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   5808篇
  免费   323篇
  国内免费   3篇
  2024年   13篇
  2023年   77篇
  2022年   76篇
  2021年   129篇
  2020年   167篇
  2019年   179篇
  2018年   272篇
  2017年   287篇
  2016年   251篇
  2015年   165篇
  2014年   202篇
  2013年   787篇
  2012年   434篇
  2011年   417篇
  2010年   253篇
  2009年   168篇
  2008年   372篇
  2007年   302篇
  2006年   290篇
  2005年   197篇
  2004年   150篇
  2003年   128篇
  2002年   124篇
  2001年   47篇
  2000年   84篇
  1999年   51篇
  1998年   37篇
  1997年   35篇
  1996年   28篇
  1995年   23篇
  1994年   34篇
  1993年   18篇
  1992年   22篇
  1991年   34篇
  1990年   33篇
  1989年   25篇
  1988年   19篇
  1987年   21篇
  1986年   12篇
  1985年   14篇
  1984年   14篇
  1983年   9篇
  1982年   9篇
  1981年   12篇
  1980年   9篇
  1979年   12篇
  1977年   7篇
  1975年   9篇
  1974年   9篇
  1973年   7篇
排序方式: 共有6134条查询结果,搜索用时 15 毫秒
101.

Prenatal smoke exposure (PSE) is a risk factor for adverse outcomes in the offspring, including those affecting psychological development. However, it is uncertain whether these associations are the direct result of PSE or other confounding factors. The aim of this study was to examine the possible relationship between PSE and behavioral development in children at 7.5 years of age, considering several prenatal, neonatal and postnatal covariates. A cohort of 266 mother-child pairs was followed from the first trimester of pregnancy until the children reached 7.5 years of age. PSE was assessed using a questionnaire from prenatal clinical records and corroborated by plasma cotinine determinations in the first and second trimesters and in the cord. Mother-child pairs were classified into one of four groups: unexposed, exposed to passive smoking, first trimester active smoking only and active smoking throughout pregnancy. Child behavior was assessed using the Child Behavior Checklist for ages 6–18 and the Childhood Autism Spectrum Test. In multiple linear regression models, smoking during pregnancy was associated with higher scores in affective problems (β?=?0.298; p?=?0.004). No significant associations were found between smoking during pregnancy and externalizing problems. Findings indicate that PSE is negatively associated with behavioral development in childhood.

  相似文献   
102.
103.
Abreu  Filipa  Garber  Paul A.  Souto  Antonio  Presotto  Andrea  Schiel  Nicola 《Animal cognition》2021,24(3):629-643

To increase efficiency in the search for resources, many animals rely on their spatial abilities. Specifically, primates have been reported to use mostly topological and rarely Euclidean maps when navigating in large-scale space. Here, we aimed to investigate if the navigation of wild common marmosets inhabiting a semiarid environment is consistent with a topological representation and how environmental factors affect navigation. We collected 497 h of direct behavioral and GPS information on a group of marmosets using a 2-min instantaneous focal animal sampling technique. We found that our study group reused not only long-route segments (mean of 1007 m) but entire daily routes, a pattern that is not commonly seen in primates. The most frequently reused route segments were the ones closer to feeding sites, distant to resting sites, and in areas sparse in tree vegetation. We also identified a total of 56 clustered direction change points indicating that the group modified their direction of travel. These changes in direction were influenced by their close proximity to resting and feeding sites. Despite our small sample size, the obtained results are important and consistent with the contention that common marmosets navigate using a topological map that seems to benefit these animals in response to the exploitation of clustered exudate trees. Based on our findings, we hypothesize that the Caatinga landscape imposes physical restrictions in our group’s navigation such as gaps in vegetation, small trees and xerophytic plants. This study, based on preliminary evidence, raises the question of whether navigation patterns are an intrinsic characteristic of a species or are ecologically dependent and change according to the environment.

