全文获取类型
收费全文 | 1055篇 |
免费 | 26篇 |
专业分类
教育 | 742篇 |
科学研究 | 48篇 |
各国文化 | 11篇 |
体育 | 185篇 |
文化理论 | 30篇 |
信息传播 | 65篇 |
出版年
2023年 | 10篇 |
2022年 | 13篇 |
2021年 | 18篇 |
2020年 | 35篇 |
2019年 | 70篇 |
2018年 | 87篇 |
2017年 | 79篇 |
2016年 | 64篇 |
2015年 | 50篇 |
2014年 | 44篇 |
2013年 | 228篇 |
2012年 | 50篇 |
2011年 | 22篇 |
2010年 | 27篇 |
2009年 | 15篇 |
2008年 | 24篇 |
2007年 | 19篇 |
2006年 | 29篇 |
2005年 | 17篇 |
2004年 | 7篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 5篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1956年 | 3篇 |
排序方式: 共有1081条查询结果,搜索用时 15 毫秒
81.
Rupprecht P Golé L Rieu JP Vézy C Ferrigno R Mertani HC Rivière C 《Biomicrofluidics》2012,6(1):14107-1410712
We have developed a method for studying cellular adhesion by using a custom-designed microfluidic device with parallel non-connected tapered channels. The design enables investigation of cellular responses to a large range of shear stress (ratio of 25) with a single input flow-rate. For each shear stress, a large number of cells are analyzed (500–1500 cells), providing statistically relevant data within a single experiment. Besides adhesion strength measurements, the microsystem presented in this paper enables in-depth analysis of cell detachment kinetics by real-time videomicroscopy. It offers the possibility to analyze adhesion-associated processes, such as migration or cell shape change, within the same experiment. To show the versatility of our device, we examined quantitatively cell adhesion by analyzing kinetics, adhesive strength and migration behaviour or cell shape modifications of the unicellular model cell organism Dictyostelium discoideum at 21 °C and of the human breast cancer cell line MDA-MB-231 at 37 °C. For both cell types, we found that the threshold stresses, which are necessary to detach the cells, follow lognormal distributions, and that the detachment process follows first order kinetics. In addition, for particular conditions’ cells are found to exhibit similar adhesion threshold stresses, but very different detachment kinetics, revealing the importance of dynamics analysis to fully describe cell adhesion. With its rapid implementation and potential for parallel sample processing, such microsystem offers a highly controllable platform for exploring cell adhesion characteristics in a large set of environmental conditions and cell types, and could have wide applications across cell biology, tissue engineering, and cell screening. 相似文献
82.
This paper proposes a new sliding mode observer for fault reconstruction, applicable for a class of linear parameter varying (LPV) systems. Observer schemes for actuator and sensor fault reconstruction are presented. For the actuator fault reconstruction scheme, a virtual system comprising the system matrix and a fixed input distribution matrix is used for the design of the observer. The fixed input distribution matrix is instrumental in simplifying the synthesis procedure to create the observer gains to ensure a stable closed-loop reduced order sliding motion. The ‘output error injection signals’ from the observer are used as the basis for reconstructing the fault signals. For the sensor fault observer design, augmenting the LPV system with a filtered version of the faulty measurements allows the sensor fault reconstruction problem to be posed as an actuator fault reconstruction scenario. Simulation tests based on a high-fidelity nonlinear model of a transport aircraft have been used to demonstrate the proposed actuator and sensor FDI schemes. The simulation results show their efficacy. 相似文献
83.
Amparo Núñez Andrés Felipe Buill Pozuelo Joaquín Regot Marimón Andrés de Mesa Gisbert 《Journal of Cultural Heritage》2012,13(1):103-106
Different techniques and tools currently exist to generate three-dimensional models of small elements, buildings and cities. Apart from being easier to interpret than two-dimensional drawings, these models facilitate data necessary for reconstruction projects, preservation or rehabilitation of the architectural or archaeological heritage. Traditional surveying only enables us to obtain discrete information of the characteristic lines that define each surface, edge, slope change etc. whereas work with massive capture techniques allows us to obtain continuous points of the surfaces. Photogrammetry or laser scanning combined with conventional photography provides information of the building in addition to its geometry. We carried out a review of the different techniques showing the advantages and disadvantages of each technique as well as the information that can be obtained by applying these techniques to the survey of the great Gate of Antioch in the town of Aleppo, declared a World Heritage Site by UNESCO in 1986, in Syria. 相似文献
84.
The aim of this paper is to characterize the distribution of number of hits and spent time by web session. It also expects to find if there are significant differences between the length and the duration of a session with regard to the point of access–search engine, link or root. Web usage mining was used to analyse 17,174 web sessions that were identified from the webometrics.info web site. Results show that both distribution of length and duration follow an exponential decay. Significant differences between the different origins of the visits were also found, being the search engines’ users those who spent most time and did more clicks in their sessions. We conclude that a good SEO policy would be justified, because search engines are the principal intermediaries to this web site. 相似文献
85.
