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   632篇
  免费   26篇
  国内免费   1篇
电工技术   1篇
化学工业   178篇
金属工艺   11篇
机械仪表   10篇
建筑科学   25篇
矿业工程   2篇
能源动力   14篇
轻工业   136篇
水利工程   6篇
石油天然气   1篇
无线电   46篇
一般工业技术   84篇
冶金工业   76篇
原子能技术   1篇
自动化技术   68篇
  2023年   2篇
  2022年   11篇
  2021年   17篇
  2020年   8篇
  2019年   13篇
  2018年   9篇
  2017年   8篇
  2016年   13篇
  2015年   11篇
  2014年   13篇
  2013年   32篇
  2012年   27篇
  2011年   40篇
  2010年   23篇
  2009年   28篇
  2008年   41篇
  2007年   39篇
  2006年   22篇
  2005年   28篇
  2004年   27篇
  2003年   22篇
  2002年   21篇
  2001年   9篇
  2000年   9篇
  1999年   10篇
  1998年   21篇
  1997年   21篇
  1996年   12篇
  1995年   13篇
  1994年   15篇
  1993年   9篇
  1992年   7篇
  1991年   10篇
  1990年   4篇
  1989年   8篇
  1988年   10篇
  1987年   7篇
  1986年   3篇
  1985年   5篇
  1984年   4篇
  1983年   3篇
  1982年   4篇
  1981年   4篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1977年   3篇
  1976年   3篇
  1975年   3篇
  1971年   1篇
排序方式: 共有659条查询结果,搜索用时 15 毫秒
651.
In the field of plasma spray technologies, new processes are developing to obtain coatings with nanostructured architectures. Difficulties of understanding and controlling the process originate from the continuous injection of a liquid material and the power instabilities of the current torches which strongly affect the heat and momentum transfers to the nanometric particles. This paper reports an original method to make TiO2 coatings by suspension plasma spraying. A direct current (DC) power supply applying time-modulated current amplitude to a custom DC torch is used to generate at low power (1.5 kW) a pulsed laminar plasma jet with periodic oscillations of its properties. To make best use of this pulsed mode, a synchronization device was developed. It allows triggering from the arc voltage an inkjet nozzle to deliver at a precise moment a single droplet to improve the control of plasma/material interaction. An ink of TiO2 anatase solid particles is formulated to be compatible with a drop-on-demand printhead dispenser. In-flight diagnostic is made by optical emission spectroscopy and a fast shutter camera. TiO2 coatings are characterized by scanning electron microscopy, x-ray diffraction and transmission electron microscopy. Results show that homogeneous TiO2 coatings of nanostructured cauliflowers shapes are obtained thanks to the controlled injection system. A competition between nucleation mechanism and liquid particles deposition are also observed. These deposits correspond to a mixture of anatase and rutile phases.  相似文献   
652.
To estimate the dietary exposure of the main minerals and trace elements from retail food typically consumed by the French population, samples were purchased and then prepared and cooked prior to analysis. A total of 1080 individual food composites samples were collected and analysed for 18 elements (arsenic, lead, cadmium, aluminium, mercury, antimony, chrome, calcium, manganese, magnesium, nickel, copper, zinc, lithium, sodium, molybdenum, cobalt and selenium). Intakes were calculated from different food consumption patterns found in France for average and high consumers among adults and children. Dietary exposures of those consumers estimated from the France 2000 Total Diet Study (FTDS) are reported, and compared with existing nutritional reference values (Lowest threshold Intake, LTI) or toxicological reference values (Provisional Tolerable Weekly Intake, PTWI or Upper Level, UL) of the respective element and from previous French studies. This study confirms for the populations concerned, the low probability of nutritional or health risks due to food consumption.  相似文献   
653.
Fine particulate matter present in urban areas seems to be incriminated in respiratory disorders. The aim of this study was to relate physicochemical characteristics of PM2.5 (particulate matter collected with a 50% efficiency for particles with an aerodynamic diameter of 2.5 microm) to their biological activities toward a bronchial epithelial cell line 16-HBE. Two seasonal sampling campaigns of particles were realized, respectively, in a kerbside and an urban background station in Paris. Sampled-PM2.5 mainly consist of particles with a size below 1 microm and are mainly composed of soot as assessed by analytical scanning electron microscopy. The different PM2.5 samples contrasted in their PAH content, which was the highest in the kerbside station in winter, as well as in their metal content. Kerbside station samples were characterized by the highest Fe and Cu content, which appears correlated to their hydroxyl radical generating properties measured by electron paramagnetic resonance. Particles were compared by their capacity to induce cytotoxicity, intracellular ROS production, and proinflammatory cytokine release (GM-CSF and TNF-alpha). At a concentration of 10 microg/cm2, all samples induced peroxide production and cytokine release to the similar extent in the absence of cytotoxicity. In conclusion, whereas the PM2.5 samples differ by their PAH and metal composition, they induce the same biological responses likely either due to components bioavailability and/ or interactions between PM components.  相似文献   
654.
The addition of fiber to foods and beverages has been linked with greater satiety and reduced energy intakes at the next meal. However, measures of satiety can be influenced by the time interval between beverage consumption and the next meal. The objective of this study was to determine how the time interval between consumption and a subsequent test meal impacts the satiating power of a low-calorie beverage supplemented with low-viscosity pectin fiber. Forty-two participants (20 men, 22 women) each participated in 4 study sessions. Study preloads were 2 low-calorie beverages (355 mL, 8 kcal) containing either 0 g fiber (no fiber) or 8 g low-viscosity fiber (added fiber). These preloads were consumed either 90 min before lunch or 15 min before lunch. Every 15 min, participants rated hunger, desire to eat, fullness, and thirst using 100-mm visual analogue scales. A test lunch was served and plate waste was measured. Beverages with added fiber reduced energy intakes at lunch relative to those without fiber. A short delay (15 min) between beverage consumption and a subsequent meal was associated with higher satiety ratings and reduced energy intakes, regardless of fiber content. The addition of low-viscosity pectin to low-calorie beverages reduced energy intakes at the next meal, presenting a possible tool for intake regulation. A short time interval between consumption of a low-calorie beverage and a meal also increased satiety and decreased food intake, reflecting the short-lived effect of volume.  相似文献   
655.
This paper presents the ability of electrostatic sprayed tin oxide (SnO2) and tin oxide doped with copper oxide (1, 2, and 4 at.% Cu) films to detect different pollutant gases, i.e., H2S, SO2, and NO2. The influence of a copper oxide dopant on the SnO2 morphology is studied using scanning electron microscopy (SEM) technique, which reveals a small decrease in the porosity and particle size when the amount of dopant is increased. The sensing properties of the SnO2 films are greatly improved by doping, i.e., the Cu-doped SnO2 films have large response to low concentration (10 ppm) of H2S at low operating temperature (100 °C). Furthermore, no cross-sensitivity to 1 ppm NO2 and 20 ppm SO2 is observed. Among the studied films, the 1 at.% Cu-doped SnO2 layer is the most sensitive in the detection of all the studied gases.  相似文献   
656.

