全文获取类型
收费全文 | 347篇 |
免费 | 7篇 |
专业分类
教育 | 235篇 |
科学研究 | 37篇 |
体育 | 48篇 |
文化理论 | 10篇 |
信息传播 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 37篇 |
2017年 | 14篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 9篇 |
2013年 | 80篇 |
2012年 | 17篇 |
2011年 | 16篇 |
2010年 | 7篇 |
2009年 | 16篇 |
2008年 | 9篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有354条查询结果,搜索用时 15 毫秒
281.
Previous literature finds that larger downstream markets fuel the innovation of new technologies by incentivizing firms to spend more on R&D. Our evidence shows that larger markets also increase the extent of licensing-based cooperation between upstream innovators and downstream commercializers. This cooperation is valuable because it pools firms’ complementary capabilities. Thus, downstream market expansions could positively impact innovative outcomes even holding R&D expenditures constant. Evidence is drawn from the drug candidate licensing market, exploiting the quasi-experimental variation introduced by the enactment of the Medicare Part D program in 2003. A model for the determination of equilibrium commercialization strategies in Markets for Technology rationalizes our finding. In this framework, cooperation gains are proportional to market size but transaction costs are not. Thus, larger downstream markets foster cooperation by reducing the relative importance of the latter. To better match the empirical context, the model extends the canonical “one technology–one application” framework of related work, to the more general case of “composite technologies,” which may have more than one end-user application. 相似文献
282.
Age‐related changes in flexibility and automaticity of reasoning about social situations were investigated. Children (N = 101; age range = 7;8–17;7) were presented with the flexibility and automaticity of social cognition (FASC), a new measure of social cognition in which cartoon vignettes of social situations are presented and participants explain what is happening and why. Scenarios vary on whether the scenario is socially ambiguous and whether or not language is used. Flexibility is determined by the number of unique, plausible explanations, and automaticity is indicated by speed of response. Overall, both flexibility and automaticity increased significantly with age. Language and social ambiguity influenced performance. Future work should investigate differences in FASC in older populations and clinical groups. 相似文献
283.
Francisco José Collado-Montero Ana Isabel Calero-Castillo Manuel Melgosa Víctor Jesús Medina 《文物保护研究》2013,58(2):90-100
ABSTRACTThe main aim of our current investigation is the colorimetric evaluation of protective treatments (consolidants) applied to traditional Islamic plasterworks, under natural ageing conditions. From analyses of the original pictorial plaster remains in the Courtyard of the Maidens of the Real Alcázar in Seville, Spain (a World Heritage Site) we prepared test specimens, using materials and techniques similar to the original ones. We analysed 56 test specimens painted with four pigments (yellow, green, blue, and red), using two different binders (animal glue and gum arabic), onto which five representative consolidants were applied: barium hydroxide, acrylic copolymer, polyvinyl butyral, ethyl silicate, and bacterial carbonatogenesis. The test specimens were subjected to natural ageing for one year (indoors and outdoors), enabling a colorimetric assessment to be made of the changes of the polychrome surfaces. The colorimetric heterogeneity of the 56 specimens after ageing registered an average value of 2.7 CIELAB units, assessed using the mean colour difference with respect to the mean. In the aged specimens, the addition of consolidants resulted in average colour differences (mainly lightness differences) of 10.7 and 6.7 CIELAB units, considering as a reference the specimens without consolidants aged indoors and outdoors, respectively. These colour differences were very similar for both binders but not for the four pigments, higher values being found for the blue and red pigments. Considering as reference the samples without consolidants aged outdoors, we found no statistically significant colour differences, either among the five consolidants (p?=?.094) nor the two binders (p?=?.674) used. In addition to the magnitude of colour differences, the choice of the most appropriate consolidants must also consider aspects related to performance and effectiveness. Overall, for the type of paints tested, the polyvinyl butyral consolidant appeared to perform the best, followed by the ethyl silicate. 相似文献
284.
