全文获取类型
收费全文 | 208篇 |
免费 | 13篇 |
专业分类
电工技术 | 10篇 |
综合类 | 1篇 |
化学工业 | 37篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 9篇 |
能源动力 | 14篇 |
轻工业 | 3篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 45篇 |
一般工业技术 | 34篇 |
冶金工业 | 34篇 |
原子能技术 | 2篇 |
自动化技术 | 23篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 3篇 |
2013年 | 19篇 |
2012年 | 3篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有221条查询结果,搜索用时 10 毫秒
61.
A method, based on principal components for localizing the sources of the background EEG, is presented which overcomes the previous limitations of this approach. The spatiotemporal source model of the EEG is assumed to apply, and the method involves attempting to fit the spatial aspects of this general model with an optimal rotation of a subset of the principal components of a particular EEG. The method is shown to be equivalent to the subspace scanning method, a special case of the MUSIC algorithm, which enables multiple sources to be localized individually rather than all at once. The novel aspect of the new method is that it offers a way of selecting the relevant principal components for the localization problem. The relevant principal components are chosen by decomposing the EEG using spatial patterns common with a control EEG. These spatial patterns have the property that they account for maximally different proportions of the combined variances in the two EEG's. An example is given using a particular EEG from a neurologic patient. Components containing spike and sharp wave potentials are extracted, with respect to a standard EEG derived from 15 normal volunteers. Spike and sharp wave potentials are identified visually using the common spatial patterns decomposition and an EEG reconstructed from these components. Four dipole sources are fitted to the principal components of the reconstructed EEG and these source account for over 88% of the temporal variance present in that EEG 相似文献
62.
A mathematical model that predicts the dynamic flows in cellular mobile networks that allocate channels using the Borrowing Channel Assignment (BCA) scheme is described in this paper. Two types of handoff procedures – the prioritized and non-prioritized schemes – will be considered in the model. Discrete event simulations were performed and the results were found to be comparable to the results obtained using the mathematical model. Application to comparative study of the dynamic behaviours of the BCA and the Fixed Channel Assignment (FCA) schemes is also presented. 相似文献
63.
Not only thyroid adenomas and carcinomas, but also the majority of single and well delimited goiter nodules, even if morphologically heterogeneous, are of clonal origin. However, it is still unknown whether the nodules of rapidly growing, recurrent goiters are clonal or polyclonal. We investigated by PCR-based analysis of exon 1 of the human androgen receptor gene clonality of nodules grown in recurrent multinodular goiters (MNG) of 14 female patients. The total goiter volume varied widely between 15 ml and 170 ml. The mean age of patients undergoing surgery for recurrent goiter at the time of their first operation was significantly lower with 34.6 +/- 10.9 yr in comparison to 50 consecutive patients who were operated for MNG for the first time (53.7 +/- 13.5 yr). The interval between first and recurrent operation was 18 +/- 8.5 yr. The mean volume of well circumscribed nodules selected for the present investigation was 3.8 +/- 1.4 ml. Assessment of clonality in at least 2 samples of each lesion revealed a polyclonal pattern in 10 out of 14 nodules, whereas only 3 nodules were clonal and in one case the result remained unclear. The unexpected finding that most nodules within MNG, that had re-grown after a first subtotal thyroidectomy, were of polyclonal rather than clonal composition, suggests that these lesions are generated by de novo-proliferation of cohorts of differing thyrocytes sharing the common trait of an exceedingly high intrinsic growth rate or alternatively, by unknown growth stimulating molecular events acting focally on clusters of cells derived from different ancestors. In addition, the relatively young age of patients with recurrent MNG at the time of their first surgery and the comparatively short interval between first and second operation point to a genetic element in the occurrence of growth-prone thyrocytes. 相似文献
64.
Chyi-YeouSoong 《热科学学报(英文版)》2003,12(1):62-76
In the present paper, fluid flow and convective heat transfer between two co-axial disks rotating independently are dealt with mainly based on the author's recent research on that topic. Three rotational modes, i.e. co-rotation, rotor-stator, and counter-rotation, are considered. Theory of rotating non-isothermal fluids with the presence of disk rotation and thermal effects is addressed. Rotational buoyancy effects on the flow structure development are highlighted. Results of flow visualization and heat transfer measurements are discussed to explore the thermal flow mechanisms involved in the two-disk flows at various rotational and geometric conditions. Potential issues open to the future investigation are also proposed. 相似文献
65.
Efficient Transdermal Delivery of DNA Nanostructures Alleviates Atopic Dermatitis Symptoms in NC/Nga Mice 下载免费PDF全文
Gabsik Yang Hye Eun Lee Seung Won Shin Soong Ho Um Jung Dae Lee Kyu‐Bong Kim Han Chang Kang Yong‐Yeon Cho Hye Suk Lee Joo Young Lee 《Advanced functional materials》2018,28(40)
DNA nanostructures have been widely studied in biomedical research contributing to targeted treatment of chronic diseases. The immunostimulatory XL‐DNA nanostructures of X‐shaped oligodeoxynucleotides complex are previously reported, activating toll‐like receptor9 in dendritic cells. This study examines whether the XL‐DNA could be therapeutically applied to treat immune diseases such as atopic dermatitis. To optimize topical delivery, liposome‐encapsulated XL‐DNA (Lipo‐XL‐DNA) is generated using emulsion transfer method with lipid layers composed of 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine, 1,2‐dioleoyl‐sn‐glycero‐3‐phospho‐(1′‐rac‐glycerol), and cholesterol. Size distribution of Lipo‐XL‐DNA ranges around 90–160 nm with mean diameter of 115.44 ± 18.72 nm. The morphology is confirmed by transmission electron microscope. Zeta potential is ?28.59 mV. Confocal microscopy shows that Lipo‐XL‐DNA is efficiently delivered into epidermis and dermis. Topical application of Lipo‐XL‐DNA effectively alleviates atopic dermatitis symptoms in mice, as shown by dermatitis score, histological evaluation, and serum immunoglobulin E levels. RNA‐seq analysis confirms that Lipo‐XL‐DNA reduces pro‐inflammatory products, but increases epidermal barrier homeostasis factors in atopic dermatitis lesions. Lipo‐XL‐DNA orchestrates immune balance by downregulating Th2 immunity, but upregulating Th1 immunity. Collectively, liposome encapsulation enables efficient transdermal delivery of XL‐DNA, for an effective treatment of atopic dermatitis in mice. The results provide a promising therapeutic strategy using XL‐DNA nanostructures to treat immune‐compromised diseases. 相似文献
66.
