全文获取类型
收费全文 | 6467篇 |
免费 | 63篇 |
国内免费 | 1篇 |
出版年
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 165篇 |
2017年 | 139篇 |
2016年 | 229篇 |
2015年 | 135篇 |
2014年 | 72篇 |
2013年 | 283篇 |
2012年 | 331篇 |
2011年 | 336篇 |
2010年 | 73篇 |
2009年 | 86篇 |
2008年 | 110篇 |
2007年 | 118篇 |
2006年 | 110篇 |
2005年 | 1384篇 |
2004年 | 733篇 |
2003年 | 514篇 |
2002年 | 204篇 |
2001年 | 60篇 |
2000年 | 42篇 |
1999年 | 51篇 |
1998年 | 38篇 |
1997年 | 32篇 |
1996年 | 34篇 |
1995年 | 31篇 |
1994年 | 42篇 |
1993年 | 34篇 |
1992年 | 49篇 |
1991年 | 58篇 |
1990年 | 87篇 |
1989年 | 74篇 |
1988年 | 55篇 |
1987年 | 59篇 |
1986年 | 54篇 |
1985年 | 49篇 |
1984年 | 51篇 |
1983年 | 39篇 |
1982年 | 29篇 |
1981年 | 24篇 |
1979年 | 41篇 |
1978年 | 33篇 |
1976年 | 28篇 |
1975年 | 43篇 |
1974年 | 37篇 |
1973年 | 41篇 |
1972年 | 31篇 |
1971年 | 31篇 |
1968年 | 20篇 |
1967年 | 22篇 |
排序方式: 共有6531条查询结果,搜索用时 15 毫秒
181.
Aged rats with extensive prior training on the radial maze retain the capacity for accurate spatial working memory (WM) for at least 3 months without practice. To investigate the temporal limits of this influence of prior experience we compared the reacquisition of spatial WM by a group of experienced 21.5-month-old rats to the original acquisition by naive 3-month-old rats. The aged rats had received 225 radial maze tests between 3 and 11 months of age. Despite 10 months without practice the old rats rapidly reacquired critical performance. Their reacquisition was markedly superior to original learning by the young rats, even when delays as long as 5 h were imposed between the rats' fourth and fifth choices during the daily tests in the eight-arm maze. Additional tests showed that neither young nor old rats employed a response strategy to maintain accurate spatial WM performance. Experience clearly confers long-lived protection against the otherwise deleterious effects of aging on spatial WM, but the mechanism by which this influence arises is unknown. 相似文献
182.
183.
Anxiety, nausea and vomiting before, during and after chemotherapy administration were studied in 50 cancer patients. In addition, patient responses to the Autonomic Perception Questionnaire (APQ) and their relation to the anxiety, nausea and vomiting scores was studied. Anticipatory anxiety occurred in 66% and anticipatory nausea in 40% of the patients; 14% showed anticipatory vomiting. The number of patients reporting anxiety decreased to 38% after chemotherapy, whereas nausea and vomiting increased to 47 and 49%, respectively. APQ scores correlated significantly with anxiety and nausea reports during all time periods, but not with the frequency of vomiting. 相似文献
184.
185.
186.
Tarja Heponiemi Marko Elovainio Laura Pulkki Sampsa Puttonen Olli Raitakari Liisa Keltikangas-J?rvinen 《Health psychology》2007,26(1):13-21
The present study examined the association of cardiac autonomic task-induced reactivity and recovery to preclinical atherosclerosis. Thirty-three men and 33 women aged 24-39 years participated in the ongoing epidemiological Cardiovascular Risk in Young Finns study. The authors measured heart rate (HR), respiratory sinus arrhythmia (RSA), and preejection period (PEP) during the mental arithmetic and speech tasks in 1999. Carotid atherosclerosis was assessed by measuring the thickness of the common carotid artery intima-media complex (IMT) with ultrasound in 2001. Higher HR, RSA, and PEP reactivity were associated with lower IMT values even after adjusting for cardiovascular risk factors (lipid levels, obesity, and blood pressure). In addition, better HR recovery after the mental arithmetic task was associated with lower IMT values, and this association persisted after all adjustments. Thus, higher task-induced cardiac autonomic reactivity and better HR recovery were related to less preclinical atherosclerosis. The authors concluded that cardiac pattern of reactivity and quick recovery may be associated with better cardiovascular health, and therefore all reactivity occurring in challenging situations should not automatically be considered as potentially pathological. 相似文献
187.
188.
189.
190.