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   5299篇
  免费   60篇
  5359篇
  2024年   48篇
  2023年   51篇
  2022年   42篇
  2021年   79篇
  2020年   103篇
  2019年   152篇
  2018年   188篇
  2017年   200篇
  2016年   216篇
  2015年   162篇
  2014年   151篇
  2013年   604篇
  2012年   303篇
  2011年   289篇
  2010年   199篇
  2009年   148篇
  2008年   223篇
  2007年   237篇
  2006年   175篇
  2005年   197篇
  2004年   182篇
  2003年   165篇
  2002年   132篇
  2001年   86篇
  2000年   83篇
  1999年   55篇
  1998年   50篇
  1997年   42篇
  1996年   49篇
  1995年   36篇
  1994年   26篇
  1993年   41篇
  1992年   47篇
  1991年   38篇
  1990年   51篇
  1989年   37篇
  1988年   39篇
  1987年   35篇
  1986年   27篇
  1985年   26篇
  1984年   33篇
  1983年   29篇
  1982年   27篇
  1981年   17篇
  1980年   16篇
  1979年   19篇
  1978年   26篇
  1977年   17篇
  1971年   13篇
  1966年   14篇
排序方式: 共有5359条查询结果,搜索用时 0 毫秒
991.
This article argues that there is no sound basis for thinking that we have a general and strong duty to rectify disparities of wealth around the world, apart from the special case where some become wealthy by theft or fraud. The nearest thing we have to a rational morality for all has to be built on the interests of all, and they include substantial freedoms, but not substantial entitlements to others’ assistance. It is also pointed out that the situation of the world’s poor is not that of victims of disasters, but simply of less-developed technology, which can be repaired by full and free trade relations with others. The true savior of the world’s poor is the businessman, not the missionary. What we do need to do is strike down barriers to commerce, rather than requisition “aid.”  相似文献   
992.
This study investigated agent and expression intensity recognition in point-light displays depicting dancing performances. In a first session, participants danced with two different expression intensities to music, solo or in dyads. In a subsequent session, they watched point-light displays of 1–5-s duration, depicting their own, their partner’s or another participant’s recorded actions, and were asked to identify the agent (self vs. partner vs. stranger) and the intended expression intensity (expressive vs. inexpressive) of the performer. The results indicate that performer identity and expression intensity could be discerned reliably from displays as short as 1 s. The accuracy in judgment increased with exposure duration and, for performer identification, with higher expression intensity. Judgment accuracy in agent and expression intensity recognition tasks correlated with self-report empathy indices. Accuracy correlated also with confidence in judgment, but only in the intensity recognition task. The results are discussed in relation to perceptual and neural mechanisms underlying action and intention recognition.  相似文献   
993.
The present study examined whether middle-aged participants, like young adults, learn movement patterns by preparing and executing integrated sequence representations (i.e., motor chunks) that eliminate the need for external guidance of individual movements. Twenty-four middle-aged participants (aged 55–62) practiced two fixed key press sequences, one including three and one including six key presses in the discrete sequence production task. Their performance was compared with that of 24 young adults (aged 18–28). In the middle-aged participants motor chunks as well as explicit sequence knowledge appeared to be less developed than in the young adults. This held especially with respect to the unstructured 6-key sequences in which most middle-aged did not develop independence of the key-specific stimuli and learning seems to have been based on associative learning. These results are in line with the notion that sequence learning involves several mechanisms and that aging affects the relative contribution of these mechanisms.  相似文献   
994.
This paper attempts to systematically characterize critical reactions in argumentative discourse, such as objections, critical questions, rebuttals, refutations, counterarguments, and fallacy charges, in order to contribute to the dialogical approach to argumentation. We shall make use of four parameters to characterize distinct types of critical reaction. First, a critical reaction has a focus, for example on the standpoint, or on another part of an argument. Second, critical reactions appeal to some kind of norm, argumentative or other. Third, they each have a particular illocutionary force, which may include that of giving strategic advice to the other. Fourth, a critical reaction occurs at a particular level of dialogue (the ground level or some meta-level). The concepts here developed shall be applied to discussions of critical reactions by Aristotle and by some contemporary authors.  相似文献   
995.
This study was an investigation of awareness, cognitions, and psychosocial and educational needs related to genetic counseling and testing among Latinas and non-Latina whites at increased risk for having a BRCA1/2 mutation. Sixty-three Latina and eighty-four non-Latina white women completed telephone surveys employing a mixture of quantitative and qualitative questions assessing awareness, benefits, risks, barriers, and genetic counseling communication preferences regarding BRCA1/2 testing. Among participants who had not previously had genetic counseling/testing, 56.9% of Latinas (29/51) and 34.8% of non-Latina white participants (24/69) were unaware of the availability of BRCA1/2 testing. In multivariate logistic regression analysis, Latina ethnicity was the only statistically significant independent factor associated with lack of awareness (OR = 0.42; 95% CI = 0.19–0.35). No appreciable differences were noted between ethnic groups regarding perceived benefits of BRCA1/2 testing or desired genetic counseling topics. These findings underscore the importance of increasing awareness of cancer genetic counseling and genetic testing among both Latina and non-Latina white populations.  相似文献   
996.
