to scanning electron or confocal light microscopes. Microsc. Res. Tech. 75:1155–1158, 2012. © 2012 Wiley Periodicals, Inc.  相似文献   
35.
A collection of lactic acid bacteria isolated from both mayonnaise-based products and raw materials used to manufacture them was tested for antimicrobial activity. Out of 144 strains (97 lactobacilli, 23 lactococci and 24 enterococci) only three supernatants of Enterococcus spp. strains (EN3, EN14 and EN15) exhibited activity against lactobacilli and lactococci. The supernatant of the strain EN3 exclusively inhibited the growth of Bacillus cereus and Listeria monocytogenes. Enterococcus strains EN3, EN14 and EN15 produced thermostable bacteriocins, which had antibacterial activity.  相似文献   
36.
Mass spectrometric imaging (MSI) has become widely used in the analysis of a variety of biological surfaces. Biological samples are spatially, morphologically, and metabolically complex. Multimodal molecular imaging is an emerging approach that is capable of dealing with this complexity. In a multimodal approach, different imaging modalities can provide precise information about the local molecular composition of the surfaces. Images obtained by MSI can be coregistered with images obtained by other molecular imaging techniques such as microscopic images of fluorescent protein expression or histologically stained sections. In order to properly coregister images from different modalities, each tissue section must contain points of reference, which are visible in all data sets. Here, we report a newly developed coregistration technique using fiducial markers such as cresyl violet, Ponceau S, and bromophenol blue that possess a combination of optical and molecular properties that result in a clear mass spectrometric signature. We describe these fiducial markers and demonstrate an application that allows accurate coregistration and 3-dimensional reconstruction of serial histological and fluorescent microscopic images with MSI images of thin tissue sections from a breast tumor model.  相似文献   
37.
Polyethylene films coated by commercially available polyvinyldichloride (PVdC) as well as nitrocellulose (NC) lacquer with addition of natamycin preparation Delvocid® (16.7% w/w of natamycin in lacquer) were studied at 6 and 23 °C to determine the preservative migration into distilled water. The films released natamycin at maximal level 2.34 ± 0.32 mg/dm2. The diffusion coefficient of 0.79 × 10−10 ± 0.29 × 10−10 cm2/s and 1.03 × 10−10 ± 0.17 × 10−10 cm2/s was determined for natamycin transport in PVdC lacquer layer at 6 and 23 °C, respectively. For nitrocellulose lacquer the diffusion coefficient of 0.89 × 10−10 ± 0.16 × 10−10 cm2/s was found at 23 °C. The coextruded polyamide/polyethylene film coated with the PVdC lacquer containing both nisin (16.7% w/w of preparation Nisaplin®) and natamycin (see above) provided inhibitory effect against selected indicator microorganisms (Penicillium expansum, Fusarium culmorum, Lactobacillus helveticus, Listeria ivanovií). This film was unsuitable for the packaging of the surface ripened cheese Olomoucké tvar??ky. On the other hand, it was able to prevent the growth of spoilage microorganisms on the surface of the packaged soft cheese Bla?ácké zlato.  相似文献   
38.
Autophagy is a process of self-degradation that plays an important role in removing damaged proteins, organelles or cellular fragments from the cell. Under stressful conditions such as hypoxia, nutrient deficiency or chemotherapy, this process can also become the strategy for cell survival. Autophagy can be nonselective or selective in removing specific organelles, ribosomes, and protein aggregates, although the complete mechanisms that regulate aspects of selective autophagy are not fully understood. This review summarizes the most recent research into understanding the different types and mechanisms of autophagy. The relationship between apoptosis and autophagy on the level of molecular regulation of the expression of selected proteins such as p53, Bcl-2/Beclin 1, p62, Atg proteins, and caspases was discussed. Intensive studies have revealed a whole range of novel compounds with an anticancer activity that inhibit or activate regulatory pathways involved in autophagy. We focused on the presentation of compounds strongly affecting the autophagy process, with particular emphasis on those that are undergoing clinical and preclinical cancer research. Moreover, the target points, adverse effects and therapeutic schemes of autophagy inhibitors and activators are presented.  相似文献   
39.
The objective of this study was to determine the effect of thermal treatment (frying) of frozen seafood on the content of minerals and heavy metals. An analysis was conducted to compare concentration of sodium, magnesium, potassium, calcium, copper, iron, manganese, zinc, as well as lead, cadmium and mercury in the analysed tissues of invertebrates (shellfish – blue mussel, Japanese squid, white shrimp and octopus). Thermal processing (in this case, frying) applied to the frozen invertebrates was found to affect significantly the content of macro‐ and microelements as well as the content of heavy metals, except for potassium and manganese content in mussels and shrimps, respectively. Frozen and thermally treated (frying) mussels are characterised by significantly higher concentrations of the analysed minerals (except Na+, Ca+2, Cu+2), as well as higher concentrations of cadmium and mercury. In turn, shrimps and squids are invertebrates with lower content of both macro‐ and microelements.  相似文献   
40.
The effectiveness of opioids in the treatment of neuropathic pain is limited. It was demonstrated that magnesium ions (Mg2+), physiological antagonists of N-methyl-D-aspartate receptor (NMDAR), increase opioid analgesia in chronic pain. Our study aimed to determine the molecular mechanism of this action. Early data indicate the cross-regulation of µ opioid receptor (MOR) and NMDAR in pain control. Morphine acting on MOR stimulates protein kinase C (PKC), while induction of NMDAR recruits protein kinase A (PKA), leading to a disruption of the MOR-NMDAR complex and promoting functional changes in receptors. The mechanical Randall-Selitto test was used to assess the effect of chronic Mg2+ and morphine cotreatment on streptozotocin-induced hyperalgesia in Wistar rats. The level of phosphorylated NMDAR NR1 subunit (pNR1) and phosphorylated MOR (pMOR) in the periaqueductal gray matter was determined with the Western blot method. The activity of PKA and PKC was examined by standard enzyme immunoassays. The experiments showed a reduction in hyperalgesia after coadministration of morphine (5 mg/kg intraperitoneally) and Mg2+ (40 mg/kg intraperitoneally). Mg2+ administered alone significantly decreased the level of pNR1, pMOR, and activity of both tested kinases. The results suggest that blocking NMDAR signaling by Mg2+ restores the MOR-NMDAR complex and thus enables morphine analgesia in neuropathic rats.  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