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   266篇
  免费   21篇
电工技术   2篇
化学工业   104篇
金属工艺   1篇
机械仪表   3篇
建筑科学   11篇
矿业工程   1篇
能源动力   3篇
轻工业   38篇
水利工程   5篇
石油天然气   2篇
无线电   12篇
一般工业技术   51篇
冶金工业   24篇
自动化技术   30篇
  2024年   1篇
  2023年   4篇
  2022年   19篇
  2021年   18篇
  2020年   10篇
  2019年   9篇
  2018年   4篇
  2017年   10篇
  2016年   14篇
  2015年   14篇
  2014年   13篇
  2013年   22篇
  2012年   12篇
  2011年   14篇
  2010年   12篇
  2009年   12篇
  2008年   14篇
  2007年   14篇
  2006年   10篇
  2005年   6篇
  2004年   5篇
  2003年   10篇
  2002年   4篇
  2001年   4篇
  2000年   5篇
  1998年   3篇
  1997年   2篇
  1996年   2篇
  1995年   4篇
  1994年   2篇
  1992年   2篇
  1990年   3篇
  1989年   1篇
  1985年   2篇
  1982年   1篇
  1981年   2篇
  1979年   2篇
  1964年   1篇
排序方式: 共有287条查询结果,搜索用时 500 毫秒
61.
This study focuses on foodborne outbreaks of microbial infection associated with fresh produce in Europe and North America from this millennium. A total of 277 outbreaks with 44 524 individual cases were identified. Foodborne pathogens associated with the most outbreak frequency include Cryptosporidium (20.5%) in Europe and Salmonella (52.2%) in North America although Norovirus (54.3%) and Salmonella (61.3%) were associated with the number of cases in Europe and North America, respectively. Vegetables were the most implicated fresh produce category with outbreak frequencies of 34.1% in Europe and 47.4% in North America. Increased consumption of fresh produce in Europe and North America, as measures to improve diets, correlates with the increased fresh produce-related outbreaks of microbial infection. This systematic review suggests the need for more rapid methodologies for traceback investigations in order to determine trends and epicentres of foodborne infections related to fresh produce.  相似文献   
62.
Clinical evaluation of outcome after treatment of carpal tunnel syndrome has not been standardized. To assess the value of various clinical and questionnaire measures for the assessment of outcome after carpal tunnel surgery, we surveyed 22 patients 1 day before and 3 months after carpal tunnel release with the following measures: the Medical Outcomes Study 36-item short form health survey, the Arthritis Impact Measurement Scale, the Brigham and Women's Hospital carpal tunnel questionnaire, wrist range of motion, power pinch grip strength, pressure sensibility, and dexterity. Significant changes, all in the direction of improved health status postoperatively, were noted in the following scales or measures: the Arthritis Impact Measurement Scale pain, satisfaction, health perception, arthritis impact, and symptom scales; the Brigham and Women's Hospital symptom and function scales; the short form health survey's physical role, emotional role, and bodily pain scales; and the measurement of dexterity. In this study, standardized questionnaires were more sensitive to the clinical change produced by carpal tunnel surgery than many commonly performed physical measures of outcome. The condition-specific questionnaire was more sensitive to change than were more generic questionnaires.  相似文献   
63.
