全文获取类型
收费全文 | 2017篇 |
免费 | 21篇 |
国内免费 | 12篇 |
专业分类
教育 | 1198篇 |
科学研究 | 281篇 |
各国文化 | 6篇 |
体育 | 348篇 |
综合类 | 24篇 |
文化理论 | 2篇 |
信息传播 | 191篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 5篇 |
2020年 | 9篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 22篇 |
2013年 | 24篇 |
2012年 | 147篇 |
2011年 | 217篇 |
2010年 | 84篇 |
2009年 | 83篇 |
2008年 | 146篇 |
2007年 | 161篇 |
2006年 | 154篇 |
2005年 | 130篇 |
2004年 | 92篇 |
2003年 | 96篇 |
2002年 | 90篇 |
2001年 | 48篇 |
2000年 | 68篇 |
1999年 | 50篇 |
1998年 | 12篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1995年 | 23篇 |
1994年 | 13篇 |
1993年 | 21篇 |
1992年 | 23篇 |
1991年 | 22篇 |
1990年 | 23篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 19篇 |
1982年 | 9篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1977年 | 5篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1948年 | 3篇 |
1937年 | 3篇 |
1927年 | 3篇 |
排序方式: 共有2050条查询结果,搜索用时 15 毫秒
41.
Islam MR Khandoker MA Afroz S Rahman MG Khan RI 《Journal of Zhejiang University. Science. B》2007,8(7):465-469
Goat ovaries were collected from the slaughterhouse and categorized as right, left, corpus luteum (CL)-present and -absent group and evaluated on the basis of weight (g), length (cm), width (cm), number of follicles, follicles aspirated and number and state ofcumulus-oocyte-complexes (COCs). Comparatively higher weight [(0.66±0.02) vs (0.64±0.02) g], length [(1.17±0.02) vs (1.1 ±0.02) cm] and width [(0.77±0.02) vs (0.74±0.02) cm] were found in right ovaries than those of left. On the other hand significantly (P〈0.05) higher weight [(0.71±0.03) vs (0.64±0.01) g] and width [(0.76±0.03) vs (0.75±0.01) cm] were found in CL-present group than those of CL-absent group of ovaries. The left ovaries contained comparatively higher number of normal COCs [(1.06±0.09) per ovary] than fight ovaries [(1.03±0.10) per ovary] and the similar trend was found in total number of follicles [(4.51±0.25) vs (4.30±0.23) per ovary] and follicles aspirated [(2.55±0.14) vs (2.52±0.12) per ovary]. But the total COCs per ovary was almost similar in both ovaries [right and left: (1.85±0.12) and (1.85±0.11) per ovary, respectively]. Higher number of total COCs [(1.87±0.09) vs (1.76±0.16) per ovary], total number of follicles [(4.45±0.19) vs (4.16±0.37) per ovary], follicles aspirated [(2.55±0.10) vs (2.48±0.21) per ovary] and normal COCs [(1.12±0.07) vs (0.76±0.14) per ovary] were found in CL-absent group than those of CL-present group of ovaries. 相似文献
42.
Genetic analysis of fruit shape traits at different maturation stages in sponge gourd 总被引:5,自引:0,他引:5
The fruit shape is important quantitative trait closely related to the fruit quality. However, the genetic model of fruit shapes has not been proposed. Therefore, in the present study, analysis of genetic effects for fruit shape traits (fruit length and fruit perimeter) in sponge gourd was conducted by employing a developmental genetic model including fruit direct effects and maternal effects. Analysis approaches of unconditional and conditional variances were applied to evaluate the genetic behavior of fruit shape traits at economical and physiological maturation times. The results of variance analysis indicated that fruit length and fruit perimeter were simultaneously affected by fruit direct genetic effects and maternal effects. Fruit direct genetic effects were relatively more important for fruit shape traits at whole developmental period. The gene expression was most active at the economical maturation stage (1-12 d after flowering) for two shape traits, and the activation of gene was mostly due to direct dominance effects at physiological maturation stage (13-60 datter flowering). The coefficients due to different genetic effects, as well as the phenotypic correlation coefficients, varied significantly between fruit shape traits themselves at various maturation stages. The results showed that it was relatively easy to improve fruit shape traits for industrial purpose by carefully selecting the parents at economical maturation stage instead of that at physiological maturation stage. 相似文献
43.
The following project aimed at promoting integrated and long-lasting learning is described for an Immunology course, but it may be adapted to other disciplines. Students were asked to develop and carry out a research project to examine the relationship between immune function and stress. The experiments were required to include the assessment of salivary cortisol and salivary IgA (sIgA) with enzyme immunoassays. All other aspects of the experiments were developed by student groups with appropriate guidance from the instructor. Data are presented for one group project that assessed the effect of music on cortisol and sIgA. Overall levels of sIgA and cortisol were consistent with reported values. Students found a significant decrease in cortisol over time. Additionally, there was a trend that supported the overall student hypothesis regarding the effect of stress and immune function. Compared with the same Immunology course that included an instructor-designed experiment using enzyme immunoassays for cortisol and sIgA, several assessments (e.g., final grades and comments on student evaluations) show that overall learning seemed to be much better in the course with the student-directed research project. 相似文献
44.
