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   5561篇
  免费   71篇
  国内免费   12篇
教育   4189篇
科学研究   283篇
各国文化   54篇
体育   448篇
综合类   3篇
文化理论   75篇
信息传播   592篇
  2022年   33篇
  2021年   50篇
  2020年   72篇
  2019年   136篇
  2018年   169篇
  2017年   188篇
  2016年   178篇
  2015年   120篇
  2014年   144篇
  2013年   1150篇
  2012年   156篇
  2011年   152篇
  2010年   171篇
  2009年   157篇
  2008年   179篇
  2007年   158篇
  2006年   129篇
  2005年   107篇
  2004年   112篇
  2003年   97篇
  2002年   111篇
  2001年   96篇
  2000年   128篇
  1999年   92篇
  1998年   84篇
  1997年   74篇
  1996年   78篇
  1995年   66篇
  1994年   77篇
  1993年   74篇
  1992年   63篇
  1991年   82篇
  1990年   60篇
  1989年   57篇
  1988年   39篇
  1987年   59篇
  1986年   66篇
  1985年   57篇
  1984年   53篇
  1983年   53篇
  1982年   40篇
  1981年   38篇
  1980年   39篇
  1979年   41篇
  1978年   41篇
  1977年   44篇
  1976年   34篇
  1975年   29篇
  1974年   29篇
  1972年   22篇
排序方式: 共有5644条查询结果,搜索用时 15 毫秒
51.
One set of measures of the quality of courses for the preparation of science teachers stems from the perceptions exit students have of their knowledge with respect to that teaching. The Discipline Review of Teacher Education in Mathematics and Science surveyed these students late in 1988 on three broad types of knowledge-science content knowledge, curriculum knowledge, and pedagogical knowledge. Some of these findings of the Review are described. In addition, the base for developing items to measure these three types of knowledge is discussed in this paper. The variety in the data that emerged is also presented and the consistency of the findings with other measures of quality is described. Specialisations: science and technology curriculum, environmental education, educational disadvantage. Specialisations: research and evaluation in teacher education, technical and further education and total quality management. Specialisations: research in educational systems.  相似文献   
52.
53.
Three experiments showed a savings procedure to be an effective and sensitive alternative to sensory preconditioning procedures as a measure of associations among neutral stimuli. Experiment 1 showed that within-compound associations developed more rapidly in reinforced appetitive serial compound conditioning when nonreinforced preexposure to the serial compound was given than when separate element or no preexposure was given. Experiment 2 showed the savings effect to be highly stimulus specific. Experiment 3 examined the facilitation of serial compound conditioning after either simultaneous or serial nonreinforced preexposure to the elements of the compound. The results of that experiment were consistent with those of analogous sensory preconditioning experiments. When preexposure involved only the two elements of the subsequently reinforced compound, serial preexposure produced more savings than simultaneous preexposure. But when preexposure involved a three-stimulus procedure like that used by Rescorla (1980b), simultaneous preexposure resulted in more savings. Advantages of the savings procedure over sensory preconditioning as a measure of association among neutral stimuli are discussed.  相似文献   
54.
Bioluminescence resonance energy transfer (BRET) is a form of Förster resonance energy transfer. BRET has been shown to support lower limits of detection than fluorescence resonance energy transfer (FRET) but, unlike FRET, has not been widely implemented on microfluidic devices for bioanalytical sensing. We recently reported a microscope-based microfluidic system for BRET-based biosensing, using a hybrid, high quantum-efficiency, form of BRET chemistry. This paper reports the first optical fiber-based system for BRET detection on a microfluidic chip, capable of quantifying photon emissions from the low quantum-efficiency BRET2 system. We investigated the effects of varying core diameter and numerical aperture of optical fibers, as well as varying microfluidic channel design and measurement conditions. We optimized the set-up in order to maximize photon counts and minimize the response time. The optimized conditions supported measurement of thrombin activity, with a limit of detection of 20 pM, which is lower than the microscope-based system and more than 20 times lower than concentrations reported to occur in plasma clots.  相似文献   
55.
