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   180篇
  免费   1篇
电工技术   1篇
化学工业   7篇
金属工艺   1篇
机械仪表   1篇
建筑科学   5篇
能源动力   1篇
轻工业   13篇
无线电   34篇
一般工业技术   20篇
冶金工业   81篇
原子能技术   1篇
自动化技术   16篇
  2023年   1篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   1篇
  2016年   1篇
  2013年   3篇
  2012年   1篇
  2011年   1篇
  2010年   2篇
  2009年   5篇
  2008年   4篇
  2007年   4篇
  2006年   7篇
  2005年   5篇
  2004年   8篇
  2003年   5篇
  2002年   9篇
  2001年   5篇
  2000年   6篇
  1999年   7篇
  1998年   24篇
  1997年   11篇
  1996年   4篇
  1995年   5篇
  1994年   9篇
  1993年   7篇
  1992年   3篇
  1991年   4篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1987年   2篇
  1986年   5篇
  1985年   3篇
  1983年   2篇
  1981年   5篇
  1979年   2篇
  1978年   1篇
  1976年   3篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有181条查询结果,搜索用时 15 毫秒
1.
Samples of connective tissue obtained from the hoof of six laminitic and eight non-laminitic adult horses were analysed zymographically to investigate whether connective tissue matrix metalloproteinases are activated or induced during laminitis. The activity or matrix metalloproteinases was substantially greater in the tissues from the laminitic horses than in the tissues from the non-laminitic horses. A comparison of the collagenolytic activity in the laminitic and control tissues showed that collagenolytic activities corresponding to the 92 kDa (P < 0.001), 72 kDa (P < 0.01) and 66 kDa (P < 0.01) bands were induced in the laminitic tissues.  相似文献   
2.
Despite a proliferation of recent research examining childhood and adolescent depression, the area still lags behind the adult depression field, particularly in the investigation of cognitive correlates of affective psychopathology. To advance cognitive research with youth, the Children's Negative Cognitive Error Questionnaire (CNCEQ) was developed to provide a measure of cognitive distortions or errors in children and adolescents. Yet, few studies have employed the CNCEQ and no evidence exists supporting the validity of its four component cognitive error scales. The purpose of the present study was to examine the construct validity of the CNCEQ and its constituent scales through the use of factor analysis and criterion-group comparisons. Groups of adolescent psychiatric inpatients, diagnosed as affective or disruptive disordered, completed the CNCEQ following admission. Results failed to support the implicit four-factor structure of the CNCEQ, instead suggesting the appropriateness of a single-factor solution labeled "negative thinking." Despite no diagnostic group differences on the CNCEQ total or other scale scores, affective disordered patients evinced more cognitive errors on the Overgeneralizing scale. Findings suggest that the CNCEQ in its current stage of development holds promise, yet requires refinement to produce a valid measure of cognitive functioning in youth.  相似文献   
3.
OBJECTIVE: This study explored psychosocial and "environmental" correlates of childhood anxiety disorders. The study examined relationships among parental psychiatric symptomatology, perceived family environment, temperament, and self-competence in children with a DSM-III-R anxiety disorder. METHOD: A community sample of third through sixth graders was screened initially for symptoms of test anxiety. Those with high and low scores were administered the Anxiety Disorders Interview Schedule for Children. Three groups (childhood anxiety disorder, test-anxious only, and normal controls) were identified and compared on the psychosocial variables. RESULTS: Children with an anxiety disorder had greater impairment on the indices of perceived self-competence and temperamental flexibility than controls, with the test-anxious children showing intermediate, yet significant, levels of disturbance. There was a trend for children with an anxiety disorder to describe their families as less promoting of independence than the other groups. Finally, measures of parental psychiatric symptomatology revealed more obsessive-compulsive symptoms for the fathers of both the anxiety disorder and test-anxious children compared with controls. CONCLUSIONS: Results are consistent with previous findings suggesting the familial transmission of anxiety disorders and recent speculations regarding a relationship between behavioral inhibition, environmental control, and anxiety. Further research may isolate psychosocial and family environmental factors as instrumental treatment targets in the management of childhood anxiety disorders.  相似文献   
4.
