全文获取类型
收费全文 | 13686篇 |
免费 | 209篇 |
国内免费 | 21篇 |
专业分类
教育 | 9592篇 |
科学研究 | 1532篇 |
各国文化 | 130篇 |
体育 | 1164篇 |
综合类 | 6篇 |
文化理论 | 101篇 |
信息传播 | 1391篇 |
出版年
2021年 | 146篇 |
2020年 | 202篇 |
2019年 | 277篇 |
2018年 | 388篇 |
2017年 | 362篇 |
2016年 | 370篇 |
2015年 | 247篇 |
2014年 | 327篇 |
2013年 | 2362篇 |
2012年 | 294篇 |
2011年 | 325篇 |
2010年 | 283篇 |
2009年 | 226篇 |
2008年 | 278篇 |
2007年 | 244篇 |
2006年 | 235篇 |
2005年 | 211篇 |
2004年 | 232篇 |
2003年 | 208篇 |
2002年 | 184篇 |
2001年 | 448篇 |
2000年 | 302篇 |
1999年 | 256篇 |
1998年 | 122篇 |
1997年 | 158篇 |
1996年 | 133篇 |
1995年 | 127篇 |
1994年 | 147篇 |
1993年 | 114篇 |
1992年 | 187篇 |
1991年 | 193篇 |
1990年 | 193篇 |
1989年 | 201篇 |
1988年 | 167篇 |
1987年 | 163篇 |
1986年 | 167篇 |
1985年 | 208篇 |
1984年 | 161篇 |
1983年 | 151篇 |
1982年 | 132篇 |
1981年 | 123篇 |
1980年 | 115篇 |
1979年 | 163篇 |
1978年 | 131篇 |
1977年 | 118篇 |
1976年 | 92篇 |
1975年 | 113篇 |
1974年 | 100篇 |
1973年 | 108篇 |
1971年 | 98篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Sylvia Hurtado June C. Han Victor B. Sáenz Lorelle L. Espinosa Nolan L. Cabrera Oscar S. Cerna 《Research in higher education》2007,48(7):841-887
The purpose of this study is to explore key factors that impact the college transition of aspiring underrepresented minority
students in the biomedical and behavioral sciences, in comparison with White, Asian students and non-science minority students.
We examined successful management of the academic environment and sense of belonging during the first college year. Longitudinal
data were derived from the Higher Education Research Institute’s (HERI) 2004 Cooperative Institutional Research Program (CIRP)
Freshman Survey and the 2005 Your First College Year (YFCY) Survey. Using a reformulation of the integration model (Nora,
Barlow, and Crisp, 2005), we find concerns about college financing, negotiating family support and responsibility, and campus
racial dynamics (perceived and behavioral) affect student adjustment and sense of integration in the first year.
This study was made possible by the support of the National Institute of General Medical Sciences, NIH Grant Number 1 RO1
GMO71968-01. This independent research and the views expressed here do not indicate endorsement by the sponsor. 相似文献
172.
173.
A new site-specific nutrient management approach was developed to break the apparent attainable yield barrier of 6 t·ha−1 in the double rice cropping system of Zhejiang. On-farm experiments involving 21 rice-growing farmer families and NPK long-term
experiments commenced in 1997 in the central part of Zhejiang Province to assess the status of soil fertility and productivity
under intensive rice-rice cropping. A new site-specific nutrient management (SSNM) approach has been developed for this studied
area. Field-specific fertilizer recommendations are calculated considering indigenous nutrient supply, reasonable grain yield
targets and corresponding nutrient demand, nutrient balance and nutrient use efficiency, as well as socio-economic factors.
The agronomic performance of SSNM was tested against the farmer's fertilizer practice (FFP) in four 1998–1999 cropping seasons.
Across seasons and years, SSNM consistently increased plant nutrient uptake, grain yield and profit by about 10%–15% compared
to the FFP. Yield levels of 7.5 t·ha−1 or more seem achievable and sustainable through introduction of SSNM and improved extension services in Zhejiang Province.
Project supported by the International Fertilizer Industry Association(IFA), the Potash and Phosphate Institute, Canada (PPIC),
and International Potash Institute(IPI). 相似文献
174.
175.
Adolescents (n=43) previously diagnosed as dyslexic/reading disabled had markedly lower IQ scores on the newly standardized Wechsler Intelligence Scale for Children (WISC-III) than on the earlier administered WISC-R. The declines for Verbal, Performance, and Full Scale IQs were 10, 12, and 11 points, respectively, which were twice as great as in a subset of the standardization sample given both versions of the WISC. The adolescents did not show a significant decline in standard scores from the Wide Range Achievement Test (Level I to Level II). However, only two subjects had current reading and spelling standard scores above the 25th percentile. The impact of lower WISC-III IQs on guidelines for classification of students as learning disabled is discussed. 相似文献
176.
A learning cycle approach to undergraduate instruction was implemented in a variety of subjects in the liberal arts and sciences. The students in the experimental program were typical representatives of an institution with liberal admissions policies. Significant gains were made in critical thinking and cognitive skill development by the experimental group. Additionally, retention of the experimental group was improved. Gains of this sort have the potential to rekindle hope in college faculties that some of the traditional goals of higher education that center on critical thinking and cognitive skill development need not be abandoned in institutions with liberal admissions policies. 相似文献
177.
178.
The purpose of the study was to investigate faculty perceptions of student evaluative information collected by three methods: objective questionnaire items, open-ended questions, and group interviews. Faculty rated three simulated evaluation reports on their potential for accuracy, trustworthiness, usefulness, comprehensiveness, believability, interpretability, and value as information used for self-improvement and promotion purposes. Faculty, in general, regarded the evaluative information to be more credible, useful, and accurate for their own self-improvement than for promotion purposes. Faculty also desired more than one type of evaluative information regardless of the purpose of evaluation. 相似文献
179.
180.
This paper reports research on the effects of variations in injection velocity and permeability on the heat transfer and flow
through a highly porous medium between two horizontal parallel plates situated at constant distance with constant suction
by the upper plate. Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional.
The governing equations are solved by adopting complex variable notations to obtain the expressions for the velocity and temperature
field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs. 相似文献