In this paper a generalisation of the h-index and g-index is given on the basis of non-negative real-valued functionals defined on subspaces of the vector space generated by the ordered samples. Several Hirsch-type measures are defined and their basic properties are analysed. Empirical properties are illustrated using examples from the micro- and meso-level. Among these measures, the h-index proved the most, the arithmetic and geometric g-indices, the least robust measures. The μ-index and the harmonic g-index provide more balanced results and are still robust enough. 相似文献
86.
Training and psychosocial patterns during the early development of Portuguese national team athletes
This study explored the early development of expert athletes compared to a group of athletes that did not achieve an expert level of performance despite being involved in youth events with their national squads. In particular, the activities, training patterns, and psychosocial influences that characterized their paths in competitive sports were examined. Male and female participants (N?=?42) from different sports were interviewed. Overall, athletes showed several commonalities. However, experts were selected to national squads later and also started thinking about investing in becoming elite athletes later. Non-experts revealed more parental pressure and less individual training with coaches. 相似文献
87.
Anjalé D. Welton Katherine Cumings Mansfield Pei-Ling Lee 《Mentoring & Tutoring: Partnership in Learning》2013,21(5):481-509
There is limited research on quantitative differences between men and women’s experiences in doctoral programs. We aim to fill that gap by sharing findings from a web-based exploratory survey of perceived gender differences on quality mentoring in educational leadership doctoral programs. According to survey results, there is limited statistical significance in terms of gender differences in programmatic supports and scholarly progress. However, women experience feelings of self-doubt due to negative experiences with advising and mentoring, including difficulties making connections to a quality mentor. Furthermore, both female and male participants shared common definitions of what constitutes quality mentorship and believed mentorship was important, but lacking in varying degrees. Finally, all participants agreed that their educational leadership preparation programs should provide additional support in terms of writing and research development. Participants also shared important recommendations for strengthening mentoring experiences as well as future research methods and foci. 相似文献
88.
Niels R. Faber Laura Maruster René J. Jorna Rob J.F. van Haren 《Educational Research and Evaluation》2013,19(6):519-539
In small businesses with no employees, learning environments have a low learning readiness. Consequently, learners need to rely on their own agency to shape their learning experiences. Results from a study of agricultural entrepreneurs indicated that the components of motivation and self-regulated learning strategies shape learner's agency and explain learning environment configuration in small businesses with no employees. Configuration of the learning environment was found to be a weak determinant of the learning performance of these learners. However, results showed that prior performance of learners in small businesses with no employees dictates how their agency operates and what learning effect is achieved; higher prior performance results in higher learning effects. We conclude that mechanisms that underlie learning in traditional learning environments work similarly in learning environments in small businesses with no employees. 相似文献
89.
Teachers' written reflections on their work, which report on a change in their practice, were the object of this research. Taking teachers' articulation of their plans and actions in teacher journals as our source, this study's aim is twofold: (1) to describe how teacher reflect in a self‐initiated and non‐framed way on their own practice, and (2) to review teacher self generated reflections in reference to models of reflection. In this way, we tried to disclose what precisely teachers write (said) when reflecting on their work (did) in order to appreciate their way of describing what matters in their work; and position this in reference to models that conceptualise (“talk”) on how to actualise (‘walk’) reflection. This ‘double’ articulation of reflection is gauged in two ways, i.e., on: a) completeness, that is, whether it includes relevant components of reflection (models) to be found in the literature, and on b) recursiveness, that is, whether the written account gives evidence of an integrated cyclical, i.e., recursive process of re‐view, which appraises and looks back on what has been accomplished. The results show that teachers do not work along the lines identified in current reflection models (i.e. providing clear problem definition, searching for evidence, planning for change, and reviewing plans). Instead, many teachers use a narrative and valuing appraisal of their accomplishments; not so much cautiously reviewing their actions but prospectively commenting on plans and solutions for future action. The data lead us to be cautious about the prominence of reflection models as advocated in the literature to be applied to teachers' written accounts of their practice. 相似文献
90.
In this study we use data from the Early Childhood Longitudinal Survey third- and fifth-grade samples to investigate teacher judgments of student achievement, the extent to which they offer a similar picture of student mathematics achievement compared to standardized test scores, and whether classroom assessment practices moderate the relationship between the two measures. Results indicate that teacher ratings correlate strongly with standardized test scores; however, this relationship varies considerably across teachers, and this variation is associated with certain classroom assessment practices. Furthermore, the evidence suggests that teachers evaluate student performance not in absolute terms but relative to other students in the school and that they may adjust their grading for some students, perhaps with basis on perceived differences in need and/or ability. 相似文献