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   23992篇
  免费   114篇
  国内免费   3篇
  2021年   27篇
  2020年   64篇
  2019年   71篇
  2018年   3526篇
  2017年   2880篇
  2016年   2309篇
  2015年   254篇
  2014年   168篇
  2013年   448篇
  2012年   707篇
  2011年   2498篇
  2010年   2586篇
  2009年   1543篇
  2008年   1815篇
  2007年   2290篇
  2006年   151篇
  2005年   333篇
  2004年   294篇
  2003年   230篇
  2002年   173篇
  2001年   117篇
  2000年   125篇
  1999年   93篇
  1998年   85篇
  1997年   63篇
  1996年   52篇
  1995年   40篇
  1994年   47篇
  1993年   41篇
  1992年   56篇
  1991年   37篇
  1990年   45篇
  1989年   36篇
  1988年   42篇
  1987年   38篇
  1986年   38篇
  1985年   45篇
  1984年   57篇
  1983年   46篇
  1982年   45篇
  1981年   56篇
  1980年   44篇
  1979年   43篇
  1978年   44篇
  1977年   34篇
  1976年   44篇
  1975年   29篇
  1974年   35篇
  1972年   26篇
  1968年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
We report a range of lateralized coping strategies adopted by large social groups of cattle in response to mild challenges posed by humans of varying degrees of familiarity. At either 14 or 18 pens at a commercial feedlot, with 90 to 200 cattle in each, we conducted a series of video recorded ‘pressure tests’. ‘Frontal’ pressure tests involved walking from a position perpendicular to the concrete feed bunk of a given pen, towards the geometric centre of the line of feeding cattle. ‘Bunk-side’ pressure tests involved experimenters walking closely past a pen of feeding cattle in one direction, before returning in the opposite direction shortly afterwards. Experimenters wore white dust masks to alter their facial features in the bunk-side pressure tests. In both frontal and bunk-side pressure tests, distance from the experimenter influenced cattle’s choice of binocular viewing, cessation of feeding, standing or stepping backwards to monitor the approach and leaving the feed bunk. The frequency of these coping strategies differed in a lateralized manner. The cattle were more likely to accept the close positioning of a generally familiar, unmasked human on their left, which is traditionally referred to as the “near” side. By contrast, when responding to the approach of an unfamiliar, masked human, cattle conformed to the general vertebrate model and were more likely to remove themselves from the potential threat viewed within the left and not right visual field. We argue that the traditional terms for livestock sidedness as “near” (left) and “off” (right) sides demonstrate a knowledge of behavioural lateralization in domestic livestock that has existed for over 300 years of stock handling.  相似文献   
962.
As with humans, vocal communication is an important social tool for nonhuman primates. Common marmosets (Callithrix jacchus) often produce whistle-like ‘phee’ calls when they are visually separated from conspecifics. The neural processes specific to phee call perception, however, are largely unknown, despite the possibility that these processes involve social information. Here, we examined behavioral and whole-brain mapping evidence regarding the detection of individual conspecific phee calls using an audio playback procedure. Phee calls evoked sound exploratory responses when the caller changed, indicating that marmosets can discriminate between caller identities. Positron emission tomography with [18F] fluorodeoxyglucose revealed that perception of phee calls from a single subject was associated with activity in the dorsolateral prefrontal, medial prefrontal, orbitofrontal cortices, and the amygdala. These findings suggest that these regions are implicated in cognitive and affective processing of salient social information. However, phee calls from multiple subjects induced brain activation in only some of these regions, such as the dorsolateral prefrontal cortex. We also found distinctive brain deactivation and functional connectivity associated with phee call perception depending on the caller change. According to changes in pupillary size, phee calls from a single subject induced a higher arousal level compared with those from multiple subjects. These results suggest that marmoset phee calls convey information about individual identity and affective valence depending on the consistency or variability of the caller. Based on the flexible perception of the call based on individual recognition, humans and marmosets may share some neural mechanisms underlying conspecific vocal perception.  相似文献   
963.
