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   1479篇
  免费   68篇
  2022年   9篇
  2021年   11篇
  2020年   38篇
  2019年   37篇
  2018年   37篇
  2017年   60篇
  2016年   44篇
  2015年   30篇
  2014年   35篇
  2013年   194篇
  2012年   73篇
  2011年   77篇
  2010年   47篇
  2009年   40篇
  2008年   55篇
  2007年   47篇
  2006年   60篇
  2005年   59篇
  2004年   44篇
  2003年   55篇
  2002年   44篇
  2001年   25篇
  2000年   36篇
  1999年   26篇
  1998年   26篇
  1997年   20篇
  1996年   17篇
  1995年   20篇
  1994年   20篇
  1993年   18篇
  1992年   12篇
  1991年   26篇
  1990年   12篇
  1989年   18篇
  1988年   9篇
  1987年   10篇
  1986年   8篇
  1985年   9篇
  1984年   12篇
  1983年   16篇
  1982年   16篇
  1981年   11篇
  1980年   8篇
  1979年   14篇
  1978年   11篇
  1977年   8篇
  1976年   13篇
  1975年   7篇
  1974年   3篇
  1969年   3篇
排序方式: 共有1547条查询结果,搜索用时 31 毫秒
811.
812.
CONTEXT: Understanding shifts in contraceptive method mix is key to helping policymakers, program managers and donor agencies meet current contraceptive demand and estimate future needs in developing countries. METHODS: Data from Demographic and Health Surveys, Reproductive Health Surveys and other nationally representative surveys were analyzed to describe trends and shifts in method mix among married women of reproductive age from 1980 to 2005. The analysis included 310 surveys from 104 developing countries. RESULTS: Contraceptive use among married women of reproductive age increased in all regions of the developing world, reaching 66% in Asia and 73% in Latin America and the Caribbean in 2000-2005, though only 22% in Sub- Saharan Africa. The proportion of married contraceptive users relying on the IUD declined from 24% to 20%, and the proportion using the pill fell from 16% to 12%. The share of method mix for injectables rose from 2% to 8%, and climbed from 8% to 26% in Sub-Saharan Africa, while the share for condoms was 5-7%. The overall proportion of users relying on female sterilization ranged from 29% to 39%, reaching 42-43% in Asia and in Latin America and the Caribbean in 2000-2005; on average, the share of all method use accounted for by male sterilization remained below 3% for all periods. Use of traditional methods declined in all regions; the sharpest drop-from 56% to 31% of users-occurred in Sub-Saharan Africa. CONCLUSIONS: To meet the rising demand for modern methods, it is critical that future programmatic efforts provide methods that are both accessible and acceptable to users.  相似文献   
813.
Age-related changes in personality variables that may contribute to the reduction of symptoms of eating disorders with adult development were examined. Undergraduate sorority women (n = 52; mean age = 19.85 years) were compared with alumnae of the same sorority (n = 34; mean age = 33.74 years). Eating pathology was correlated with greater discrepancy between the real (current) and the ideal (desired) self-image and with perfectionism. Both self-image discrepancy and perfectionism were markedly lower among the alumnae. Variance in these variables together accounted for the lowered level of eating pathology among the older participants. Specific content domains of the real and ideal self-image and different facets of perfectionism showed distinctive age-related changes and differential relationships with eating pathology.  相似文献   
814.
We found mothers’ history of depression and symptoms of depression among their adolescent children were both associated with the type of events that mothers made adolescents feel guilty about and with the mothers’ reactions to those events. Adolescents (20 male, 23 female) described incidents in which their mothers made them feel guilty and what happened afterward. Offspring of mothers with (versus without) a history of depression more often reported guilt when not at fault and over failing to meet maternal needs; reactions did not resolve matters and involved unregulated maternal emotions. Adolescents of mothers without a depression history more often felt guilty about specific events (e.g., breaking rules, bad grades) and reactions resulted in closure (through discipline, apologies, or forgiveness). Adolescents’ depressive symptoms were more severe when incidents were unresolved and involved maternal emotions and less severe when incidents were specific. In addition, maternal use of self-serving forms of guilt induction related to adolescent and parent depression.  相似文献   
815.