A survey was conducted in eight secondary schools located in two watersheds in Gujarat and Rajasthan (semi-arid region of India) to assess students’ perceptions about groundwater scarcity issues and the impact of the scarcity on their educational opportunities. Survey responses to a detailed questionnaire by a cohort of students in both watersheds; school attendance records of year 8 class students (13–14 years old) and responses gathered via a socio-economic survey involving 500 families in the study area were used in the study. In both watersheds, >90% students identified groundwater scarcity as a major issue. Required to work at home or farm, about 65% students in Gujarat and 60% in Rajasthan missed school for up to 2 days/month; and a smaller proportion (~ 30%) missed schools for 4 or more days/month. School absenteeism was found to be linked with gender; female students missed schools more frequently than their male counterpart. The school attendance records in Rajasthan showed that the frequency of female students missing schools for 5 or more days/month was on an average 2–10 times greater than that for males. The gender difference in absenteeism in all schools was statistically significant (P?<?.018**). The study highlighted that groundwater scarcity in the study area, and consequent demand on their time for household work including fetching drinking water are contributing factors towards limiting their educational and economic opportunities. Groundwater scarcity can be one of the key factors that can limit inclusiveness and empowerment of women and need to be considered in policy-making.  相似文献   
56.
Child-directed (CD) speech segments produced by 20 mothers who varied in self-reported symptoms of depression, recorded during a structured play interaction with their 2- to 6-month-old infants, were used as conditioned stimuli with face reinforcers in a conditioned attention paradigm. After pairings of speech segments and faces, speech segments were assessed for their ability to increase time spent looking at a novel checker-board pattern (summation test) using 225 4-month-old infants of nondepressed mothers. Significant positive summation, an index of associative learning, was obtained in groups of infants tested with speech produced by mothers with comparatively fewer self-reported symptoms of depression (Beck Depression Inventory or BDI < or = 15). However, significant positive summation was not achieved using speech samples produced by mothers with comparatively more symptoms of depression (BDI > 15). These results indicate that the CD speech produced by mothers with symptoms of depression does not promote associative learning in infants.  相似文献   
57.
The Competitive State Anxiety Inventory-2 (CSAI-2) is one of the most frequently used instruments when assessing competitive state anxiety in sport psychology research. However, doubts have been expressed about the factorial validity of both the English and the Greek versions of the scale. Hence, a revised version of the inventory (CSAI-2R) has recently been suggested to be more psychometrically sound (Cox et al., 2003). In the present study, the aim was to evaluate the psychometric properties of the Swedish version of the CSAI-2 using confirmatory factor analyses. A total of 969 athletes (571 men and 398 women) competing in 26 different sports completed the Swedish version of the CSAI-2. Three different factor structures were evaluated: the original three-factor model (with cognitive anxiety, somatic anxiety and self-confidence), a two-factor model in which self-confidence was excluded, and a three-factor model containing 17 items (CSAI-2R). The results revealed that only the 17-item model displayed an acceptable fit to the data. Although some doubts remain about the amount of variance that can be attributed to error variance in the subscales, the results suggest that it is better to use the CSAI-2R rather than the original CSAI-2.  相似文献   
58.
This paper examines the need for re-evaluating archival principles and practices. Opportunities created to enhance and enrich archival work and difficulties of archiving digital information, because of its nature, are reviewed. “Records series” are used to illustrate the consequences in terms of selection and appraisal of records. The preservation of digital information also raises new challenges. The impact of digital information on the ethical, legal and societal issues (protection, confidentiality, privacy, etc.) is emphasized.  相似文献   
59.
The paper presents a model that evaluates how upgraded technological capabilities of emerging country based multinationals (EMNCs) and an increase in the domestic market size of large emerging countries affect value chain location choices and the competitiveness of emerging country based firms versus advanced country based ones. The model shows that, even without possessing a competitive advantage in terms of technology and/or brands, EMNCs from large or rapidly technologically advancing countries can become dominant players in the global system. The model highlights the central role of firm level technological intensity and product differentiation in determining the location of value chain activities as well as defining organisational boundaries. Empirical analysis of the location choices of the world's top multinationals from large advanced and emerging countries in 2010 supports the model's predictions.  相似文献   
60.
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