Objective

Reducing the rates of death, trauma and sequelae associated with road accidents is the prime goal of road safety authorities, and success requires having data on victims’ outcomes in the long term. The present study examined the outcome of adult road accident victims one year after their accident.

Design

A follow-up study.

Methods

The cohort comprised 886 injured road-accident victims, aged ≥16 years, and living in the Rhône administrative Département, France (taken from the ESPARR Cohort). Data were collected on victim characteristics at the time of crash, and self-reported outcomes one year later. The population of respondents at the one-year questionnaire follow-up was divided into two categories according to injury severity, as mild-to-moderate (M.AIS < 3) or severe (M.AIS 3+). Qualitative variables were compared between these 2 groups using Chi2 or Fisher exact tests.

Results

At one year post-accident, 45% of the mild-to-moderate injury group versus only 20% of severely injured subjects reported full recovery of health (p < 0.001). 20% of the cohort, as a whole, reported permanent pain. More than half of the severely injured subjects reported that the accident had had an impact on the everyday life of their family; this was twice as many as in the mild-to-moderate injury group (55% vs. 22%). Most of the severely injured reported impact on leisure, projects and emotional life: 20% reported relational difficulties in the couple, 16% reported impaired sexual life, and the rate of separation was significantly higher than in the mild-to-moderate injury group (5% vs. 1%; p < 0.001). Mean time off work was significantly longer in the severe injury group: 245 ± 158 days vs. 75 ± 104 days (p < 0.001); and 32% of the severe injury group (p < 0.001) who had stopped work had not returned at 1 year, compared to 5% of the mild-to-moderate injury group.

Conclusions

One year after a road accident, the consequences for victims remain significant. In terms of physical impact, pain frequently persists, impairing daily life for many. There is an elevated rate of chronic PTSD (post-traumatic stress disorder) and a non-negligible impact on affective and occupational life.  相似文献   
657.
This paper discusses the efficiency of several Compactly Supported Radial Basis Functions (CSRBFs) for the eigenanalysis of 3D acoustic cavities using the Particular Integral Method. Starting with the two most popular CSRBF families due to Wendland and Wu, a third family proposed by Buhmann is suggested. Results on rectangular parallelepiped highlight the benefit of CSRBFs compared to the classical conical function, especially when dealing with cavities discretized by few elements. On the other hand, when the mesh is refined, numerical difficulties arise and particular attention should be paid to the order of the employed CSRBF. Indeed, and while the conical function is likely to be the most robust function, high-order CSRBFs should be avoided. However, the proposed Buhmann's functions appear to bring significant improvements on eigenanalysis when compared to their Wendland and Wu counterparts.  相似文献   
658.
Flaxseeds are typically consumed either as whole flaxseed, ground flaxseed, flaxseed oil, partially defatted flaxseed meal, or as a milk alternative. They are considered a rich source of vitamins, minerals, proteins and peptides, lipids, carbohydrates, lignans, and dietary fiber, which have shown hypolipidemic, antiatherogenic, anticholesterolemic, and anti-inflammatory property activity. Here, an in vitro batch culture model was used to investigate the influence of whole milled flaxseed and partially defatted milled flaxseed press cake on the gut microbiota and the liberation of flaxseed bioactives. Microbial communities were profiled using 16S rRNA gene-based high-throughput sequencing with targeted mass spectrometry measuring lignan, cyclolinopeptide, and bile acid content and HPLC for short-chain fatty acid profiles. Flaxseed supplementation decreased gut microbiota richness with Firmicutes, Proteobacteria, and Bacteroidetes becoming the predominant phyla. Secoisolariciresinol, enterodiol, and enterolactone were rapidly produced with acetic acid, butyric acid, and propionic acid being the predominant acids after 24 h of fermentation. The flaxseed press cake and whole flaxseed were equivalent in microbiota changes and functionality. However, press cake may be superior as a functional additive in a variety of foods in terms of consumer acceptance as it would be more resistant to oxidative changes.  相似文献   
659.
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