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   3514篇
  免费   65篇
  国内免费   5篇
教育   2573篇
科学研究   224篇
各国文化   46篇
体育   429篇
综合类   7篇
文化理论   82篇
信息传播   223篇
  2023年   27篇
  2022年   56篇
  2021年   93篇
  2020年   139篇
  2019年   209篇
  2018年   271篇
  2017年   265篇
  2016年   222篇
  2015年   158篇
  2014年   168篇
  2013年   750篇
  2012年   201篇
  2011年   125篇
  2010年   90篇
  2009年   81篇
  2008年   82篇
  2007年   69篇
  2006年   60篇
  2005年   55篇
  2004年   44篇
  2003年   41篇
  2002年   48篇
  2001年   28篇
  2000年   26篇
  1999年   13篇
  1998年   21篇
  1997年   14篇
  1996年   20篇
  1995年   17篇
  1994年   14篇
  1993年   10篇
  1992年   14篇
  1991年   9篇
  1990年   15篇
  1989年   11篇
  1988年   6篇
  1987年   5篇
  1986年   4篇
  1982年   6篇
  1981年   5篇
  1980年   8篇
  1979年   5篇
  1978年   6篇
  1977年   6篇
  1976年   5篇
  1974年   5篇
  1972年   5篇
  1956年   3篇
  1872年   4篇
  1870年   4篇
排序方式: 共有3584条查询结果,搜索用时 15 毫秒
961.
研究目的:优化获得血红密孔菌(P.sanguineus)的最佳培养基组成,提高耐热漆酶的产量。创新要点:获得了目前文献报道的最高水平的漆酶活力。研究方法:通过单因素试验研究了不同培养基(番茄汁、麦麸、麦芽提取物和葡萄糖细菌蛋白胨培养基)和不同组合诱导剂(大豆油、阿魏酸、没食子酸、二甲基苯胺、酸性蓝62和活性蓝19分别与硫酸铜组合诱导剂)对P.sanguineus产耐热漆酶的影响。在此基础上采用中心组合试验设计,进一步研究了番茄汁培养基结合硫酸铜和大豆油组合诱导剂对P.sanguineus产耐热漆酶的影响。利用SAS10.0和响应面分析方法对试验结果进行了统计分析和建立回归模型。重要结论:通过中心组合设计优化得出P.sanguineus产耐热漆酶的最优培养基条件:以36.8%番茄汁为培养基,以3 mmol/L硫酸铜和1%大豆油作为组合诱导剂。该条件下在10 L搅拌槽生物反应器中漆酶活力达到了143 000 IU/L(2,2'-联氮双(3-乙基苯并噻唑啉-6-磺酸)为底物,pH值为3.0)。  相似文献   
962.
To address the low literacy achievement of minority students, the sociocultural movement of the New Literacy Studies (NLS) encourages us to expand on current understandings of literacy. Instead of thinking of literacy as a neutral set of skills transferable from one setting to another, NLS researchers encourage us to contextualize literacy within individuals’ social and cultural realms. In this view, there are multiple literacies. As a literacy teacher of students who are deaf, I have witnessed students struggling with school-based literacy learning. As I began to examine what I was doing within the classroom, I realized that my assumptions about literacy instruction were the main source of students' struggles. In this study I explore how I used the theoretical perspective of the NLS to expand my understanding of literacy. The findings suggest that, in order to base literacy instruction on students' resources, teachers need to learn to negotiate conflicting educational Discourses on reading and writing, to create a space within the classroom for students to bring in their literacy practices, and to recognize and preserve students' agency and identity in their learning. Findings also indicate the vital role of writing in deaf students' learning of Icelandic.  相似文献   
963.
Although the environmental light/dark cycle is the main zeitgeber for the human species, the social cues seem to be important in the synchronization of circadian rhythms. In Brazil, the existence of two school schedules—one with only morning classes (MG) and other with only afternoon classes (AG)—allows the investigation of the effect of school activities on light exposure and sleep/wake patterns in children. Forty‐seven children wore wrist actimeters for a week for registration of light and sleep data. MG children presented shorter sleep duration on school days than the children from the AG. The results showed that during school days MG children were exposed to bright light earlier in the morning when compared to AG children. Nevertheless, there were no differences in light exposure after sunset. The results reflect the role of school schedules and artificial light in shaping light exposure, and its association with sleep timing in children.  相似文献   
964.
965.
