全文获取类型
收费全文 | 8213篇 |
免费 | 79篇 |
国内免费 | 176篇 |
专业分类
教育 | 5958篇 |
科学研究 | 1430篇 |
各国文化 | 88篇 |
体育 | 197篇 |
综合类 | 282篇 |
文化理论 | 21篇 |
信息传播 | 492篇 |
出版年
2023年 | 19篇 |
2022年 | 21篇 |
2021年 | 66篇 |
2020年 | 116篇 |
2019年 | 289篇 |
2018年 | 327篇 |
2017年 | 273篇 |
2016年 | 218篇 |
2015年 | 215篇 |
2014年 | 438篇 |
2013年 | 895篇 |
2012年 | 416篇 |
2011年 | 529篇 |
2010年 | 434篇 |
2009年 | 503篇 |
2008年 | 531篇 |
2007年 | 498篇 |
2006年 | 508篇 |
2005年 | 470篇 |
2004年 | 406篇 |
2003年 | 369篇 |
2002年 | 213篇 |
2001年 | 208篇 |
2000年 | 125篇 |
1999年 | 56篇 |
1998年 | 43篇 |
1997年 | 41篇 |
1996年 | 23篇 |
1995年 | 25篇 |
1994年 | 23篇 |
1993年 | 17篇 |
1992年 | 15篇 |
1991年 | 19篇 |
1990年 | 5篇 |
1989年 | 20篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 24篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 1篇 |
排序方式: 共有8468条查询结果,搜索用时 15 毫秒
1.
In addition to money or other compensation, other motives for selling sex may be important in a welfare country such as Sweden. The aim of this study was to carry out an exploratory investigation of adolescents’ motives for selling sex in a population-based survey in Sweden. A total of 5839 adolescents from the third year of Swedish high school, mean age 18.0 years, participated in the study. The response rate was 59.7% and 51 students (0.9%) reported having sold sex. Exploratory factor analysis and hierarchical cluster analysis were used to identify groups of adolescents according to underlying motives for selling sex. Further analyses were carried out for characteristics of selling sex and risk factors. Three groups of adolescents were categorized according to their motives for selling sex: Adolescents reporting; 1) Emotional reasons, being at a greater risk of sexual abuse, using sex as a means of self-injury and having a non-heterosexual orientation. 2) Material but no Emotional reasons, who more often receive money as compensation and selling sex to a person over 25 years of age, and 3) Pleasure or no underlying motive for selling sex reported, who were mostly heterosexual males selling sex to a person under 25 years of age, the buyer was not known from the Internet, the reward was seldom money and this group was less exposed to penetrative sexual abuse or using sex as a means of self-injury. In conclusion, adolescents selling sex are a heterogeneous group in regard to underlying motives. 相似文献
2.
目的:探讨不同负荷运动训练对大鼠骨骼肌线粒体三羧酸循环的影响及其机制。方法:将雄性Wistar大鼠50只随机均分为5组:安静对照组(C)、低负荷运动训练组(LT)、中等负荷运动训练组(MT)、高负荷运动训练组(HT)和极高负荷运动训练组(ST),每组10只。各运动组分别进行6周的跑台运动训练。训练方案结束后,取腓肠肌样本,提取线粒体,测定线粒体柠檬酸合成酶(CS)、异柠檬酸脱氢酶(ICD)和α-酮戊二酸脱氢酶(α-KGDHC)活性;线粒体Ga2+含量、胞浆NADH、NAD+、ATP和ADP含量,以及ICD mRNA转录水平。结果:(1)不同负荷运动训练组线粒体CS、ICD和α-KGDHC的活性均显著高于安静对照组(P < 0.01),且CS和ICD活性由高到低顺序均为:MT组 > HT组 > ST组 > LT组 > C组,α-KGDHC活性由高到低顺序为:HT组 > MT组 > ST组 > LT组 > C组。(2)不同负荷运动训练组线粒体Ca2+ 含量均显著高于安静对照组(P < 0.01),其含量由高到低顺序为:MT组 > HT组 > ST组 > LT组 > C组;胞浆NADH/NAD+和ATP/ADP的比值均显著低于安静对照组(P < 0.01),其比值由低到高顺序为:MT组 < ST组 < HT组 < LT组 < C组。(3)不同负荷运动训练组ICD mRNA转录水平均高于安静对照组(P < 0.01),其水平由高到低顺序为: MT组 > HT组 > ST组 > LT组 > C组。结论:低负荷、中等负荷、高负荷及极高负荷运动训练均可提高大鼠骨骼肌线粒体三羧酸循环功能,且中等负荷运动训练效果最佳。其机制与胞浆NADH/NAD+和ATP/ADP比值、线粒体摄钙能力及限速酶基因的表达有关。 相似文献
3.
