全文获取类型
收费全文 | 1385篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 195篇 |
金属工艺 | 14篇 |
机械仪表 | 12篇 |
建筑科学 | 53篇 |
矿业工程 | 1篇 |
能源动力 | 18篇 |
轻工业 | 148篇 |
水利工程 | 7篇 |
石油天然气 | 4篇 |
无线电 | 67篇 |
一般工业技术 | 183篇 |
冶金工业 | 588篇 |
原子能技术 | 17篇 |
自动化技术 | 103篇 |
出版年
2022年 | 13篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 17篇 |
2016年 | 17篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 71篇 |
2012年 | 38篇 |
2011年 | 67篇 |
2010年 | 41篇 |
2009年 | 46篇 |
2008年 | 59篇 |
2007年 | 57篇 |
2006年 | 62篇 |
2005年 | 53篇 |
2004年 | 24篇 |
2003年 | 40篇 |
2002年 | 36篇 |
2001年 | 25篇 |
2000年 | 26篇 |
1999年 | 19篇 |
1998年 | 72篇 |
1997年 | 39篇 |
1996年 | 46篇 |
1995年 | 33篇 |
1994年 | 34篇 |
1993年 | 29篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 29篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 29篇 |
1986年 | 24篇 |
1985年 | 27篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 17篇 |
1976年 | 14篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有1413条查询结果,搜索用时 31 毫秒
91.
Thomas Jennifer D.; Sather Tamie Miura; Whinery Lynn A. 《Canadian Metallurgical Quarterly》2008,122(6):1264
Children exposed to alcohol prenatally may suffer from severe brain damage, expressed as a variety of behavioral problems, including hyperactivity and learning deficits. There is a critical need to identify effective treatments for fetal alcohol effects. Physical exercise enhances cognitive ability and increases neurogenesis in the hippocampus, a brain area important for learning and memory. Thus, the present study examined whether physical exercise might reduce the severity of alcohol-induced behavioral alterations. Sprague-Dawley rats were intubated with 5.25 g/kg/day ethanol during the third trimester equivalent (postnatal days [PDs] 4-9). Intubated sham control and nontreated controls were included. From PD 21 to PD 51, half of the subjects were given access to running wheels. On PD 52, subjects were tested on the Morris water maze, and on PD 60, open field activity levels were measured. Morris maze performance was significantly impaired among ethanol-exposed subjects; exercise significantly improved performance of all groups. Similarly, ethanol-exposed subjects were overactive in the open field, an effect attenuated with exercise. In sum, these data suggest that exercise may increase neuronal plasticity not only in controls, but also in subjects exposed to alcohol during development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
92.
Fuchs Douglas; Fuchs Lynn S.; Thompson Anneke; Otaiba Stephanie Al; Yen Loulee; Yang Nancy J.; Braun Mary; O'Connor Rollanda E. 《Canadian Metallurgical Quarterly》2001,93(2):251
The purpose of the present study was to examine the effectiveness and feasibility of phonological awareness training, with and without a beginning decoding component. 33 teachers in 8 urban schools were assigned randomly within their schools to 3 groups: control, phonological awareness training, and phonological awareness training with beginning decoding instruction and practice. Following training, teachers in the 2 treatment groups conducted the treatments for about 20 wks. In each teacher's class, pre- and posttreatment data were collected on 12–14 children (N?=?404); 312 children were tested again the following fall. At the end of kindergarten, the 2 treatment groups performed comparably and outperformed controls on the phonological awareness measures. On alphabetic (reading and spelling) tasks, however, the group participating in phonological awareness training with beginning decoding instruction did better than the other 2 groups. In the fall of the next year, many of these between-group differences remained but were less impressive. Implications are discussed for bridging research and practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
Janneke de Jonge Hans van Trijp Ellen Goddard Lynn Frewer 《Food quality and preference》2008,19(5):439-451
A thorough understanding of consumer confidence in the safety of food and the factors by which this is influenced is necessary for the development of adequate and effective risk management and communication regarding food safety issues. As food chains become globalized, risk management and communication are increasingly applied at international levels. As a consequence, cross-culturally valid theoretical models are needed to investigate consumer confidence in the safety of food. In this study, consumer confidence in the safety of food in Canada and the Netherlands was systematically compared. On the basis of two nationally representative samples, it was examined to what extent differences in consumer confidence between the two countries resulted from differences in the relative importance of the determinants of confidence, and differences in the means of the constructs. No differences between Canada and the Netherlands were found regarding the relative importance of the determinants, which provides support for the generalizability of the framework. However, results indicated that Dutch consumers had a higher level of optimism and a lower level of pessimism regarding the safety of food, which appeared to be mainly related to Dutch consumers’ lower level of concern about factors related to production. The results also indicated cross-national differences in consumer recall of food safety issues in the media. 相似文献
94.
Carol Lynn Berseth Susan Hazels Mitmesser Ekhard E Ziegler John D Marunycz Jon Vanderhoof 《Nutrition journal》2009,8(1):27-7
Background
Parents who perceive common infant behaviors as formula intolerance-related often switch formulas without consulting a health professional. Up to one-half of formula-fed infants experience a formula change during the first six months of life. 相似文献95.