  相似文献   
104.
Background/ObjectiveThe main aim of this study was to compare coping strategies in obsessive-compulsive disorder (OCD) patients and a healthy control group during COVID-19 lockdown and to analyze the relationship with some variables which may influence results (depression, anxiety, comorbidity, subtype of obsession-compulsion). Method: There were 237 participants, 122 OCD and 115 healthy controls, aged 17-61 years old (M = 33.48, SD = 11.13). Results: Groups showed differences in the use of some adaptive strategies (positive reinterpretation, acceptance, humor) and maladaptive (denial, self-blame). Within obsessive-compulsive group, comorbidity affected the greater use of inappropriate strategies (denial, substance abuse and self-blame) while type of obsession-compulsion did not influence use. Anxiety and depression levels were related to the use of less adaptive strategies. Conclusions: These findings strengthen the need for training in the use of effective and adaptive coping strategies, making it necessary to improve clinical follow-up of these patients. It is relevant to be in contact with healthcare professionals, review medication and observe the anxiety and depression levels.  相似文献   
105.
There is currently much interest in the potential impact of psychological factors on immune responses. An attempt was made to assess the effects of dominant/subordinate polarity in male mice on the cytotoxic activities of their natural-killer (NK) cells. On the basis of repeated agonistic encounters, categories of subordinate and dominat animals were selected. These animals were compared with manipulated controls (introduced to a novel test cage without an opponent on each occasion) and undisturbed controls (who remained in isolation without manipulation). In terms of NK activity, immunosuppression was observed in both dominant and subordinate categories when compared to undisturbed controls. There were, however, no differences between the fighting exposed subjects and the manipulated controls, suggesting that stress accounts for any changes. © 1994 Wiley-Liss, Inc.  相似文献   
106.
Effects of timing of social isolation on play fighting and serious fighting were studied at different ages in male golden hamsters. Litters were isolated at 21, 35, and 65 days of age, and tested in a resident-intruder paradigm. Behaviors were compared within grous and with a fourth group of socially reared conspecifics. The earlier the pups were isolated, the more they engaged in play activities. Later, in adulthood, the aggression level of the same animals was retested using the same paradigm. The three isolated groups showed a high level of aggression, with significant differences among them. When compared with socially reared subjects, a reliable difference in the level of aggression was also found. These results support the view that early social experience is important, suggesting that isolation during early critical periods of socialization has a significant impact on play fighting, whereas short periods of isolation may be enough to trigger adult agonistic behavior. © 1994 Wiley-Liss, Inc.  相似文献   
107.
This study assessed whether two types of non-aggressive “standard opponents” (“intact” and “anosmic” group-housed males) produced similar behavioral changes in isolated OF1 male mice given several experiences of victory. Experimental groups confronted either intact or anosmic opponents every two days until they had completed four encounters. The behavioral changes were recorded using a detailed ethologically inspired analysis. These changes were clearly different depending on the opponent type. When intact opponents were used, experimental subjects increased the time spent in digging, non-social exploration, explore from a distance, and attack over encounters, but showed decreased time spent in threat and a decreased latency to the first attack. In encounters with anosmic opponents, only declines in the latencies to threat and attack were noted. Moreover, the experimental groups differed in their behaviors over encounters. Those confronting intact opponents spent less time in social investigation, more time in explore from a distance and threat, and showed a shorter latencies to threat and attack than counterparts confronting anosmics. These results suggest that, although both types of “standard opponents” are similar in their non-aggressiveness, they elicit rather different behavioral responses in their adversaries. These findings provide additional support for the view that the type of opponent used in studies on intermale aggression is of paramount importance. Indeed, the use of different types of “standardized non-aggressive opponents” appears to be an important source of variability between studies. © 1994 Wiley-Liss, Inc.  相似文献   
108.
There is a frequent need to measure the degree of agreement among R observers who independently classify n subjects within K nominal or ordinal categories. The most popular methods are usually kappa-type measurements. When = 2, Cohen's kappa coefficient (weighted or not) is well known. When defined in the ordinal case while assuming quadratic weights, Cohen's kappa has the advantage of coinciding with the intraclass and concordance correlation coefficients. When > 2, there are more discrepancies because the definition of the kappa coefficient depends on how the phrase ‘an agreement has occurred’ is interpreted. In this paper, Hubert's interpretation, that ‘an agreement occurs if and only if all raters agree on the categorization of an object’, is used, which leads to Hubert's (nominal) and Schuster and Smith's (ordinal) kappa coefficients. Formulae for the large-sample variances for the estimators of all these coefficients are given, allowing the latter to illustrate the different ways of carrying out inference and, with the use of simulation, to select the optimal procedure. In addition, it is shown that Schuster and Smith's kappa coefficient coincides with the intraclass and concordance correlation coefficients if the first coefficient is also defined assuming quadratic weights.  相似文献   
109.
110.
Causal illusion has been proposed as a cognitive mediator of pseudoscientific beliefs. However, previous studies have only tested the association between this cognitive bias and a closely related but different type of unwarranted beliefs, those related to superstition and paranormal phenomena. Participants (n = 225) responded to a novel questionnaire of pseudoscientific beliefs designed for this study. They also completed a contingency learning task in which a possible cause, infusion intake, and a desired effect, headache remission, were actually non-contingent. Volunteers with higher scores on the questionnaire also presented stronger causal illusion effects. These results support the hypothesis that causal illusions might play a fundamental role in the endorsement of pseudoscientific beliefs.  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