全文获取类型
收费全文 | 2394篇 |
免费 | 191篇 |
国内免费 | 129篇 |
专业分类
电工技术 | 43篇 |
综合类 | 89篇 |
化学工业 | 189篇 |
金属工艺 | 156篇 |
机械仪表 | 77篇 |
建筑科学 | 391篇 |
矿业工程 | 31篇 |
能源动力 | 16篇 |
轻工业 | 602篇 |
水利工程 | 25篇 |
石油天然气 | 32篇 |
武器工业 | 4篇 |
无线电 | 253篇 |
一般工业技术 | 229篇 |
冶金工业 | 248篇 |
原子能技术 | 137篇 |
自动化技术 | 192篇 |
出版年
2024年 | 5篇 |
2023年 | 40篇 |
2022年 | 64篇 |
2021年 | 125篇 |
2020年 | 107篇 |
2019年 | 113篇 |
2018年 | 108篇 |
2017年 | 112篇 |
2016年 | 103篇 |
2015年 | 79篇 |
2014年 | 103篇 |
2013年 | 358篇 |
2012年 | 131篇 |
2011年 | 145篇 |
2010年 | 100篇 |
2009年 | 129篇 |
2008年 | 101篇 |
2007年 | 105篇 |
2006年 | 110篇 |
2005年 | 75篇 |
2004年 | 92篇 |
2003年 | 70篇 |
2002年 | 63篇 |
2001年 | 41篇 |
2000年 | 29篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 30篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1979年 | 2篇 |
1963年 | 3篇 |
1962年 | 2篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1957年 | 3篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2714条查询结果,搜索用时 31 毫秒
1.
This study examined airborne emissions from cigarette butts for styrene, 2-methyl-2-cyclopenten-1-one, naphthalene, triacetin, and nicotine. Ten experiments were conducted by placing butts in a stainless steel chamber and measuring the chemical concentrations in chamber air. Emission rates were determined from the concentrations. Triacetin and nicotine concentrations were roughly 50% of initial concentrations after 100 hours, while concentrations of other chemicals decayed to less than 10% of initial concentrations within 24 hours. Initial emission rates per cigarette butt ranged from 200 to 3500 ng h−1. Triacetin and nicotine emission rates at 25°C were 1.6 to 2.2 times higher than the rates at 20°C, while the emission rates of other chemicals at 25°C were 1.1 to 1.3 times higher than the rates at 20°C only during the first sampling period. The chemical concentrations and emission rates at 30°C were comparable or lower than the values at 25°C, possibly due to different batches of cigarettes used. The 24-hours emitted mass of nicotine from a cigarette butt at 25°C could be up to 14% of the literature reported nicotine masses emitted from a burning cigarette. 相似文献
2.
Chidhathai Petchuay Phongdittha Moradok Somsak Intamat 《The International journal of environmental studies》2018,75(4):642-649
The paper reports a health risk assessment of pesticide exposure among chilli-growing farmers living in Na-Krasaeng Sub-District, Det Udom District, Ubon Ratchathani Province, Thailand. Personal air samples were collected from 46 participants spraying pesticide. These samples were analysed to investigate the farmers’ exposure by inhalation of the organophosphate, chlorpyrifos, which is the predominant pesticide used in the study area. The potential health risk of the farmers through inhalation was estimated by calculating the Hazard Quotient (HQ). The results showed that chlorpyrifos concentrations in inhaled air samples from the farmers ranged from less than the limit of detection, <LOD, to 0.041 mg/m3 with an average of 0.0072 mg/m3. Average daily doses (ADD) of exposure were calculated to be in the range 0–0.007 mg/kg/day with a mean value of 0.0014 mg/kg/day. The estimated risk quotient was 0 to 2.35 and the mean value was 0.84. Accordingly, the chilli-growing farmers were not considered to be a population at risk (mean value of HQ ≤ 1). But, the estimated risk of 17.38% of the study population was higher than the acceptable level (HQ > 1). This indicated that some participants were considered as an individual risk which should be of concern. 相似文献
3.
