全文获取类型
收费全文 | 668篇 |
免费 | 10篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 48篇 |
建筑科学 | 45篇 |
能源动力 | 5篇 |
轻工业 | 45篇 |
水利工程 | 4篇 |
无线电 | 19篇 |
一般工业技术 | 183篇 |
冶金工业 | 261篇 |
原子能技术 | 3篇 |
自动化技术 | 64篇 |
出版年
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 27篇 |
2017年 | 33篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 5篇 |
2013年 | 67篇 |
2012年 | 39篇 |
2011年 | 29篇 |
2010年 | 50篇 |
2009年 | 30篇 |
2008年 | 25篇 |
2007年 | 21篇 |
2006年 | 18篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 14篇 |
2002年 | 31篇 |
2001年 | 15篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 2篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1890年 | 1篇 |
排序方式: 共有678条查询结果,搜索用时 15 毫秒
671.
Laurie Ricciuto Hedy Ip Valerie Tarasuk 《Revue canadienne de la pratique et de la recherche en diététique》2005,66(4):252-255
PURPOSE: Modifications to the amount and type of fat in the diet are recommended as strategies to help reduce heart disease risk. Individuals can choose from a variety of margarines and oils to alter their intakes of different types of fats, and nutrient content claims on product labels (e.g., 'low in saturated fat') can help them quickly identify healthful products. However, margarines and oils vary in price. METHODS: To examine the relationship between the price and amounts of saturated and trans fats in margarines and oils, and the relationship between price and the presence of nutrient content claims, price and label information were recorded for margarines (n=229) and oils (n=342) sold in the major supermarkets within the Greater Toronto Area. RESULTS: Linear regression analysis revealed a negative relationship between the price and amounts of saturated fat and trans fats in margarines, but not in oils. Margarines with a nutrient content claim were significantly more expensive than were those without a claim. CONCLUSIONS: The findings for margarines are of particular concern for lower income groups for whom budgetary constraints result in the purchase of lower priced foods, and also raise important questions about the usefulness of nutrient content claims in guiding food selections. 相似文献
672.
673.
Eggs of double-crested and pelagic cormorants were collected between 1973 and 1998 from colonies in the Strait of Georgia, BC, Canada, and assayed for concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and non-ortho- and mono-ortho-biphenyls (PCBs). Double-crested cormorant eggs contained (on average) up to 433 ng kg(-1) wet weight 1,2,3,6,7,8-HxCDD, 151 ng kg(-1) 1,2,3,7,8-PnCDD, and 74 ng kg(-1) 2,3,7,8-TCDD, whereas pelagic cormorant eggs contained up to 300, 99, and 28 ng kg(-1) wet weight of these respective congeners. The dominant non-ortho-PCB was CB-126, which ranged as high as 2263 ng kg(-1) in double-crested cormorant eggs. Concentrations of PCDDs and PCDFs fell dramatically in the early 1990s, following both severe restrictions on the use of chlorophenolic wood preservatives and antisapstains and a switch from molecular chlorine bleaching to alternative bleaching technologies at pulp mills in the region. Concentrations of PCBs did not show similar marked declines over time. On the basis of total TEQs > or = 148 ng kg(-1) and previously published documentation of effects in siblings of the cormorant eggs analyzed here, double-crested cormorant young may have exhibited significantly elevated EROD activity and/or brain asymmetries at all colonies from 1973 to 1989 and even at some colonies during the 1990s. Pelagic cormorant eggs collected from a few colonies in 1988-1989 also contained total TEQs greater than the threshold value estimated for double-crested cormorants. 相似文献
674.
Fanie Rautenbach Mieke Faber Sunette Laurie Robert Laurie 《Journal of food science》2010,75(5):C400-C405
Abstract: The antioxidant contents (β-carotene, chlorogenic acid, and vitamin C) as well as the antioxidant capacity (ORAC, FRAP, and ABTS) of 4 sweetpotato varieties were measured in this study. The sweetpotato varieties were cultivated under different water regimes and also subjected to thermal processing. The results show that the 2 orange-fleshed varieties (Resisto and W-119) contain significant more β-carotene, chlorogenic acid, and vitamin C than the 2 cream-fleshed varieties (Bosbok and Ndou). Thermal processing decreased the carotenoid and vitamin C content of all the varieties but increased the chlorogenic acid content and antioxidant capacity. Drought stress appears to increase the β-carotene, vitamin C, and chlorogenic acid contents as well as the antioxidant capacity of some of the sweetpotato varieties, especially W-119. 相似文献
675.
