全文获取类型
收费全文 | 279篇 |
免费 | 25篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 64篇 |
金属工艺 | 9篇 |
机械仪表 | 6篇 |
建筑科学 | 16篇 |
能源动力 | 15篇 |
轻工业 | 30篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
无线电 | 32篇 |
一般工业技术 | 51篇 |
冶金工业 | 30篇 |
原子能技术 | 1篇 |
自动化技术 | 38篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 14篇 |
2019年 | 18篇 |
2018年 | 20篇 |
2017年 | 16篇 |
2016年 | 19篇 |
2015年 | 5篇 |
2014年 | 21篇 |
2013年 | 41篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1978年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有304条查询结果,搜索用时 31 毫秒
101.
Given an unlabeled, unweighted, and undirected graph with n vertices and small (but not necessarily constant) treewidth k, we consider the problem of preprocessing the graph to build space-efficient encodings (oracles) to perform various queries efficiently. We assume the word RAM model where the size of a word is Ω(logn) bits. The first oracle, we present, is the navigation oracle which facilitates primitive navigation operations of adjacency, neighborhood, and degree queries. By way of an enumeration argument, which is of interest in its own right, we show the space requirement of the oracle is optimal to within lower order terms for all graphs with n vertices and treewidth k. The oracle supports the mentioned queries all in constant worst-case time. The second oracle, we present, is an exact distance oracle which facilitates distance queries between any pair of vertices (i.e., an all-pairs shortest-path oracle). The space requirement of the oracle is also optimal to within lower order terms. Moreover, the distance queries perform in O(k 3log3 k) time. Particularly, for the class of graphs of popular interest, graphs of bounded treewidth (where k is constant), the distances are reported in constant worst-case time. 相似文献
102.
In the nervous system, extracellular matrix (ECM) molecules have been shown to have effects on cell migration, process outgrowth and the survival of neurons. Recently we have described the molecular cloning of SC1, a putative brain extracellular matrix glycoprotein, showing partial similarity to the ECM glycoprotein SPARC/osteonectin. We have now examined the expression of SC1 during the development of the rat cerebellum at both the protein and mRNA levels. Our results indicate that SC1 is both temporally and spatially regulated during this process. Bergmann glial cells express SC1 mRNA and the resultant protein is deposited along the length of their radial fibres during the process of granule cell migration in the developing cerebellum. SC1 mRNA and protein is also found in the adult cerebellum, concentrated in the Bergmann glial cells and their radial processes, indicating that this putative ECM molecule continues to play roles in the central nervous system after migration and proliferative events have ceased. 相似文献
103.
Optimization of the heterogeneous Fenton-oxidation of the model pollutant 2,4-xylidine using the optimal experimental design methodology 总被引:1,自引:0,他引:1
Miguel Rios-Enriquez Nabil Shahin Carmen Durn-de-Bazúa Josef Lang Esther Oliveros Stefan H. Bossmann Andr M. Braun 《Solar Energy》2004,77(5):491-501
Among advanced oxidation processes (AOP), the photochemically enhanced Fenton reaction (photo-Fenton) may be particularly effective for the treatment of industrial waste water, and the possibility to use solar light is an additional advantage of this process. In the present work, a Fe3+-exchanged zeolite Y was tested as a heterogeneous photo-Fenton catalyst for the degradation of the model organic pollutant, 2,4-xylidine. The performance of the catalyst was investigated using a bench photochemical reactor as well as solar reactors. The incident solar radiant powers (determined by ferrioxalate actinometry) showed linear correlations with the outputs of a Si-photodiode and a bolometer mounted on the solar unit, and could therefore be easily estimated from the on-line observation of the sensor outputs. The experimental design methodology was used for planning the experiments under normalized conditions and for modeling the rates of 2,4-xylidine oxidation as a function of the concentrations of the additives (Fe3+-exchanged zeolite catalyst and hydrogen peroxide). Although a direct quantitative comparison between both reactors is difficult (different geometries and volumes, different spectral distribution of the radiation sources), the performance of the solar reactor appears to compare favorably with that of the bench photochemical reactor. 相似文献
104.
Shahin Salehi 《Chemical engineering science》2008,63(2):395-403
In this paper, two nonlinear observer based controllers for temperature control of a continuous stirred tank reactor in which a special class of parallel exothermic reactions take place are proposed. A reduced order nonlinear observer is constructed to estimate the concentration in the reactor. The observer is coupled with two nonlinear controllers, designed based on two well-known techniques, namely input-output linearization and backstepping for controlling the reactor temperature. For dampening the effect of observer error dynamics, a compensating term is used in each control law. The asymptotical stability of the closed-loop system is shown by the Lyapunov's stability theorem. The effectiveness of the proposed controllers has been demonstrated through computer simulations. 相似文献
105.