Tool use relies on numerous cognitive functions, including sustained attention and understanding of causality. In this study, we investigated the effects of tool-use training on cognitive performance in primates. Specifically, we applied the Primate Cognition Test Battery to three long-tailed macaques (Macaca fascicularis) at different stages of a training procedure that consisted of using a rake to retrieve out-of-reach food items. In addition, we evaluated a control group (n?=?3) performing a grasping task, in order to account for possible effects related to a simple motor act. Our results showed that tool-use training enhances mean performance in the physical cognition domain, i.e. the understanding of spatial relations, numerosity and causality. In particular, causal cognition (evaluating noise- and shape-related causality and understanding of tool properties) showed significant improvement after training, whereas spatial cognition (evaluating spatial memory, object permanence, rotation and transposition) showed a trend to improvement. Despite these findings, none of our trained monkeys succeeded in the tool-use task of the Primate Cognition Test Battery, which involved an unfamiliar tool. Some training-related effects did not persist after a 35-day resting period, suggesting that continuous practice may be necessary, or that a longer training period before resting may be needed to better maintain cognitive performance. In contrast with the training group, the control group did not display any change in cognitive performance. This finding paves the way to further investigation into the link between tool-use behaviour and the evolution of primate cognition.  相似文献   
964.
The spatial-numerical association of response codes (SNARC) effect is the tendency for humans to respond faster to relatively larger numbers on the left or right (or with the left or right hand) and faster to relatively smaller numbers on the other side. This effect seems to occur due to a spatial representation of magnitude either in occurrence with a number line (wherein participants respond to relatively larger numbers faster on the right), other representations such as clock faces (responses are reversed from number lines), or culturally specific reading directions, begging the question as to whether the effect may be limited to humans. Given that a SNARC effect has emerged via a quantity judgement task in Western lowland gorillas and orangutans (Gazes et al., Cog 168:312–319, 2017), we examined patterns of response on a quantity discrimination task in American black bears, Western lowland gorillas, and humans for evidence of a SNARC effect. We found limited evidence for SNARC effect in American black bears and Western lowland gorillas. Furthermore, humans were inconsistent in direction and strength of effects, emphasizing the importance of standardizing methodology and analyses when comparing SNARC effects between species. These data reveal the importance of collecting data with humans in analogous procedures when testing nonhumans for effects assumed to bepresent in humans.  相似文献   
965.
We report a study examining interspecies emotion transfer via body odors (chemosignals). Do human body odors (chemosignals) produced under emotional conditions of happiness and fear provide information that is detectable by pet dogs (Labrador and Golden retrievers)? The odor samples were collected from the axilla of male donors not involved in the main experiment. The experimental setup involved the co-presence of the dog’s owner, a stranger and the odor dispenser in a space where the dogs could move freely. There were three odor conditions [fear, happiness, and control (no sweat)] to which the dogs were assigned randomly. The dependent variables were the relevant behaviors of the dogs (e.g., approaching, interacting and gazing) directed to the three targets (owner, stranger, sweat dispenser) aside from the dogs’ stress and heart rate indicators. The results indicated with high accuracy that the dogs manifested the predicted behaviors in the three conditions. There were fewer and shorter owner directed behaviors and more stranger directed behaviors when they were in the “happy odor condition” compared to the fear odor and control conditions. In the fear odor condition, they displayed more stressful behaviors. The heart rate data in the control and happy conditions were significantly lower than in the fear condition. Our findings suggest that interspecies emotional communication is facilitated by chemosignals.  相似文献   
966.
Recent research on Problematic Internet Use and Problematic Facebook Use (PIU and PFU) has focused on the idea that people who engage in PIU or PFU are more likely to present with mental health problems. The goal of the present study was to examine the contribution of positive mental health (PMH) to PIU and PFU among adolescents and young adults. A total of 1927 Italian adolescents and young adults participated in the study. Structural equation modeling showed that PMH is negatively linked to both PIU and PFU, indicating that PMH may be an important antecedent for both PIU and PFU among adolescents and young adults. In conclusion, dimensions of PMH may be taken into account by researchers and educational practitioners in preventing both PIU and PFU.  相似文献   
967.
