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   20756篇
  免费   27篇
  2024年   3篇
  2023年   4篇
  2021年   4篇
  2020年   7篇
  2019年   18篇
  2018年   3496篇
  2017年   2822篇
  2016年   2263篇
  2015年   207篇
  2014年   85篇
  2013年   106篇
  2012年   572篇
  2011年   2390篇
  2010年   2518篇
  2009年   1480篇
  2008年   1711篇
  2007年   2178篇
  2006年   40篇
  2005年   221篇
  2004年   175篇
  2003年   114篇
  2002年   71篇
  2001年   34篇
  2000年   57篇
  1999年   27篇
  1998年   27篇
  1997年   23篇
  1996年   13篇
  1995年   10篇
  1994年   6篇
  1993年   6篇
  1992年   10篇
  1991年   3篇
  1990年   12篇
  1989年   3篇
  1988年   3篇
  1987年   3篇
  1986年   4篇
  1984年   3篇
  1981年   3篇
  1979年   3篇
  1978年   5篇
  1974年   6篇
  1973年   5篇
  1971年   3篇
  1970年   5篇
  1969年   2篇
  1968年   4篇
  1967年   4篇
  1966年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
This paper discusses the results of a systematic review of the Condom Social Marketing (CSM) program which was implemented in Fiji by a non-profit organization for a period of 5?years. The CSM program was introduced during a decade when Fiji was recording an escalating number of new Human Immunodeficiency Virus (HIV) infections. The aim of the program was to increase the awareness and utilization of safe sexual practices among the most vulnerable group??the youths??which had reported the highest incidences of sexually transmitted infections. Program assessment revealed that the CSM program had reportedly increased the acceptability, accessibility, and usage of their TRY TiME condoms in Fiji. We conducted a survey on a sample of sexually active people during January?CFebruary 2009 to examine their prevailing level of knowledge about HIV/AIDS, sexual behavior/practices, and risk perception. The results showed that, despite the high level of awareness about HIV/AIDS among survey participants, people did not consistently practice safe sexual behavior and commonly identified themselves as at low risk of acquiring HIV. This paper concludes that more extensive behavior change programs are needed in order to influence people to change their risky sexual practices and reassess their risk perceptions.  相似文献   
172.
In 2008 a young man committed suicide while his webcam was running. 1,500 people apparently watched as the young man lay dying: when people finally made an effort to call the police, it was too late. This closely resembles the case of Kitty Genovese in 1964, where 39 neighbours supposedly watched an attacker assault and did not call until it was too late. This paper examines the role of internet mediation in cases where people may or may not have been good Samaritans and what their responsibilities were. The method is an intuitive one: intuitions on the various potentially morally relevant differences when it comes to responsibility between offline and online situations are examined. The number of onlookers, their physical nearness and their anonymity have no moral relevance when it comes to holding them responsible. Their perceived reality of the situation and ability to act do have an effect on whether we can hold people responsible, but this doesn’t seem to be unique to internet mediation. However the way in which those factors are intrinsically connected to internet mediation does seem to have a diminishing effect on responsibility in online situations.  相似文献   
173.
174.
Infants begin to segment novel words from speech by 7.5 months, demonstrating an ability to track, encode and retrieve words in the context of larger units. Although it is presumed that word recognition at this stage is a prerequisite to constructing a vocabulary, the continuity between these stages of development has not yet been empirically demonstrated. The goal of the present study is to investigate whether infant word segmentation skills are indeed related to later lexical development. Two word segmentation tasks, varying in complexity, were administered in infancy and related to childhood outcome measures. Outcome measures consisted of age‐normed productive vocabulary percentiles and a measure of cognitive development. Results demonstrated a strong degree of association between infant word segmentation abilities at 7 months and productive vocabulary size at 24 months. In addition, outcome groups, as defined by median vocabulary size and growth trajectories at 24 months, showed distinct word segmentation abilities as infants. These findings provide the first prospective evidence supporting the predictive validity of infant word segmentation tasks and suggest that they are indeed associated with mature word knowledge. A video abstract of this article can be viewed at http://www.youtube.com/watch?v=jxzLi5oLZQ8 .  相似文献   
175.
The relation between temperament and happiness was assessed in a sample of 441 children aged 7–14 years drawn from a population in Northern India. Parents assessed their children’s happiness and rated their children’s temperament using the Emotionality, Activity, and Sociability Temperament Survey (EAS). Children self-reported their own happiness using a single-item measure, the Oxford Happiness Scale Short Form, and the Subjective Happiness Scale. Parents’ temperament ratings conformed to the four factor structure proposed by Buss and Plomin (Temperament: early developing personality traits. Lawrence Erlbaum Associates, Hillsdale, 1984): Emotionality, Activity, Sociability, and Shyness. Temperament accounted for between 4 and 11% of the variance in children’s happiness depending on the measures. Children who were more social and active, and less shy, were happier. This result parallels the well-established relation between happiness and personality in adults and is similar to recent research on happiness and temperament in children; temperament traits akin to extraversion were positively associated with happiness. However, despite that neuroticism and its temperament counterpart are strongly and consistently linked to happiness in adults, the relation between happiness and the temperament trait associated with neuroticism (i.e., Emotionality) was weak. This suggests that the relations between temperament and happiness in children may not completely generalize across cultures.  相似文献   
176.