Extreme multistability is the coexistence of a large number of attractors which can be reached by varying initial conditions. In this paper we show how this fascinating phenomenon can be used for secure communication. The main advantage of the communication system based on extreme multistability over a conventional chaos-based communication system is its exceptionally high security. The proposed system consists of two identical six-order oscillators; one in the transmitter and another one in the receiver, each exhibiting the coexistence of a large number of chaotic attractors. The oscillators are synchronized using a private channel through one of the system variables, while the information is transmitted via a public channel through another variable. The information is encrypted by varying the initial condition of one of the state variables in the transmitter using a chaotic map, adhering message packages in a staggered form to the coexisting attractors within the same time series of another state variable, which leads to switching among the coexisting chaotic attractors. To ensure communication security, the duration of the packages is shorter than synchronization time, so that synchronization attacks are ineffective.  相似文献   
966.
This study adds to the literature on household sector (HHS) innovation by investigating how user and professional designer teams differ in their ability to translate knowledge diversity into collective creative output. We test our hypotheses on a unique data set of more than 5,000 board game design projects conducted by either teams of professional game designers or by hobbyist (user) designers. Our study lends support for the notion that knowledge diversity is a double-edged sword that has opposing effects on the two dimensions of team creativity, novelty and usefulness. We argue and find that teams composed of self-rewarded users in the household sector are better able than teams of professionals to translate the informational benefits of knowledge diversity into novel concepts and game designs. Finally, we find that user teams are in general more likely to create truly creative (i.e. novel and useful) game designs. This particular result emphasizes the relevance of research on HHS innovation and shows that user designers from the HHS are able to conduct collective development work more effectively than teams of professional designers.  相似文献   
967.
In times of major global interconnectedness and environmental change, the pressure to identify, create, and exploit new resources is certain to intensify. Given that there are unavoidable trade-offs, conflicts, and arenas for violence involved when increasingly more material and immaterial things are turned into resources, we call for explicit research on the very process – a process that we label resourcification. The concept of resourcification shifts attention from essentialist queries about the nature of resources to a focus on the social processes through which things are turned into resources. In search of a better understanding of resources in the Anthropocene and, in particular, an understanding about the way resources emerge and are used, resourcification offers a new conceptual framework that allows for a systematic search for knowledge about the diversity of contexts, conditions, modes, and temporalities of resourcification. This Resourcification Manifesto offers a theoretical and empirical framework for a radical and disruptive approach to innovation, sustainability, and management studies and policies.  相似文献   
968.
Public libraries have a huge potential to be creators and facilitators of social innovation in communities and society. Qualitative research based on interviews with 27 librarians showed that social innovation in libraries can take the form of educational and cultural activities, leisure and networking activities and social support services. The main goal of the research was to find out what factors support and make these innovations difficult in public libraries. A four-layer model of barriers and stimulators for social innovation is presented, which includes structural, local, organizational and personnel levels. The model could serve to inform librarians, their stakeholders and governments about all levels of barriers and stimulators connected to innovation of library services and social re-positioning of public libraries in the future.  相似文献   
969.
Educational ergonomics focuses on the interaction between educational performance and educational design. By improving the design or pointing out the possible problems, educational ergonomics can be utilized to have positive impacts on the student performance and thus on education process. Laptops and tablet computers are becoming widely used by school children and beginning to be used effectively for educational purposes. As the latest generation of laptops and tablet computers are mobile and lightweight compared to conventional personal computers, they support student-centred interaction-based learning. However, these technologies have been introduced into schools with minimal adaptations to furniture or attention to ergonomics. There are increasing reports of an association between increased musculoskeletal (MSK) problems in children and use of such technologies. Although children are among the users of laptops and tablet computers both in their everyday lives and at schools, the literature investigating MSK activities and possible MSK discomfort regarding children using portable technologies is limited. This study reviews the literature to identify published studies that investigated posture, MSK activities, and possible MSK discomfort among children using mobile technologies (laptops or tablet computers) for educational purposes. An electronic search of the literature published in English between January 1994 and January 2014 was performed in several databases. The literature search terms were identified and combined to search the databases. The search results that the resources investigating MSK outcomes of laptop or tablet use of children are very scarce. This review points out the research gaps in this field, and identifying areas for future studies.  相似文献   
970.
This study used a mixed-methods approach to examine the effects of the Advancement Via Individual Determination (AVID) program from the student perspective, specifically focusing on factors associated with student resilience. The AVID program aims to close the achievement gap among predominantly minority and low-income students without a family history of college attendance. Qualitative focus groups were conducted to better understand student perceptions of the program and quantitative survey results were used to compare scores on measures of school support, school engagement, and resilience among AVID and non-AVID students. Both qualitative and quantitative results provided evidence suggesting that the AVID program improved school support and engagement, as well as in the development of individual resilience factors, such as self-awareness, problem-solving ability, and self-esteem. Qualitative results also highlight the importance of providing consistency for students in the learning environment. Future directions and recommendations are provided.  相似文献   
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