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排序方式: 共有86条查询结果,搜索用时 15 毫秒
1.
The lateral stability of reaction fronts in simple autocatalytic models with the components carrying various charges is investigated
when the system is exposed to an inhomogeneous electric field parallel to the direction of propagation. The enhanced migrational
flux of the reactant destabilizes the planar front giving rise to a cellular structure because the electric field strength
is greater on the reactant side of the reaction front. The onset of instability depends not only on the charge difference
between the reactant and the autocatalyst but also on the variation of specific conductance in the course of the reaction,
which results in a difference in electric field strength on the opposite sides of the reaction front. 相似文献
2.
DECODE: a new method for discovering clusters of different densities in spatial data 总被引:4,自引:0,他引:4
Tao Pei Ajay Jasra David J. Hand A.-Xing Zhu Chenghu Zhou 《Data mining and knowledge discovery》2009,18(3):337-369
When clusters with different densities and noise lie in a spatial point set, the major obstacle to classifying these data
is the determination of the thresholds for classification, which may form a series of bins for allocating each point to different
clusters. Much of the previous work has adopted a model-based approach, but is either incapable of estimating the thresholds
in an automatic way, or limited to only two point processes, i.e. noise and clusters with the same density. In this paper,
we present a new density-based cluster method (DECODE), in which a spatial data set is presumed to consist of different point
processes and clusters with different densities belong to different point processes. DECODE is based upon a reversible jump
Markov Chain Monte Carlo (MCMC) strategy and divided into three steps. The first step is to map each point in the data to
its mth nearest distance, which is referred to as the distance between a point and its mth nearest neighbor. In the second step, classification thresholds are determined via a reversible jump MCMC strategy. In
the third step, clusters are formed by spatially connecting the points whose mth nearest distances fall into a particular bin defined by the thresholds. Four experiments, including two simulated data
sets and two seismic data sets, are used to evaluate the algorithm. Results on simulated data show that our approach is capable
of discovering the clusters automatically. Results on seismic data suggest that the clustered earthquakes, identified by DECODE,
either imply the epicenters of forthcoming strong earthquakes or indicate the areas with the most intensive seismicity, this
is consistent with the tectonic states and estimated stress distribution in the associated areas. The comparison between DECODE
and other state-of-the-art methods, such as DBSCAN, OPTICS and Wavelet Cluster, illustrates the contribution of our approach:
although DECODE can be computationally expensive, it is capable of identifying the number of point processes and simultaneously
estimating the classification thresholds with little prior knowledge. 相似文献
3.
Balagani KS Phoha VV 《IEEE transactions on pattern analysis and machine intelligence》2007,29(10):1866-1868
Wong and Poon [1] showed that Chow and Liu's tree dependence approximation can be derived by minimizing an upper bound of the Bayes error rate. Wong and Poon's result was obtained by expanding the conditional entropy H(w|X). We derive the correct expansion of H(w|X) and present its implication. 相似文献
4.
Nanoclays for polymer nanocomposites, paints, inks, greases and cosmetics formulations, drug delivery vehicle and waste water treatment 总被引:2,自引:0,他引:2
Hasmukh A. Patel Rajesh S. Somani Hari C. Bajaj Raksh V. Jasra 《Bulletin of Materials Science》2006,29(2):133-145
An overview of nanoclays or organically modified layered silicates (organoclays) is presented with emphasis placed on the
use of nanoclays as the reinforcement phase in polymer matrices for preparation of polymer/layered silicates nanocomposites,
rheological modifier for paints, inks and greases, drug delivery vehicle for controlled release of therapeutic agents, and
nanoclays for industrial waste water as well as potable water treatment to make further step into green environment. A little
amount of nanoclay can alter the entire properties of polymers, paints, inks and greases to a great extent by dispersing 1nm
thick layered silicate throughout the matrices. The flexibility of interlayer spacing of layered silicates accommodates therapeutic
agents which can later on be released to damaged cell. Because the release of drugs in drug-intercalated layered materials
is controllable, these new materials have a great potential as a delivery host in the pharmaceutical field. The problem of
clean water can be solved by treating industrial and municipal waste water with organoclays in combination with other sorbents
like activated carbon and alum. Organoclays have proven to be superior to any other water treatment technology in applications
where the water to be treated contains substantial amounts of oil and grease or humic acid. 相似文献
5.