The Bengalese finch (Lonchura striata var. domestica) is a species of songbird. Males sing courtship songs with complex note-to-note transition rules, while females discriminate these songs when choosing their mate. The present study uses serial reaction time (RT) to examine the characteristics of the Bengalese finches’ sequential behaviours beyond song production. The birds were trained to produce the sequence with an “A–B–A” structure. After the RT to each key position was determined to be stable, we tested the acquisition of the trained sequential response by presenting novel and random three-term sequences (random test). We also examined whether they could abstract the embedded rule in the trained sequence and apply it to the novel test sequence (abstract test). Additionally, we examined rule abstraction through example training by increasing the number of examples in baseline training from 1 to 5. When considered as (gender) groups, training with 5 examples resulted in no statistically significant differences in the abstract tests, while statistically significant differences were observed in the random tests, suggesting that the male birds learned the trained sequences and transferred the abstract structure they had learned during the training trials. Individual data indicated that males, as opposed to females, were likely to learn the motor pattern of the sequence. The results are consistent with observations that males learn to produce songs with complex sequential rules, whereas females do not.  相似文献   
177.
Non-human primates possess species-specific repertoires of acoustically distinct call types that can be found in adults in predictable ways. Evidence for vocal flexibility is generally rare and typically restricted to acoustic variants within the main call types or sequential production of multiple calls. So far, evidence for context-specific call sequences has been mainly in relation to external disturbances, particularly predation. In this study, we investigated extensively the vocal behaviour of free-ranging and individually identified Diana monkeys in non-predatory contexts. We found that adult females produced four vocal structures alone (‘H’, ‘L’, ‘R’ and ‘A’ calls, the latter consisting of two subtypes) or combined in non-random ways (‘HA’, ‘LA’ and ‘RA’ call combinations) in relation to ongoing behaviour or external events. Specifically, the concatenation of an introductory call with the most frequently emitted and contextually neutral ‘A’ call seems to function as a contextual refiner of this potential individual identifier. Our results demonstrate that some non-human primates are able to increase the effective size of their small vocal repertoire not only by varying the acoustic structure of basic call types but also by combining them into more complex structures. We have demonstrated this phenomenon for a category of vocalisations with a purely social function and discuss the implications of these findings for evolutionary theories of primate vocal communication.  相似文献   
178.
It has been speculated that cage mesh exerts a shaping influence on reaching behavior by captive apes, which is then misconstrued as pointing by human observers. Although this notion is clearly falsified by the pointing of captive language-trained apes—who point in the absence of intervening cage mesh—nevertheless, the degree to which cage mesh might influence pointing hand shapes by captive great apes in other housing environments remains relatively unexplored. We examined 259 pointing gestures displayed in archival footage from over 18 h of observation by three nonlanguage-trained chimpanzees housed at a biomedical research center. We coded points in relation to how close to the boundaries of the diamond-shaped cage mesh their points were displayed. We found that points with the whole hand were significantly more likely to be displayed away from the mesh boundaries, relative to points with the index finger or other single-digit points. However, points of each hand shape were displayed at each location, demonstrating that these physical parameters do not fully account for the number of fingers extended while pointing by chimpanzees.  相似文献   
179.
Although rats are able to build complex spatial representations of their surroundings during exploration, the nature of the encoded information is still a matter for debate. In particular, it is not well established if rats can process the topological structure of the environment in such a way that they are aware of the connections existing between remote places. Here, rats were first exposed for four 5-min trials to a complex environment divided into several sectors that were separated by doors allowing either unrestricted or restricted access to other sectors. In the fifth test trial, we measured the behavior of the animals while they explored the same environment in which, however, they faced changes that either altered or did not alter the topological structure of the environment. In experiment 1, closing previously opened doors prevented the rat from having direct access between corresponding sectors. In experiment 2, opening previously closed doors allowed direct access between sectors that had not been directly accessible. In each experiment, control doors allowed us to discard the mere influence of door manipulation. We compared the rats’ exploratory behavior in response to door manipulations that either strongly altered or did not alter the ability to commute between sectors and found evidence that the animals displayed differential reactions to the two types of door manipulations. This implies that during exploration rats build a precise map of the connectivity of space that can be flexibly updated and used for efficient navigation.  相似文献   
180.
Uneconomical choices by humans or animals that evaluate reward options challenge the expectation that decision-makers always maximize the return currency. One possible explanation for such deviations from optimality is that the ability to sense differences in physical value between available alternatives is constrained by the sensory and cognitive processes for encoding profitability. In this study, we investigated the capacity of a nectarivorous bat species (Glossophaga commissarisi) to discriminate between sugar solutions with different concentrations. We conducted a two-alternative free-choice experiment on a population of wild electronically tagged bats foraging at an array of computer-automated artificial flowers that recorded individual choices. We used a Bayesian approach to fit individual psychometric functions, relating the strength of preferring the higher concentration option to the intensity of the presented stimulus. Psychometric analysis revealed that discrimination ability increases non-linearly with respect to intensity. We combined this result with a previous psychometric analysis of volume perception. Our theoretical analysis of choice for rewards that vary in two quality dimensions revealed regions of parameter combinations where uneconomic choice is expected. Discrimination ability may be constrained by non-linear perceptual and cognitive encoding processes that result in uneconomical choice.  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