Child discipline is a central component of parent-child interactions. Evidence suggests corporal discipline impairs children’s physical, cognitive, and socioemotional development and compromises their future chances, especially since it is more frequently used against at-risk children. Using geocoded data for 1209 children under the age of five and their mothers, this study analyses the relation between the occurrence of crimes in close proximity to households in four major urban municipalities of Colombia and a particularly violent corporal discipline practice: hitting children with objects. Results indicate that exposure to violent crimes, such as homicides and personal injuries, predicts a higher probability of hitting children with objects, even after controlling for a set of individual, family, and neighborhood characteristics. Sensitivity analyses suggest violent crimes are not related to other discipline methods, and less threatening crimes, such as robbery and drug trafficking, are not associated with hitting children with objects. These findings suggest households’ walls are permeable, and outside threats may interfere with families’ dynamics and well-being. Future directions and implications are discussed. 相似文献
4.
BackgroundMaltreated youth are at an elevated risk for the development of problem behaviors. Coping with the death of a family member or close friend during adolescence, referred to as bereavement, is a stressful event that could potentiate risk linked to maltreatment. However, developmental research suggests that youth adjustment is a product of multiple risk and protective factors. Although maltreated youth who experience loss may be particularly vulnerable to behavior problems, personal and contextual factors may attenuate or exacerbate youths’ risk for internalizing and externalizing psychopathology.ObjectiveThe overarching goal of this study is to examine individual, family, and community-level protective factors for maltreated youth who experience bereavement. Specifically, we aim to examine the effect of age 12 bereavement on age 16 internalizing and externalizing psychopathology, and to investigate the moderating role of multi-level protective factors at ages 14 and 16.MethodsThe study consisted of a sample of 800 youth (52.4% female, 45.1% African-American) drawn from the Longitudinal Studies of Child Abuse and Neglect (LONGSCAN), collected from 1998 to 2011.ResultsMaltreated youth who experienced significant loss were at increased risk for externalizing symptoms, compared to non-bereaved maltreated youth (β = 0.085, p < .05). Individual future orientation (β = 0.103, p < .05) family future orientation (β = −0.120, p < .05), parental monitoring (β = −0.123, p< .01), and neighborhood collective efficacy (β = −0.126, p < .01) each significantly moderated the association between bereavement and externalizing symptoms.ConclusionsThese results have implications for future interventions aimed towards reducing problem behaviors in adolescents with a history of child maltreatment and who experience bereavement. 相似文献
5.
朱强 《浙江传媒学院学报》2003,10(4):70-72
校园网络系统在学校的教学和管理工作中发挥着越来越重要的作用,本文从当前Internet/Intranet及MIS系统的发展出发,在比较当前流行的数据存取及信息处理技术基础上,阐述TASP的作用与优点及其在校园网信息处理中的应用。 相似文献
6.
邢傲伟跳马侧手翻直体侧空翻转体810°的运动学分析 总被引:7,自引:3,他引:4
通过运动学等研究方法,揭示了我国优秀运动员邢傲伟完成的跳马侧手翻直体侧空翻转体810°的运动学规律与技术特点,对于进一步发展笠松类高难动作,提高我国男女跳马技术水平有促进作用. 相似文献
7.
8.
根据工况将不同的设备组合成不同的工作流程,以集散控制技术为基础,应用PLC网络实现了对输煤设备的现场控制、电控室控制和中控室控制。并以FIX软件为工具,通过定义PLC的I/O端口映射表方法,以时间、事件、故障为触发手段,设计了实时监控软件,并实现了输煤量与数据库系统的数据接口。 相似文献
9.
通过分析与探讨汉族普通人群ACE基因I/D多态频率分布特征,试图为中国优秀耐力运动员的基因选材研究提供中国人相关人群ACE基因I/D多态频率分布的基础数据。选择18-22岁汉族学生216名作为研究对象,观察其ACE基因I/D多态频率分布。结果显示:北方汉族青年的ACE基因I/D多态频率分布,与国内相关研究结果一致,与欧美人群有非常显著差异。研究认为:从种族单一性、样本数量和年龄段的选择等因素考虑.研究结果不仅可以作为北方汉族青年ACE基因I/D多态频率分布的代表,而且对于杰出耐力的多态性标记研究来讲是理想的对照群体。 相似文献
10.
与中国的媒介资本市场相比 ,美国媒介上市的操作程序市场化与公开化的色彩更加突出 ,证券主管机关的权力仅在于保证媒介发行证券的公开条款得到遵守 ,保证媒介提供的各项陈述的真实性。在美国证券市场上 ,传媒业整体受到投资者的追捧 ,但媒介的个股表现却是苦乐不均。投资者对上市公司未来业绩增长的预期决定了媒介个股的市场表现 相似文献