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   20689篇
  免费   618篇
  国内免费   54篇
教育   15962篇
科学研究   1253篇
各国文化   269篇
体育   1423篇
综合类   44篇
文化理论   118篇
信息传播   2292篇
  2022年   132篇
  2021年   253篇
  2020年   346篇
  2019年   530篇
  2018年   716篇
  2017年   760篇
  2016年   684篇
  2015年   529篇
  2014年   664篇
  2013年   4538篇
  2012年   617篇
  2011年   649篇
  2010年   579篇
  2009年   539篇
  2008年   569篇
  2007年   502篇
  2006年   498篇
  2005年   443篇
  2004年   323篇
  2003年   287篇
  2002年   254篇
  2001年   397篇
  2000年   324篇
  1999年   286篇
  1998年   183篇
  1997年   172篇
  1996年   208篇
  1995年   176篇
  1994年   174篇
  1993年   154篇
  1992年   232篇
  1991年   225篇
  1990年   265篇
  1989年   228篇
  1988年   188篇
  1987年   197篇
  1986年   200篇
  1985年   190篇
  1984年   186篇
  1983年   177篇
  1982年   144篇
  1981年   140篇
  1980年   136篇
  1979年   193篇
  1978年   165篇
  1977年   116篇
  1976年   124篇
  1975年   112篇
  1973年   104篇
  1971年   117篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
In this paper in general the dynamic effects are considered and described, caused by different stand-ing waves in discrete and distributed systems with impacts and other strongly positional non-linear fac-tors, introduction of which in the models of me-chanical objects is dictated by the necessity to con-sider processes, accompanied with impacts of me-chanical subsystems of different nature.  相似文献   
992.
用不同于已有文献的方法研究了一类高阶中立型微分方程,本文不需要条件f∞t0Q(s)ds=∞,获得了这类方程振动性的几个新的结果.  相似文献   
993.
People still use documents in many everyday government processes. From tax payments to passport requests, citizens have to interact with low-interactivity information artifacts such as reports, maps and datasets, among many others. Despite efforts to improve information delivery in the public sector, effective information usage remains a critical topic of action and research. The user experience of government documents has rarely been assessed, despite them being regularly published and frequently used. Considering this, the two following research questions arise: 1) How can government documents be classified (or grouped) in terms of user experience? 2) How can the user experience of government documents be monitored over time in order to inform design decisions? Working with a public agency in Chile, we develop and test a classification and monitoring framework based on two online surveys (N?=?338 and N?=?298). We then propose a framework for understanding user experience of government documents in these three dimensions: interaction goal, volume of information and ease of understanding. Using a graphical representation to classify user experience provides greater visibility of the current status of information produced by a public organization. Furthermore, by monitoring the user experience of a government document at different times, organizations can understand the effect of their design decisions and improve their service quality by implementing user-centered processes.  相似文献   
994.
The combined effects of pH and temperature on red pigment production and fungal morphology were evaluated in a submerged culture of Penicillium purpurogenum GH2, using Czapek-Dox media with d-xylose as a carbon source. An experimental design with a factorial fix was used: three pH values (5, 7, and 9) and two temperature levels (24 and 34 °C) were evaluated. The highest production of red pigment (2.46 g/L) was reached with a pH value of 5 and a temperature of 24 °C. Biomass and red pigment production were not directly associated. This study demonstrates that P. purpurogenum GH2 produces a pigment of potential interest to the food industry. It also shows the feasibility of producing and obtaining natural water-soluble pigments for potential use in food industries. A strong combined effect (p<0.05) of pH and temperature was associated with maximal red pigment production (2.46 g/L).  相似文献   
995.

Objective  

The influence of hormone replacement therapy (HRT) on hemostasis processes depends on the type of hormone, the combination of doses, the time of taking HRT, and the route of administration (oral, transdermal, implanted). The aim of the current study was to assess some parameters of coagulation, especially tissue factor pathway inhibitor (TFPI) and tissue factor (TF) in postmenopausal women using oral or transdermal HRT.  相似文献   
996.
997.
During economic development, modern museums face competition from various leisure activities and entertainment sites, and to achieve sustainable development, museums should reflect on providing high‐quality service to satisfy visitors’ expectations. Based on service design‐related theories, this research team conducted a case study to explore the planning, implementation, and meaning of Mobile Museums. It investigated design development from the perspective of public service design and summarized the policy, design, and service satisfaction results for Mobile Museums. Finally, the similarities in service processes are discussed between Mobile Museums and the general service industry. According to this study, attracting more visitors is the biggest issue facing museums today, as are the ways in which museums must actively provide service and become recognized to compete with others. This study identifies the onstage and backstage support of museums as well as their cultural features and non‐profit services.  相似文献   
998.
Spatial skills are a central component of intellect and show marked individual differences. There is evidence that variations in the spatial language young children hear, which directs their attention to important aspects of the spatial environment, may be one of the mechanisms that contributes to these differences. To investigate how play affects variations in language, parents and children were assigned to 1 of 3 conditions: free play with blocks, guided play, or play with preassembled structures (Study 1). Parents in the guided play condition produced significantly higher proportions of spatial talk than parents in the other two conditions, and children in the guided play condition produced significantly more spatial talk than those in the free play condition. Study 2 established baselines of spatial language during activities not involving spatial materials. Proportions of spatial words were lower than those in any of the conditions of Experiment 1. In sum, interaction with blocks naturally elicits elevated levels of spatial language, especially in the context of guided play, suggesting simple‐to‐execute educational interventions.  相似文献   
999.
In the United States today, urban schools serve the majority of high-poverty and high minority populations including large numbers of Hispanic students. While many Hispanic students perform below grade level in middle school science, the science teaching community as a whole is lacking elements of diversity as teachers struggle to meet the needs of all learners. Researchers have recognized that science teacher effectiveness, one consequence of self-efficacy among teachers, is associated with future science achievement and science-related careers of their students. This qualitative study explores how three science teachers’ effectiveness in the classroom impacts students’ science self-efficacy beliefs at one urban middle school. Hispanic students were the focus of this investigation due to demographics and history of underperformance within this district. Teachers’ perspectives, as well as outside observer evaluations of instructional strategies and classroom climates were triangulated to explore dynamics that influence students’ interests and motivation to learn science using a framework to link teachers’ sense of efficacy (focusing on student outcomes). Findings suggest the impact teacher effectiveness can have on student outcomes, including strengthened student science self-efficacy and increased science achievement. Building awareness and support in teachers’ sense of efficacy, as well as developing respectful and supportive relationships between educator/facilitator and pupil during the transition to middle school may construct permanence and accomplishment for all in science.  相似文献   
1000.
Science education in the United States will increasingly be driven by testing and accountability requirements, such as those mandated by the No Child Left Behind Act, which rely heavily on learning outcomes, or "standards," that are currently developed on a state-by-state basis. Those standards, in turn, drive curriculum and instruction. Given the importance of standards to teaching and learning, we investigated the quality of life sciences/biology standards with respect to genetics for all 50 states and the District of Columbia, using core concepts developed by the American Society of Human Genetics as normative benchmarks. Our results indicate that the states' genetics standards, in general, are poor, with more than 85% of the states receiving overall scores of Inadequate. In particular, the standards in virtually every state have failed to keep pace with changes in the discipline as it has become genomic in scope, omitting concepts related to genetic complexity, the importance of environment to phenotypic variation, differential gene expression, and the differences between inherited and somatic genetic disease. Clearer, more comprehensive genetics standards are likely to benefit genetics instruction and learning, help prepare future genetics researchers, and contribute to the genetic literacy of the U.S. citizenry.  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