Shahin Farshchi Aleksey Pesterev Paul H Nuyujukian Istvan Mody Jack W Judy 《IEEE transactions on information technology in biomedicine》2007,11(6):611-618
Wireless-enabled processor modules intended for communicating low-frequency phenomena (i.e., temperature, humidity, and ambient light) have been enabled to acquire and transmit multiple biological signals in real time, which has been achieved by using computationally efficient data acquisition, filtering, and compression algorithms, and interfacing the modules with biological interface hardware. The sensor modules can acquire and transmit raw biological signals at a rate of 32 kb/s, which is near the hardware limit of the modules. Furthermore, onboard signal processing enables one channel, sampled at a rate of 4000 samples/s at 12-bit resolution, to be compressed via adaptive differential-pulse-code modulation (ADPCM) and transmitted in real time. In addition, the sensors can be configured to filter and transmit individual time-referenced "spike" waveforms, or to transmit the spike height and width for alleviating network traffic and increasing battery life. The system is capable of acquiring eight channels of analog signals as well as data via an asynchronous serial connection. A back-end server archives the biological data received via networked gateway sensors, and hosts them to a client application that enables users to browse recorded data. The system also acquires, filters, and transmits oxygen saturation and pulse rate via a commercial-off-the-shelf interface board. The system architecture can be configured for performing real-time nonobtrusive biological monitoring of humans or rodents. This paper demonstrates that low-power, computational, and bandwidth-constrained wireless-enabled platforms can indeed be leveraged for wireless biosignal monitoring. 相似文献
106.
Mohammad Ali Shokrgozar Shahin Bonakdar Mohammad Mehdi Dehghan Shahriar Hojjati Emami Leila Montazeri Shahram Azari Mohsen Rabbani 《Journal of materials science. Materials in medicine》2013,24(10):2449-2460
Polyvinyl alcohol (PVA) hydrogel chains were crosslinked by urethane pre-polymer (PPU) in order to fabricate a new substitute for cartilage lesions. The microscopy images showed that the cultured chondrocytes had spherical morphology on PVA–PPU sample after 4 weeks of isolation in vitro. The alcian blue and safranin O staining proved the presence of proteoglycan on the surface of PVA–PPU sample secreted by cultured chondrocytes. This was confirmed by the detection of sulfate ions in the wavelength dispersive X-ray (WDX) analysis. In addition, the expression of collagen type II and aggrecan were observed in chondrocytes cultured on PVA–PPU by RT-PCR. Moreover, the implantation of the PVA–PPU sample with autologous cultured chondrocytes revealed the formation of neocartilage tissue in a rabbit model during 12 weeks follow up. In conclusion, the results verified that isolated chondrocytes cultured on PVA–PPU retain their original phenotype and this composition can be considered as promising substrate for cartilage tissue engineering. 相似文献
107.
This article presents a detailed analysis of the crosstalk-affected delay of coupled interconnects considering process variations. We utilise a distributed RC-π model of the interconnections to accurately model process variations. In particular, we perform a detailed investigation of various crosstalk scenarios and study the impact of different parameters on crosstalk delay. Although accounting for the effect of correlations among parameters of the neighbouring wire segments, statistical properties of the crosstalk-affected propagation delays are characterised and discussed. Monte Carlo-based simulations using Spice demonstrate the effectiveness of the proposed approach in accurately modeling the correlation-aware process variations and their impact on interconnect delay in the presence of crosstalk. 相似文献
108.
The effect of carbon nanoreinforcements of different shapes on the mechanical properties of epoxy‐based composites is studied. It is found that while nanodiamond and fibrous (carbon nanotube and nanofiber) particles provided better tensile properties, platelet (graphene oxide) nanoreinforcements lead to a considerable increase in the fracture toughness of the composites. The trend of the results is explained on the basis of the geometrical characteristics of the reinforcements. The accuracy of several micromechanics‐based criteria for predicting the Young's modulus of composites is investigated for different nanoparticle shapes. The state of dispersion of nanofillers and the fracture surface features of all composites are examined using TEM and SEM.
109.
Mohammad Hossein Jandaghian Abdolhannan Sepahi Shahin Hosseini Romina Esmaeilzade Ehsan Nikzinat Maryam Masoori Kamal Afzali 《应用聚合物科学杂志》2024,141(11):e55078
This study integrates advanced mathematical modeling and experimental methodologies to investigate the simultaneous impact of modifications in the split ratio and molecular weight (MW) of chains on the rheological and mechanical properties of bimodal polyethylene (BiPE) resins. The outcomes underscored the viability of fine-tuning the molecular weight distribution (MWD) of a BiPE resin by augmenting the MW of high molecular weight (HMW) chains while simultaneously diminishing their proportion in the final alloy formulation. In addition, the experimental results illuminated the prospect of attaining a targeted melt flow index for the final polymers by elevating the MW of HMW chains alongside an increase in the proportion of low molecular weight chains. Significantly, these adjustments resulted in remarkable enhancements in the shear thinning index and strain hardening modulus of the fabricated resins. 相似文献
110.