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21.
水平井分段多簇压裂在现场得到了广泛运用,其压裂过程中普遍存在缝间干扰现象。缝间干扰有助于形成复 杂裂缝网络以提高储层导流能力,但是也会导致起裂困难,甚至形成砂堵。因此有必要对分段多簇压裂的缝间干扰问 题进行研究。对此,基于弹性力学建立了分析多簇裂缝诱导应力的数学模型,从起裂压力、裂缝宽度、簇间距等多方面 研究了缝间干扰对水平井分段多簇压裂施工的影响。模拟结果显示,诱导应力会导致起裂压力升高、裂缝变窄,严重 时将造成压裂施工失败。通过进行分析,给出了起裂过程及延伸过程中缝间干扰的影响关系。分析认为,利用缝间干 扰提高改造体积时应当控制簇间距防止对压裂施工造成负面影响。研究结论对优化水平井分段多簇压裂设计具有指 导意义。  相似文献   
22.
In recent years, the migration of Spanish people to other countries in Europe has increased; however, there are hardly any studies on this phenomenon. The aim of this study is to identify the predictive sociodemographic and psychosocial factors of psychological adjustment (life satisfaction and absence of internalizing symptoms) of emigrants and to determine the indirect effects of these factors through perceived stress. This study also seeks to examine whether the psychological adjustment of Spanish emigrants was similar to Spanish non-emigrants. The sample was made up of a group of Spanish emigrants to Germany and England (n = 858) and an equivalent control group of Spanish non-emigrants (n = 328). The results show that fulfilment of expectations, emotional support and job quality are the best predictors of perceived stress and psychological adjustment. These factors are confirmed to have indirect effects on psychological adjustment through perceived stress. Finally, the mental health of emigrants and non-emigrants was similar, and the implications of these findings are discussed.  相似文献   
23.
Child‐ and family‐related factors that predict internalizing symptoms are understudied in preschool years and have a negative influence on children's functioning. We examined observational assessments of preschoolers' temperamental fearfulness and exuberance, mother reports of negative control, warmth, and parenting stress in a sample of 109 Turkish preschoolers. High temperamental fearfulness and low joyful/exuberant positive affectivity in addition to low warmth and high parenting stress had significant effects on internalizing symptoms. Parenting stress had both direct and indirect relations to internalizing symptoms via lower maternal warmth. When comorbid elevations in externalizing symptoms were controlled, the results were consistent with the interpretation that poor parenting practices and stress associated with the parenting role predict maladaptation in general but that the specific form of maladaptation may be best predicted by individual differences in children's temperamental characteristics. This study contributes to our understanding of risk and protective factors that predict preschoolers' internalizing symptoms with a sample from a non‐Western population. These findings can guide early prevention and intervention programs to address internalizing problems in a culturally‐sensitive way.  相似文献   
24.
Two types of bivariate models for categorical response variables are introduced to deal with special categories such as ‘unsure’ or ‘unknown’ in combination with other ordinal categories, while taking additional hierarchical data structures into account. The latter is achieved by the use of different covariance structures for a trivariate random effect. The models are applied to data from the INSIDA survey, where interest goes to the effect of covariates on the association between HIV risk perception (quadrinomial with an ‘unknown risk’ category) and HIV infection status (binary). The final model combines continuation-ratio with cumulative link logits for the risk perception, together with partly correlated and partly shared trivariate random effects for the household level. The results indicate that only age has a significant effect on the association between HIV risk perception and infection status. The proposed models may be useful in various fields of application such as social and biomedical sciences, epidemiology and public health.  相似文献   
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以泰州某大跨度连续梁桥的静动载试验为例,建立ANSYS和桥梁博士模型进行静动力有限元数值计算。将试验结果与模型计算值进行比较,试验结果表明,该桥结构刚度和承载能力满足设计要求。  相似文献   
27.
本文根据地质力学和岩体结构力学原理,探讨水平扭剪应力场在大裂缝系统形成、转化和分布中的重要控制作用及其物理模型.文中认为,大裂缝系统是较大的直压型裂缝网络与扭剪型裂缝网络叠加的产物,主要分布在较强的水平扭剪应力和术平直压应力复合作用的区块;水平扭剪应力场是改造和控制大裂缝网络结构异向性的最重要因素。这为研究和勘探较大的隐伏裂缝系统,提供了新的成藏模式和理论依据。  相似文献   
28.
“重陆轻海”与“通洋裕国”之海洋观刍议   总被引:1,自引:0,他引:1  
明清两朝正处于世界性海洋历史发展的"千古变局"时代,但统治者沿袭传统模式,在立国思想上"重农抑商"、"重陆轻海",在国防战略上以"禁海"代替海防,禁海迁界、"守土防御",反映其海洋观念的淡薄;而东南沿海地方官员,尤其郑成功"通洋裕国"思想的提出和实践,显露出"以商立国",向海洋空间发展的意涵;传统时代"重陆轻海"与"通洋裕国"所反映的海洋观念,对国家民族发展的影响在某种程度上可以忽略不计,但大航海时代,海洋作为人类的第二生存空间影响到世界历史走向和发展格局时,"重陆轻海"观念所带来的深层影响会因此而改变国家和民族的命运。  相似文献   
29.
Drawing upon both heuristic‐ and threat‐based approaches, we sought to examine whether perceived similarity with injury‐prone people and perceived control over injury occurrence would directly contribute to perceived risk and whether these variables would mediate the previous injury–perceived risk relationship. Judokas (n = 207) reported the number of injuries experienced in the past year and then completed measures of perceived similarity, perceived control, and injury risk perception. Analyses revealed that perceived similarity and perceived control directly contributed to perceived risk of injury; only perceived similarity acted as a partial mediator of the injury–perceived risk relationship. These findings are discussed in relation to the potential influence of the sport context, which universally involves the acceptance of a high risk of injury.  相似文献   
30.
With the increasing importance of self-help groups, professionals need to augment their understanding of how groups work in order to help clients make effective use of them. Three conceptual frameworks-social networks, social learning and cognitive theory-explain the basic psychosocial processes of self-help groups. Practice implications indicate how clients can benefit from self-help groups and suggest how professionals might enable their clients to realize the full benefits of participation in them.  相似文献   
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