The initial steps in the autoxidation of CLA methyl ester are poorly understood. The aim of this study was to determine the stereochemistry of the hydroperoxides formed during autoxidation of CLA methyl ester in the presence of a good hydrogen atom donor. For this purpose, 9-cis, 11-trans CLA methyl ester was autoxidized in the presence of α-tocopherol under atmospheric oxygen at 40°C in the dark. The CLA methyl ester hydroperoxides were isolated, reduced to the corresponding hydroxy derivatives, and separated by HPLC. The stereochemistry of seven hydroxy-CLA methyl esters was investigated. The position of the hydroxy group was determined by GC-MS. The geometry as well as the position of the double bonds in the alkyl chain was determined by NMR. In addition, the 13C NMR spectra of six hydroxy-CLA methyl esters were assigned using COSY, gradient heteronuclear multiple bond correlation, gradient heteronuclear single quantum correlation, and total correlation spectroscopy experiments. The autoxidation of 9-cis, 11-trans CLA methyl ester in the presence of a good hydrogen atom donor is stereoselective in favor of one geometric isomer, namely the 13-(R,S)-hydroperoxy-9-cis, 11-trans-octadecadienoic acid methyl ester. Three types of conjugated diene hydroperoxides are formed as primary hydroperoxides: trans,trans hydroperoxides (12-OOH-8t,10t and 9-OOH-10t,12t), a cis,trans hydroperoxide with the trans double bond adjacent to the hydroperoxide-bearing carbon atom (13-OOH-9c,11t), and a new type of cis,trans lipid hydroperoxide with the cis double bond adjacent to the hydroperoxide-bearing carbon atom (8-OOH-9c,11t). In addition, three nonkinetic hydroperoxides (13-OOH-9t,11t, 8-OOH-9t,11t, and 9-OOH-10t,12c) are formed. This study supports the theory that CLA methyl ester autoxidizes at least partly through an autocatalytic free radical reaction. The complexity of the hydroperoxide mixture is due to formation of two different pentadienyl radicals. Moreover, the stereoslectivity in favor of one geometric isomer can be explained by the selectivity of the two previous steps: the preferential formation of a W-conformer of the pentadienyl radical over the Z-conformer, and regioselectivity of the oxygen addition to the pentadienyl radical.  相似文献   
64.
Software variability is an ability to change (configure, customize, extend) software artefacts (e.g. code, product, domain requirements, models, design, documentation, test cases) for a specific context. Optimized variability management can lead a software company to 1) shorter development lead time, 2) improved customer and improved user satisfaction, 3) reduced complexity of product management (more variability, same $) and 4) reduced costs (same variability, less $). However, it is not easy for software companies, especially small and medium size of enterprises to deal with variability. In this paper we present variability challenges and used practices collected from five SMEs. Our study indicates that increased product complexity can lead growing SMEs to the time-consuming decision-making. Many of the analyzed medium size of companies also expect improved tool support to help them to boost their productivity when managing increasingly complex products and increasing amount of variants In fact, in many of the analysed SMEs, a high level of automation in design, release management and testing are or become a key factor for market success By introducing the challenges and used practices related to variability the paper deepens understanding of this highly relevant but relatively under-researched phenomenon and contributes to the literature on software product line engineering.  相似文献   
65.
ABSTRACT: BACKGROUND: Single-walled carbon nanotubes (SWCNT) trigger pronounced inflammation and fibrosis in the lungs of mice following administration via pharyngeal aspiration or inhalation. Human exposure to SWCNT in an occupational setting may occur in conjunction with infections and this could yield enhanced or suppressed responses to the offending agent. Here, we studied whether the sequential exposure to SWCNT via pharyngeal aspiration and infection of mice with the ubiquitous intracellular parasite Toxoplasma gondii would impact on the immune response of the host against the parasite. METHODS: C57BL/6 mice were pre-exposed by pharyngeal administration of SWCNT (80 + 80 mug/mouse) for two consecutive days followed by intravenous injection with either 1x103 or 1x104 green fluorescence protein and luciferase-expressing T. gondii tachyzoites. The dissemination of T. gondii was monitored by in vivo bioluminescence imaging in real time for 7 days and by plaque formation. The inflammatory response was analysed in bronchoalveolar lavage (BAL) fluid, and by assessment of morphological changes and immune responses in lung and spleen. RESULTS: There were no differences in parasite distribution between mice only inoculated with T. gondii or those mice pre-exposed for 2 days to SWCNT before parasite inoculum. Lung and spleen histology and inflammation markers in BAL fluid reflected the effects of SWCNT exposure and T. gondii injection, respectively. We also noted that CD11c positive dendritic cells but not F4/80 positive macrophages retained SWCNT in the lungs 9 days after pharyngeal aspiration. However, co-localization of T. gondii with CD11c or F4/80 positive cells could not be observed in lungs or spleen. Pre-exposure to SWCNT did not affect the splenocyte response to T. gondii. CONCLUSIONS: Taken together, our data indicate that pre-exposure to SWCNT does not enhance or suppress the early immune response to T. gondii in mice.  相似文献   
66.
