全文获取类型
收费全文 | 875篇 |
免费 | 65篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 248篇 |
金属工艺 | 13篇 |
机械仪表 | 9篇 |
建筑科学 | 30篇 |
矿业工程 | 3篇 |
能源动力 | 18篇 |
轻工业 | 190篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 38篇 |
一般工业技术 | 121篇 |
冶金工业 | 117篇 |
原子能技术 | 4篇 |
自动化技术 | 135篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 37篇 |
2021年 | 58篇 |
2020年 | 25篇 |
2019年 | 32篇 |
2018年 | 26篇 |
2017年 | 29篇 |
2016年 | 24篇 |
2015年 | 33篇 |
2014年 | 44篇 |
2013年 | 74篇 |
2012年 | 54篇 |
2011年 | 65篇 |
2010年 | 44篇 |
2009年 | 48篇 |
2008年 | 37篇 |
2007年 | 33篇 |
2006年 | 32篇 |
2005年 | 24篇 |
2004年 | 28篇 |
2003年 | 27篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1960年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有943条查询结果,搜索用时 234 毫秒
81.
Nanoparticles (NPs) play an increasingly important role in the fabrication of functional advanced materials. Two major steps need to be carried out in order to achieve control of the material properties. First of all, the properties of the single NPs have to be under control, especially in relation to colloidal stability; aggregation and corrosion negate all the benefits associated to the nanoscopic dimensions. Secondly, the assembly process has to be controlled to achieve a material with the desired properties. We propose here to use stabilized ceramic NPs consisting of a magnetite core, coated by a poly(ethylene glycol) (PEG) shell and study their assembly at polar/ non-polar liquid interfaces, en route to fabricating functional NP membranes. These NPs show extraordinary stability in aqueous solutions achieved by anchoring linear PEG chains through an end-terminating nitroDOPA group to their surface. Furthermore, the core and shell sizes of these NPs can be independently varied with ease. We first describe the details of the NP synthesis and stabilization in bulk solutions, discussing the PEG molecular weight needed to achieve bulk stability. Subsequently, we demonstrate self-assembly of these particles at liquid-liquid interfaces (SALI) into monolayers of stable properties. SALI has been chosen as path for the assembly given its suitability for fabricating two-dimensional materials. We report here results from pendant drop tensiometry which illustrate the kinetics of NP adsorption at the liquid-liquid interface and highlight the role played by the molecular weight of the PEG shell in the interfacial assembly. In particular we show that the requisites to ensure particle stability at a liquid interface are more stringent compared to the bulk case. 相似文献
82.
Murtola M Zaramella S Yeheskiely E Strömberg R 《Chembiochem : a European journal of chemical biology》2010,11(18):2606-2612
Several different cationic nonapeptides have been synthesized and investigated with respect to how they can influence the thermal melting of 2′‐O‐methylRNA/RNA and DNA/DNA duplexes. Each peptide has a C‐terminal L ‐phenylalanine unit and is otherwise uniformly composed of a sequence of a specific basic D ‐amino acid that in most cases will be largely charged at neutral pH. These N‐terminal octamer stretches are composed variously of the amino acids D ‐lysine, D ‐diaminobutyric acid (D ‐Dab), D ‐diaminopropionic acid (D ‐Dap), or D ‐histidine. None of the peptides substantially affected the thermal melting of DNA/DNA duplexes, which was in sharp contrast with their effects on 2′‐O‐methylRNA/RNA duplexes. In particular, the peptides based on diaminopropionic and diaminobutyric acid units had strong positive effects on the melting temperatures of the 2′‐O‐methylRNA duplexes (up to 16 °C higher with 1 equivalent of peptide) at pH 7, whereas at pH 6 the effect was even more drastic (ΔTm up to +25 °C). The shorter R groups of the Dap and Dab groups appear to have a better length than lysine for enhancement of the thermal melting of the 2′‐O‐methylRNA/RNA duplex, an effect that is more pronounced at lower pH but substantial even at pH 7, although the Dap derivative is not likely to be fully protonated. The dramatic difference between the influence, or lack thereof, on the 2′‐O‐methylRNA/RNA and the DNA/DNA thermal meltings suggest that, although electrostatic interactions probably play a role, there is another major and structurally dependent component influencing the properties of the duplexes. This is also seen in the observation that the oligo‐Dap and oligo‐Dab peptides give greater melting point enhancements than both the lysine peptide (with a longer side chain) and a β‐linked Dap peptide with a shorter side chain and a longer backbone. 相似文献
83.