Fatty acid analysis of blood serum, seminal plasma, and spermatozoa of normozoospermic vs. Asthernozoospermic males 总被引:2,自引:0,他引:2
Docosahexaenoic acid (DHA; 22∶6n−3) is found in extremely high levels in human ejaculate with the majority occurring in the
spermatozoa. However, the relative concentration of DHA and other fatty acids, in blood serum, seminal plasma, and spermatozoa
of asthenozoospermic vs. normozoospermic individuals is not known. We analyzed the phospholipid fatty acid composition of
blood serum, seminal plasma, and spermatozoa of normozoospermic men and asthenozoospermic men in order to determine if DHA
levels, as well as the levels of other fatty acids, differed. The serum phospholipid DHA levels were similar in the two groups,
suggesting similar intakes of dietary DHA. On the other hand, seminal plasma levels of DHA (3.0 vs. 3.7%) and total polyunsaturated
fatty acids (PUFA) (11.8 vs. 13.5%) were significantly lower in asthenozoospermic vs. normozoospermic men, respectively, while
18∶1 (19.0 vs. 16.8%) and monounsaturated fatty acids (MUFA) (24.2 vs. 21.7%) were significantly higher in the asthenozoospermic
vs. the normozoospermic men. Spermatozoa from asthenozoospermic men had higher levels of 18∶1, 20∶0, 22∶0, 22∶1, and 24∶0
than sperm from normozoospermic men, and lower levels of 18∶0 and DHA (8.2 vs. 13.8%). Furthermore, total MUFA (19.3 vs. 16.5%)
was higher and total PUFA (19.0 vs. 24.0%), n−3 fatty acids (9.3 vs. 14.6%), and the ratio of n−3 to n−6 fatty acids (1.0
vs. 1.6) were lower in the asthenozoospermic men. Therefore, in asthenozoospermic individuals, lower levels of DHA in the
seminal plasma, but not in the blood serum, mimic the decreased concentrations of DHA in the spermatozoa. This suggests that
the lower concentrations of spermatozoon DHA in these individuals are due not to dietary differences but to some type of metabolic
difference in the asthenozoopermic men. 相似文献
96.
Mensinger Janell Lynn; Lynch Kevin G.; TenHave Thomas R.; McKay James R. 《Canadian Metallurgical Quarterly》2007,75(5):775
A previous randomized trial with 224 alcohol and/or cocaine addicts who had completed an initial phase of treatment indicated that 12 weeks of telephone-based continuing care yielded higher abstinence rates over 24 months than did group counseling continuing care. The current study examined mediators of this treatment effect. Results suggested that self-help involvement during treatment and self-efficacy and commitment to abstinence 3 months after treatment mediated subsequent abstinence outcomes. These analyses controlled for substance use prior to the assessment of mediators. Conversely, there was no evidence that self-help beliefs or social support mediated the treatment effect. These results are consistent with a model in which treatment effects are first accounted for by changes in behavior, followed by changes in self-efficacy and in commitment to abstinence. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
97.
98.
James McGregor Zhenyu Huang Edward P.J. Parrott J. Axel Zeitler K. Lien Nguyen Jeremy M. Rawson Albert Carley Thomas W. Hansen Jean-Philippe Tessonnier Dang Sheng Su Detre Teschner Elaine M. Vass Axel Knop-Gericke R. Schlögl Lynn F. Gladden 《Journal of Catalysis》2010,269(2):329-339
The catalytic dehydrogenation (DH) and oxidative dehydrogenation (ODH) of light alkanes are of significant industrial importance. In this work both carbonaceous material deposited on VOx/Al2O3 catalysts during reaction and unsupported carbon nanofibres (CNFs) are shown to be active for the dehydrogenation of butane in the absence of gas-phase oxygen. Their activity in these reactions is shown to be dependent upon their structure, with different reaction temperatures yielding structurally different coke deposits. Terahertz time-domain spectroscopy (THz-TDS), among other techniques, has been applied to the characterisation of these deposits – the first time this technique has been employed in coke studies. TEM and other techniques show that coke encapsulates the catalyst, preventing access to VOx sites, without a loss of activity. Studies on CNFs confirm that carbonaceous materials act as catalysts in this reaction. Carbon-based catalysts represent an important new class of potential catalysts for DH and ODH reactions. 相似文献
99.
The effect of hydrogen on ZnO while annealing at 1370 K under oxygen-poor conditions with excess Zn vapor or Ti metal is studied.
ZnO turns red only when hydrogen is present in a complex with oxygen vacancies. A practical method is described to remove
hydrogen from ZnO in a sealed ampoule and to bind it to Ti metal. Hydrogen coupled to an oxygen vacancy is the simplest defect
to explain the observations. The coloration is reversible at 1370 K by adding or removing hydrogen, consistent with an activation
energy >1.5 eV. In red ZnO Hall data show a shallow donor level around 45 meV. 相似文献
100.