67.
This article presents an integrated approach for the authentication of five Russian icons through the study of their paint materials (elemental composition and stratigraphic mapping), state of conservation and artistic technique. The results of the applied analytical protocol, involving optical and scanning electron microscopy coupled with energy‐dispersive X‐ray spectrometry and Fourier transformed infrared spectroscopy/microspectroscopy, led to the conclusion that the five icons belong to the same group and iconographic school (from Northern Russia) and date from the end of the 16th century to the beginning of 17th century. Because of massive overpainting, the icons “suffered” a change in iconographic style and significance, and restoration treatment brought to light the original painting and its attribution. Identification of the composition of the original chromatic palette used by the iconographer, the stratigraphic mapping and the conservation state of the painting materials, along with the features of the original artistic technique, furnished key elements for the icons' authentication. Here, we present the first experimental data concerning the identification of the authentication characteristics, being part of a large project that has as its final aim the evaluation of the effectiveness and effects of the cleaning agent on the paint layers. Microsc. Res. Tech. 2009. © 2009 Wiley‐Liss, Inc.  相似文献   
68.
The influence of the type of sugar in the osmotic solution and of the time of processing on the volatile compounds of strawberries was studied, in order to optimize the technique as a pre-treatment to further processing. Strawberries of cultivar ‘Camarosa’, cut into 1 cm thick slices, were subjected to osmotic dehydration at 30 °C for 1, 2, 4 and 6 h using either 60% (w/w) sucrose or 60% (w/w) sorbitol solutions. Volatile compounds of fresh and processed strawberry slices were analyzed by static headspace—gas chromatography. Osmotic treatments provoked a loss in volatile compounds due to the migration, mainly of esters, into the osmotic media. The variations in the volatile pattern depended on both time of treatment and type of osmotic solution. The greater changes occurred after 2 h in sucrose; with a promotion of fermentative volatiles (acetaldehyde, ethyl acetate), and a decrease in the other volatiles. Using sorbitol as osmotic agent, the major variations in the volatile pattern occurred after 4 h of osmosis, and the fermentative process was less important than in sucrose, as sorbitol could be less effective in forming a peripheral layer at the fruit surface and/in reducing tissue porosity.  相似文献   
69.
Coordinated construction logistics is an increasingly discussed topic in the Swedish construction industry. It is suggested as a means to increase efficiency in transportation, decrease material usage, coordinate health and safety on-site, etc. Much research on construction logistics has been done from a supply chain management perspective, often highlighting construction logistics as a necessary rational tool to improve efficiency in construction industry. However, could there be other ways to study this phenomenon? The purpose of this paper is to map empirically found coordinated construction logistics models and explore them as different types of innovation. The findings suggest that coordinated construction logistics models should be regarded as not being a fully embedded innovation as they have not yet changed the processes in the way they set out to do initially. Furthermore, differences are identified between company-based models, project-based models and system-based models, and suggest that differences in, for example, development, impact and objectives should be regarded both when conducting research on and when implementing coordinated construction logistics in practice. Finally, it is concluded that commitment, communication and cooperation are important when implementing coordinated construction logistics, which is in line with findings within the supply chain management literature.  相似文献   
70.
Nano Research - New strategies for spatially controlled growth of human neurons may provide viable solutions to treat and recover peripheral or spinal cord injuries. While topography cues are known...  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