Many short-duration science outreach interventions have important societal goals of raising science literacy and increasing the size and diversity of the science workforce. Yet, these long-term outcomes are inherently challenging to evaluate. We present findings from a qualitative research study of an inquiry-based, life science outreach program to K-12 classrooms that is typical in design and excellent in execution. By considering this program as a best case of a common outreach model, the "scientist in the classroom," the study examines what benefits may be realized for each participant group and how they are achieved. We find that K-12 students are engaged in authentic, hands-on activities that generate interest in science and new views of science and scientists. Teachers learn new science content and new ways to teach it, and value collegial support of their professional work. Graduate student scientists, who are the program presenters, gain teaching and other skills, greater understanding of education and diversity issues, confidence and intrinsic satisfaction, and career benefits. A few negative outcomes also are described. Program elements that lead to these benefits are identified both from the research findings and from insights of the program developer on program design and implementation choices. 相似文献
45.
The perceived spatiotemporal continuity of objects depends on the way they appear and disappear as they move in the spatial layout. This study investigated whether infants' predictive tracking of a briefly occluded object is sensitive to the manner by which the object disappears and reappears. Five-, 7-, and 9-month-old infants were shown a ball rolling across a visual scene and briefly disappearing via kinetic occlusion, instantaneous disappearance, implosion, or virtual occlusion. Three different measures converged to show that predictive tracking increased with age and that infants were most likely to anticipate the reappearance of the ball following kinetic occlusion. These results suggest that infants' knowledge of the permanence and nonpermanence of objects is embodied in their predictive tracking. 相似文献
46.
Teachers' education, classroom quality, and young children's academic skills: results from seven studies of preschool programs 总被引:10,自引:0,他引:10
Early DM Maxwell KL Burchinal M Alva S Bender RH Bryant D Cai K Clifford RM Ebanks C Griffin JA Henry GT Howes C Iriondo-Perez J Jeon HJ Mashburn AJ Peisner-Feinberg E Pianta RC Vandergrift N Zill N 《Child development》2007,78(2):558-580
In an effort to provide high-quality preschool education, policymakers are increasingly requiring public preschool teachers to have at least a Bachelor's degree, preferably in early childhood education. Seven major studies of early care and education were used to predict classroom quality and children's academic outcomes from the educational attainment and major of teachers of 4-year-olds. The findings indicate largely null or contradictory associations, indicating that policies focused solely on increasing teachers' education will not suffice for improving classroom quality or maximizing children's academic gains. Instead, raising the effectiveness of early childhood education likely will require a broad range of professional development activities and supports targeted toward teachers' interactions with children. 相似文献
47.
Subtypes, severity, and structural stability of peer victimization: what does latent class analysis say? 总被引:2,自引:1,他引:1
This study uses latent class analysis (LCA) to empirically identify victimization groups during middle school. Approximately 2,000 urban, public middle school students (mean age in sixth grade = 11.57) reported on their peer victimization during the Fall and Spring semesters of their sixth, seventh, and eighth grades. Independent LCA analyses at each semester yielded 3 victim classes based on victimization degree rather than type (e.g., physical vs. relational). The most victimized class always represented the smallest proportion of the sample, decreasing from 20% in sixth grade to 6% by the end of eighth grade. This victimized class also always reported feeling less safe at school concurrently and more depressed than others 1 semester later, illustrating the validity of the LCA approach. 相似文献
48.
Veenstra R Lindenberg S Zijlstra BJ De Winter AF Verhulst FC Ormel J 《Child development》2007,78(6):1843-1854
For this study, information on Who Bullies Who was collected from 54 school classes with 918 children (M age = 11) and 13,606 dyadic relations. Bullying and victimization were viewed separately from the point of view of the bully and the victim. The two perspectives were highly complementary. The probability of a bully-victim relationship was higher if the bully was more dominant than the victim, and if the victim was more vulnerable than the bully and more rejected by the class. In a bully-victim dyad, boys were more often the bullies. There was no finding of sex effect for victimization. Liking reduced and disliking increased the probability of a bully-victim relationship. 相似文献
49.
Improbable or impossible? How children reason about the possibility of extraordinary events 总被引:1,自引:1,他引:0
The present study investigated the development of possibility-judgment strategies between the ages of 4 and 8. In Experiment 1, 48 children and 16 adults were asked whether a variety of extraordinary events could or could not occur in real life. Although children of all ages denied the possibility of events that adults also judged impossible, children frequently denied the possibility of events that adults judged improbable but not impossible. Three additional experiments varied the manner in which possibility judgments were elicited and confirmed the robustness of preschoolers' tendency to judge improbable events impossible. Overall, it is argued that children initially mistake their inability to imagine circumstances that would allow an event to occur for evidence that no such circumstances exist. 相似文献
50.
Ortiz R Jiménez JE García Miranda E Guzmán Rosquete R Hernández-Valle I Rodrigo M Estévez A Díaz A Hernández Expósito S 《Journal of learning disabilities》2007,40(1):80-92
The aims of this study were (a) to determine whether Spanish children with reading disabilities (RD) show a speech perception deficit and (b) to explore the locus and nature of this perceptive deficit. A group of 29 children with RD, 41 chronological age-matched controls, and 27 reading ability-matched younger controls were tested on tasks of speech perception. The effect of linguistic unit (word vs. syllable) and type of phonetic contrast (voicing, place and manner of articulation) were analyzed in terms of the number of errors and the response time. The results revealed a speech perception deficit in Spanish children with RD that was independent of the type of phonetic contrast and of linguistic unit. 相似文献