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   56884篇
  免费   2360篇
  国内免费   23篇
  2020年   574篇
  2019年   622篇
  2018年   935篇
  2017年   895篇
  2016年   987篇
  2015年   707篇
  2014年   864篇
  2013年   3974篇
  2012年   1614篇
  2011年   1639篇
  2010年   983篇
  2009年   1019篇
  2008年   1472篇
  2007年   1457篇
  2006年   1287篇
  2005年   1210篇
  2004年   1145篇
  2003年   1070篇
  2002年   1044篇
  2001年   1873篇
  2000年   1839篇
  1999年   1354篇
  1998年   600篇
  1997年   526篇
  1992年   1221篇
  1991年   1125篇
  1990年   1187篇
  1989年   1041篇
  1988年   1007篇
  1987年   973篇
  1986年   1022篇
  1985年   1133篇
  1984年   870篇
  1983年   778篇
  1982年   561篇
  1981年   519篇
  1979年   950篇
  1978年   644篇
  1977年   584篇
  1976年   578篇
  1975年   830篇
  1974年   949篇
  1973年   996篇
  1972年   847篇
  1971年   771篇
  1970年   732篇
  1969年   738篇
  1968年   970篇
  1967年   871篇
  1966年   824篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
51.
To understand how individuals adapt to and anticipate each other in joint tasks, we employ a bidirectional delay–coupled dynamical system that allows for mutual adaptation and anticipation. In delay–coupled systems, anticipation is achieved when one system compares its own time‐delayed behavior, which implicitly includes past information about the other system’s behavior, with the other system’s instantaneous behavior. Applied to joint music performance, the model allows each system to adapt its behavior to the dynamics of the other. Model predictions of asynchrony between two simultaneously produced musical voices were compared with duet pianists’ behavior; each partner performed one voice while auditory feedback perturbations occurred at unpredictable times during live performance. As the model predicted, when auditory feedback from one musical voice was removed, the asynchrony changed: The pianist’s voice that was removed anticipated (preceded) the actions of their partner. When the auditory feedback returned and both musicians could hear each other, they rapidly returned to baseline levels of asynchrony. To understand how the pianists anticipated each other, their performances were fitted by the model to examine change in model parameters (coupling strength, time‐delay). When auditory feedback for one or both voices was removed, the fits showed the expected decrease in coupling strength and time‐delay between the systems. When feedback about the voice(s) returned, the coupling strength and time‐delay returned to baseline. These findings support the idea that when people perform actions together, they do so as a coupled bidirectional anticipatory system.  相似文献   
52.
Do the conditions under which promises are made determine whether they ought to be kept? Philosophers have placed a number of conditions on promising which, they hold, must be met in order to make promise-keeping obligatory. In so doing, they have distinguished valid promises from invalid promises and justified promises from promises that are not justified. Considering such conditions, one by one, we argue that they are mistaken. In the first place, the conditions they lay down are not necessary for either valid or justified promise-making. In the second place, promises need not meet such conditions in order to create moral obligations. In general, such analyses of promising fail because they suffer from a confusion between promise-making and promise-keeping. Philosophers have wrongly supposed that obligations to keep promises are dependent upon, or derivable from, the quality of the promises themselves, at the time they are made, instead of focusing on conditions that must be satisfied at the time when promises are supposed to be kept. It is not the quality of a promise that determines an obligation to keep it but the rightness or wrongness of performing the promised act.  相似文献   
53.
54.
55.
56.
OBJECTIVE: This report reviews the evidence that informs the role of health and mental health care providers in addressing youth smoking cessation. DESIGN: Qualitative literature review. RESULTS: Physicians do not consistently screen adolescents for tobacco use and fail to provide recommended cessation advice. Challenges to addressing smoking cessation include the need for procedures to ensure confidentiality and the existence of competing demands to provide other services. Few published studies have specifically addressed the effectiveness of clinical interventions. Interventions that require return visits or follow-up phone contacts are technically difficult to implement in this population. Successful interventions may require resources not available in nonresearch settings. Most studies have used brief clinical intervention as a control condition, making it impossible to evaluate its effectiveness. CONCLUSION: There is little evidence that supports current clinical smoking cessation guidelines for adolescents. More research is needed to develop inexpensive, efficient clinical interventions that can provide youths access to smoking cessation help. Future challenges include reorganizing clinical systems to offer greater counseling by support staff or in electronic formats and to provide effective booster messages and follow-up care in a population that is difficult to track.  相似文献   
57.
An electronic apparatus using infrared beams for monitoring the movements of individual bees under dark conditions is described. The searching behavior of workers in an arena was monitored over 2-h periods. Mean ambulatory velocity for one bee over a distance of 100 mm was 45.6±1.51 mm/sec (n=45). Thigmokinesis and temporal activity patterns are illustrated.  相似文献   
58.
59.
Previous work on children's intuitive knowledge about the natural world has documented their difficulty in acquiring an overarching concept of biological life that includes plants as well as humans and non‐human animals. It has also suggested that the acquisition of fundamental biological concepts like alive and die may be influenced by the language used to describe them, as evidenced by differences between English‐ and Indonesian‐speaking children's performance in tasks involving these concepts. Here, we examine one particularly important source of linguistic information available to children during this acquisition process: everyday conversations with their parents. We take a cross‐linguistic approach in analysing the evidence available to English‐ and Indonesian‐speaking children as they acquire meanings for words corresponding to the concepts alive and die . Our analysis illustrates that young children acquiring English and Indonesian are faced with distinct problems, but that parental input in both languages does little to support the acquisition of broad, inclusive biological concepts.  相似文献   
60.
This paper examines college students' attributions about suicide as a function of gender and context (athletic vs. relationship failure). Results indicated that male athletes who suicided were considered more emotionally well-adjusted compared to males who suicided because of a relationship failure and all females. Male and female athletes who suicided were seen as more competent and less distressed compared to those who suffered a failed relationship. Females were also seen as more distressed compared to males. These results are discussed in terms of a positive bias toward athletes in our society as well as gender stereotypes. Implications of these findings as well as methodological limitations are discussed.  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