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91.
经扫描电镜观察,我国常绿栎类的叶表皮共发现有10种不同类型的毛,它们分别是:单列毛、单   分枝毛、泡状毛、莲座毛、单毛、束毛、短柄束毛、多出毛、星状毛和并合星状毛。  不同的分类单位有不同   毛类型的组合。所有常绿栎类的叶表皮上都出现有非腺毛类型的毛,而腺毛则仅限于某些分类单位   中。这两种基本类型的毛在结构和功能上有着本质的区别,分别代表了物种的生存适应方式和进化途   径。按叶表皮毛的基本类型将我国常绿栎类划分为腺毛类群和非腺毛类群两个类群,支持将常绿栎类   分成高山栎组(Sect.Suber(Reichenb.)Spach)和巴东栎组(Sect.Englerianae(A. Camus)Hsu et   Jen)的分组处理。综合叶表皮毛的类型、密度以及分枝特征提出了我国常绿栎类各分类单位之间的亲  缘关系图。  相似文献   
92.
    本文分析溲疏属的重要形态特征的演化趋势,讨论亲缘属的系统位置和地理分布及区系特点,分类系统的修订和补充,并编写了分种检索表。认为雄蕊不定数,花瓣覆瓦状排列,花丝无齿,子房半下位的是属于原始性状,而雄蕊定数,花瓣镊合状排列,花丝具齿,子房下位的是进化性状,因此新溲疏组应包括在溲疏属内,该组与中间溲疏组是原始类群,而溲疏组是进化类群。国产52种被分为2组,4亚组和17系。溲疏属基本上是属于北温带分布类型,而我国的横断山脉至秦岭南部和华中一带为本属的现代分布和分化中心。  相似文献   
93.
青藏古植被的演变与青藏高原的隆起   总被引:2,自引:0,他引:2  
 西藏北部,在早石炭世晚期位于欧亚古陆的南缘,其植物群与当时印度次大     陆的不同。在晚二叠世,藏北属华夏植物区(即大羽羊齿植物区);印度河-雅鲁     藏布江大断裂带以南的地区出现舌羊齿植物群,  因而属冈瓦纳古陆的一部分。     到晚三叠世藏北植物群的面貌与我国西南同时代的植物群相似,与印度的则迥     然不同,显示藏北晚三叠世的植物群与南半球植物群也没有直接联系。  柴达木     侏罗纪植物群和拉萨附近早白垩世植物群与北半球的植物群有密切的关系。日     喀则晚白垩世植物群和阿里早始新世植物群也是如此。他们与印度德干玄武岩     夹层中出现的古新世植物群和印度北部始新世植物群也没有联系。  当时,西藏     的北部和南部属于两个不同的古陆,欧亚古陆和冈瓦纳古陆。  两者之间应有一     个很宽阔的特提斯海。因而,青藏的植物化石强有力地支持了大陆漂移的观点,     印度地块在晚侏罗世—白垩纪时是由非洲东南隅分离向北漂移,到始新世才与     亚洲连接,成为现在的南亚次大陆。  欧亚大陆与印度地块的接合线或许就是印     度河-雅鲁藏布江大断裂带。       从晚石炭世到早始新世的植物群的性质上看,藏北地势多半低洼。     中新世时,西藏中部和北部的植被是以落叶阔叶林为主,虽然某些地区有一     些常绿树存在,反映在中新世以前西藏中部和北部的地面已经上升到一定的程     度。在上新世时,藏北的常绿阔叶林逐渐减缩。柴达木盆地的植被转变成落叶     阔叶林-针叶林,以后转变成草原和半荒漠或荒漠,显示西藏和青海的地面进一     步抬升。       到晚上新世,藏北和青海的植被再行演变。然而,喜马拉雅地区的植被仍然     具有常绿栎林和雪松林。可能那时喜马拉雅山不像现在那么高。印度洋的季风     可以吹过喜马拉雅山,没有高山的阻碍。       第四纪是青藏山系和青藏地面上升最剧烈的时期。此时藏北已无常绿阔叶     树的存在。  到第四纪后期西藏大部分地区的植被逐渐演变为高寒荒漠。  最后,    青藏高原变成现在的情况。  相似文献   
94.
