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   381篇
  免费   7篇
电工技术   7篇
化学工业   64篇
金属工艺   3篇
机械仪表   5篇
建筑科学   1篇
能源动力   4篇
轻工业   14篇
无线电   18篇
一般工业技术   75篇
冶金工业   169篇
原子能技术   6篇
自动化技术   22篇
  2023年   2篇
  2021年   4篇
  2020年   5篇
  2019年   2篇
  2018年   8篇
  2017年   3篇
  2016年   4篇
  2014年   3篇
  2013年   13篇
  2012年   10篇
  2011年   16篇
  2010年   13篇
  2009年   16篇
  2008年   23篇
  2007年   7篇
  2006年   5篇
  2005年   14篇
  2004年   9篇
  2003年   10篇
  2002年   7篇
  2001年   3篇
  2000年   4篇
  1999年   11篇
  1998年   38篇
  1997年   28篇
  1996年   18篇
  1995年   13篇
  1994年   10篇
  1993年   15篇
  1992年   3篇
  1991年   3篇
  1990年   7篇
  1989年   7篇
  1988年   8篇
  1987年   7篇
  1986年   10篇
  1985年   4篇
  1984年   2篇
  1983年   5篇
  1982年   3篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1978年   3篇
  1977年   5篇
  1976年   1篇
  1973年   1篇
  1970年   1篇
排序方式: 共有388条查询结果,搜索用时 15 毫秒
1.
Stress measurements are required to prevent collapse accidents of structures. Surface SH‐wave acoustoelasticity can measure principal stress difference nondestructively and easily. Currently, surface SH‐wave acoustoelasticity can measure with high precision using a T‐type surface SH‐wave sensor in ideal environments such as in the laboratory. However, in actual environments, it cannot be measured with high precision due to change in the temperature of the specimen. In this paper, temperature dependence of surface SH‐wave acoustoelastic constants was verified to investigate the influence of specimen temperature on surface SH‐wave acoustoelasticity. In addition, the measuring system of surface SH‐wave acoustoelasticity using a cross T‐type surface SH‐wave sensor to reduce the influence of specimen temperature was developed.  相似文献   
2.
In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO3 was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO3 mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO3 maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237.  相似文献   
3.
4.
5.
Polypeptide hydrogels were prepared by cross-linking of hydrophobically-modified poly[N5-(2-hydroxyethyl) l-glutamine] having alkyl side chains –CnH2n+1. Chain length of the alkyl group was n = 8, 16, and 18, and their mole fractions in the polypeptide were varied in the range of 0.05–0.16. Shape memory ability of the prepared polypeptide hydrogels was investigated. After deformation at 60 °C, the hydrogel was cooled in order to fix the temporary deformed shape. It was found that crystallization of the alkyl side chains did not occur, and the fixation ability of the hydrogel at 0 °C was low. In the subsequent heating process, the deformed temporary shape spontaneously recovered to the original shape gradually with increasing temperature, in other words, the shape recovery ratio varied with depending on the recovery temperature. From these observations, it was proposed that the shape fixation of the polypeptide hydrogel was achieved by strong segregation of the hydrophobic alkyl chains at low temperature, and the shape recovery of the deformed hydrogel was accompanied by the gradual decrease of the segregation strength with the temperature increase.  相似文献   
6.
[Correction Notice: An erratum for this article was reported in Vol 103(3) of Psychological Bulletin (see record 2008-10688-001). Tables 1 and 2 contain several errors. The correct data is provided in the erratum. These errors do not influence any of the main points or conclusions in this article.] Obesity is a common problem in children and is associated with an increased risk of adult obesity. Twenty-four studies on the behavioral treatment of childhood obesity are reviewed. Studies involving comparisons of behavioral treatment with no treatment or placebos have shown the superiority of behavioral treatment. In addition, the effects of a number of treatment factors on outcome are suggested. These factors include parental involvement, the arrangement of treatment contingencies, and exercise. Several directions for future research are presented, including selecting which children to treat, individualizing treatment, prevention, community programs, and the side effects of weight control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
A high resolution camera has been developed for the small angle X-ray diffraction measurement of long-periodic layered structures such as Langmuir-Blodgett multilayers, superlattices and liquid crystals. A block collimation system known as a Kratky camera is used to produce a very narrow incident beam. The camera is mounted on a computer-controlled goniometer whose sample holder is rotated around a vertical Θ axis by a pulse motor. Measurements can be carried out in a θ-2θ scan, and also in θ or 2θ scans. Processing of the collected data includes smoothing, and correction for absorption, polarization factor and instrumental broadening. The performance of the present system has been demonstrated by observation of diffraction patterns of a Langmuir-Blodgett film of cadmium arachidate and a GaAs/AlAs superlattice.  相似文献   
8.
This study was a 5-year follow-up of obese children who participated in a family-based behavioral weight-control program targeting and reinforcing children and parents for weight loss (Epstein, Wing, Koeske, Andrasik, & Ossip, 1981). Children in the parent-plus-child group showed significantly greater weight reductions after 5 years (–22.7% overweight) than did children in a child-alone target group or in a no-target control group (4.3% and 8.2% overweight, respectively). One third of children in the parent-plus-child group were within 20% of normal weight in comparison with 5% of the children in the no-target control group. Height percentile decreased from the 72nd to the 60th percentile; these changes were negatively related to weight change. These children remained taller than the average child after weight loss, and children of short and medium-height parents were still relatively taller than their parents after 5 years. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
We examined situational antecedents of dieting relapse crises and dieters' attempts to cope with temptations to overeat. We analyzed postreatment interviews with 57 obese Ss with Type II diabetes, comparing situations in which Ss lapsed with those in which they overcame temptation to overeat. Cluster analysis yielded 3 categories of relapse crises: mealtime, low-arousal, and emotional upset situations. The cluster differed in outcome: Upset situations almost always resulted in overeating; situational factors, especially food-related cues, increased relapse risk; but performance of coping was the strongest correlate of outcome. Cognitive and behavioral coping responses were each equally associated with positive outcomes. When Ss reported combining both types of coping, they were less likely to report overeating. The dynamics of relapse crises among dieters resemble those that govern relapse crises in addictive behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
This longitudinal study examined how depressive symptoms relate to children's self-perceptions and to estimates of children's cognitive distortions about the self in a nonclinical sample of children who were followed from 4th grade (n=248) through 6th grade (n=227). Report card grades measured children's academic competence, and teachers' ratings of children's level of peer acceptance at school indicated social acceptance. Self-reported depressive symptoms predicted a change in children's negative views of the self. Moreover, the self-perceptions of children who exhibited more symptoms of depression appeared to reflect an underestimation of their actual competence. Children's negative self-perceptions and underestimations about the self were not associated with a subsequent change in depressive symptoms. The implications of the findings for cognitive theories of depression and future research with this population are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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