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   43篇
  免费   0篇
化学工业   18篇
机械仪表   4篇
轻工业   3篇
无线电   3篇
一般工业技术   3篇
冶金工业   11篇
自动化技术   1篇
  2022年   2篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2014年   1篇
  2013年   3篇
  2011年   1篇
  2010年   1篇
  2009年   1篇
  2008年   1篇
  2007年   1篇
  2006年   2篇
  2005年   1篇
  2004年   1篇
  2002年   1篇
  1998年   5篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1993年   2篇
  1988年   1篇
  1984年   1篇
  1981年   2篇
  1962年   1篇
  1961年   2篇
  1960年   2篇
  1956年   1篇
排序方式: 共有43条查询结果,搜索用时 488 毫秒
11.
The primary aim of this study was to estimate heritabilities for different types of claw and foot disorders and the genetic relationship of disorders with milk yield and selected conformation traits by applying logistic models in Holstein dairy cattle. The study included data from 5634 Holstein cows kept on large-scale dairy farms in Eastern Germany. Dichotomous response variables were the presence or absence of the disorder in 2003. Cows that were present in herds for <6 wk in 2003 were excluded from the analysis. Incidences, disregarding repeated measurements, for digital dermatitis (DD), sole ulceration (SU), wall disorder (WD), and interdigital hyperplasia (IH) in rear legs were 13.2, 16.1, 9.6, and 6.3%, respectively. The herd effect was highly significant for all disorders. Incidences increased with increasing parities for SU and WD, but were highest among heifers for DD. High milk yield at the first 2 test d after calving was associated with a greater risk for claw and foot disorders in the same lactation. Estimates of heritability were 0.073 for DD, 0.086 for SU, 0.104 for WD, and 0.115 for IH. Genetically, health problems appear to occur in clusters (i.e., a cow showing one disease has an increased genetic risk of showing another claw disease). This phenomenon was also observed between claw and foot disorders and the somatic cell score. Genetic correlations between milk yield in early lactation and disorders were 0.240 for DD, 0.057 for SU, 0.270 for WD, and 0.336 for IH, indicating a physiological antagonism. Correlations between breeding values for claw and foot disorders of bulls and official breeding values for functional type traits were mostly favorable. Routine recording of claw data will offer a new chance to improve claw health within the population as was elaborated by different scenarios applying selection index procedures.  相似文献   
12.
Colocalization analysis is a powerful tool for the demonstration of spatial and temporal overlap in the distribution patterns of fluorescent probes. In unprocessed images, background affects image quality by impairing resolution and obscuring image detail in the low-intensity range. Because confocal images suffer from background levels up to 30% maximum intensity, colocalization analysis, which is a typical segmentation process, is limited to high-intensity signal. In addition, noise-induced, false-positive events ("dust") may skew the results. Therefore, suppression of background is crucial for this type of image analysis. Analysis of synthetic and biological objects demonstrates that median filtering is able to eliminate noise-induced colocalization events successfully. Its disadvantages include the occasional generation of false-positive and false-negative results as well as the inherent impairment of resolution. In contrast, image restoration by deconvolution suppresses background to very low levels (<10% maximum intensity), which makes additional objects in the low-intensity but high-frequency range available for analysis. The improved resolution makes this technique extremely suitable for examination of objects of near resolution size as demonstrated by correlation coefficients. Deconvolution is, however, sensitive to overestimation of the background level. Conclusions for practical application are: (1) In raw images, colocalization analysis is limited to the intensity range above the background level. This means the higher the RS/N the better. Unfortunately, images of most biological specimens have a low RS/N. (2) Filtering improves the result substantially. The reduction of background levels and the concomitant increase of the RS/N are generated at the expense of resolution. This is a quick and simple method in cases where resolution is not a major concern. (3) If colocalization in the low-intensity range and/or maximum resolution play a role, deconvolution should be used.  相似文献   
13.
Summary Films of cocoa butter, highly hydrogenated cottonseed oil, mixtures of highly hydrogenated cottonseed oil and cottonseed oil, chocolate liquor, and sweet milk chocolate were prepared; and their permeability to water vapor was determined by the cup method. The permeability constant was calculated in terms of grams of water diffusing through a centimeter cube in one second under a vapor pressure gradient of one millimeter of mercury across the cube. Under the test conditions employed, the permeability constant for cocoa butter at room temperature was found to vary from 5.8×10−12 to 81.6×10−12. The permeability constants for the highly hydrogenated cottonseed oil and the cocoa butter, under comparable conditions at room temperature, was found to be approximately 1.3×10−12 and 33×10−12, respectively. From data obtained with cocoa butter it was concluded that the permeability constant increased with moderate increases in film thickness. Polymorphism was found to have a large effect on permeability, an approximately 15-fold difference was found between quickly chilled and tempered films of cocoa butter at 3°C. (37.4°F.). The percentage of liquid component in the fat was found to have a large effect on permeability. The increasing of the percentage of liquid cottonseed oil in highly hydrogenated cottonseed oil from 0 to 40% increased the permeability constant from 1.3×10−12 to about 420×10−12. The permeability of chocolate liquor and sweet milk chocolate at room temperature was increased greatly when the relative humidity on the wet side of the films was increased to 100%. The nonfat components absorbed enough moisture to impair the structure of the film. Presented at the 32nd Fall Meeting of the American Oil Chemists' Society, Chicago, Ill., October 20–22, 1958. Fellow, National Confectioners' Association. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.  相似文献   
14.
