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   28859篇
  免费   2223篇
  国内免费   742篇
耳鼻咽喉   72篇
儿科学   306篇
妇产科学   282篇
基础医学   1235篇
口腔科学   288篇
临床医学   2171篇
内科学   3785篇
皮肤病学   219篇
神经病学   1975篇
特种医学   216篇
外科学   741篇
综合类   3803篇
现状与发展   1篇
一般理论   5篇
预防医学   3136篇
眼科学   377篇
药学   11576篇
  12篇
中国医学   980篇
肿瘤学   644篇
  2024年   47篇
  2023年   419篇
  2022年   598篇
  2021年   938篇
  2020年   972篇
  2019年   1162篇
  2018年   1122篇
  2017年   1226篇
  2016年   1030篇
  2015年   948篇
  2014年   1932篇
  2013年   4125篇
  2012年   1786篇
  2011年   1802篇
  2010年   1536篇
  2009年   1254篇
  2008年   1183篇
  2007年   1193篇
  2006年   1080篇
  2005年   950篇
  2004年   757篇
  2003年   682篇
  2002年   589篇
  2001年   565篇
  2000年   460篇
  1999年   396篇
  1998年   347篇
  1997年   311篇
  1996年   249篇
  1995年   194篇
  1994年   232篇
  1993年   187篇
  1992年   210篇
  1991年   221篇
  1990年   142篇
  1989年   121篇
  1988年   88篇
  1987年   76篇
  1986年   110篇
  1985年   137篇
  1984年   128篇
  1983年   80篇
  1982年   76篇
  1981年   52篇
  1980年   43篇
  1979年   12篇
  1978年   17篇
  1977年   11篇
  1976年   10篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
2.
3.
4.
5.
6.
ABSTRACT

Although communication about sexuality is a significant pathway through which peers influence adolescent sexual development, little research has examined the role of peer networks in the use of sexualized media. We applied a social network approach to assess the role of close peers in adolescent pornography use and sexting in a sample of Croatian high school students. Sexual conversation networks’ characteristics did not correlate with pornography use. In contrast, sexting was associated with the proportion of same gender peers, the proportion of older peers and the proportion of sexually experienced peers in the network – pointing to the role of peer influence. Participants’ gender did not moderate these associations. Specific mechanisms underlying the observed associations and the role of peer selection remain important tasks for future research.  相似文献   
7.
Abstract

Gaining a better grasp on factors related to changes in alcohol use is of particular interest for clinicians. Past research has highlighted a negative link between future time perspective (i.e. a disposition guiding how individuals consider and act regarding their future) and alcohol misuse. However, much remains at stake in the understanding of this association. The objective of this research was to explore bidirectional relationships between future time perspective and severity of alcohol-related problems, in a clinical setting. The sample includes 79 patients followed up in an outpatient alcohol treatment centre. Two measurement times were planned: at entry into care and 6 months later. Multiple linear regression analyses were carried out, controlling for sociodemographic variables. We found that baseline future time perspective predicted level of alcohol-related problems after 6 months in treatment, even when effects of baseline alcohol-related problems and sociodemographic variables were controlled. This study shows that the way patients see and position themselves regarding their future can affect level of alcohol-related problems. It may be useful for clinicians to identify patients with low future time perspective to offer tailored interventions and consider this dimension as a resource for change.  相似文献   
8.
《Brain stimulation》2022,15(2):337-351
BackgroundAbnormalities in frontoparietal network (FPN) were observed in many neuropsychiatric diseases including substance use disorders. A growing number of studies are using dual-site-tACS with frontoparietal synchronization to engage this network. However, a computational pathway to inform and optimize parameter space for frontoparietal synchronization is still lacking. In this case study, in a group of participants with methamphetamine use disorders, we proposed a computational pathway to extract optimal electrode montage while accounting for stimulation intensity using structural and functional MRI.MethodsSixty methamphetamine users completed an fMRI drug cue-reactivity task. Four main steps were taken to define electrode montage and adjust stimulation intensity using 4x1 high-definition (HD) electrodes for a dual-site-tACS; (1) Frontal seed was defined based on the maximum electric fields (EF) predicted by simulation of HD montage over DLPFC (F3/F4 in EEG 10–10), (2) frontal seed-to-whole brain context-dependent correlation was calculated to determine connected regions to frontal seeds, (3) center of connected cluster in parietal cortex was selected as a location for placing the second set of HD electrodes to shape the informed montage, (4) individualized head models were used to determine optimal stimulation intensity considering underlying brain structure. The informed montage was compared to montages with large electrodes and classic frontoparietal HD montages (F3-P3/F4-P4) in terms of tACS-induced EF and ROI-to-ROI task-based/resting-state connectivity.ResultsCompared to the large electrodes, HD frontoparietal montages allow for a finer control of the spatial peak fields in the main nodes of the FPN at the cost of lower maximum EF (large-pad/HD: max EF[V/m] = 0.37/0.11, number of cortical sub-regions that EF exceeds 50% of the max = 77/13). For defining stimulation targets based on EF patterns, using group-level head models compared to a single standard head model results in comparable but significantly different seed locations (6.43 mm Euclidean distance between the locations of the frontal maximum EF in standard-space). As expected, significant task-based/resting-state connections were only found between frontal-parietal locations in the informed montage. Cue-induced craving score was correlated with frontoparietal connectivity only in the informed montage (r = ?0.24). Stimulation intensity in the informed montage, and not in the classic HD montage, needs 40% reduction in the parietal site to reduce the disparity in EF between stimulation sites.ConclusionThis study provides some empirical insights to montage and dose selection in dual-site-tACS using individual brain structures and functions and proposes a computational pathway to use head models and functional MRI to define (1) optimum electrode montage for targeting FPN in a context of interest (drug-cue-reactivity) and (2) proper transcranial stimulation intensity.  相似文献   
9.
Despite preventive efforts, HIV exposure is still a concern for public health. The current prevalence is related to unsafe sex, which is based on socio-cognitive variables. Therefore, information about these variables is required to verify whether the past preventive strategies have been effective and improve the future ones. However, there is not updated information to adjust future preventive interventions. For this reason, this study analyzes trends by gender in Spanish young people over the past two decades in perceived susceptibility to HIV, severity perceived to HIV, condom confidence and the intention of condom use, from 1999 to 2020. For this purpose, 11,665 Spanish young people (from 17 to 40 years old) completed the AIDS Prevention Questionnaire in each year. Following our results, in general, the socio-cognitive variables have revealed an unsatisfactory trend: a low perceived susceptibility to HIV and a behavioral intention that have remained stable or even declined slightly over the past years. Particularly, men are more likely to report a riskier level in socio-cognitive variables although, in the latest evaluations, women would decrease condom use intention largely than men. In general, regarding age, young adult would report better levels of condom confidence, but early youth would get higher results in perceived severity, as well as better scores in the latest evaluations of condom use intention. Considering these results, policies should make an effort in HIV prevention programs, and emphasize the attention to attitudinal beliefs and behavioral intention to improve their effectiveness.  相似文献   
10.
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