Inhibition was assessed in 144 Swedish children when they averaged 16 months of age using a composite measure tapping sociability toward strange adults, noninvolvement in peer play, and parental ratings of fearfulness. 91 children entered out-of-home care within 2 weeks of these initial assessments. Children were observed in this setting playing with peers; teachers and parents also rated children's adjustment to the out-of-home care settings. 1 and 2 years later, the children were assessed again, both at home and in the alternative care settings. Results showed that individual differences in inhibition were stable over the 2 years of the study. Inhibited children engaged in less high-quality peer play both at home and in the alternative care settings, and they were less able to play alone in their mothers' absence. On contemporaneous but not subsequent ratings, inhibited children had more difficulty adjusting to out-of-home care. Inhibition was not itself affected by out-of-home care experiences, and there were no sex differences in inhibition.  相似文献   
95.
In this study, the effectiveness of the application of speech-to-text recognition (STR) technology on enhancing learning and concentration in a calm state of mind, hereafter referred to as meditation (An intentional and self-regulated focusing of attention in order to relax and calm the mind), was investigated. This effectiveness was further explored with regard to foreign language ability and gender. Finally, students’ perceptions towards STR-texts were surveyed. 60 non-native English speaking undergraduates participated in this study. All students were randomly assigned into either a control or an experimental group, with 30 students in each group. Two lectures, both in English but at different levels of difficulty, were given in a classroom environment. Students in the control group received a lecture containing only a video of the instructor and slides; students in the experimental group received the video of the instructor and slides as well as STR-texts of the lecture. The following main findings were obtained: First, STR-texts had a positive effect on the learning performance, attention and meditation of students. In addition, most students had positive perceptions regarding the usefulness of STR-texts for learning. This is because students in the experimental group received instructional content in both verbal (i.e., speech) and visual (i.e., STR-texts) forms, which made the content more comprehensible and easier to process. Second, during lectures with STR, high ability and female students had higher levels of attention and meditation in most cases compared to their counterparts. This finding can be explained by the difference in learning motivation and in the use of learning strategies. That is, high ability and female students are more interested in learning and display greater use of various learning strategies. Based on these results, it is suggested that educators and researchers integrate STR-texts during lectures in English in order to enhance learning and to increase the level of attention and meditation of non-native English speaking students.  相似文献   
96.
This exploratory study examined the contribution of the RC Approach over a two‐year period. The RC Approach integrates social and academic learning in order to produce classroom environments that are conducive to learning by integrating social and academic learning. Two questions are addressed. First, how does teachers' use of RC practices contribute to children's academic and social growth? Second, how is the relation between teachers' use of RC practices and children's academic and social growth moderated by the presence of environmental adversity in the home? Participants included 62 teachers and 157 children at six schools. Findings showed that teachers' use of RC practices was associated with students' improved reading achievement, greater closeness between teachers and children, better pro‐social skills, more assertiveness, and less fearfulness, even after controlling for family risk and children's previous years' performance. Family risk did not moderate the relation between RC practices and children's performance. These findings suggest to the positive contribution of the RC Approach in relation to children's gains over a one‐year period. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 397–413, 2007.  相似文献   
97.
Computer programming is a subject that requires problem-solving strategies and involves a great number of programming logic activities which pose challenges for learners. Therefore, providing learning support and guidance is important. Collaborative learning is widely believed to be an effective teaching approach; it can enhance learners’ social interaction and offer a learning environment which provides rich learning experiences. However, the social interaction in collaborative learning does not occur automatically. Without proper guidance strategies or supporting tools for collaborative learning, the learning effects can be disappointing. To solve such a problem, a problem posing-based practicing strategy was proposed to support the development of a collaborative learning activity in a computer programming practice course. The students were guided to raise computer programming problems to boost the discussion among team members. The problems raised in each team were then exchanged and solved by another team to examine the coding and to provide feedback. To investigate the effectiveness of the proposed approach, an experiment was conducted in a C# programming course. Two classes of students from a university participated in the experiment. One class with 25 students was randomly assigned as the experimental group, and learned with a collaborative learning activity using the problem posing-based practicing strategy; the other class with 28 students was the control group, which learned with a conventional collaborative learning activity. The results show that the proposed strategy benefited the students in terms of improving their learning achievement, in particular, their programming skills. Moreover, it was found that the students who learned with the proposed approach had higher self-efficacy and lower cognitive load than those who learned with the conventional collaborative learning approach.  相似文献   
98.
