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   2530篇
  免费   367篇
  国内免费   344篇
  2024年   6篇
  2023年   44篇
  2022年   60篇
  2021年   89篇
  2020年   142篇
  2019年   141篇
  2018年   140篇
  2017年   147篇
  2016年   173篇
  2015年   92篇
  2014年   134篇
  2013年   440篇
  2012年   115篇
  2011年   129篇
  2010年   75篇
  2009年   106篇
  2008年   127篇
  2007年   125篇
  2006年   98篇
  2005年   105篇
  2004年   106篇
  2003年   89篇
  2002年   84篇
  2001年   64篇
  2000年   42篇
  1999年   29篇
  1998年   28篇
  1997年   25篇
  1996年   20篇
  1995年   19篇
  1994年   26篇
  1993年   29篇
  1992年   19篇
  1991年   12篇
  1990年   14篇
  1989年   8篇
  1988年   8篇
  1987年   5篇
  1986年   12篇
  1985年   13篇
  1984年   6篇
  1983年   3篇
  1982年   9篇
  1981年   8篇
  1980年   7篇
  1979年   11篇
  1978年   21篇
  1977年   13篇
  1976年   13篇
  1975年   7篇
排序方式: 共有3241条查询结果,搜索用时 62 毫秒
121.
Bottlenose dolphins are unusual among non-human mammals in their ability to learn new sounds. This study investigates the importance of vocal learning in the development of dolphin signature whistles and the influence of social interactions on that process. We used focal animal behavioral follows to observe six calves in Sarasota Bay, Fla., recording their social associations during their first summer, and their signature whistles during their second. The signature whistles of five calves were determined. Using dynamic time warping (DTW) of frequency contours, the calves signature whistles were compared to the signature whistles of several sets of dolphins: their own associates, the other calves associates, Tampa Bay dolphins, and captive dolphins. Whistles were considered similar if their DTW similarity score was greater than those of 95% of the whistle comparisons. Association was defined primarily in terms of time within 50 m of the mother/calf pair. On average, there were six dolphins with signature whistles similar to the signature whistles of each of the calves. These were significantly more likely to be Sarasota Bay resident dolphins than non-Sarasota dolphins, and (though not significantly) more likely to be dolphins that were within 50 m of the mother and calf less than 5% of the time. These results suggest that calves may model their signature whistles on the signature whistles of members of their community, possibly community members with whom they associate only rarely.  相似文献   
122.
同事评价教师绩效的结构验证性因素分析   总被引:9,自引:0,他引:9       下载免费PDF全文
考察了教师绩效同事评价结果的因素结构。通过文献回顾、开放式调查、关键事件访谈和理论分析,提出了教师绩效的结构,通过验证性因素分析验证了同事评价教师绩效的结构。发现教师绩效包含6个维度,即职业道德、职务奉献、助人合作、教学效能、教学价值与师生互动,前3个维度组成关系绩效,其余维度组成任务绩效。关系绩效与任务绩效有较高的相关。  相似文献   
123.
人口逆淘汰及其预防   总被引:2,自引:0,他引:2  
对人口逆淘汰必须全面、动态地加以认识.必须阻止人口逆淘汰,提高人口质量,变"人口"为"人力".教育是关键措施,医疗卫生和环境改善十分重要,但决不能鼓励高学历人口多生育而限制农村人口的出生.  相似文献   
124.
Aguiar A  Baillargeon R 《Cognition》2003,88(3):277-316
In the present research, 6.5-month-old infants perseverated in a violation-of-expectation task designed to examine their reasoning about width information in containment events. After watching a familiarization event in which a ball was lowered into a wide container, the infants failed to detect the violation in a test event in which the same ball was lowered into a container only half as wide as the ball (narrow-container test event). This negative result (which was replicated in another experiment) was interpreted in terms of a recent problem-solving account of infants' perseverative errors in various means-end tasks (Aguiar, A., & Baillargeon, R. (2000). Perseveration and problem solving in infancy. In H. W. Reese (Ed.), Advances in child development and behavior (Vol. 27, pp. 135-180). San Diego, CA: Academic Press). It was assumed that the infants in the present experiments (1) did not attend to the relative widths of the ball and container in their initial analysis of the narrow-container test event, (2) categorized the event as similar to the familiarization event shown on the preceding trials, and (3) retrieved the expectation they had formed for that event ("the ball will fit into the container"), resulting in a perseverative error. This interpretation was supported by additional experiments in which different modifications were introduced that led to non-perseverative responding, indicating that 6.5-month-old infants could detect the violation in the narrow-container test event. The present findings are important for several reasons. First, they provide the first demonstration of perseverative responding in a violation-of-expectation task. Second, they make clear the breadth and usefulness of the problem-solving account mentioned above. Finally, they add to the evidence for some degree of continuity between infants' and adults' problem-solving abilities.  相似文献   
125.
