首页 | 官方网站   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   418篇
  免费   24篇
工业技术   442篇
  2023年   1篇
  2021年   19篇
  2020年   7篇
  2019年   10篇
  2018年   15篇
  2017年   9篇
  2016年   12篇
  2015年   6篇
  2014年   18篇
  2013年   24篇
  2012年   25篇
  2011年   35篇
  2010年   28篇
  2009年   21篇
  2008年   21篇
  2007年   21篇
  2006年   17篇
  2005年   18篇
  2004年   11篇
  2003年   9篇
  2002年   7篇
  2001年   5篇
  2000年   5篇
  1999年   5篇
  1998年   7篇
  1997年   13篇
  1996年   7篇
  1995年   10篇
  1994年   9篇
  1993年   4篇
  1992年   2篇
  1991年   2篇
  1990年   6篇
  1989年   3篇
  1988年   5篇
  1987年   2篇
  1986年   2篇
  1985年   4篇
  1984年   3篇
  1983年   1篇
  1982年   3篇
  1977年   2篇
  1976年   4篇
  1970年   2篇
  1967年   2篇
排序方式: 共有442条查询结果,搜索用时 203 毫秒
61.
62.
198 men and 413 women responded to random telephone surveys in Fargo, North Dakota and Memphis, Tennessee. Each S was given the Smoking Attitudes Survey, which assesses generalized health beliefs and health-related problems associated with smoking. Ss' knowledge of smoking-associated diseases and diseases not associated with smoking was also assessed. Stepwise regression analysis of composite knowledge scores revealed 4 predictors of the health consequences of smoking: education, race, smoking status, and income. Smokers reported less knowledge and less concern about health consequences of smoking, were more likely to be male, and were more concerned about health consequences of cholesterol. The best predictor of smokers who had never attempted cessation was their greater concern over weight control, compared with smokers with a history of smoking-cessation attempts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
63.
Fog formation on transparent substrates constitutes a major challenge in several optical applications requiring excellent light transmission characteristics. Anti-fog coatings are hydrophilic, enabling water to spread uniformly on the surface rather than form dispersed droplets. Despite the development of several anti-fog coating strategies, the long-term stability, adherence to the underlying substrate, and resistance to cleaning procedures are not yet optimal. We report on a polymer-based anti-fog coating covalently grafted onto glass surfaces by means of a multistep process. Glass substrates were first activated by plasma functionalization to provide amino groups on the surface, resulting in the subsequent covalent bonding of the polymeric layers. The anti-fog coating was then created by the successive spin coating of (poly(ethylene-maleic anhydride) (PEMA) and poly(vinyl alcohol) (PVA) layers. PEMA acted as an interface by covalently reacting with both the glass surface amino functionalities and the PVA hydroxyl groups, while PVA added the necessary surface hydrophilicity to provide anti-fog properties. Each step of the procedure was monitored by XPS, which confirmed the successful grafting of the coating. Coating thickness was evaluated by profilometry, nanoindentation, and UV visible light transmission. The hydrophilic nature of the anti-fog coating was assessed by water contact angle (CA), and its anti-fog efficiency was determined visually and tested quantitatively for the first time using an ASTM standard protocol. Results show that the PEMA/PVA coating not only delayed the initial period required for fog formation but also decreased the rate of light transmission decay. Finally, following a 24 hour immersion in water, these PEMA/PVA coatings remained stable and preserved their anti-fog properties.  相似文献   
64.
The objective of this study was to determine i) if Camembert cheese micro-organisms could be detected in fecal samples after regular consumption by human subjects and ii) the consequence of this consumption on global metabolic activities of the host colonic microbiota. An open human protocol was designed where 12 healthy volunteers were included: a 2-week period of fermented products exclusion followed by a 4-weeks Camembert ingestion period where 2x40 g/day of Camembert cheese was consumed. Stools were collected from the volunteers before consumption, twice during the ingestion period (2nd and 4th week) and once after a wash out period of 2 weeks. During the consumption of Camembert cheese, high levels of Lactococcus lactis and Leuconostoc mesenteroides were measured in fecal samples using real-time quantitative PCR, reaching median values of 8.2 and 7.5 Log(10) genome equivalents/g of stool. For Ln. mesenteroides, persistence was observed 15 days after the end of Camembert consumption. The survival of Geotrichum candidum was also assessed and the fecal concentration reached a median level of 7.1 Log(10) CFU/g in stools. Except a decreasing trend of the nitrate reductase activity, no significant modification was shown in the metabolic activities during this study.  相似文献   
65.
5H-Dibenzol[b,f]azepine-10,11-epoxide and 10,11-dihydro-10,11-dihydroxy-5H-dibenzo[b,f]azepine were identified by gas chromatography-mass spectrometry in rat urine as the main biotransformation products in the metabolism of 5H-dibenzo[b,f]azepine (iminostilbene). The presence of these metabolites was confirmed in vitro by incubating iminostilbene with rat liver microsomal enzymes.  相似文献   
66.
67.
In this quasi-experimental study among staff of 29 oncology wards, the authors evaluated the effects of a team-based burnout intervention program combining a staff support group with a participatory action research approach. Nine wards were randomly selected to participate in the program. Before the program started (Time 1), directly after the program ended (Time 2), and 6 months later (Time 3), study participants filled out a questionnaire on their work situation and well-being. Results of multilevel analyses showed that staff in the experimental wards experienced significantly less emotional exhaustion at both Time 2 and Time 3 and less depersonalization at Time 2, compared with the control wards. Moreover, changes in burnout levels were significantly related to changes in the perception of job characteristics over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
68.
We synthesized aligned multiwalled carbon nanotube multilayers by aerosol-assisted catalytic chemical vapor deposition through sequential injections of aerosols containing both carbon and catalyst precursors. Each sequence was traced by a specific duration or precursor mixture, with the carbon source being possibly enriched in (13)C isotope labels. We discovered that any sequence involved the growth of a new layer on the substrate surface, under any pre-existing one by lifting it up, giving definitive evidence of a base-growth mechanism.  相似文献   
69.
70.
During the 2002 environmental satellite Envisat mid-latitude validation campaign, a new upgraded configuration of the Infrared Balloon Experiment (IBEX) Fourier transform spectrometer, which had its first flight in 1978, performed a stratospheric balloon flight across the Mediterranean Sea. Among the substantial upgrades made to the instrument, the use of photon-noise-limited detectors permitted us to reach the theoretical limits in terms of signal-to-noise ratio. Also, important modifications were made to the interferometric system and electronics, such as the installation of a solid-state laser reference source and an onboard data recording system. During the flight, measurement of volume-mixing-ratio vertical profiles of O3, HNO3, N2O, and ClO from an altitude of approximately 38 km were performed with a vertical resolution of approximately 1.5 km.  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-23

京公网安备 11010802026262号