Maternal depression in families having a child with a disability has been the subject of considerable research over the past 25 years. This review was designed to describe the literature on maternal depression, critique its research methodology, identify consensus findings across studies, and make recommendations for future research. A particular emphasis is on the distinction between exhibiting depressive symptoms and meeting clinical criteria for a depressive disorder, how or whether research studies made this distinction, and implications for our understanding of maternal adaptation to disability in a family member. Of the 42 articles reviewed, only eight were clinically diagnosed depression; most of them used a scale rating depressive symptoms. Across the studies, mothers of children with disabilities generally exhibited a higher than average rate of depressive symptoms and are more at risk for clinical depression, but the incidence may be lower than reported in previous literature. Child behavior problems, maternal stress, coping style, and support were consistently associated with depressive symptoms. We conclude that we know relatively little about clinical depression in mothers of children with disabilities. The distinction between clinical depression and depressive symptoms may be important in conceptualizing how a child with a disability can influence family members and the nature of support that may need to be provided. Future research should incorporate gold standard diagnostic tools and assess history, severity, and type of depression. Research is also needed to study treatments to reduce the occurrence of both depressive symptoms and clinical depression.  相似文献   
816.
A course focusing on ethical issues in physics has been taught to undergraduate students at Eastern Michigan University since 1988. The course covers both responsible conduct of research and ethical issues associated with how physicists interact with the rest of society. Since most undergraduate physics majors will not have a career in academia, it is important that a course such as this address issues that will be relevant to physicists in a wide range of job situations. There is a wealth of published work that can be drawn on for reading assignments.  相似文献   
817.
This study assessed associations between a number of demographic, medical and psychological risk factors and post-traumatic stress disorder (PTSD) symptoms following stroke. Individuals (N = 102) who had experienced a stroke within the previous year participated in the study. Participants completed questionnaires containing measures of PTSD symptoms and a range of psychological risk factors (i.e., anxiety, depression, negative affect, dissociation, cognitive appraisals). Regression analyses revealed the variables under consideration were able to explain large proportions of the variance in the number (R(2) = .54, p < 0.001) and severity (R(2) = .58, p < 0.001) of PTSD symptoms. Number of strokes, negative affect and cognitive appraisals emerged as significant predictors of both the number and severity of PTSD symptoms. The present findings suggest that a significant proportion of stroke patients may benefit from the detection and treatment of PTSD symptoms.  相似文献   
818.
In the present experiment, we used a deferred imitation paradigm to explore the effect of crawling on memory retrieval by 9-month-old human infants. Infants observed an experimenter demonstrate a single target action with a novel object and their ability to reproduce that action was assessed after a 24-hr delay. Some infants were tested with the demonstration stimulus in the demonstration context and some infants were tested with a different stimulus in a different context. Half of the infants in each test condition were crawling at the time of participation and half were not. Both crawling and non-crawling infants exhibited retention when tested with the demonstration stimulus in the demonstration context, but only infants who were crawling by 9 months of age exhibited retention when tested with a different stimulus in a different context. These findings demonstrate that the onset of independent locomotion is associated with more flexible memory retrieval during the first year of life.  相似文献   
819.
This is a prospective examination of the cognitive performance and cognitive course of persons in an asymptomatic "preclinical" phase who eventually developed Alzheimer's disease (AD). We compared performances on the Mayo Cognitive Factor Scales (MCFS) of 20 persons in a neurologically normal cohort who subsequently developed AD to the performances of 60 persons who remained free of dementia symptoms. For the AD patients, exams occurred prior to the appearance of dementia symptoms (an average of 4.2 and 1.5 years prior to symptom onset). Results reveal strong group differences on learning and retention, with eventual AD patients scoring lower than controls years prior to reporting symptoms of the disease. There was no significant interaction effect (group x testing session) for memory retention, suggesting that memory decline in this preclinical period may be too slow to be a useful indicator of future AD. A significant interaction (but no group effect) was seen for verbal comprehension.  相似文献   
820.
Tool use is rare amongst rodents and has never been recorded in connection with agonistic displays. We witnessed a behaviour, stick display (StD), involving tool use in free-living Eurasian beavers (Castor fiber) that we conclude is a display behaviour. Two beavers were the main performers of the signal that was observed in at least six beavers from three families. Beavers reacted to displays by increased evasive and agonistic behaviours compared with their usual behavioural patterns when at territory borders. The behaviour was almost exclusively seen between rivals at territory borders. We suggest that the display is used in agonistic encounters, mainly in a territorial context. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  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