全文获取类型
收费全文 | 4219篇 |
免费 | 54篇 |
专业分类
教育 | 3001篇 |
科学研究 | 325篇 |
各国文化 | 64篇 |
体育 | 365篇 |
综合类 | 3篇 |
文化理论 | 51篇 |
信息传播 | 464篇 |
出版年
2022年 | 24篇 |
2021年 | 41篇 |
2020年 | 77篇 |
2019年 | 125篇 |
2018年 | 145篇 |
2017年 | 136篇 |
2016年 | 122篇 |
2015年 | 76篇 |
2014年 | 127篇 |
2013年 | 959篇 |
2012年 | 93篇 |
2011年 | 107篇 |
2010年 | 90篇 |
2009年 | 91篇 |
2008年 | 90篇 |
2007年 | 96篇 |
2006年 | 108篇 |
2005年 | 91篇 |
2004年 | 83篇 |
2003年 | 82篇 |
2002年 | 63篇 |
2001年 | 57篇 |
2000年 | 68篇 |
1999年 | 58篇 |
1998年 | 60篇 |
1997年 | 58篇 |
1996年 | 42篇 |
1995年 | 41篇 |
1994年 | 39篇 |
1993年 | 44篇 |
1992年 | 37篇 |
1991年 | 43篇 |
1990年 | 50篇 |
1989年 | 45篇 |
1988年 | 45篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 37篇 |
1984年 | 40篇 |
1983年 | 46篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 26篇 |
1979年 | 46篇 |
1978年 | 38篇 |
1977年 | 29篇 |
1976年 | 32篇 |
1974年 | 27篇 |
1973年 | 28篇 |
1969年 | 19篇 |
排序方式: 共有4273条查询结果,搜索用时 15 毫秒
81.
A Methylome‐Wide Association Study of Trajectories of Oppositional Defiant Behaviors and Biological Overlap With Attention Deficit Hyperactivity Disorder 下载免费PDF全文
Edward D. Barker Esther Walton Charlotte A.M. Cecil Richard Rowe Sara R. Jaffee Barbara Maughan Thomas G. O'Connor Argyris Stringaris Alan J. Meehan Wendy McArdle Caroline L. Relton Tom R. Gaunt 《Child development》2018,89(5):1839-1855
In 671 mother–child (49% male) pairs from an epidemiological birth cohort, we investigated (a) prospective associations between DNA methylation (at birth) and trajectories (ages 7–13) of oppositional defiant disorder (ODD), and the ODD subdimensions of irritable and headstrong; (b) common biological pathways, indexed by DNA methylation, between ODD trajectories and attention deficit hyperactivity disorder (ADHD); (c) genetic influence on DNA methylation; and (d) prenatal risk exposure associations. Methylome‐wide significant associations were identified for the ODD and headstrong, but not for irritable. Overlap analysis indicated biological correlates between ODD, headstrong, and ADHD. DNA methylation in ODD and headstrong was (to a degree) genetically influenced. DNA methylation associated with prenatal risk exposures of maternal anxiety (headstrong) and cigarette smoking (ODD and headstrong). 相似文献
82.
83.
Suneesh Kumar Pachathundikandi Earaly Thomas Varghese 《Indian journal of clinical biochemistry : IJCB》2006,21(2):114-117
Blood zinc protoporphyrin (ZPP), serum total protein (TP), and total cholesterol (TC) levels in automobile workshop workers
in relation to lead toxicity were analysed. In the present study, automobile workshop workers (healthy male workers at an
age between 28 and 35 from four major automobile workshops in Kottayam, Kerala State, India) and the control (male healthy
adults at an age between 28 and 35 residing at Aymanam, a distant village at Kottayam District, Kerala having reduced or no
chance of lead exposure) displayed significant difference in blood lead (BPb) and blood ZZP (BZPP) level. The mean value of
BPb in automobile workshop workers was 15.76±0.33 μg/dl, while in the control it was 8.20±0.15 μg/dl. In automobile workshop
workers, the mean value of BZPP was 34.2±0.62 μg/dl. The control group exhibited a mean of 11.5±0.22 μg/dl. Automobile workshop
workers exhibited significant increase in BZPP was corresponding to the increase in BPb level. The total protein levels estimated
in automobile workshop workers showed significant decrease compared to control individuals, but was within the reference range
of healthy individuals. The mean value of TP level in automobile workshop workers and control was 6.9±0.13 g/dl and 7.71±0.18
g/dl, respectively. There was no significant difference in blood haemoglobin (BHb) level among the automobile workshop workers
and control. The serum TC level in automobile workshop workers showed significant decrease compared to the control individuals,
but was with in the reference range of healthy individuals. The mean level of serum TC in automobile workshop workers was
162.00±3.44 mg/dl and the same in control was 172.86±4.32 mg/dl. The present study affirms occupational lead toxicity in automobile
workshop workers and its effect on serum protein and cholesterol levels. 相似文献
84.