Smelling our appetite? The influence of food odors on congruent appetite,food preferences and intake
We are surrounded by sensory food cues, such as odors, that may trigger (un)conscious decisions and even lead to (over)eating, it is therefore crucial to better understand the effect of food odors on behavioral responses. Food odor exposure has been shown to enhance appetite for food products with similar properties: sensory-specific appetite. This suggests that based on previous encounters with foods, we have learned to detect the nutritional content of foods, through our sense of smell. We investigated the influence of aware exposure of macronutrient-related odors on various measures of eating behavior, in a cross-over intervention study. Thirty two normal-weight healthy and unrestrained Dutch females took part in five test sessions. On each test session, they were exposed to one of five conditions (active smelling of clearly noticeable odors representing food high in carbohydrates, protein, and fat, low in calories, and a no-odor condition for 3-min) and assessed on specific appetite, food preferences and intake. Odor exposure increased congruent appetite after protein-related odor exposure. Similarly, protein-related odor exposure influenced the liking for protein foods and the preference ranking for savory products. However, food intake was not affected by smelling congruent food odors. Together this indicates that exposure to (aware) food odors may mostly influence appetite, but does not impact subsequent food intake. Moreover, appetite seems to be triggered by taste qualities rather than macronutrient information of the food, as signaled by olfactory cues. Future studies should investigate the role of awareness in more detail, to fully understand how odors might be used to steer people towards healthier food choices. 相似文献
4.
G. C. Morrison H. V. Andersen L. Gunnarsen D. Varol E. Uhde B. Kolarik 《Indoor air》2018,28(1):188-197
Polychlorinated biphenyl (PCB) contamination of buildings continues to pose an exposure threat, even decades after their application in the form of calks and other building materials. In this research, we investigate the ability of clothing to sorb PCBs from contaminated air and thereby influence exposure. The equilibrium concentration of PCB‐28 and PCB‐52 was quantified for nine used clothing fabrics exposed for 56 days to air in a Danish apartment contaminated with PCBs. Fabric materials included pure materials such as cotton and polyester, or blends of polyester, cotton, viscose/rayon, and/or elastane. Air concentrations were fairly stable over the experimental period, with PCB‐28 ranging from 350 to 430 ng/m3 and PCB‐52 ranging from 460 to 550 ng/m3. Mass accumulated in fabric ranged from below detection limits to 4.5 mg/g of fabric. Cotton or materials containing elastane sorbed more than polyester materials on a mass basis. Mass‐normalized partition coefficients above detection limits ranged from 105.7 to 107.0 L/kg. Clothing acts as a reservoir for PCBs that extends dermal exposure, even when outside or in uncontaminated buildings. 相似文献
5.
Oxygenated VOCs,aqueous chemistry,and potential impacts on residential indoor air composition 下载免费PDF全文
Dampness affects a substantial percentage of homes and is associated with increased risk of respiratory ailments; yet, the effects of dampness on indoor chemistry are largely unknown. We hypothesize that the presence of water‐soluble gases and their aqueous processing alters the chemical composition of indoor air and thereby affects inhalation and dermal exposures in damp homes. Herein, we use the existing literature and new measurements to examine the plausibility of this hypothesis, summarize existing evidence, and identify key knowledge gaps. While measurements of indoor volatile organic compounds (VOCs) are abundant, measurements of water‐soluble organic gases (WSOGs) are not. We found that concentrations of total WSOGs were, on average, 15 times higher inside homes than immediately outside (N = 13). We provide insights into WSOG compounds likely to be present indoors using peer‐reviewed literature and insights from atmospheric chemistry. Finally, we discuss types of aqueous chemistry that may occur on indoor surfaces and speculate how this chemistry could affect indoor exposures. Liquid water quantities, identities of water‐soluble compounds, the dominant chemistry, and fate of aqueous products are poorly understood. These limitations hamper our ability to determine the effects of aqueous indoor chemistry on dermal and inhalation exposures in damp homes. 相似文献
6.
7.
Whereas large-scale consumption of energy-dense foods contributes to climate change, we investigated whether exposure to climate change-induced food scarcity affects preferences toward these foods. Humans’ current psychological mechanisms have developed in their ancestral evolutionary past to respond to immediate threats and opportunities. Consequently, these mechanisms may not distinguish between cues to actual food scarcity and cues to food scarcity distant in time and space. Drawing on the insurance hypothesis, which postulates that humans should respond to environmental cues to food scarcity through increased energy consumption, we predicted that exposing participants to climate change-induced food scarcity content increases their preferences toward energy-dense foods, with this effect being particularly pronounced in women. Three experiments—including one preregistered laboratory study—confirm this notion. Our findings jointly demonstrate that receiving information about food shortages distant in time and space can influence current food preferences. 相似文献
8.
