全文获取类型
收费全文 | 1481篇 |
免费 | 147篇 |
国内免费 | 78篇 |
专业分类
电工技术 | 11篇 |
综合类 | 58篇 |
化学工业 | 679篇 |
金属工艺 | 23篇 |
机械仪表 | 11篇 |
建筑科学 | 47篇 |
矿业工程 | 33篇 |
能源动力 | 77篇 |
轻工业 | 65篇 |
水利工程 | 9篇 |
石油天然气 | 32篇 |
武器工业 | 8篇 |
无线电 | 15篇 |
一般工业技术 | 96篇 |
冶金工业 | 242篇 |
原子能技术 | 278篇 |
自动化技术 | 22篇 |
出版年
2023年 | 8篇 |
2022年 | 31篇 |
2021年 | 49篇 |
2020年 | 61篇 |
2019年 | 49篇 |
2018年 | 36篇 |
2017年 | 37篇 |
2016年 | 53篇 |
2015年 | 41篇 |
2014年 | 62篇 |
2013年 | 224篇 |
2012年 | 58篇 |
2011年 | 85篇 |
2010年 | 61篇 |
2009年 | 84篇 |
2008年 | 61篇 |
2007年 | 65篇 |
2006年 | 67篇 |
2005年 | 72篇 |
2004年 | 64篇 |
2003年 | 52篇 |
2002年 | 48篇 |
2001年 | 65篇 |
2000年 | 40篇 |
1999年 | 29篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1974年 | 1篇 |
1967年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有1706条查询结果,搜索用时 54 毫秒
121.
《Journal of Nuclear Science and Technology》2013,50(3):318-319
By making use of the isotope approximation; neglecting squares of relative mass differences among the isotopes, the authors derived analytically approximations to ordinary diffusion coefficients in a 3- and 4- component isotope mixture. Moreover, approximations to multi-component diffusion coefficients were given on the analogy of those to the 3- and 4-component coefficients, and these approximations were verified to satisfy constrains on the exact ordinary diffusion coefficients. For 4-component mixture of uranium hexafluoride isotopes, 234UF6- 235UF6- 236UF6- 238UF6, composition dependences of the approximation were equal to those of the exact diffusion coefficients. In addition, relative errors between the exact and the approximations were less than 0.2% for 5-component mixture of krypton 80–82-83-84-86 isotopes. 相似文献
122.
An investigation on recycling the recovered uranium from electro-refining process in a CANDU reactor
Feasibility studies for recycling the recovered uranium from electro-refining process of pyroprocessing into a Canada Deuterium Uranium (CANDU) reactor have been carried out with a source term analysis code ORIGEN-S, a reactor lattice analysis code WIMS-AECL, and a Monte Carlo analysis code MCNPX. The uranium metal can be recovered in a solid cathode during an electro-refining process and has a form of a dendrite phase with about 99.99% expecting recovery purity. Considering some impurities of transuranic (TRU) elements and fission products in the recovered uranium, sensitivity calculations were also performed for the compositions of impurities. For a typical spent PWR fuel of 3.0 wt.% of uranium enrichment, 30 GWD/tU burnup and 10 years cooling, the recovered uranium exhibited an extended burnup up to 14 GWD/tU. And among the several safety parameters, the void reactivity at the equilibrium state was estimated 15 mk. Additionally, a simple sphere model was constructed to analyze surface dose rates with the Monte Carlo calculations. It was found that the recovered uranium from the spent PWR fuel by electro-refining process has a significant radioactivity depending on the impurities such as fission products. 相似文献
123.
Reports an error in "A process model of adolescents' triangulation into parents' marital conflict: The role of emotional reactivity" by Cheryl Buehler and Deborah P. Welsh (Journal of Family Psychology, 2009[Apr], Vol 23[2], 167-180). In the article “A Process Model of Adolescents’ Triangulation Into Parents’ Marital Conflict: The Role of Emotional Reactivity” by Cheryl Buehler and Deborah P. Welsh (Journal of Family Psychology, 2009, Vol. 23, No. 2, pp. 167–180), the abstract contains an error. The sample size for the study was 416 rather than 426. (The following abstract of the original article appeared in record 2009-04780-005.) This study examined adolescents' emotional reactivity to parents' marital conflict as a mediator of the association between triangulation and adolescents' internalizing problems in a sample of 2-parent families (N = 426). Four waves of annual, multiple-informant data were analyzed (youth ages 11–15 years). The authors used structural equation modeling and found that triangulation was associated with increases in adolescents' internalizing problems, controlling for marital hostility and adolescent externalizing problems. There also was an indirect pathway from triangulation to internalizing problems across time through youths' emotional reactivity. Moderating analyses indicated that the 2nd half of the pathway, the association between emotional reactivity and increased internalizing problems, characterized youth with lower levels of hopefulness and attachment to parents. The findings help detail why triangulation is a risk factor for adolescents' development and which youth will profit most from interventions focused on emotional regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
124.
