首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   243篇
  免费   15篇
电工技术   1篇
化学工业   75篇
金属工艺   5篇
机械仪表   6篇
建筑科学   5篇
矿业工程   1篇
能源动力   28篇
轻工业   13篇
水利工程   3篇
石油天然气   2篇
无线电   27篇
一般工业技术   53篇
冶金工业   14篇
原子能技术   4篇
自动化技术   21篇
  2023年   7篇
  2022年   3篇
  2021年   10篇
  2020年   11篇
  2019年   10篇
  2018年   14篇
  2017年   9篇
  2016年   13篇
  2015年   10篇
  2014年   18篇
  2013年   32篇
  2012年   9篇
  2011年   13篇
  2010年   11篇
  2009年   12篇
  2008年   15篇
  2007年   10篇
  2006年   4篇
  2005年   3篇
  2004年   2篇
  2003年   3篇
  2002年   2篇
  2001年   2篇
  2000年   5篇
  1999年   1篇
  1998年   8篇
  1997年   3篇
  1996年   2篇
  1993年   1篇
  1992年   2篇
  1990年   1篇
  1988年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1978年   2篇
  1976年   2篇
  1974年   1篇
  1973年   2篇
排序方式: 共有258条查询结果,搜索用时 15 毫秒
51.
The reduced solubility of proteins near the isoelectric pH limits their use in food formulations whose pH lies in the range 5.0–6.0 because of poor functionality. In the present study, the effect of salt on the functionality of native and denatured cashew nut kernel protein isolates at the isoelectric pH was investigated. Both isolates showed improvement in their functional properties, but the improvement was greater for the denatured protein isolate. The solubilities of denatured and native protein isolates at the isoelectric pH increased from 26.4 g l?1 and 64 g l?1, respectively, without salt to maxima of 363 and 308 g l?1, respectively, at 0.75 M salt concentration. The water binding capacity of the isolates increased with increase in NaCl concentration from 1.70 ml g?1 to 1.77, 1.82, 1.92 and 2.2 ml g?1 for denatured protein isolate and from 1.45 ml g?1 to 1.65, 1.69, 1.82 and 1.97 ml g?1 for native protein isolate at 0.25, 0.50, 0.75 and 1.0 M salt concentrations, respectively. When the properties of the isolates in 0.75 M NaCl solutions were compared with those in salt‐free water there were 15% and 116% increases in emulsifying capacity, 40‐fold and 45‐fold increases in emulsifying activity and 4.6‐fold and 40‐fold increases in emulsion stability for native and denatured protein isolates, respectively, whilst the corresponding foaming capacities increased from 4 to 5.5 and 0 to 8.9 ml g?1 protein. Statistically, no difference in the foaming capacity of either of the isolates was observed above 0.5 M NaCl. The foam stability also exhibited similar behaviour. Copyright © 2004 Society of Chemical Industry  相似文献   
52.
53.
Selective oxidation of 5-hydroxymethyl-2-furfural (HMF) to 2,5-diformylfuran (DFF) toward industrial production was studied over Ru supported γ-alumina catalyst using molecular oxygen as an oxidant. From the solvents screening, considering recyclability after reaction, toluene was found to be the best solvent and gave maximum conversion of 99% with 97% DFF selectivity at 130 °C and 40 psi O2 pressure. Catalyst was washed with NaOH solution of pH = 12 to remove the adsorbed polymer impurities and then reused up to 5 cycles. The product could be purified by simple evaporation of the solvent, which could add advantage for industrial process.  相似文献   
54.
This paper presents the current status of Turkey's electricity power sector, efforts for introducing competition in the Turkey's power industry, and concerns with the restructuring in Turkey. Turkey include long-term high-cost agreements, low quality of power, and therefore restrictions for synchronization with UCTE network, increase in the reliance on imported natural gas, and the urgent need for highly qualified staff that would be capable of fast and reliable implementation of ongoing reforms in the electricity sector. The contribution of the exploiting wind energy potential in Turkey to reconstruction of Turkey electricity structure is investigated. The strong development of wind energy in Turkey is expected to continue in the coming years.  相似文献   
55.
Chitosan is synthesized by deacetylating chitin with NaOH solution under microwave irradiation. The process describes a rapid synthesis procedure in comparison to conventional methods. The microwave-synthesized chitosan was characterized by Ninhydrin test, Fourier transform-infrared spectroscopy and X-ray diffraction measurements. The experimental results show that the degree of deacetylation increased with increasing irradiation time. A degree of deacetylation of 85.3% was achieved after irradiating chitin with 45% NaOH solution in a microwave for 5.5 min at 900-watt power. This method can be very useful for synthesizing low molecular weight chitosan with rapid and clean chemistry.  相似文献   
56.