Package design influences consumers’ expectations of a product’s sensory properties and expected healthiness and/or tastiness, and potentially also changes actual product perception during consumption. The robustness of these effects is far from clear, however. This study investigated the influence of package cues signalling either hedonic or healthy product properties on expectations and subsequent product evaluation over repeated consumption.In a between-subjects design, 92 participants evaluated product expectations and taste perceptions of a chocolate-sesame flavoured biscuit with a package emphasizing either its healthy (n = 44) or hedonic (n = 48) aspects, both at a central location (CLT) and during six home use tests (HUT), using both explicit (questionnaires) and implicit (IAT) measures.Package design significantly affected (p < 0.05) consumers’ expectations of the product. They expected the biscuit to be tastier, less attractive and less healthy in the hedonic package condition, and less tasty, more attractive and healthier in the healthy package condition. However, these effects did not transfer to actual product evaluations upon tasting, either blind or tasting in combination with viewing the package during the HUTs. Implicit attitudes did change as a result of repeated exposures, depending on the package consumers were provided with, indicating product-package interactions over time (p < 0.05).In conclusion, package design influences product expectations and associations with its healthiness and attractiveness, which is of relevance in product choice and purchase settings. However, at the stage of (repeated) consumption, intrinsic (sensory) properties become the dominant drivers of products’ sensory and hedonic evaluations, and the impact of package cues seems less potent. 相似文献
9.
Association of size‐fractionated indoor particulate matter and black carbon with heart rate variability in healthy elderly women in Beijing 下载免费PDF全文
W. Dong L. Pan H. Li M. R. Miller M. Loh S. Wu J. Xu X. Yang J. Shan Y. Chen F. Deng X. Guo 《Indoor air》2018,28(3):373-382
Associations between size‐fractionated indoor particulate matter (PM) and black carbon (BC) and heart rate variability (HRV) and heart rate (HR) in elderly women remain unclear. Twenty‐nine healthy elderly women were measured for 24‐hour HRV/HR indices. Real‐time size‐fractionated indoor PM and BC were monitored on the same day and on the preceding day. Mixed‐effects models were applied to investigate the associations between pollutants and HRV/HR indices. Increases in size‐fractionated indoor PM were significantly associated with declines in power in the high‐frequency band (HF), power in the low‐frequency band (LF), and standard deviation of all NN intervals (SDNN). The largest decline in HF was 19% at 5‐minute moving average for an interquartile range (IQR) increase (24 μg/m3) in PM0.5. The results showed that smaller particles could lead to greater reductions in HRV indices. The reported associations were modified by body mass index (BMI): Declines in HF at 5‐minute average for an IQR increase in PM0.5 were 34.5% and 1.0% for overweight (BMI ≥25 kg/m2) and normal‐weight (BMI <25 kg/m2) participants, respectively. Moreover, negative associations between BC and HRV indices were found to be significant in overweight participants. Increases in size‐fractionated indoor PM and BC were associated with compromised cardiac autonomic function in healthy elderly women, especially overweight ones. 相似文献
10.
In May 2018,the primetime news casted a shocking report saying that radon concentration on a certain model of bed mattress found to be as high as 2 200 Bq/m3.After a humble,the Nuclear Safety and Security Commission(NSSC) of Korea confirmed that significant amount of thoron gas is emanated from several mattress models marketed by a company claiming beneficial health effects of negative ions.Laboratory analysis showed that some internal fabric sheets of those mattresses contain high concentration of Th-232.It was revealed that the manufacture treated the material with so-called ‘negative ion powder’ procured from the market and NSSC found that its radioactive content is the monazite powder.Although measurements with reliable instruments resulted in somewhat lower values,the tentative but conservative estimates of doses to the users are still remarkable,ranging from a few to 14 mSv a year.Most of the affected models have been marketed from 2010 but earlier models,with lower thorium content,were supplied from 2006.As many as 88,000 mattresses have been produced.The manufacturer with help of the government,recalled all the affected models and separated the radioactive internals.A large amount of waste is waiting for the government decision on disposal method.Similar problems were identified in other consumer products including latex mattresses and pillows imported,hot pads,and several models of sanitary or health-aid goods.These episodes called for revisiting NORM control strategy in Korea. 相似文献