The objective of this study is to shed light on the identification of the internal and external factors that affect the attitudes towards innovation of companies located in regions situated on the periphery of economic centres. The main research questions are as follows: (1) What are the internal factors that predispose companies to seek access to innovation? (2) To what extent do external factors such as location and technological opportunities condition or stimulate favourable attitudes towards innovation? To test the hypotheses put forward to answer these questions, we formulate and estimate econometric specifications, taking a sample of more than 2000 companies situated in Andalusia (one of the less-favoured regions in Spain). Our results show that the cost of innovation and the level of indebtedness of a company have a statistically significant and negative effect on attitudes to innovation, whereas the technical qualifications of the employees, the propensity to export, and the company size (measured by the number of employees) have a significant and positive effect on a company's attitude towards innovation. Furthermore, technological opportunities and location exert positive effects on attitudes towards innovation. 相似文献
285.
Modeling educational choices. A binomial logit model applied to the demand for Higher Education 总被引:2,自引:0,他引:2
This paper presents a microeconomic analysis of the choice of universitydegree course that individuals make on finishing their Secondary studies(four-year university degree or three-year university degree), andcontains the theoretical framework as well as empirical results. Themodel selected for our analysis is a binomial logit model. This model,which can be seen as a special case of a general model of utilitymaximization, deals with those aspects of the economics of educationalchoice that are regarded as important in the literature of this subject:academic aptitude, the social background in which the students havegrown up, family income, employment prospects, etc. By using survey dataon educational choices of Spanish High School graduates (cross-sectionaldata), we investigate to what extent the theoretical determinants areconfirmed in practice. The results of the estimation by maximumlikelihood of the logit model, and which allow us to analyze theinfluence of the explanatory variables on the probability of choosing afour-year university degree, show how social background, family earningsand scholastic ability explain, mainly, the educational choice ofstudents. The students from higher socioeconomic status as well as thosewith the best High School curricula are more likely to follow auniversity degree of greater duration. 相似文献
286.
Twenty isolates ofMycobacterium tuberculosis resistant to rifampicin(RIF), isoniazid(INH) and streptomycin(STR) were analysed by Polymerase Chain Reaction (PCR) amplification
of rpoB, katG and rrs genes to evaluate comparative diagnostic significance of genetic assays. Mutations were identified by
single strand conformation polymorphism (SSCP) and cleavase fragment length polymorphism (CFLP) and were confirmed by DNA
sequencing. SSCP of 4 RIF resistant and 14 INH resistant isolates showed an extra peak at the level of 75-bp and 85-bp respectively,
while 2 STR resistant isolates showed 2 peaks with 9 bases difference. CFLP showed a different pattern among RIF, INH and
STR sensitive and resistant isolates Thus SSCP and CFLP can be used as alternative diagnostic methods for identification of
mutations in RIF, INH and STR resistant strains of M.tuberculosis. 相似文献
287.
The concept of justice has gradually colonized sports’ narratives in general and professional football ones in particular. Discourses on justice often give rise to ambiguous, unclear narrations with a great deal of noise and opportunism. The aim of this article is to apply the concept of justice devices to clarify the range of measures used and link these to the diverse agents that attempt to gain legitimacy and power through them. In an initial characterisation, we highlight conventional and post-conventional models of ethics of justice. Subsequently, we compare these models to the systems of justice employed by football’s governing institutions, FIFA and UEFA. Finally, we analyse a paradigmatic event of judicial interpretation by various actors using the case of ‘Luiz Adriano’. In this article, we reveal some of the specific uses, settings and strategic aims of justice devices employed by the main actors involved in international football. 相似文献
288.