Smith Bruce W.; Ortiz J. Alexis; Steffen Laurie E.; Tooley Erin M.; Wiggins Kathryn T.; Yeater Elizabeth A.; Montoya John D.; Bernard Michael L. 《Canadian Metallurgical Quarterly》2011,79(5):613
Objective: This study investigated the association between mindfulness, other resilience resources, and several measures of health in 124 urban firefighters. Method: Participants completed health measures of posttraumatic stress disorder (PTSD) symptoms, depressive symptoms, physical symptoms, and alcohol problems and measures of resilience resources including mindfulness, optimism, personal mastery, and social support. The Mindful Awareness and Attention Scale (MAAS; Brown & Ryan, 2003) was used to assess mindfulness. Participants also completed measures of firefighter stress, number of calls, and years as a firefighter as control variables. Hierarchical multiple regressions were conducted with the health measures as the dependent variables with 3 levels of independent variables: (a) demographic characteristics, (b) firefighter variables, and (c) resilience resources. Results: The results showed that mindfulness was associated with fewer PTSD symptoms, depressive symptoms, physical symptoms, and alcohol problems when controlling for the other study variables. Personal mastery and social support were also related to fewer depressive symptoms, firefighter stress was related to more PTSD symptoms and alcohol problems, and years as a firefighter were related to fewer alcohol problems. Conclusions: Mindfulness may be important to consider and include in models of stress, coping, and resilience in firefighters. Future studies should examine the prospective relationship between mindfulness and health in firefighters and others in high-stress occupations. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
676.
Mintz Laurie B.; Rideout Christina A.; Bartels Kim M. 《Canadian Metallurgical Quarterly》1994,25(3):221
268 psychology interns reported perceptions of training received on counseling women and the atmosphere of their graduate training. Results were mixed. Although the majority received training on issues such as rape and incest, women's issues were not incorporated into core courses, few reported courses on counseling women, and most had not received information on the Principles Concerning the Counseling and Therapy of Women (see record 1979-29494-001). Sex, program type, and internship setting differences were found. Although the majority did not report experiencing sex bias in terms of mentors, funding, and dissertation support, an alarming number of women experienced sexual harassment from male faculty and clinical supervisors. Implications for graduate training programs and internship sites are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
677.
Lee Tiffany T. Y.; Charrier Isabelle; Bloomfield Laurie L.; Weisman Ronald G.; Sturdy Christopher B. 《Canadian Metallurgical Quarterly》2006,120(3):217
The acoustic frequency ranges in birdsongs provide important absolute pitch cues for the recognition of conspecifics. Black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata) were trained to sort tones contiguous in frequency into 8 ranges on the basis of associations between response to the tones in each range and reward. All 3 species acquired accurate frequency-range discriminations, but zebra finches acquired the discrimination in fewer trials and to a higher standard than black-capped or mountain chickadees, which did not differ appreciably in the discrimination. Chickadees' relatively poorer accuracy was traced to poorer discrimination of tones in the higher frequency ranges. During transfer tests, the discrimination generalized to novel tones when the training tones were included, but not when they were omitted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
678.
Globally, millions of individuals are victims of sex trafficking and are compelled to perform sexual acts through force, fraud, or coercion. Law enforcement agencies, non-profit organisations, and social entrepreneurs increasingly are using information technology as a resource to locate, identify, and rescue victims and find, arrest, and convict traffickers. In this qualitative case study, we partnered with a non-profit organisation that trains law enforcement officers to use information technology to counter sex trafficking. For this research study, we observed training courses, interviewed law enforcement officers and non-profit staff, and reviewed technology usage logs and other data sources. Some officers readily used the new information technology post-training, while others failed to use the new technology. Using conservation of resources theory as a sensitising lens, we identify two factors affecting the use of new technology post-training: the level of organisational resources available to individuals and the individual's perceptions of the new information technology as a resource. With these findings, we develop the Resources Model of Information Technology Use to explain how perceptions of organisational and technology resources affect information technology usage patterns and outcomes. 相似文献