Vir K. Handa 《Building Research & Information》2013,41(2):106-115
Professor Vir Handa's abiding interest in low‐cost housing for the lower‐income earners is demonstrated in his paper from the University of Waterloo, Ontario. He draws experience from time spent at the Building Research Institute, Roorkee, under the United Nations TOKTEN Programme and illustrates his paper with pictures from Trinidad, where he is an External Examiner at the University of the West Indies. He argues that although shelter communities are being built without any government help and without any awareness of any codes and standards, the job of the expert should be to determine new affordable code requirements. 相似文献
6.
K.P. PrasanthPhani Rallapalli Manoj C. RajH.C. Bajaj Raksh Vir Jasra 《International Journal of Hydrogen Energy》2011,36(13):7594-7601
Metal-Organic Frameworks (MOFs) have emerged as potential hydrogen storage media due to their high surface area, pore volume and adjustable pore sizes. The large void space generated by cages in MOFs is not completely utilized for hydrogen storage application owing to weak interactions between the walls of MOFs and H2 molecules. These unutilized volumes in MOFs can be effectively utilized by incorporation of other microporous materials such as single walled carbon nanotubes into the pores of MOFs which could effectively tune the pore size and pore volume of the material towards hydrogen sorption. Single walled carbon nanotubes (SWNT) incorporated MIL-101 composite MOF material (SWNT@MIL-101) was synthesized by adding purified single walled carbon nanotube (SWNT) in situ during the synthesis of MIL-101. The powder X-ray diffraction patterns of SWNT@MIL-101 showed the structure of MOF was not disturbed by SWNT incorporation. Hydrogen sorption capacities of MIL-101 was observed to increase from 6.37 to 9.18 wt% at 77 K up to 60 bar and from 0.23 to 0.64 wt% at 298 K up to 60 bar. The increment in the hydrogen uptake capacities of composite MOF materials was attributed to the decrease in the pore size and enhancement of micropore volume of MIL-101 by single walled carbon nanotube incorporation. 相似文献
7.
Photocatalytic degradation of dyes and organic contaminants in water using nanocrystalline anatase and rutile TiO2 总被引:1,自引:0,他引:1
Rajesh J. Tayade Praveen K. Surolia Ramchandra G. Kulkarni Raksh V. Jasra 《Science and Technology of Advanced Materials》2007,8(6):455-462
Nanocrystalline TiO2 was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N2 adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO2 for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO2 for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO2 for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO2 is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst. 相似文献
8.
Aasif A. Dabbawala Jaydeep N. Parmar Raksh V. Jasra Hari C. Bajaj Eric Monflier 《Catalysis communications》2009,10(14):1808-1812
The cobalt catalyzed hydroformylation of higher olefins in the presence of chemically modified cyclodextrins was investigated in an aqueous biphasic system. The effect of various parameters, such as the nature of the cyclodextrin and olefin, the temperature, the CO/H2 pressure, the concentration of the cyclodextrin and TPPTS was studied. The results demonstrate that the partially methylated β-cyclodextrin gives good conversion (>92%) and selectivity (>92%) for the hydroformylation of higher olefins without impeding the recovery of the catalytic system. 相似文献
9.
Fruit preservation and packaging have been practiced since ages to maintain the constant supply of seasonal fruits over lengthened periods round the year. However, health and safety issues have attracted attention in recent decades. The safety and quality assurance of packaged fruits/fruit products are vital concerns in present day world-wide–integrated food supply chains. The growing demand of minimally or unprocessed packaged fruits has further aggravated the safety concerns which fuelled in extensive research with objectives to develop novel techniques of food processing, preservation, and packaging as well as for rapid, accurate, and early detection of contaminant products/microbes. Nevertheless, fruits and fruit-based products have yet to observe a panoramic introduction. Tropics and subtropics are the stellar producers of a variety of fruits; majority if not all is perishable and prone to postharvest decay. This evoked the opportunity to critically review the global scenario of emerging and novel techniques for fruit preservation and packaging, hence providing insight for their future implementation. This review would survey key nanotechnology innovations applied in preservation, packaging, safety, and storage of fruits and fruit-based products. The challenges and pros and cons of wider application of these innovative techniques, their commercial potential, and consumer acceptability have also been discussed. 相似文献
10.
R.I. Kureshy N.H. Khan S.H.R. Abdi I. Ahmad S. Singh R.V. Jasra 《Catalysis Letters》2003,91(3-4):207-210
Dicationic chiral Mn(III) salen complex (0.4 mol%) immobilized in the interlayer of montmorillonite clay 4A, epoxidize bulkier alkenes (epoxide yield 68–99%) with high chiral induction (up to 95% ee) with a catalyst reusability of up to four cycles. 相似文献