Alegre LM Jiménez F Gonzalo-Orden JM Martín-Acero R Aguado X 《Journal of sports sciences》2006,24(5):501-508
The aims of this study were to assess changes in muscle architecture, isometric and dynamic strength of the leg extensor muscles, resulting from dynamic resistance training, and the relationships between strength and muscle architecture variables. The participants (n = 30) were randomly assigned to one of two groups. The training group (n = 16; age 21.8 +/- 2.3 years, body mass 74.8 +/- 9.2 kg, height 1.75 +/- 0.08 m) performed dynamic resistance training for 13 weeks. The control group (n = 14; age 19.9 +/- 1.5 years, body mass 74.0 +/- 8.5 kg, height 1.76 +/- 0.05 m) did not perform any resistance training. Maximal dynamic and isometric strength were tested in both groups, before and after the training period. The members of the training group used the free-weight squat lift (90 degrees ) as their training exercise. The concentric phase of the squat was performed explosively. Skeletal muscle architecture of the vastus lateralis was visualized using ultrasonography. At the end of the study, significant increases in vastus lateralis muscle thickness (+6.9%, P < 0.001), fascicle length (+10.3%, P < 0.05), one-repetition maximum (+8.2%, P < 0.05), rate of force development (+23.8%, P < 0.05) and average force produced in the first 500 ms (+11.7%, P < 0.05) were seen only in the training group. Adaptations to the muscle architecture in the training group limited the loss of fibre force, and improved the capacity for developing higher velocities of contraction. The architectural changes in the training group were similar to those seen in studies where high-speed training was performed. In conclusion, dynamic resistance training with light loads leads to increases in muscle thickness and fascicle length, which might be related to a more efficient transmission of fibre force to the tendon. 相似文献
289.
Pérez-Soriano P Llana-Belloch S Morey-Klapsing G Perez-Turpin JA Cortell-Tormo JM van den Tillaar R 《Sports biomechanics / International Society of Biomechanics in Sports》2010,9(4):245-257
Shock absorption and stability during landings is provided by both, gymnast ability and mat properties. The aims of this study were to determine the influence of different mat constructions on their energy absorption and stability capabilities, and to analyse how these properties affect gymnast's plantar pressures as well as subjective mat perception during landing. Six mats were tested using a standard mechanical drop test. In addition, plantar pressures and subjective perception during landing were obtained from 15 expert gymnasts. The different mats influenced plantar pressures and gymnasts' subjective perception during landing of gymnasts. Significant correlations between plantar pressures at the medial metatarsal and lateral metatarsal zones of the gymnasts' feet with the different shock absorption characteristics of the mats were found. However, subjective perception tests were not able to discriminate mat functionality between the six mats as no significant correlations between the mechanical mat properties with the subjective perception of these properties were found. This study demonstrated that plantar pressures are a useful tool for discriminating different landing mats. Using similar approaches, ideally including kinematics as well, could help us in our understanding about the influences of different mats upon gymnast-mat interaction. 相似文献
290.
Sandra Prez-Rodríguez Stephanie A. Huang Carlos Borau Jos Manuel García-Aznar William J. Polacheck 《Biomicrofluidics》2021,15(5)
Extravasation of circulating cells is an essential process that governs tissue inflammation and the body''s response to pathogenic infection. To initiate anti-inflammatory and phagocytic functions within tissues, immune cells must cross the vascular endothelial barrier from the vessel lumen to the subluminal extracellular matrix. In this work, we present a microfluidic approach that enables the recreation of a three-dimensional, perfused endothelial vessel formed by human endothelial cells embedded within a collagen-rich matrix. Monocytes are introduced into the vessel perfusate, and we investigate the role of luminal flow and collagen concentration on extravasation. In vessels conditioned with the flow, increased monocyte adhesion to the vascular wall was observed, though fewer monocytes extravasated to the collagen hydrogel. Our results suggest that the lower rates of extravasation are due to the increased vessel integrity and reduced permeability of the endothelial monolayer. We further demonstrate that vascular permeability is a function of collagen hydrogel mass concentration, with increased collagen concentrations leading to elevated vascular permeability and increased extravasation. Collectively, our results demonstrate that extravasation of monocytes is highly regulated by the structural integrity of the endothelial monolayer. The microfluidic approach developed here allows for the dissection of the relative contributions of these cues to further understand the key governing processes that regulate circulating cell extravasation and inflammation. 相似文献