997.
Extinction of instrumental responses is an essential skill for adaptive behavior such as foraging. So far, only few studies have focused on extinction following appetitive conditioning in mice. We studied extinction of appetitive operant lever-press behavior in six standard inbred mouse strains (A/J, C3H/HeJ, C57BL/6J, DBA/2J, BALB/cByJ and NOD/Ltj) and eight recombinant inbred mouse lines. From the response rates at the end of operant and extinction training we computed an extinction index, with higher values indicating better capability to omit behavioral responding in absence of reward. This index varied highly across the mouse lines tested, and the variability was partially due to a significant heritable component of 12.6%.To further characterize the relationship between operant learning and extinction, we calculated the slope of the time course of extinction across sessions. While many strains showed a considerable capacity to omit responding when lever pressing was no longer rewarded, we found a few lines showing an abnormally high perseveration in lever press behavior, showing no decay in response scores over extinction sessions.No correlation was found between operant and extinction response scores, suggesting that appetitive operant learning and extinction learning are dissociable, a finding in line with previous studies indicating that these forms of learning are dependent on different brain areas. These data shed light on the heritable basis of extinction learning and may help develop animal models of addictive habits and other perseverative disorders, such as compulsive food seeking and eating.  相似文献   
998.
Phosphodiesterase 10A (PDE10A) hydrolyzes both cAMP and cGMP, and is a key element in the regulation of medium spiny neuron (MSN) activity in the striatum. In the present report, we investigated the effects of targeted disruption of PDE10A on spatial learning and memory as well as aversive and appetitive conditioning in C57BL/6 J mice. Because of its putative role in motivational processes and reward learning, we also determined the expression of the immediate early gene zif268 in striatum and anterior cingulate cortex. Animals showed decreased response rates in scheduled appetitive operant conditioning, as well as impaired aversive conditioning in a passive avoidance task. Morris water maze performance revealed not-motor related spatial learning and memory deficits. Anxiety and social explorative behavior was not affected in PDE10A-deficient mice. Expression of zif268 was increased in striatum and anterior cingulate cortex, which suggests alterations in the neural connections between striatum and anterior cingulate cortex in PDE10A-deficient mice. The changes in behavior and plasticity in these PDE10A-deficient mice were in accordance with the proposed role of striatal MSNs and corticostriatal connections in evaluative salience attribution.  相似文献   
999.
The aim of this study was to test the hypothesis that a combined relaxation (applied tension release, ATR) and specific shooting training regimen may enhance shooting ability of biathlon athletes. Seven biathletes of high national level were randomized into an experimental group (age 20 ± 5 years; Vo2max 60 ± 8 mL kg(-1) min(-1)) and were asked to add this special training intervention to their regular training for 10 weeks, while five other biathletes served as controls (age 19 ± 2 years; Vo2max 57 ± 10 mL kg(-1) min(-1)). The shooting ability of the subjects was assessed before and after the intervention at rest and after roller skiing on a treadmill in a laboratory-based competition simulating assessment. After the intervention period, the experimental group demonstrated a significantly enhanced shooting performance compared to the control group. No changes in Vo2max or in heart rate and Vo2 responses were observed before and after the intervention in either group and there were no differences between the groups in these parameters. Thus, the preliminary conclusion is that a combination of ATR and specific shooting training seems to be instrumental in enhancing the shooting performance in biathlon.  相似文献   
1000.
The multiple-look notion holds that the difference limen (DL) decreases with multiple observations. We investigated this notion for temporal discrimination in isochronous sound sequences. In Experiment 1, we established a multiple-look effect when sequences comprised nine standard time intervals (S) followed by an increasing number of comparison time intervals (C), but no multiple-look effect when one trailing C interval was preceded by an increasing number of S intervals. In Experiment 2, we extended the design. There were four sequential conditions: (a) 9 leading S intervals followed by 1, 2, …, or 9 C-intervals; (b) 9 leading C intervals followed by 1, 2, …, or 9 S intervals; (c) 9 trailing C-intervals preceded by 1, 2, …, or 9 S-intervals; and (d) 9 trailing S-intervals preceded by 1, 2, …, or 9 C-intervals. Both the interval accretions before and after the tempo change caused multiple-look effects, irrespective of the time order of S and C. Complete deconfounding of the number of intervals before and after the tempo change was accomplished in Experiment 3. The multiple-look effect of interval accretion before the tempo change was twice as big as that after the tempo change. The diminishing returns relation between the DL and interval accretion could be described well by a reciprocal function.  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