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   1302篇
  免费   12篇
  1314篇
  2019年   14篇
  2018年   26篇
  2017年   24篇
  2016年   45篇
  2015年   23篇
  2014年   32篇
  2013年   135篇
  2012年   55篇
  2011年   45篇
  2010年   33篇
  2009年   27篇
  2008年   39篇
  2007年   51篇
  2006年   33篇
  2005年   44篇
  2004年   46篇
  2003年   37篇
  2002年   44篇
  2001年   22篇
  2000年   16篇
  1999年   24篇
  1998年   16篇
  1997年   14篇
  1996年   10篇
  1995年   11篇
  1994年   13篇
  1993年   14篇
  1992年   21篇
  1991年   12篇
  1990年   20篇
  1989年   12篇
  1988年   23篇
  1987年   11篇
  1986年   10篇
  1985年   11篇
  1984年   16篇
  1983年   18篇
  1982年   13篇
  1981年   17篇
  1980年   17篇
  1979年   17篇
  1978年   14篇
  1977年   14篇
  1976年   18篇
  1975年   16篇
  1974年   20篇
  1973年   21篇
  1970年   13篇
  1967年   10篇
  1966年   8篇
排序方式: 共有1314条查询结果,搜索用时 15 毫秒
71.
72.
Many cells use calcium signaling to carry information from the extracellular side of the plasma membrane to targets in their interior. Since virtually all cells employ a network of biochemical reactions for Ca2+ signaling, much effort has been devoted to understand the functional role of Ca2+ responses and to decipher how their complex dynamics is regulated by the biochemical network of Ca2+-related signal transduction pathways. Experimental observations show that Ca2+ signals in response to external stimuli encode information via frequency modulation (FM) or alternatively via amplitude modulation (AM). Although minimal models can capture separately both types of dynamics, they fail to exhibit different and more advanced encoding modes. By arguments of bifurcation theory, we propose instead that under some biophysical conditions more complex modes of information encoding can also be manifested by minimal models. We consider the minimal model of Li and Rinzel and show that information encoding can occur by AM of Ca2+ oscillations, by FM or by both modes (AFM). Our work is motivated by calcium signaling in astrocytes, the predominant type of cortical glial cells that is nowadays recognized to play a crucial role in the regulation of neuronal activity and information processing of the brain. We explain that our results can be crucial for a better understanding of synaptic information transfer. Furthermore, our results might also be important for better insight on other examples of physiological processes regulated by Ca2+ signaling.  相似文献   
73.
74.
Although word recognition deficits (WRD) are a known cause of reading comprehension deficits (RCD), other contributions to RCD, including executive function (EF), have not been fully explored. We examined the contribution of EF (working memory and planning), along with attention, decoding, fluency, and vocabulary to reading comprehension in 60 children (including 16 WRD and 10 RCD), ages 9–15 years. After controlling for commonly accepted contributors to reading comprehension (i.e., attention, decoding skills, fluency, and vocabulary), EF continued to make a significant contribution to reading comprehension but not to word recognition skills. These findings highlight the need for consideration of the role of EF in RCD.  相似文献   
75.
The current status of research on the memory drum theory is evaluated with emphasis on the issues raised by Marteniuk and MacKenzie (1981). A general theme emerging from this review is that response programming is not the only process which can influence RT and that distinguishing programming from non-programming effects clarifies rather than “clouds? the issues.  相似文献   
76.
Vignette and autobiographical recall studies have often been used to test models of the appraisals associated with specific emotions. Recently, critiques of both methodologies have called into question the applicability of appraisal theory to naturally-occurring emotional responses. This study examined supporter's responses to Ross Perot's withdrawal from the 1992 presidential race to assess the extent to which appraisal models accurately capture responses to a naturally-occurring event. Supporters in Riverside County, California (N = 227) completed questionnaires concerning their interpretations of the event, their initial emotional reactions, changes in their reactions in the weeks immediately following Perot's withdrawal, and their plans. Appraisal models correctly predicted the dimensions of agency and coping potential that served to differentiate sadness from anger, and the appraisals and plans associated with hope. Appraisal models did not predict the strong focus of sad supporters on their past goals and beliefs, and the plans associated with sadness and anger. Changes in emotional intensity occurred as a function of changes in goals and plans rather than merely as a function of time. These findings demonstrate the applicability of appraisal theory to naturally-occurring emotional responses, but also show that models may understate the complexity of the planning processes associated with emotions.  相似文献   
77.
This article develops the cognitive—emotional forager (CEF) model, a novel application of a neural network to dynamical processes in foraging behavior. The CEF is based on a neural network known as the gated dipole, introduced by Grossberg, which is capable of representing short-term affective reactions in a manner similar to Solomon and Corbit’s (1974) opponent process theory. The model incorporates a trade-off between approach toward food and avoidance of predation under varying levels of motivation induced by hunger. The results of simulations in a simple patch selection paradigm, using a lifetime fitness criterion for comparison, indicate that the CEF model is capable of nearly optimal foraging and outperforms a run-of-luck rule-of-thumb model. Models such as the one presented here can illuminate the underlying cognitive and motivational components of animal decision making.  相似文献   
78.
79.
Levine SR 《CNS spectrums》2005,10(7):567-578
Blood disorders have been implicated in approximately 5% to 10% of ischemic stroke, with an increased frequency in younger patients. Most disorders are associated with an increased thrombotic tendency and, therefore, an increased risk of ischemic stroke. Less commonly, a bleeding diathesis may predispose a patient to intracranial hemorrhage. While many conditions predisposing to thrombosis have been associated with stroke, there are relatively few prospective, epidemiological studies addressing hypercoagulable states and arterial stroke compared with the number of studies on the genetic thrombophilias, which are predominantly associated with venous thrombosis. When ordering tests of coagulation in stroke patients, one should keep in mind whether the results will influence therapy and/or patient outcome. It is generally not advocated to screen all stroke patients for a "hypercoagulable workup". Typically, patients to be screened for coagulation defects will have a prior history of one or more unexplained thromboembolic events. The yield for diagnosing a hypercoagulable state is typically greatest for young stroke patients or those with a family history of thrombosis and who have no other explanations for their stroke (cryptogenic stroke). The yield in typically low in unselected ischemic stroke patients and older patients. Treatment of a first stroke with a documented hypercoagulable state is typically long-term or indefinite duration warfarin, although there is a paucity of clinical trial data supporting this clinical approach.  相似文献   
80.
Development of proportional reasoning: where young children go wrong   总被引:1,自引:0,他引:1  
Previous studies have found that children have difficulty solving proportional reasoning problems involving discrete units until 10 to 12 years of age, but can solve parallel problems involving continuous quantities by 6 years of age. The present studies examine where children go wrong in processing proportions that involve discrete quantities. A computerized proportional equivalence choice task was administered to kindergartners through 4th-graders in Study 1, and to 1st- and 3rd-graders in Study 2. Both studies involved 4 between-subjects conditions that were formed by pairing continuous and discrete target proportions with continuous and discrete choice alternatives. In Study 1, target and choice alternatives were presented simultaneously; in Study 2, target and choice alternatives were presented sequentially. In both studies, children performed significantly worse when both the target and choice alternatives were represented with discrete quantities than when either or both of the proportions involved continuous quantities. Taken together, these findings indicate that children go astray on proportional reasoning problems involving discrete units only when a numerical match is possible, suggesting that their difficulty is due to an overextension of numerical equivalence concepts to proportional equivalence problems.  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