I examine the relationship between economic position relative to local neighbors and life satisfaction in rural Bangladesh. In particular, I exploit a novel household level census of three villages that includes the geospatial coordinates of every household and a perception measure of economic position relative to neighbors. This allows for exploring the sensitivity of the aforementioned relationship to (1) different objective definitions of neighborhood, and (2) the type of positional measure used, objective or perceived. I find that a higher perceived position improves life satisfaction while objective position has no statistically significant effect. This difference stems from a very low correlation between the objective and perceived positional measures. The low correlation can be explained by individual specific heterogeneity in definitions of neighbor. However, observable socioeconomic and demographic variables cannot explain the difference.  相似文献   
968.
Examining how animals direct social learning during skill acquisition under natural conditions, generates data for examining hypotheses regarding how transmission biases influence cultural change in animal populations. We studied a population of macaques on Koram Island, Thailand, and examined model-based biases during interactions by unskilled individuals with tool-using group members. We first compared the prevalence of interactions (watching, obtaining food, object exploration) and proximity to tool users during interactions, in developing individuals (infants, juveniles) versus mature non-learners (adolescents, adults), to provide evidence that developing individuals are actively seeking information about tool use from social partners. All infants and juveniles, but only 49% of mature individuals carried out interacted with tool users. Macaques predominantly obtained food by scrounging or stealing, suggesting maximizing scrounging opportunities motivates interactions with tool users. However, while interactions by adults was limited to obtaining food, young macaques and particularly infants also watched tool users and explored objects, indicating additional interest in tool use itself. We then ran matrix correlations to identify interaction biases, and what attributes of tool users influenced these. Biases correlated with social affiliation, but macaques also preferentially targeted tool users that potentially increase scrounging and learning opportunities. Results suggest that social structure may constrain social learning, but the motivation to bias interactions towards tool users to maximize feeding opportunities may also socially modulate learning by facilitating close proximity to better tool users, and further interest in tool-use actions and materials, especially during development.  相似文献   
969.
This study aimed to empirically analyze the magnitude of discrimination within the South Korean labor market between immigrant and native women in light of different employment patterns. Using an extended version of the Oaxaca decomposition method, special analytical attention was paid to the heavy concentration of immigrant women in the informal sector of the labor market rather than the formal sector. The extensive data for the study came from the Korea National Survey of Multicultural Families and the 12th wave of the Korean Labor and Income Panel Study, both conducted in 2009. Overall, the results presented a strong case that immigrant women are more susceptible to discrimination than their native counterparts in terms of obtaining a secure job in the formal sector. After controlling for a range of individual characteristics, a significant proportion of this employment disparity remained unexplained, giving credence to the existence of systematic discrimination endemic in the labor market.  相似文献   
970.
The main purpose of this exploratory study is to work out and describe the labour migrant’s linguodidactic profile, to verify its didactic capacity of an instrument of pedagogic measurement of social, cognitive, ethnocultural, educational and other significant characteristics of migrants affecting the efficiency of the Russian language training courses. The interdisciplinary methodology of the research integrates principles and approaches of methods for teaching Russian as a foreign language, interdidactics, migration sociolology, culturology, anthropology and cognitive science. The Russian language training courses have a strong potential for linguocultural adaptation and integration of labour migrants because the language functions as a depository and translator of the hosting nation’s moral norms and values. The effectiveness of the Russian language training course depends upon the strict consideration of all significant characteristics of its addressees, i.e. labour migrants. These characteristics were identified and then integrated into the linguodidactic profile which was taken as a basis for the language training course. The didactic capacity of the linguodidactic profile was proved on the example of language teaching and testing of migrants from the Republic of Tajikistan, since foreigners from this country form the majority (47%) of labour immigration flows to the Russian Federation. The role and capacity of the linguodidactic profile in teaching Russian as a foreign language have been verified experimentally. The analyses and comparisons of the final examination results proved the efficiency of the training course worked out with consideration for the labour migrant’s typical linguodidactic profile and, consequently, its high didactic capacity.  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