125.
Simulation has been used to estimate the error in reactivity measurement in relation to the response rate in an instrument which integrates the input signal or by a converter with a constant measurement time without integration. 相似文献
126.
Coonfield Daniel L.; Kiefer Stephen W.; Ferraro Frank M. III; Sinclair John David 《Canadian Metallurgical Quarterly》2004,118(5):1089
Three experiments examined the effect of acute naltrexone treatment on both taste reactivity and consumption of ethanol in high ethanol-preferring rat lines: Alko Alcohol-Accepting (AA) rats (Experiments 1 and 2) and Alcohol-Preferring (P) rats (Experiment 3). A 3.0 mg/kg naltrexone dose was ineffective at altering ethanol palatability for either line, whereas 7.5 mg/kg was effective at reducing palatability of 10% ethanol for AA, but not P, rats, as reflected by both a decrease in ingestive responding and an increase in aversive responding. The effects of naltrexone on ethanol consumption were quite consistent: At both dosages, acute naltrexone treatment significantly decreased consumption of 10% ethanol. Termination of naltrexone resulted in an immediate increase in ethanol consumption to control levels. Results show that ethanol palatability and consumption can be dissociated in the rat and that the organization of opioidergic mechanisms that mediate ethanol responses may vary between rat lines. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
127.
Hufford Michael R.; Shields Alan L.; Shiffman Saul; Paty Jean; Balabanis Mark 《Canadian Metallurgical Quarterly》2002,16(3):205
A. A. Stone and S. Shiffman (1994) defined ecological momentary assessment (EMA) as monitoring or sampling strategies that assess phenomena at the moment they occur in natural settings, thus maximi7ing ecological validity while avoiding retrospective recall. To address the extent to which EMA affects the behavior and cognitions under observation, the authors examined behavioral and motivational reactivity to EMA among male and female undergraduate problem drinkers (n = 33). Participants completed a 2-week monitoring protocol using palmtop computers as well as pre- and postmonitoring measures of their drinking behavior and motivation for change. The findings suggest that the magnitude of reactivity to EMA is small. Suggestions for future research Are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
128.
1 IntroductionAnumber of high-energy heterocyclic and carbocyclicsubstances have been prepared and characterized[1,2]aspotential substitutes for 1,3,5,7-tetranitro-1,3,5,7-tet-razocane(HMX),2,4,6-triamino-1,3,5-trinitrobenzene(TATB)and 2,2′,4,4′,6,6′-hexanitrostilbene(HNS)inweapon systems[1,2]and downhole well[3-5]applications.2,4,6,4′,6′,2″,4″,6″-Octanitro[1,1′,3′,1″]-terphenyl(ONT)[6,7]and 2,2′,2″,4,4′,4″,6,6′,6″-nonanitro[1,1′,3′,1″]-terphenyl(NONA)[8,9].belong amo… 相似文献
129.
Forcier Kathleen; Stroud Laura R.; Papandonatos George D.; Hitsman Brian; Reiches Meredith; Krishnamoorthy Jenelle; Niaura Raymond 《Canadian Metallurgical Quarterly》2006,25(6):723
A meta-analysis of published studies with adult human participants was conducted to evaluate whether physical fitness attenuates cardiovascular reactivity and improves recovery from acute psychological stressors. Thirty-three studies met selection criteria; 18 were included in recovery analyses. Effect sizes and moderator influences were calculated by using meta-analysis software. A fixed effects model was fit initially; however, between-studies heterogeneity could not be explained even after inclusion of moderators. Therefore, to account for residual heterogeneity, a random effects model was estimated. Under this model, fit individuals showed significantly attenuated heart rate and systolic blood pressure reactivity and a trend toward attenuated diastolic blood pressure reactivity. Fit individuals also showed faster heart rate recovery, but there were no significant differences in systolic blood pressure or diastolic blood pressure recovery. No significant moderators emerged. Results have important implications for elucidating mechanisms underlying effects of fitness on cardiovascular disease and suggest that fitness may be an important confound in studies of stress reactivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
130.
Anger may have greater effects on chronic pain severity than other negative emotions and may do so by increasing muscle tension near the site of injury (symptom-specific reactivity). For patients with chronic low back pain (CLBP), relevant muscles are lower paraspinals (LP). Ninety-four CLBP patients and 79 controls underwent anger and sadness recall interviews. EMG and cardiovascular activity were recorded. Patients exhibited greater LP tension increases during anger and slower recovery than controls. Only patients showed greater LP reactivity during anger than sadness. For both groups, trapezius reactivity during anger and sadness did not differ. LP reactivity to anger correlated with everyday pain severity for patients. Anger-induced symptom-specific LP reactivity may be linked to chronic pain aggravation among CLBP patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献