全文获取类型
收费全文 | 214篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
教育 | 156篇 |
科学研究 | 46篇 |
各国文化 | 3篇 |
体育 | 3篇 |
信息传播 | 11篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 21篇 |
2017年 | 7篇 |
2016年 | 21篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 24篇 |
2012年 | 15篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有219条查询结果,搜索用时 15 毫秒
41.
M.O. Ahmad C.H. Reddy V. Ramachandran M.N.S. Swamy 《Journal of The Franklin Institute》1979,307(2):71-81
Necessary and sufficient conditions are obtained for the realization of an m-variable positive real function (PRF) as the impedence function of a resistively-terminated ladder network of m lossless two-ports connected in cascade. Each two-port is a single-variable lossless ladder with all of its transmission zeros either at the origin or at finity. Conditions are also obtained when each of the two-ports is a Fujisawa-type lowpass ladder. 相似文献
42.
For most open universities, in fact for most universities, there will arise occasions when some online activities will have to be completed by all students in a very short time interval. These occasions usually result in a great rush to get online as quickly as possible; the rush is often made worst by the limited good choices on offer such that usually only the earliest can get the best. Choosing and confirming elective subjects, when only a limited number for each are offered, on a first-come-first-served basis is an example.At the Open University Malaysia the rush occurs when confirming offered subjects and choosing face-to-face meeting timetable. Most students rushed to be earliest to ensure choice slots in the timetable are obtained.Available I. T. resources such as Internet bandwidth and servers cannot cope with these short-term sustained peak demands. Unless these peak demands are met, however, online services will slow down drastically resulting in long queues of users waiting to be served. Providing excess capacity, if at all possible, to ensure these short duration peak demands can be met would not be cost-effective since most of the time these resources are not utilised. This paper will look at some cost-effective approaches to meeting these short-term peak demands. 相似文献
43.
Mahdi Dehghan Maryam Biabani Ahmad Ali Abin 《Information processing & management》2019,56(3):1067-1079
Cost optimization continues to be a critical concern for many human resources departments. The key is to balance between costs and business value. In particular, computer science organizations prefer to hire people who are expert in only one skill area and have a slight superficial knowledge in other areas that gives them the ability to collaborate across different aspects of project. Community Question Answering networks provide good platforms for people and organizations to share knowledge and find experts. An important issue in expert finding is that an expert has to constantly update his knowledge after being saturated in his field of expertise to still be identified as expert. A person who fails to preserve his expertise is likely to lose his expertise. This work justifies this question that does take the concept of time into account improve the quality of expertise retrieval. We propose a new method for T-shaped expert finding that is based on temporal expert profiling. The proposed method takes the temporal property of expertise into account to mine the shape of expertise for each candidate expert based on his profile. To this end, for each candidate expert, we take snapshots of his expertise trees at regular time intervals and learn the relation between temporal changes in different expertise trees and candidates’ profile. Finally, we use a filtering technique that is applied on top of the profiling method, to find shape of expertise for candidate experts. Experimental results on a large test collection show the superiority of the proposed method in terms of quality of results in comparison with state-of-the-art. 相似文献
44.
45.
Ahmad Sadeghi Iran Baghban Fatemeh Bahrami Ahmad Ahmadi Peter Creed 《International Journal for Educational and Vocational Guidance》2011,11(1):29-38
A short 33-item form of the Career Development Inventory was validated on a sample of 310 Iranian high school students. Factor
analysis indicated that attitude and cognitive subscale items loaded on their respective factors, and that internal reliability
coefficients at all levels were satisfactory to good. Support for validity was demonstrated by associations in the expected
direction for career decidedness and career decision-making self-efficacy. This short form of the inventory shows promise
as a measure of career maturity with students from a non-Western country. 相似文献
46.
Motahareh Waezi-Zadeh Ahmad Ghazanfari Shahin Noorbakhsh 《Journal of Zhejiang University. Science. B》2010,11(7):482-488
Date pits for feed preparation or oil extraction are soaked in water to soften before milling or extrusion. Knowledge of water absorption by the date pits helps in better managing the soaking duration. In this research, the process of water absorption by date pits was modeled and analyzed using Fick's second law of diffusion, finite element approach, and Peleg model. The moisture content of the pits reached to its saturation level of 41.5% (wet basis) after 10 d. The estimated coefficient of diffusion was 9.89×10-12 m2/s. The finite element model with a proposed ellipsoid geometry for a single date pit and the analytical model fitted better to the experimental data with R2 of 0.98. The former model slightly overestimated the moisture content of the pits during the initial stages of the soaking and the latter model generally underestimated this variable through the entire stages of soaking process. 相似文献
47.
Bread wheat varieties as influenced by different nitrogen levels 总被引:4,自引:2,他引:2
INTRODUCTION Dera Ismail Khan lies in Pakistan’s arid zone (71.07° longitude, 31.57° latitude and 500 m above sea level). This zone is in the extreme south of (NWFP) Pakistan at the bank of the River Indus. Dera Ismail Khan is bounded by Sulaiman Range to the West, the Indus River on the East, Marwat and Bhit- tani Ranges on the North and Vehowa Nala (Punjab) on the South. Besides certain local variability the area is comprised of four basic divisions viz mountains, a series … 相似文献
48.
Xiaole Mao Ahmad Ahsan Nawaz Sz-Chin Steven Lin Michael Ian Lapsley Yanhui Zhao J. Philip McCoy Wafik S. El-Deiry Tony Jun Huang 《Biomicrofluidics》2012,6(2):024113-024113-9
In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle focusing and detection components on-chip, including a “microfluidic drifting” based three-dimensional (3D) hydrodynamic focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics. 相似文献
49.
Mao X Nawaz AA Lin SC Lapsley MI Zhao Y McCoy JP El-Deiry WS Huang TJ 《Biomicrofluidics》2012,6(2):24113-241139
In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle focusing and detection components on-chip, including a "microfluidic drifting" based three-dimensional (3D) hydrodynamic focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics. 相似文献
50.
天然植物色素可以作为研制染料敏化太阳能电池的一种颜料(光敏剂)。西藏核桃果皮富含丰富色素,本文利用萃取、色谱分离技术提取了西藏林芝核桃果皮色素。用蒸馏水从500g干核桃果皮中提取获得了21.03g色素,产率达4.21%。用四氯化碳从500g鲜核桃果皮中提取获得了0.35g色素。利用紫外可见光度计对以上两种萃取流程获得的色素进行了吸光度测定。结果显示核桃果皮色素对波长越短的光吸收能力越强。紫外区有最大的吸光度,然后随着波长的增大,吸光度逐渐变小。为今后研制色素增感型太阳能电池提供了萃取色素颜料技术。 相似文献