全文获取类型
收费全文 | 2692篇 |
免费 | 38篇 |
国内免费 | 39篇 |
专业分类
教育 | 2151篇 |
科学研究 | 259篇 |
各国文化 | 1篇 |
体育 | 89篇 |
综合类 | 174篇 |
信息传播 | 95篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 12篇 |
2021年 | 24篇 |
2020年 | 33篇 |
2019年 | 21篇 |
2018年 | 22篇 |
2017年 | 28篇 |
2016年 | 40篇 |
2015年 | 56篇 |
2014年 | 161篇 |
2013年 | 160篇 |
2012年 | 201篇 |
2011年 | 234篇 |
2010年 | 154篇 |
2009年 | 135篇 |
2008年 | 194篇 |
2007年 | 207篇 |
2006年 | 177篇 |
2005年 | 169篇 |
2004年 | 165篇 |
2003年 | 153篇 |
2002年 | 120篇 |
2001年 | 97篇 |
2000年 | 78篇 |
1999年 | 31篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有2769条查询结果,搜索用时 15 毫秒
1.
2.
Benjamin Kane Williams Ross H. Sanders Joong Hyun Ryu Pitre C. Bourdon Philip Graham-Smith Peter J. Sinclair 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(2):202-214
Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0–90°, with static data collected at 10° increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE ≤ 0.03°). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50° and ICC showed very high correlations (r ≥ 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were ≤2.20°. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics. 相似文献
3.
根据2003—2015年我国31个省份技术市场发展的基本数据,采用莫兰指数(Moran’s I)分析我国技术市场发展的时空分布特征,利用空间误差模型探究技术市场发展对经济增长的促进作用。研究发现:(1)2003—2015年间各省份技术市场发展存在显著的正向空间关系,但空间集聚程度有所减弱;(2)各省份技术市场发展的空间格局相对稳定,但空间差异显著性有所降低,临近省份技术市场成交额影响下的人均地区生产总值具有明显的集聚特点,各省份技术市场发展下的经济增长之间呈现显著的正向空间相关;(3)分类型技术市场发展模型中,技术服务对经济的产出弹性系数(0.4380)明显高于技术咨询的产出弹性(0.2754)。 相似文献
4.
5.
《Research Policy》2019,48(7):1855-1865
Quantitative research evaluation requires measures that are transparent, relatively simple, and free of disciplinary and temporal bias. We document and provide a solution to a hitherto unaddressed temporal bias – citation inflation – which arises from the basic fact that scientific publication is steadily growing at roughly 4% per year. Moreover, because the total production of citations grows by a factor of 2 every 12 years, this means that the real value of a citation depends on when it was produced. Consequently, failing to convert nominal citation values into real citation values produces significant mis-measurement of scientific impact. To address this problem, we develop a citation deflator method, outline the steps to generalize and implement it using the Web of Science portal, and analyze a large set of researchers from biology and physics to demonstrate how two common evaluation metrics – total citations and h-index – can differ by a remarkable amount depending on whether the underlying citation counts are deflated or not. In particular, our results show that the scientific impact of prior generations is likely to be significantly underestimated when citations are not deflated, often by 100% or more of the nominal value. Thus, our study points to the need for a systemic overhaul of the counting methods used evaluating citation impact – especially in the case of researchers, journals, and institutions – which can span several decades and thus several doubling periods. 相似文献
6.
Jie Mei Aminul Islam Abidalrahman Moh’d Yajing Wu Evangelos Milios 《Information processing & management》2018,54(6):874-887
Modern OCR engines incorporate some form of error correction, typically based on dictionaries. However, there are still residual errors that decrease performance of natural language processing algorithms applied to OCR text. In this paper, we present a statistical learning model for post-processing OCR errors, either in a fully automatic manner or followed by minimal user interaction to further reduce error rate. Our model employs web-scale corpora and integrates a rich set of linguistic features. Through an interdependent learning pipeline, our model produces and continuously refines the error detection and suggestion of candidate corrections. Evaluated on a historical biology book with complex error patterns, our model outperforms various baseline methods in the automatic mode and shows an even greater advantage when involving minimal user interaction. Quantitative analysis of each computational step further suggests that our proposed model is well-suited for handling volatile and complex OCR error patterns, which are beyond the capabilities of error correction incorporated in OCR engines. 相似文献
7.
干扰对齐(IA)是一种有效消除干扰的管理机制。为了彻底消除干扰信号对期望信号的影响,通过预编码技术处理使干扰在接收端重叠,使接收端的干扰信号与期望信号有效分开。在传统最小均方误差(Minimum Mean Square Error,MMSE)算法和最小二乘(least square,LS)算法基础上,提出基于符号检测辅助的最小均方误差(Symbol Detection Aided Minimum Mean Square Error,SDA-MMSE)算法和最小二乘(Symbol Detection Aided Least Square,SDA-LS)算法。分别基于传统算法和改进算法进行迭代计算,通过仿真可看出SDA-MMSE算法的MSE较SDA-LS算法的MSE降低约20%。理论分析与仿真结果表明,改进算法较传统算法具有更好的系统性能,且SDA-MMSE算法系统性能最优。 相似文献
8.
DNN芯片作为星载芯片应用到卫星系统中时会受到太空辐照的影响,其中单粒子翻转对存储单元的干扰会使得存储器单元的参数出现错误,该错误映射到神经网络中会造成神经网络最后的输出结果出现偏差。结合单粒子翻转概率模型,对用于网络推断的神经网络的权值参数进行注错后分析实验结果准确率,从激活函数的非线性特性分析并通过实验验证具有双边抑制效果的函数容错能力更强。进一步在网络卷积层后加入BN层和在训练过程中考虑L2正则化提高网络的容错能力,并通过实验验证其可行性。 相似文献
9.
10.