Thomas B. Åstebro 《Research Policy》2005,34(9):1404-1418
Research on technological opportunity has typically focused on the impact of broad industry characteristics on R&D intensity of firms. This study complements such approaches by examining the impact of a multidimensional vector that measures technological opportunity on independent inventors’ decisions to patent and commercialize inventions. Using data from 559 inventions and controlling for demand, appropriability, and competitive conditions, we found two of four tested dimensions of technological opportunity - technical performance and technical uncertainty - to be significant and important determinants of the likelihood of commercialization. Technical feasibility appears important in affecting patenting but unimportant in affecting commercialization. Technical significance carries a negative, although insignificant, sign conditioning commercialization. 相似文献
85.
Thomas E. Gaston Francesca Ounsworth Tessa Senders Sarah Ritchie Emma Jones 《Learned Publishing》2020,33(2):154-162
Previous research has found that researchers rank journal reputation and impact factor (IF) amongst the key selection criteria when choosing where to submit. We explored the actual effect upon submission numbers of several possible factors. We retrieved 10 years of submission data from over a thousand journals, as well as data on IF, retractions, and other factors. We performed statistical analysis and identified correlations. We also undertook case study research on the 55 most significant submission decreases. We found a statistically significant correlation between changes in IF, ISI percentage ranking, and changes in submissions numbers in subsequent years. We also found a statistically significant effect on submission numbers in the year following the publication of a retraction. Our case studies identified other factors, including negative feedback on the peer review process. Our findings regarding IF confirm previous indications about the significance of IF on submissions. We explain the correlation with retractions through the concept of ‘peer review reputation’. These results indicate that editors and publishers need to focus on a journal's peer review practices, as well as a journal's IF, if they are to maintain and grow submissions. 相似文献
86.
Result merging methods in distributed information retrieval with overlapping databases 总被引:5,自引:0,他引:5
In distributed information retrieval systems, document overlaps occur frequently among different component databases. This
paper presents an experimental investigation and evaluation of a group of result merging methods including the shadow document
method and the multi-evidence method in the environment of overlapping databases. We assume, with the exception of resultant
document lists (either with rankings or scores), no extra information about retrieval servers and text databases is available,
which is the usual case for many applications on the Internet and the Web.
The experimental results show that the shadow document method and the multi-evidence method are the two best methods when
overlap is high, while Round-robin is the best for low overlap. The experiments also show that [0,1] linear normalization
is a better option than linear regression normalization for result merging in a heterogeneous environment.
相似文献
Sally McCleanEmail: |
87.
PURPOSE: This paper examines individual, family, and neighborhood level predictors of resilience in adolescence and young adulthood and describes changes in resilience over time from adolescence to young adulthood in abused and neglected children grown up. METHOD: We use documented cases of childhood physical and sexual abuse and neglect (n=676) from a Midwestern county area during the years 1967-1971 and information from official records, census data, psychiatric assessments, and self-reports obtained through 1995. Analyses involve logistic regressions, replicated with Mplus to test for possible contextual effects. RESULTS: Almost half (48%) of the abused and neglected children in adolescence and nearly one-third in young adulthood were resilient. Over half of those who were resilient in adolescence remained resilient in young adulthood, whereas 11% of the non-resilient adolescents were resilient in young adulthood. Females were more likely to be resilient during both time periods. Being white, non-Hispanic decreased and growing up in a stable living situation increased the likelihood of resilience in adolescence, but not in young adulthood. Stressful life events and a supportive partner promoted resilience in young adulthood. Neighborhood advantage did not exert a direct effect on resilience, but moderated the relationship between household stability and resilience in adolescence and between cognitive ability and resilience in young adulthood. CONCLUSIONS: Ecological factors appear to promote or interfere with the emergence and stability of resilience following childhood maltreatment. 相似文献
88.
Matthew Krehl Edward Thomas Benjamin Jay Whitburn 《British Journal of Sociology of Education》2019,40(2):159-173
This article examines the constraints of modern temporality which are antithetical to the careful consideration that working with diverse learners requires for the development of inclusive, democratic education. We take up the conceptual construct of time to explore how it mediates systemic practices that impact policy positions of inclusion in initial teacher education and schooling. Our analysis demonstrates that temporality shapes the possibilities of inclusive practice within which a dominant agenda of compliance frames classroom complexities – both in schooling and higher education environments – into fragmented and preconceived responses to challenging situations. Education systems position educators in risk discourses concentrated on compliance and performance, in part through an emphasis that is placed on the diagnosis of learner differences and subsequent compartmentalised responses. Through schisms in modern time, we demonstrate the ways in which inclusion, like other educational demands, may be supported through a diffraction in time rather than subjugated to it. 相似文献
89.
90.
Thomas R. Robbins 《Decision Sciences Journal of Innovative Education》2019,17(2):104-125
Project Management is an important skill for business students to develop. Although project‐oriented activity is very common, the success rate for projects is poor. Many projects fail due to poor planning. This article describes a multipart class exercise used to teach elements of a project management methodology to undergraduate and graduate business students. Over the course of the eight‐part exercise, student teams iteratively develop a project plan and Gantt chart, an initial and detailed project charter, a variance analysis model, and a status report. Students are taught an iterative top‐down planning process using a technique we term the ODW (Objectives–Deliverables–Workplan) model. Students are introduced to Microsoft Project and use the tool to develop a project plan that becomes part of a more detailed Project Charter. In the final stages of the exercise, students collect results, update their plan, and produce a project status report. 相似文献