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排序方式: 共有233条查询结果,搜索用时 15 毫秒
1.
本文报道了东亚植物区系中双子叶植物9个种的体细胞染色体新计数,其中6个是属的新计数,并对这些资料与有关的科或属在系统学和进化上的意义作了讨论。 相似文献
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This paper is concerned with the problem of global asymptotical tracking of single-input single-output (SISO) nonlinear time-delay control systems. Based on the input-output feedback linearization technique and Lyapunov method for nonlinear state feedback synthesis, a robust globally asymptotical output tracking controller design methodology for a broad class of nonlinear time-delay control systems is developed. The underlying theoretical approaches are the differential geometry approach and the composite Lyapunov approach. One utilizes the parameterized co-ordinate transformation to transform the original nonlinear system into singularly perturbed model and the composite Lyapunov approach is then applied for output tracking. For the view of practical application, the proposed control methodology has been successfully applied to the famous nonlinear automobile idle-speed control system. 相似文献
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Che-Yu Kuo Tsung-Hau Jen Ying-Shao Hsu 《International Journal of Science Education》2013,35(14):2326-2357
The potential of computer-based assessments for capturing complex learning outcomes has been discussed; however, relatively little is understood about how to leverage such potential for summative and accountability purposes. The aim of this study is to develop and validate a multimedia-based assessment of scientific inquiry abilities (MASIA) to cover a more comprehensive construct of inquiry abilities and target secondary school students in different grades while this potential is leveraged. We implemented five steps derived from the construct modeling approach to design MASIA. During the implementation, multiple sources of evidence were collected in the steps of pilot testing and Rasch modeling to support the validity of MASIA. Particularly, through the participation of 1,066 8th and 11th graders, MASIA showed satisfactory psychometric properties to discriminate students with different levels of inquiry abilities in 101 items in 29 tasks when Rasch models were applied. Additionally, the Wright map indicated that MASIA offered accurate information about students’ inquiry abilities because of the comparability of the distributions of student abilities and item difficulties. The analysis results also suggested that MASIA offered precise measures of inquiry abilities when the components (questioning, experimenting, analyzing, and explaining) were regarded as a coherent construct. Finally, the increased mean difficulty thresholds of item responses along with three performance levels across all sub-abilities supported the alignment between our scoring rubrics and our inquiry framework. Together with other sources of validity in the pilot testing, the results offered evidence to support the validity of MASIA. 相似文献
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Knowledge management systems (KMSs) support high-quality services while shaping and improving positioning of services. Given such strategic importance of KMS, this study explores the effects of different types of KMS, which respond to the attributes (i.e., diversity and tacitness) of collective knowledge, on service (re-)positioning. Through a case study of a financial consulting company at the core of KMSs, combinations of the two knowledge attributes are used to determine which type of KMS (i.e., information library, deepened stock, thought islands, and shared brain) offers the greatest efficiency and effectiveness in service (re-)positioning. The joint concerns of service innovation scope and specificity are also considered. Finally, the study discusses the theoretical and practical implications on KMS design and functionality in the new business age of service innovation. 相似文献
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Myat Noe Hsu Rongcong Luo Kerwin Zeming Kwek Yong Chen Por Yong Zhang Chia-Hung Chen 《Biomicrofluidics》2015,9(5)
The poor solubility of many newly discovered drugs has resulted in numerous challenges for the time-controlled release of therapeutics. In this study, an advanced drug delivery platform to encapsulate and deliver hydrophobic drugs, consisting of poly (lactic-co-glycolic acid) (PLGA) nanoparticles incorporated within poly (ethylene glycol) (PEG) microgels, was developed. PLGA nanoparticles were used as the hydrophobic drug carrier, while the PEG matrix functioned to slow down the drug release. Encapsulation of the hydrophobic agents was characterized by fluorescence detection of the hydrophobic dye Nile Red within the microgels. In addition, the microcomposites prepared via the droplet-based microfluidic technology showed size tunability and a monodisperse size distribution, along with improved release kinetics of the loaded cargo compared with bare PLGA nanoparticles. This composite system has potential as a universal delivery platform for a variety of hydrophobic molecules. 相似文献
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Yu-Hsiang Chung Yi-Hsing Hsiao Wei-Lun Kao Chia-Hsien Hsu Da-Jeng Yao Chihchen Chen 《Biomicrofluidics》2015,9(2)
A vital aspect affecting the success rate of in vitro fertilization is the culture environment of the embryo. However, what is not yet comprehensively understood is the affect the biochemical, physical, and genetic requirements have over the dynamic development of human or mouse preimplantation embryos. The conventional microdrop technique often cultures embryos in groups, which limits the investigation of the microenvironment of embryos. We report an open microwell platform, which enables micropipette manipulation and culture of embryos in defined sub-microliter volumes without valves. The fluidic environment of each microwell is secluded from others by layering oil on top, allowing for non-invasive, high-resolution time-lapse microscopy, and data collection from each individual embryo without confounding factors. We have successfully cultured mouse embryos from the two-cell stage to completely hatched blastocysts inside microwells with an 89% success rate (n = 64), which is comparable to the success rate of the contemporary practice. Development timings of mouse embryos that developed into blastocysts are statistically different to those of embryos that failed to form blastocysts (p–value < 10−10, two-tailed Student''s t-test) and are robust indicators of the competence of the embryo to form a blastocyst in vitro with 94% sensitivity and 100% specificity. Embryos at the cleavage- or blastocyst-stage following the normal development timings were selected and transferred to the uteri of surrogate female mice. Fifteen of twenty-two (68%) blastocysts and four of ten (40%) embryos successfully developed into normal baby mice following embryo transfer. This microwell platform, which supports the development of preimplanted embryos and is low-cost, easy to fabricate and operate, we believe, opens opportunities for a wide range of applications in reproductive medicine and cell biology. 相似文献
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Recent advances in microscale flow propulsion through bioinspired artificial cilia provide a promising alternative for lab-on-a-chip applications. However, the ability of actuating artificial cilia to achieve a time-dependent local flow control with high accuracy together with the elegance of full integration into the biocompatible microfluidic platforms remains remote. Driven by this motive, the current work has constructed a series of artificial cilia inside a microchannel to facilitate the time-dependent flow propulsion through artificial cilia actuation with high-speed (>40 Hz) circular beating behavior. The generated flow was quantified using micro-particle image velocimetry and particle tracking with instantaneous net flow velocity of up to 101 μm/s. Induced flow patterns caused by the tilted conical motion of artificial cilia constitutes efficient fluid propulsion at microscale. This flow phenomenon was further measured and illustrated by examining the induced flow behavior across the depth of the microchannel to provide a global view of the underlying flow propulsion mechanism. The presented analytic paradigms and substantial flow evidence present novel insights into the area of flow manipulation at microscale. 相似文献
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