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   15702篇
  免费   218篇
  国内免费   119篇
教育   10756篇
科学研究   2062篇
各国文化   119篇
体育   1403篇
综合类   11篇
文化理论   124篇
信息传播   1564篇
  2021年   112篇
  2020年   211篇
  2019年   313篇
  2018年   439篇
  2017年   379篇
  2016年   393篇
  2015年   250篇
  2014年   323篇
  2013年   2684篇
  2012年   301篇
  2011年   347篇
  2010年   253篇
  2009年   250篇
  2008年   259篇
  2007年   296篇
  2006年   280篇
  2005年   282篇
  2004年   262篇
  2003年   252篇
  2002年   246篇
  2001年   257篇
  2000年   277篇
  1999年   277篇
  1998年   147篇
  1997年   152篇
  1996年   183篇
  1995年   172篇
  1994年   134篇
  1993年   145篇
  1992年   219篇
  1991年   229篇
  1990年   233篇
  1989年   261篇
  1988年   212篇
  1987年   227篇
  1986年   221篇
  1985年   254篇
  1984年   222篇
  1983年   213篇
  1982年   179篇
  1981年   168篇
  1980年   159篇
  1979年   245篇
  1978年   191篇
  1977年   180篇
  1976年   149篇
  1975年   132篇
  1974年   151篇
  1973年   133篇
  1971年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
This study assessed the feasibility of doing hearing screening in Migrant, American Indian and Early Head Start programs using otoacoustic emissions (OAE) technology. Staff members were trained to screen 0–3-year-old children for hearing loss using hand-held OAE equipment and a multi-step screening and referral protocol. Of the 3486 children screened as a part of the study, 77% passed an OAE screening at the first step, 18% more passed an OAE screening at the second step, and 5% were ultimately referred for medical or audiological follow-up. Eighty children were identified as having a hearing loss or disorder of the outer, middle or inner ear requiring treatment. Of these 80, six had permanent bilateral or unilateral hearing loss. Although the protocol suggested that the multi-step screening procedure should be completed within a 4-week time period or less, analysis of the data showed that for children requiring more than an initial OAE screening, the length of time over which the screening was completed ranged from 7 to 12 weeks. The median time required to complete a single OAE screening session was 4 minutes per child. The results demonstrate that OAE screening of young children using this protocol is practical and effective. The implications for conducting periodic hearing screening throughout early childhood are discussed.  相似文献   
162.
163.
164.
This study examined the similarities and differences in experienced secondary science teachers' planning, teaching, and reflecting on their teaching, when teaching in their science area of certification and when teaching in another science area. The study also focused on the influence of these teachers' content knowledge, pedagogical knowledge, and pedagogical content knowledge on their planning, teaching, and reflecting. Experienced teachers were observed and interviewed while teaching classes in their science area of certification, and in another science area they were teaching for the first or second time. Both similarities and differences in teaching were found in the two areas for all three teachers. For example, their planning and postlesson reflections were similar in both areas. In the interactive phase of teaching more differences were observed. Many aspects of their teaching resembled that of expert teachers in other studies. In the unfamiliar science area, the teachers sometimes acted like novice teachers. However, they were able to draw upon their pedagogical knowledge to provide a framework for their teaching in both science areas. Their wealth of pedagogical knowledge, and pedagogical content knowledge for general science topics, seemed to sustain them in whatever content they were teaching. Recommendations for further study and implications for teacher education are discussed.  相似文献   
165.
166.
167.
Cerdán  R.  Pérez  A.  Vidal-Abarca  E.  Rouet  J. F. 《Reading and writing》2019,32(8):2111-2124
Reading and Writing - The present study investigates the effectiveness of question paraphrases in supporting students’ understanding of a specific task. Secondary school students (i.e.,...  相似文献   
168.
The results of the perianal portion of a project designed to collect normative data of the anogenital anatomy from a representative sample of prepubertal children is presented. A total of 318 children were examined by three physicians from a child sexual abuse evaluation program. After screening for the onset of puberty and the possibility of undetected abuse, 267 subjects remained. The sample included 161 girls and 106 boys ranging in age from 2 months to 11 years. The perianal findings that were encountered with the greatest frequency included erythema (41%), increased pigmentation (30%), and venous engorgement (52%) after two minutes in the knee-chest position. Wedge-shaped smooth areas in the midline, with or without depressions, were found both anterior and posterior to the anus in 26% of the children. Anal skin tags/folds were discovered anterior to the anus in 11%. In 49% of the children there was some dilatation of the anus which opened and closed intermittently in 62%. Flattening of the anal verge and rugae occurred during dilatation by the midpoint of the examination in 44% and 34%, respectively. Perianal findings that were found infrequently in all subgroups included skin tags/folds (0%) and scars (1%) outside the midline, anal dilatation greater than 20 mm without the presence of stool in the rectal ampulla (1.2%), irregularity of the anal orifice after complete dilatation (3%), and prominence of the anal verge (3%). No abrasions, hematomas, fissures, or hemorrhoids were encountered. Less commonly detected findings within specific subgroups included perianal erythema in girls (32%) as compared to boys (57%), pigmentation in the lighter skinned white children (22%) when compared to black (53%) and Hispanic (58%) children, and venous congestion at the beginning of the examination (7%) when compared to the same findings after four minutes in the knee-chest position (73%). There were no perianal skin tags/folds found in the boys. The relatively high incidence of perianal soft tissue changes that were found in this study, when compared to the frequency of similar observations in children suspected of having been sexually abused, reemphasizes the caution medical examiners must exercise in rendering an opinion as to the significance of medical findings.  相似文献   
169.
Qualitative studies of the teacher labor market suggest that problems and remedies generated by quantitative research fail to capture the most dynamic variables which are affecting the supply and demand of public school teachers. For example, quantitative research has not accounted for (1) the continual exiting and reentering of urban teachers, (2) the considerable bifurcation between urban and rural teacher labor markets as reflected in teacher mobility and cultural economic opportunities, (3) local definitions of labor market needs and teacher quality, and (4) the demanding and stressful working conditions of teaching, which are having a systemic and adverse effect on the occupation.  相似文献   
170.

Purpose

Metalloproteinases are a key component of the pathogenesis of abdominal hernias. Obesity is considered a risk factor in herniogenesis and hernia recurrence. The aim of this study was to evaluate the serum concentrations of metalloproteinase-2 (MMP-2), MMP-9, MMP-13, and adiponectin in morbidly obese and nonoverweight controls.

Materials and methods

The participants were recruited from among patients undergoing bariatric and non-bariatric surgery and divided into two groups: I (body mass index (BMI)≥35 kg/m2, n=40) and II (BMI<25 kg/m2, n=30). Serum concentrations of MMP-2, MMP-9, MMP-13, and adiponectin were measured using enzyme-linked immunosorbent assay (ELISA).

Results

A statistically significant difference between groups was observed for MMP-2 concentration. The median MMP-9 concentration was higher in the obese group, but the difference was not statistically significant. Median MMP-13 concentrations did not differ between groups. Serum adiponectin concentration was insignificantly higher in the non-obese group.

Conclusions

The elevated serum MMP-2 and MMP-9 concentrations in obese individuals may be related to the higher incidence of incisional hernias in this population.
  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