全文获取类型
收费全文 | 11122篇 |
免费 | 140篇 |
国内免费 | 122篇 |
专业分类
教育 | 7287篇 |
科学研究 | 1255篇 |
各国文化 | 103篇 |
体育 | 1674篇 |
综合类 | 20篇 |
文化理论 | 69篇 |
信息传播 | 976篇 |
出版年
2021年 | 90篇 |
2020年 | 171篇 |
2019年 | 235篇 |
2018年 | 312篇 |
2017年 | 318篇 |
2016年 | 306篇 |
2015年 | 212篇 |
2014年 | 271篇 |
2013年 | 1789篇 |
2012年 | 229篇 |
2011年 | 241篇 |
2010年 | 211篇 |
2009年 | 235篇 |
2008年 | 214篇 |
2007年 | 212篇 |
2006年 | 224篇 |
2005年 | 194篇 |
2004年 | 401篇 |
2003年 | 370篇 |
2002年 | 360篇 |
2001年 | 421篇 |
2000年 | 263篇 |
1999年 | 179篇 |
1998年 | 125篇 |
1997年 | 125篇 |
1996年 | 104篇 |
1995年 | 123篇 |
1994年 | 118篇 |
1993年 | 90篇 |
1992年 | 160篇 |
1991年 | 124篇 |
1990年 | 150篇 |
1989年 | 166篇 |
1988年 | 115篇 |
1987年 | 139篇 |
1986年 | 135篇 |
1985年 | 144篇 |
1984年 | 132篇 |
1983年 | 129篇 |
1982年 | 102篇 |
1981年 | 85篇 |
1980年 | 97篇 |
1979年 | 140篇 |
1978年 | 92篇 |
1977年 | 76篇 |
1976年 | 92篇 |
1975年 | 70篇 |
1974年 | 74篇 |
1973年 | 69篇 |
1971年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
913.
914.
P V Sukumaran 《Resonance》2001,6(11):4-17
The prebiotic organic synthesis occurred in a reducing or mildly oxidising atmosphere. There was no dearth of energy sources
to drive this reaction. The speculation that life originated in ocean floor vent habitats is supported by the recent discovery
of fossil microbes in a mid-Archaean vent ecosystem. Evidence from nucleic acid sequencing that the last common ancestor of
all extant life is a hyperthermophile also lends credence to this hypothesis. The first living molecule that held heritable
genetic information was probably ribonucleicacid. The course of events that nature would have followed to reach the RNA-world
is fairly clear, but simulating this course in the laboratory to reach RNA remains a formidable problem and has little relevance
to an early Earth setting. A prolonged period of abiotic chemical evolution undoubtedly preceded the emergence of the first
living molecule.
P V Sukumaran took his M Tech degree in applied geology from the University of Saugar and has been with the Geological Survey
of India since 1974. His interests include petrology, geochemistry, palaeoceanography and organic evolution. He is presently
posted as Director in the Department at Nagpur 相似文献
915.
916.
917.
Measurement of ground reaction force (GRF) in running provides a direct indication of the loads to which the body is subjected
at each foot-ground contact, and can provide an objective explanation for performance outcomes. Traditionally, the collection
of three orthogonal component GRF data in running requires an athlete to complete a series of return loops along a laboratory
based runway, within which a force platform is embedded, in order to collect data from a discrete footfall. The major disadvantages
associated with this GRF data collection methodology include the inability to assess multiple consecutive foot contacts and
the fact that measurements are typically confined to the laboratory. The objective of this research was to investigate the
potential for wearable instrumentation to be employed, in conjunction with artificial neural network (ANN) and multiple linear
regression (MLR) models, for the estimation of GRF in middle distance running. A modular wearable data acquisition system
was developed to acquire in-shoe force (ISF) data. Matched data sets from wearable instrumentation (source data) and force
plate (target data) records were collected from elite middle-distance runners under controlled laboratory conditions for the
purposes of ANN and MLR model development (MD) and model validation (MV).
In terms of statistical measures of prediction accuracy the MLR model was found to provide a superior level of accuracy for
the prediction of the vertical and medio-lateral components of GRF and alternatively, the ANN model provided the most accurate
predictions of the anterior-posterior component of GRF. The prediction accuracy of each component of GRF was found to be governed
by the inherent signal variability, in which case the vertical and anterior-posterior components were more reliable and subsequently
predicted significantly more accurately than the medio-lateral component.
The emerging capability for obtaining continuous GRF records from wearable instrumentation has the potential to permit unprecedented
quantification of training stress and competition demands in running. 相似文献
918.
目前关于体育教学实习成绩的评定,各院校做法不一,还没有定论。但就目前各校的评估量表看,普遍较复杂,计算量大,指标多,内容不具体,因而不适用。而且对体育教学大都只重视一次公开课或检查课,对平时课堂教学不大重视。因此,制定出客观、全面、简便易行的评估指标体系就具有很重要的意义。 相似文献
919.
影响女大学生参与体育活动的因素分析 总被引:5,自引:3,他引:2
运用行为科学理论,通过对665名女大学生参与体育活动情况的调查,揭示了女大学生对待体育活动的认识和实践的状况,分析了影响女大学生参与体育活动的主、客观原因。 相似文献
920.
足球对抗的实质是相互间知行能力的竞争较量,足球对抗的知行特征为对抗中的知彼知己和避实击虚。 相似文献