Based on the cognitive-affective theory, the present study designed a science inquiry learning model, predict-observe-explain (POE), and implemented it in an app called “WhyWhy” to examine the effectiveness of students’ science inquiry learning practice. To understand how POE can affect the cognitive-affective learning process, as well as the learning progress, a pretest and a posttest were given to 152 grade 5 elementary school students. The students practiced WhyWhy during six sessions over 6 weeks, and data related to interest in learning science (ILS), cognitive anxiety (CA), and extraneous cognitive load (ECL) were collected and analyzed through confirmatory factor analysis with structure equation modeling. The results showed that students with high ILS have low CA and ECL. In addition, the results also indicated that students with a high level of self-confidence enhancement showed significant improvement in the posttest. The implications of this study suggest that by using technology-enhanced science learning, the POE model is a practical approach to motivate students to learn.  相似文献   
99.
Teachers’ professional development (PD) receives a great deal of attention in current educational settings. However, research has shown that many teachers hesitate to attend PD programs. In this study, data were collected from 270 elementary school teachers and were subjected to confirmatory factor analysis and structural equation modeling to examine their intention to attend the weekly PD programs on Wednesday afternoons (PDWAP). The results revealed that the participants value the acquisition of pedagogical content knowledge (PCK) more than they value pedagogical knowledge (PK) and content knowledge (CK) because of the expected usefulness of each for teaching. Moreover, the results of this study have implications for PD program design, and call for a stronger focus on PCK.

AbbreviationAdjusted Goodness of Fit Index (AGFI); Analysis of Moment Structures(AMOS); average variance (AVE); Chi-square(); content knowledge (CK); continuing professional development (CPD); Comparative Fit Index (CFI); degree of freedom (df); expectancy-value theory (EVT); Goodness of Fit Index (GFI); Incremental Fit Index (IFI); Mean(M); Parsimonious Goodness of Fit Index (PGFI); Parsimonious Normed Fit Index (PNFI); Parsimonious comparative-fit-index (PCFI); pedagogical content knowledge (PCK); pedagogical knowledge (PK); professional development (PD); professional development programs on Wednesday afternoons (PDWAP); Root Mean Square Error of Approximation (RMSEA); standard deviation (SD); structural equation modeling (SEM); square of multiple correlation coefficients (R2); Teaching Beliefs Survey (TBS); theory of planned behavior (TPB); Tucker-Lewis Index (TLI); United Kingdom (UK)  相似文献   

100.
The interpretation of computed tomographs (CTs) and magnetic resonance images (MRIs) to diagnose clinical conditions requires basic knowledge of sectional anatomy. Sectional anatomy has traditionally been taught using sectioned cadavers, atlases, and/or computer software. The computer software commonly used for this subject is practical and efficient for students but could be more advanced. The objective of this research was to present browsing software developed from the Visible Korean images that can be used for teaching sectional anatomy. One thousand seven hundred and two sets of MRIs, CTs, and sectioned images (intervals, one millimeter) of a whole male cadaver were prepared. Over 900 structures in the sectioned images were outlined and then filled with different colors to elaborate each structure. Software was developed where four corresponding images could be displayed simultaneously; in addition, the structures in the image data could be readily recognized with the aid of the color-filled outlines. The software, distributed free of charge, could be a valuable tool to teach medical students. For example, sectional anatomy could be taught by showing the sectioned images with real color and high resolution. Students could then review the lecture by using the sectioned and color-filled images on their own computers. Students could also be evaluated using the same software. Furthermore, other investigators would be able to replace the images for more comprehensive sectional anatomy.  相似文献   
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