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   3篇
化学工业   7篇
建筑科学   1篇
矿业工程   1篇
能源动力   10篇
轻工业   8篇
水利工程   1篇
无线电   1篇
一般工业技术   2篇
冶金工业   11篇
自动化技术   4篇
  2023年   1篇
  2022年   3篇
  2021年   2篇
  2020年   4篇
  2019年   1篇
  2016年   1篇
  2015年   2篇
  2014年   2篇
  2013年   1篇
  2012年   4篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2008年   1篇
  2007年   1篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
  1998年   7篇
  1997年   2篇
  1992年   3篇
  1989年   1篇
  1986年   1篇
  1977年   1篇
  1976年   1篇
排序方式: 共有46条查询结果,搜索用时 265 毫秒
31.
    
In this study, two distinct nanoparticles: aluminum oxide (Al2O3) and copper (Cu) are chosen as nanomaterials to examine the effects of nonlinear electrically conducting magnetohydrodynamic radiation on the flow of tangential hyperbolic hybrid nanofluid across a nonlinearly stretched sheet with convective boundary conditions. The equations that regulate fluid flow are represented as partial differential equations. These equations are reduced to their equivalent ordinary differential equations, which are solved using the homotopy analysis approach with the help of similarity variables. The effect of essential physical factors on fluid velocity, temperature, skin friction coefficient, and local Nusselt number is investigated and discussed. Results ascertain that the heat transfer rate of Cu/H2O nanofluid becomes high when equated to Cu–Al2O3/H2O nanofluid. Furthermore, the temperature distribution enhances with the rise in solid volume fraction while it diminishes with improved magnetic field for both nanofluid and hybrid nanofluid.  相似文献   
32.
33.
CONTEXT: A large number of epidemiologic studies have reported on associations between various "inflammatory" factors and coronary heart disease (CHD). OBJECTIVE: To assess the associations of blood levels of fibrinogen, C-reactive protein (CRP), and albumin and leukocyte count with the subsequent risk of CHD. DATA SOURCES: Meta-analyses of any long-term prospective studies of CHD published before 1998 on any of these 4 factors. Studies were identified by MEDLINE searches, scanning of relevant reference lists, hand searching of cardiology, epidemiology, and other relevant journals, and discussions with authors of relevant reports. STUDY SELECTION: All relevant studies identified were included. DATA EXTRACTION: The following information was abstracted from published reports (supplemented, in several cases, by the authors): size and type of cohort, mean age, mean duration of follow-up, assay methods, degree of adjustment for confounders, and relationship of CHD risk to the baseline assay results. DATA SYNTHESIS: For fibrinogen, with 4018 CHD cases in 18 studies, comparison of individuals in the top third with those in the bottom third of the baseline measurements yielded a combined risk ratio of 1.8 (95% confidence interval [CI], 1.6-2.0) associated with a difference in long-term usual mean fibrinogen levels of 2.9 pmol/L (0.1 g/dL) between the top and bottom thirds (10.3 vs 7.4 pmol/L [0.35 vs 0.25 g/dL]). For CRP, with 1053 CHD cases in 7 studies, the combined risk ratio of 1.7 (95% CI, 1.4-2.1) was associated with a difference of 1.4 mg/L (2.4 vs 1.0 mg/L). For albumin, with 3770 CHD cases in 8 studies, the combined risk ratio of 1.5 (95% CI, 1.3-1.7) was associated with a difference of 4 g/L (38 vs 42 g/L, ie, an inverse association). For leukocyte count, with 5337 CHD cases in the 7 largest studies, the combined risk ratio of 1.4 (95% CI, 1.3-1.5) was associated with a difference of 2.8 x 10(9)/L (8.4 vs 5.6 x 10(9)/L). Each of these overall results was highly significant (P<.0001). CONCLUSIONS: The published results from these prospective studies are remarkably consistent for each factor, indicating moderate but highly statistically significant associations with CHD. Hence, even though mechanisms that might account for these associations are not clear, further study of the relevance of these factors to the causation of CHD is warranted.  相似文献   
34.
We present an extension to the WET & STICKY model. A method of modelling textured and shiny paint is described using bump mapping and standard illumination models. The qualities of the paint are used to supply input to the texture and lighting models. We demonstrate that a dynamic model of textured paint provides the user with valuable visual cluesfor the production of realistic painted images. We also propose further extensions which would allow the use of different lighting models for different paints, allowing for paint attributes which are unachievable either with traditional painting or with earlier forms of electronic painting.  相似文献   
35.
We present a series of 38 cases of longitudinal splitting of the peroneus brevis tendon revealed by MR imaging (12 lesions were confirmed at surgery). MRI enabled classification in four surgical grades. The frequency of such lesions in chronic ankle instability as observed in our series is often reported in the literature. Bilateral cases are common. Asymptomatic cases do occur, especially in grades I and II. MRI has been shown to be a very effective investigation for demonstrating this tendinous lesion; the proton density weighted sequence in the axial plane is the most adequate sequence.  相似文献   
36.
