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   11300篇
  免费   49篇
  国内免费   2篇
电工技术   38篇
综合类   5篇
化学工业   412篇
金属工艺   99篇
机械仪表   66篇
建筑科学   79篇
矿业工程   5篇
能源动力   49篇
轻工业   236篇
水利工程   24篇
石油天然气   10篇
武器工业   1篇
无线电   401篇
一般工业技术   335篇
冶金工业   9297篇
原子能技术   25篇
自动化技术   269篇
  2021年   23篇
  2020年   17篇
  2019年   20篇
  2018年   21篇
  2017年   33篇
  2016年   32篇
  2015年   25篇
  2014年   45篇
  2013年   118篇
  2012年   64篇
  2011年   83篇
  2010年   77篇
  2009年   88篇
  2008年   90篇
  2007年   92篇
  2006年   93篇
  2005年   86篇
  2004年   67篇
  2003年   82篇
  2002年   56篇
  2001年   67篇
  2000年   49篇
  1999年   346篇
  1998年   2905篇
  1997年   1641篇
  1996年   1055篇
  1995年   623篇
  1994年   501篇
  1993年   596篇
  1992年   116篇
  1991年   153篇
  1990年   143篇
  1989年   132篇
  1988年   136篇
  1987年   127篇
  1986年   135篇
  1985年   106篇
  1984年   35篇
  1983年   49篇
  1982年   70篇
  1981年   63篇
  1980年   109篇
  1979年   27篇
  1978年   31篇
  1977年   227篇
  1976年   483篇
  1975年   21篇
  1972年   21篇
  1971年   17篇
  1970年   20篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
161.
162.
163.
OBJECTIVE: The relationship between intentions to use alcohol and risk factors was examined among fifth and sixth graders. METHOD: Subjects completed a questionnaire that assessed intentions to use alcohol and eight risk factors. Risk factors included peer and parental use and attitudes toward use, sensation seeking, tolerance of deviance, rejection of parental authority, and family cohesion. RESULTS: Multivariate analyses showed that the risk factors were able to discriminate between those who intended to use alcohol and those who did not. Family factors showed stronger relationships to intentions among fifth graders, and peer factors were more strongly related to intentions among sixth graders. CONCLUSIONS: Risk factors can be used to target preadolescents who may be at risk for early alcohol use, and programs that attempt to prevent early initiation of alcohol use among adolescents can be designed.  相似文献   
164.
165.
We evaluated the influence of supplemental dietary NaHCO3 on K metabolism of young dairy calves. Thirty-two Holstein and Jersey male and female calves were blocked at 56 to 70 d after birth according to breed, sex, and age and assigned randomly to a 2 x 2 factorial arrangement of dietary treatments for 8 wk: .4% K with 0% NaHCO3, .4% K with 2% NaHCO3, .6% K with 0% NaHCO3, and .6% K with 2% NaHCO3. Feed intake was not affected by dietary KCl or NaHCO3 supplementation, but average daily gain increased with increased K and tended to be reduced by dietary NaHCO3. Plasma K was elevated by increased dietary K but generally was unaffected by NaHCO3. Urinary Ca excretion appeared to be reduced by NaHCO3; urine pH increased with supplemental NaHCO3. Results indicate 1) the K requirement of the growing calf is between .40 and .55% of diet DM, 2) because urinary K excretion was elevated by dietary NaHCO3, the K requirement may be increased when the diet is supplemented with NaHCO3, and 3) average daily gain and plasma K are sensitive indicators of dietary K in the growing calf.  相似文献   
166.
167.
168.
The purpose of this study was to investigate self-disclosure, emotion-focused, and problem-focused coping styles among men with borderline hypertension and two groups of normotensive men differentiated by parental hypertension. Because blood pressure reactivity may discriminate between hypertensive and normotensive men, subjects in these three groups were categorized as high or low cardiovascular reactors based on their blood pressure response to a mental arithmetic task. Self-disclosure and coping styles were investigated in relation to status effects within the doctor-patient relationship. Men with exaggerated blood pressure reactivity were less self-disclosive and used fewer emotion-focused coping strategies than men with no blood pressure reactivity. Normotensives with a history of parental hypertension were less self-disclosive than normotensives without a history of parental hypertension.  相似文献   
169.
The present study estimated the unique contribution of self-efficacy to work-related performance controlling for personality (the Big 5 traits), intelligence or general mental ability, and job or task experience. Results, based on a meta-analysis of the relevant literatures, revealed that overall, across all studies and moderator conditions, the contribution of self-efficacy relative to purportedly more distal variables is relatively small. Within moderator categories, there were several cases in which self-efficacy made unique contributions to work-related performance. For example, self-efficacy predicted performance in jobs or tasks of low complexity but not those of medium or high complexity, and self-efficacy predicted performance for task but not job performance. Overall, results suggest that the predictive validity of self-efficacy is attenuated in the presence of individual differences, though this attenuation does depend on the context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
170.
This study examined the moderating effects of temperamental resistance to control on the link between development of sleep problems and development of externalizing behaviors over a 5-year period. Resistance to control was assessed with mothers' retrospective reports of temperament in infancy, provided when children were 5 years of age. Sleep problems were assessed with mother reports on an annual basis from age 5 to age 9. Externalizing behaviors were assessed with teacher reports on an annual basis from age 5 to age 9. A cross-domain latent growth curve model indicated that sleep problem trajectories were positively associated with externalizing behavior trajectories only for children high in resistance to control. In addition, resistance to control was positively associated with initial (age 5) sleep problems and initial (age 5) externalizing behaviors. The authors speculate that the development of sleep problems promotes the development of behavior problems for resistant children, whose self-regulatory abilities are especially tenuous. Implications for prevention and treatment of conduct problems are considered. (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