What response times tell of children's behavior on the balance scale task   总被引:4,自引:0,他引:4  
Analysis of accuracy of responses to balance scale problems gives a global idea of the cognitive processes that underlie problem-solving behavior on this task. We show that response times (RTs) provide additional detailed information about the kind and duration of these processes. We derive predictions about the RTs from Siegler's (1981) model for the balance scale task, including the counterintuitive prediction that young adults are slower than children in solving particular balance scale problems. The predictions were tested in a study in which 191 6- to 22-year-old participants were presented with a computerized balance scale task. RTs were analyzed with regression models. In addition to qualitative differences between items, we also modeled quantitative differences between items in the regression models. Analyses supported the predictions and provided additional knowledge on the rules. Rule II was reformulated as a rule that always involves the encoding, but not always the correct application of the distance cue. RTs provided evidence for the use of a buggy-rule and not an addition-rule. Finally, a relation between rule inconsistency and increased RT was found.  相似文献   
126.
The present paper focuses on two studies, one on English (Schneiderman & Saddy, 1988) and the other on Italian (De Vreese, Neri Rubichi, & Salvioli, 1996), which report on right hemisphere damaged subjects' inability to correctly insert a word or phrase into an already well-formed sentence under certain stimulus conditions. Despite their strikingly similar findings, the results of the studies are interpreted quite differently. Schneiderman & Saddy consider the deficit to be syntactic, while De Vreese et al. view it as occurring at the lexical category or morphological level. An analysis and regrouping of the stimulus items from both studies indicate that a single syntactic interpretation could account for their results. Suggestions are made for further analyses and research to increase our understanding of the syntactic capacities of the intact right hemisphere.  相似文献   
127.
《孔丛子》六卷当出自“汉魏孔氏家学” ,其前三卷记孔子、子思言行 ,可能是辑先秦孔氏遗文。《孔丛子·记义》篇载有一大段孔子对《诗》的评论 ,其与上博简《孔子诗论》有着内在的关系 ,可以将它们视为同一个体系而相互参释和补充。《孔丛子》“诗论”与上博简《诗论》都反映了先秦儒家早期说诗的风格和内容 ,而与汉代形成的《诗序》传统不同。《孔丛子》“诗论”对朱熹的《诗经集传》有一定影响 ,在从汉代诗学向宋代诗学的转变过程中起了一定的作用。  相似文献   
128.
The papers in this special issue of Clinical Child and Family Psychology Review provided an overview of what is known about children's exposure to domestic violence, and include indications of gaps in extant research. These gaps and research needs are summarized in this conclusion. Specifically, there is need for further research in several broad areas: definition and measurement of children's exposure to domestic violence; development of research methods and statistical designs that provide detailed information and provide for evidence of intervention effectiveness; impact of domestic violence on parenting and family functioning; the role of child factors and exposure to violence factors in predicting developmental risk and resilience; medical and health consequences of exposure to violence; and the nature of child-system interaction in response to domestic violence. Research needs in these areas are discussed in greater detail, and specific questions are raised for further development.  相似文献   
129.
The long-term effect of transplanting embryonic frontal cortex into a unilateral frontal cortex lesion has been studied in adult rats. Before surgery, activity in an open field, muscular strength of both forelimbs, and performance in a paw-reaching-for-food task were scored in 26 rats. In 21 animals a unilateral cortex lesion was then made in the forelimb motor area of the hemisphere contralateral to the preferred paw in the paw-reaching-for-food task, while the other 5 animals were sham-operated. On retesting, the lesion animals changed the preferred paw. A solid homotopic transplant of embryonic tissue (embryonic day 17) was then placed in the lesion cavity in 11 of the lesion rats. Three months later neither lesion alone nor lesion plus transplantation affected open field behavior and muscular strength, but the lesion permanently affected performance in the paw-reaching-for-food task, as shown by a change of preferred paw and a functional deficit in the paw contralateral to the lesion. Transplantation ameliorated the deficits caused by the lesion, but this was only evident when animals were forced to reach with the paw contralateral to the lesion plus transplant. The behavioral results were independent of the size of the lesion and graft. Connections between graft and host tissue were studied by means of the fluorescent tracer 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI). A dense array of labeled fibers was found in the host cortex adjacent to the transplant. The results suggest that functional recovery depends on grafting but is only evident when the animal is obliged to use the affected limb.  相似文献   
130.
Three frames of reference for engineering ethics are discussed—individual, professional and social—which can be further broken down into “microethics” concerned with individuals and the internal relations of the engineering profession and “macroethics” referring to the collective social responsibility of the engineering profession and to societal decisions about technology. Few attempts have been made at integrating microethical and macroethical approaches to engineering ethics. The approach suggested here is to focus on the role of professional engineering societies in linking individual and professional ethics and in linking professional and social ethics. A research program is outlined using ethics support as an example of the former, and the issuance of position statements on product liability as an example of the latter. An earlier version of this paper was presented at the International Symposium on Technology and Society 2000 (ISTAS 2000), Rome, Italy, 7 September 2000. Joseph R. Herkert directs a dual-degree program in engineering and humanities/social sciences and is editor of Social, Ethical, and Policy Implications of Engineering (Wiley/IEEE Press).  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