Line positions, strengths, and absolute energies are calculated for the pure rotational spectrum of water in the region between 0 cm?1 and 877 cm?1. These calculations are done in the context of a reduced centrifugal distortion Hamiltonian, and are based on microwave measurements of this spectrum to 1 THz, and Far Infrared measurements between 32 cm?1 and 715 cm?1.  相似文献   
5.
Comparative optimism has been studied extensively in adults and is a significant component of social- cognitive models about health. In contrast, little is known about comparative optimism in children or about the wider social- cognitive processes that underpin their health-related behavior. This study investigated comparative optimism for health- and nonhealth-related topics in 101 children 8 or 9 years of age, the youngest ages that have been investigated so far. Children were shown to be unrealistically optimistic for health and nonhealth events. The implications of these findings for understanding comparative optimism in children are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
7.
This study presents an assessment of local definitions and perceptions concerning healthy eating through a study in four resource-poor border communities in El Salvador. The study included focus groups, key-informant interviews, and observations of the food environment. Local definitions of healthy eating elicited through focus groups were compared to the national Salvadoran dietary guidelines recommendations. The comparison revealed several areas of overlap (including the importance of dietary variety, fruits, and vegetables, among others) and omissions (mention of limiting sweets/candy, salt, sugar, and alcohol). Focus group participants expressed concerns over the origin of their foods and whether food contained harmful chemicals. These conversations also revealed the contradictions between nutrition knowledge and preferences for foods classified as unhealthy. This article concludes with a discussion about barriers to healthy eating identified in the focus groups and through the food environment assessment.  相似文献   
8.
We present preliminary results of the High Density Plasma Injection Experiment at the Maryland Centrifugal Experiment (MCX). HyperV Technologies Corp. has designed, built, and installed a prototype coaxial gun to drive rotation in MCX. This gun has been designed to avoid the blow-by instability via a combination of electrode shaping and a tailored plasma armature. An array of diagnostics indicates the gun is capable of plasma jets with a mass of 160 μg at 70 km/s with an average plasma density above 1015 cm−3. Preliminary measurements are underway at MCX to understand the penetration of the plasma jet through the MCX magnetic field and the momentum transfer from the jet to the MCX plasma. Data will be presented for a wide range of MCX field parameters, and the prospects for future injection experiments will be evaluated.  相似文献   
9.
Circular dichroism (CD) spectroscopy was successfully used for the stereochemical characterization of the hydroxylated metabolites formed during the in vitro biotransformation of (R)- and (S)-thalidomide. Incubation extracts of the individual enantiomers were analyzed by HPLC on an achiral stationary phase combined with CD detection. The CD data of the almost enantiopure eluates of the metabolites were compared with the CD spectra quantum chemically calculated for the respective structures. The results allowed us a reliable determination of the absolute stereostructure for all of the metabolites. The chiral center of thalidomide is unaffected by the stereoselective biotransformation process. (3'R,5'R)-trans-5'-hydroxythalidomide is the main metabolite of (R)-thalidomide, which epimerizes spontaneously to give the more stable (3'S,5'R)-cis isomer. On the contrary, (S)-thalidomide is preferentially metabolized by hydroxylation in the phthalimide moiety, resulting in the formation of (S)-5-hydroxythalidomide.  相似文献   
10.
: Gaussian mixture modelling is used to provide a semi-parametric density estimate for a given data set. The fundamental problem with this approach is that the number of mixtures required to adequately describe the data is not known in advance. In our previous work , we described an algorithm, termed Predictive Validation, which attempted to automatically select the number of components. The aim of this paper is to investigate the influence of the various parameters in our model selection method in order to develop it into an operational tool. In this paper, we demonstrate the successful application of model validation to three applications in which the selected models are used for supervised classification, unsupervised classification and outlier detection tasks. Received: 23 Novenber 2000, Received in revised form: 24 April 2001, Accepted: 21 May 2001  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