PURPOSE: Patients with active pars planitis have increased levels of a 36 kDa protein (p-36) in their circulation. The current studies were undertaken to determine the primary structure of this protein. METHODS: A degenerate oligonucleotide probe based on the amino terminal sequence of p-36 was used to identify a clone from a human spleen cDNA library. The cDNA insert was subcloned into the EcoR1 site of pUC-19, and both strands were sequenced. Southern blot analysis was used to study the genomic hybridization pattern. p-36 cDNA was subcloned in a pSG5 expression vector, and the construct was used to transfect COS-7 cells. RESULTS: The cDNA sequence contained an open reading frame of 966 base pairs encoding a protein of 322 amino acids, an untranslated region of 322 base pairs, and 2693 base pairs at the 5' and 3' ends, respectively. The deduced amino acid sequence showed 96.8% identity with the carboxy-terminal region of a yeast nucleopore complex protein, nup 100. Southern blot analysis of human genomic DNA revealed a simple hybridization pattern. Transfection of p-36 cDNA in COS-7 cells resulted in the presence of p-36 mRNA and expression of protein. CONCLUSIONS: The 36 kDa protein (p-36) detected at increased levels in the blood of patients with active pars planitis was cloned from a human spleen cDNA library. Its deduced amino acid sequence is homologous with the carboxy-terminal region of a nucleopore complex protein. Thus, we refer to this protein as nup36.  相似文献   
57.
The development of Pt‐free electrocatalysts for the hydrogen evolution reaction (HER) recently is a focus of great interest. While several strategies are developed to control the structural properties of non‐Pt catalysts and boost their electrocatalytic activities for the HER, the generation of highly reactive defects or interfaces by combining a metal with other metals, or with metal oxides/sulfides, can lead to notably enhanced catalytic performance. Herein, the preparation of cactus‐like hollow Cu2‐x S@Ru nanoplates (NPs) that contain metal/metal sulfide heterojunctions and show excellent catalytic activity and durability for the HER in alkaline media is reported. The initial formation of Ru islands on presynthesized Cu1.94S NPs, via cation exchange between three Cu+ ions and one Ru3+, induces the growth of the Ru phase, which is concomitant with the dissolution of the Cu1.94S nanotemplate, culminating in the formation of a hollow nanostructure with numerous thin Ru pillars. Hollow Cu2‐x S@Ru NPs exhibit a small overpotential of 82 mV at a current density of ?10 mA cm?2 and a low Tafel slope of 48 mV dec?1 under alkaline conditions; this catalyst is among state‐of‐the‐art HER electrocatalysts in alkaline media. The excellent performance of hollow Cu2‐x S@Ru NPs originates from the facile dissociation of water in the Volmer step.  相似文献   
58.
59.
Many models of plasticity are built using multiple, simple yield surfaces. Examples include geomechanical models and crystal plasticity. This leads to numerical difficulties, most particularly during the stress update procedure, because the combined yield surface is nondifferentiable, and when employing implicit time stepping to solve numerical models, because the Jacobian is often poorly conditioned. A method is presented that produces a single C2 differentiable and convex yield function from a plastic model that contains multiple yield surfaces that are individually C2 differentiable and convex. C2 differentiability ensures quadratic convergence of implicit stress-update procedures; convexity ensures a unique solution to the stress update problem, whereas smoothness means the Jacobian is much better conditioned. The method contains just one free parameter, and the error incurred through the smoothing procedure is quantified in terms of this parameter. The method is illustrated through three different constitutive models. The method's performance is quantified in terms of the number of iterations required during stress update as a function of the smoothing parameter. Two simple finite-element models are also solved to compare this method with existing approaches. The method has been added to the open-source “MOOSE” framework, for perfect, nonperfect, associated, and nonassociated plasticity.  相似文献   
60.
Indoor and cell‐edge coverage has been a major issue of concern for predeployed traditional macrocell (MC)–based homogeneous cellular network. Moreover, with the extensive increase of mobile users and developments of smart and highly specified devices, user demands and activities have led to huge cellular traffic. The key solutions to these that include network upgradation, overlaying of small cells (SCs), and scaling of resources have turned out to be the major causes for intercell interference (ICI) and energy‐efficiency degradation in heterogeneous cellular networks (HetCNs). In this paper, authors have tried to analyze the downlink performance metrics of cell boundary users with MCs overlaying SCs for three‐cell circular and seven‐cell sectorized networks through frequency reuse (FR) schemes. This paper also discusses the impact of ICI being encountered by users and the effect of SCs on the energy efficiency of the network. The locations for SCs are perceived where user density is large and demands high data rate such as at hot‐spot (HS) areas, railway stations, shopping malls, working farms, and organization. The performance metrics sum rate, average user throughput, and energy efficiency are compared by employing FR‐1 (full spectrum) and FR‐3 (three subbands) among MCs and deployed SCs. For both scenarios, simulation results and analyses depict that without SCs, utilization of FR‐1 results in performance degradation due to ICI effects. However, the downlink performance of cell boundary user and energy efficiency of the network could be enhanced by overlaying SCs near cell boundaries of preexisting MCs along with the allocation of FR‐1.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号