So Yeon Ahn Jin Liu Srivithya Vellampatti Yuzhou Wu Soong Ho Um 《Advanced functional materials》2021,31(12):2008279
Due to its unique physical and chemical characteristics, DNA, which is known only as genetic information, has been identified and utilized as a new material at an astonishing rate. The role of DNA has increased dramatically with the advent of various DNA derivatives such as DNA–RNA, DNA–metal hybrids, and PNA, which can be organized into 2D or 3D structures by exploiting their complementary recognition. Due to its intrinsic biocompatibility, self-assembly, tunable immunogenicity, structural programmability, long stability, and electron-rich nature, DNA has generated major interest in electronic and catalytic applications. Based on its advantages, DNA and its derivatives are utilized in several fields where the traditional methodologies are ineffective. Here, the present challenges and opportunities of DNA transformations are demonstrated, especially in biomedical applications that include diagnosis and therapy. Natural DNAs previously utilized and transformed into patterns are not found in nature due to lack of multiplexing, resulting in low sensitivity and high error frequency in multi-targeted therapeutics. More recently, new platforms have advanced the diagnostic ability and therapeutic efficacy of DNA in biomedicine. There is confidence that DNA will play a strong role in next-generation clinical technology and can be used in multifaceted applications. 相似文献
67.
Junsung Bang Woo Seok Lee Byeonghak Park Hyungmok Joh Ho Kun Woo Sanghyun Jeon Junhyuk Ahn Chanho Jeong Tae‐il Kim Soong Ju Oh 《Advanced functional materials》2019,29(32)
Highly sensitive temperature sensors are designed by exploiting the interparticle distance–dependent transport mechanism in nanocrystal (NC) thin films based on a thermal expansion strategy. The effect of ligands on the electronic, thermal, mechanical, and charge transport properties of silver (Ag) NC thin films on thermal expandable substrates of poly(dimethylsiloxane) (PDMS) is investigated. While inorganic ligand‐treated Ag NC thin films exhibit a low temperature coefficient of resistance (TCR), organic ligand‐treated films exhibit extremely high TCR up to 0.5 K?1, which is the highest TCR exhibited among nanomaterial‐based temperature sensors to the best of the authors' knowledge. Structural and electronic characterizations, as well as finite element method simulation and transport modeling are conducted to determine the origin of this behavior. Finally, an all‐solution based fabrication process is established to build Ag NC‐based sensors and electrodes on PDMS to demonstrate their suitability as low‐cost, high‐performance attachable temperature sensors. 相似文献
68.
The toughening behavior of polycarbonate modified with core‐shell type particles was investigated. The alloys were found to exhibit maximum impact strength upon addition of a modifier with a poly(butyl acrylate) rubbery core of 0.25 μm diameter. The incorporation of particles with diameter greater than 0.25 μm resulted in decreased impact strength. The influence of rubber phase contents on toughness was also studied. It was observed that the alloys exhibited maximum impact strength upon addition of 4 wt % rubber phase. Further increase in the rubber phase content resulted in reduced impact strength. Fractography of the samples showed that, below 4 wt % rubber phase content, the fracture occurs mainly by internal crazing and, from 4 wt % onward, only by shear deformation. When the effect of dual particle size distribution was analyzed, it was found that there was only a moderate increase in toughness compared with alloys containing monosized particles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 748–755, 2005 相似文献
69.
A unified approach to the analysis of models of cellular communication networks with queues of data calls was developed. Consideration was given to the models with two types of strategies for admission to the cell channels and the buffer. In one strategy, admission to the voice call channels is based on reservation of channels for handover of calls of the given type, and in the other strategy, on the scheme of truncating the calls of the given type. In both models, the strategy of buffer admission by the data calls relies on the scheme of place reservation for handover of the calls of the given type. The models with finite and infinite data call queues were studied. For different admission strategies, algorithms to calculate the servicing performance indices were given, and the results of their comparative analysis were presented. 相似文献
70.
Assessment of the separation necessary to prevent seismic pounding between linear structural systems
This study examines the accuracy of the Double Difference Combination (DDC) rule (also known simply as the CQC rule) in predicting the separation necessary to prevent seismic pounding between linear structural systems. Seismic excitations were modeled as modulated and filtered modulated Gaussian white noise random processes, and adjacent structures were modeled as 5%-damped SDOF systems having a wide range of values of natural periods. Results obtained through Monte Carlo simulations indicate that the accuracy of the DDC rule depends not only on the ratio of the natural periods of the structures, but also on the relationship between the values of the natural periods and the value of the period associated with the main frequency of the excitation. 相似文献