South African power stations generate large amounts of highly alkaline fly ash (FA). This waste product has a serious impact on the environment. Acid mine drainage (AMD) is another environmental problem associated with mining. AMD has high heavy metal content in addition to high sulphate concentrations. Several studies have shown that 80–90% of sulphates can be removed when FA is co-disposed with AMD rich in Fe and Al. In South Africa, sources of contaminated mine waters, unlike AMD have circumneutral pH and much lower concentrations of Fe and Al, but rich in Ca and Mg. Treatment of such waters with FA resulted in no significant removal of sulphates when treated to pH less than 10. Subsequent treatment of circumneutral mine water to pH greater than 11 resulted in more than 60% sulphate removal. Treatment of circumneutral mine water to pH greater than 11 with FA followed by seeding with gypsum crystals and the addition of amorphous Al(OH)3 resulted in removal of sulphate to levels below the Department of Water Affairs and Forestry (DWAF) water quality effluent limit (500 ppm).  相似文献   
37.
The aim of this study was to determine whether an increase in circulating estrogen concentrations would increase percentage pregnant per artificial insemination (PP/AI) in a timed AI protocol in high-producing lactating dairy cows. We analyzed only cows having a synchronized ovulation to the last GnRH of the Ovsynch protocol (867/1,084). The control group (n = 420) received Ovsynch (GnRH - 7 d - PGF - 56 h - GnRH - 16 h - timed AI). The treatment group (n = 447) had the same timed AI protocol with the addition of 1 mg of estradiol-17β (E2) at 8 h before the second GnRH injection. Ovarian ultrasound and blood samples were taken just before E2 treatment of both groups. In a subset of cows (n = 563), pressure-activated estrus detection devices were used to assess expression of estrus at 48 to 72 h after PGF2α treatment. Ovulation was confirmed by ultrasound 7 d after timed AI. Treatment with E2 increased expression of estrus but overall PP/AI did not differ between E2 and control cows. There was an interaction between treatment and expression of estrus such that PP/AI was greater in E2-treated cows that showed estrus than in E2-treated or control cows that did not show estrus and tended to be greater than control cows that showed estrus. There was evidence for a treatment by ovulatory follicle size interaction on PP/AI. Supplementation with E2 improved PP/AI in cows ovulating medium (15 to 19 mm) but not smaller or larger follicles. The E2 treatment also tended to improve PP/AI in primiparous cows with low (≤2.5) body condition score, and in cows at first postpartum service compared with Ovsynch alone. In conclusion, any improvements in PP/AI because of E2 treatment during a timed AI protocol appear to depend on expression of estrus, parity, body condition score, and size of ovulatory follicle.  相似文献   
38.
In this paper, we study the thermal behavior of an assembly of rotating cylinders aligned in a cross-flow. The objective is to maximize the heat transfer rate density of the assembly, i.e. the overall heat transfer dissipated per unit of volume, under fixed pressure drop. A numerical model is used to solve the governing equations. Two configurations are studied: i) the cylinders rotate in the same direction, and ii) consecutive cylinders rotate in opposite directions. The spacing between consecutive cylinders is optimized in each case. The second configuration proved to be the more efficient. In that configuration, it is also possible to optimize further the architecture by using a smaller spacing for the flow passage in which the flow is in the direction of the cylinders rotation, and larger spacing for the flow passage in which the cylinders oppose the main stream.  相似文献   
39.
Titanium deposited from TiCl4 on crystalline or amorphous SiO2 catalyses the hydroxylation of phenol with aqueous H2O2. The amorphous silica-supported titanium shows a high rate of hydrogen peroxide conversion, however with a low selectivity towards aromatic hydroxylation products. A silicalite-supported titanium catalyst exhibits an efficiency towards hydroxylation products, based on hydrogen peroxide conversion, that is equal to that of titanium-silicalite-1 (TS-1), however with a lower activity.  相似文献   
40.
Berries, especially members of several families, such as Rosaceae (strawberry, raspberry, blackberry), and Ericaceae (blueberry, cranberry), belong to the best dietary sources of bioactive compounds (BAC). They have delicious taste and flavor, have economic importance, and because of the antioxidant properties of BAC, they are of great interest also for nutritionists and food technologists due to the opportunity to use BAC as functional foods ingredients. The bioactive compounds in berries contain mainly phenolic compounds (phenolic acids, flavonoids, such as anthocyanins and flavonols, and tannins) and ascorbic acid. These compounds, either individually or combined, are responsible for various health benefits of berries, such as prevention of inflammation disorders, cardiovascular diseases, or protective effects to lower the risk of various cancers. In this review bioactive compounds of commonly consumed berries are described, as well as the factors influencing their antioxidant capacity and their health benefits.  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