Summary A palm kernel oil, mbocaya, possessing a relatively high iodine value, approximately 30, is being produced in Paraguay. Production can be expanded. One possible use for the oil is as a component of shortenings. As expected, consistency measurements showed the oil to be unsuited for conversion to shortening of the all-hydrogenated type. Blends with hydrogenated cottonseed oil yielded products having acceptable consistency characteristics. However, for a given consistency, the proportion of hydrogenated cottonseed oil needed was greater than that needed for a comparable blend with cottonseed oil. The difference was attributed to the formation of solid solutions or mixed crystals in the latter blend. A mixture of hydrogenated palm kernel oil and cottonseed oil was prepared and found to possess consistency characteristics better than those of a typical shortening of the all-hydrogenated type. Presented at the 28th Fall Meeting of the American Oil Chemists’ Society, Minneapolis, Minn., Oct. 11–13, 1954. Formerly Chief Chemist, Coindu, Asuncion, Paraguay. Sponsored by Institute of Inter-American Affairs under Point IV program. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.  相似文献   
15.
The transition from fossil fuels to renewable energy sources requires economic, high-performance electrochemical energy storage. High-temperature sodium-metal chloride batteries combine long cycle and calendar life, with high specific energy, no self-discharge, and minimum maintenance requirements, while employing abundant raw materials. However, large-scale deployment in mobility and stationary storage applications is currently hindered by high production cost of the complex, commercial tubular cells and limited rate capability. The present study introduces sodium-metal chloride cells with a simple, planar architecture that provide high specific power while maintaining the inherent high specific energy. Rational cathode design, considering critical transport processes and the effect of cathode composition on the cell resistance, enables the development of high-performance cells with average discharge power of 1022 W kg−1 and discharge energy per cycle of 258 Wh kg−1 on cathode composite level, shown over 140 cycles at an areal capacity of 50 mAh cm−2. This corresponds to a 3.2C discharge over 80% of full charge. Compared to the best performing planar sodium-metal chloride cells with similar cycling stability and mass loading in the literature, the presented performance represents an increase in specific power by more than a factor of four, while also raising the specific energy by 74%.  相似文献   
16.
简析干燥对皮革面积和柔软度的影响   总被引:1,自引:0,他引:1  
制革工作者都知道干燥是怎么回事,尽管这是道简单工序,但却在相当程度上决定皮革的特性,以及整个制革工艺的赢利率。  相似文献   
17.
Plant sterols (PSs) cannot be synthesized in mammals and are exclusively diet-derived. PSs cross the blood-brain barrier and may have anti-neuroinflammatory effects. Obesity is linked to lower intestinal uptake and blood levels of PSs, but its effects in terms of neuroinflammation—if any—remain unknown. We investigated the effect of high-fat diet-induced obesity on PSs in the brain and the effects of the PSs campesterol and β-sitosterol on in vitro microglia activation. Sterols (cholesterol, precursors, PSs) and polyunsaturated fatty acid-derived lipid mediators were measured in the food, blood, liver and brain of C57BL/6J mice. Under a PSs-poor high-fat diet, PSs levels decreased in the blood, liver and brain (>50%). This effect was reversible after 2 weeks upon changing back to a chow diet. Inflammatory thromboxane B2 and prostaglandin D2 were inversely correlated to campesterol and β-sitosterol levels in all brain regions. PSs content was determined post mortem in human cortex samples as well. In vitro, PSs accumulate in lipid rafts isolated from SIM-A9 microglia cell membranes. In summary, PSs levels in the blood, liver and brain were associated directly with PSs food content and inversely with BMI. PSs dampen pro-inflammatory lipid mediators in the brain. The identification of PSs in the human cortex in comparable concentration ranges implies the relevance of our findings for humans.  相似文献   
18.
A multistep procedure for the conversion of ergosterol into the tetrahydropyranyl ether of (24R)-24,25-dihydroxyprovitamin D3 using 1,4-dihydrophthalazine-1,4-dione as diene protecting agent was compared with an established route, which uses 4-phenyl-1,2,4-triazoline-3,5-dione for the protection of the diene system. The disclosed reaction sequence allows to double the overall yield. The 1,4-dioxo-1,2,3,4-tetrahydrophthalazin-2,3-ylene group proved to be the better diene protecting group in the ozonolytic degradation of the ergosterol side chain. Maintaining the protecting group in the next reaction steps offered further advantages by diminishing the air and light sensitivity of the intermediates.  相似文献   
19.
Severe Acute Respiratory Syndrome Corona Virus 2 has altered life on a global scale. A concerted effort from research labs around the world resulted in the identification of potential pharmaceutical treatments for CoVID-19 using existing drugs, as well as the discovery of multiple vaccines. During an urgent crisis, rapidly identifying potential new treatments requires global and cross-discipline cooperation, together with an enhanced open-access research model to distribute new ideas and leads. Herein, we introduce an application of a deep neural network based drug screening method, validating it using a docking algorithm on approved drugs for drug repurposing efforts, and extending the screen to a large library of 750,000 compounds for de novo drug discovery effort. The results of large library screens are incorporated into an open-access web interface to allow researchers from diverse fields to target molecules of interest. Our combined approach allows for both the identification of existing drugs that may be able to be repurposed and de novo design of ACE2-regulatory compounds. Through these efforts we demonstrate the utility of a new machine learning algorithm for drug discovery, SSnet, that can function as a tool to triage large molecular libraries to identify classes of molecules with possible efficacy.  相似文献   
20.
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