Alexandra Manos‐Turvey Esther M. M. Bulloch Dr. Peter J. Rutledge Dr. Edward N. Baker Prof. J. Shaun Lott Dr. Richard J. Payne Dr. 《ChemMedChem》2010,5(7):1067-1079
Mycobacterium tuberculosis salicylate synthase (MbtI), a member of the chorismate‐utilizing enzyme family, catalyses the first committed step in the biosynthesis of the siderophore mycobactin T. This complex secondary metabolite is essential for both virulence and survival of M. tuberculosis, the etiological agent of tuberculosis (TB). It is therefore anticipated that inhibitors of this enzyme may serve as TB therapies with a novel mode of action. Herein we describe the first inhibition study of M. tuberculosis MbtI using a library of functionalized benzoate‐based inhibitors designed to mimic the substrate (chorismate) and intermediate (isochorismate) of the MbtI‐catalyzed reaction. The most potent inhibitors prepared were those designed to mimic the enzyme intermediate, isochorismate. These compounds, based on a 2,3‐dihydroxybenzoate scaffold, proved to be low‐micromolar inhibitors of MbtI. The most potent inhibitors in this series possessed hydrophobic enol ether side chains at C3 in place of the enol‐pyruvyl side chain found in chorismate and isochorismate. 相似文献
84.
A biofilm model for flowing systems in the food industry 总被引:1,自引:0,他引:1
den Aantrekker ED Vernooij WW Reij MW Zwietering MH Beumer RR van Schothorst M Boom RM 《Journal of food protection》2003,66(8):1432-1438
When bacteria attach to the walls of pipelines, they can form biofilms, which can cause the recontamination of food products. In order to quantify such recontamination, a one-dimensional biofilm model was developed taking into account adsorption, desorption, and the growth of cells. The model consisted of two mass balances describing increases in biofilm formation at the wall and the accumulation of cells in the liquid phase. The necessary parameters for the model were obtained in laboratory biofilm experiments. These experiments involved a flowing system and the use of Staphylococcus aureus as a model pathogen and silicon tubing as a testing material. S. aureus was inoculated into the system for 2 h, and then the system was changed to a sterile medium. Both biofilm formation and the release of cells into the flowing liquid were measured until steady-state conditions were reached (for up to 9 days). The experiments were performed in duplicate for different flow conditions (i.e., for Reynolds numbers of 3.2, 32, and 170). It was shown that at higher Reynolds numbers, the biofilm developed faster, probably owing to an increase in the transfer of nutrients to the surface. The proposed biofilm model was capable of describing the data obtained for the three different flow conditions with the use of the specific growth rate in the biofilm and the desorption coefficient as fit parameters. The specific growth rates were 0.16, 0.27, and 0.49 h(-1) for Reynolds numbers of 3.2, 32, and 170, respectively, and the desorption coefficients were about 1% of these values. 相似文献
85.
86.
Regional economic dynamics and convergence in the European Union 总被引:4,自引:1,他引:3
Enrique López-Bazo Esther Vayá Antonio J. Mora Jordi Suriñach 《The Annals of Regional Science》1999,33(3):343-370
This paper uses an alternative approach to convergence analysis, which, in our opinion, is richer than those traditionally
proposed. We believe that the evolution of the whole regional distribution is what matters, not that of an average or representative economy, implicit in the or convergence concepts. Moreover, when analyzing inequality among regional economies, geographic space acquires a preeminent
role. We therefore apply spatial association tests recently developed in the spatial econometrics literature and relate them
to convergence analysis. Specifically, we apply this methodology to the analysis of regional dynamics and convergence in the
European Union (EU). In this context, the progress made in the integration process has highlighted the question of economic
disparities at regional level. The process of convergence came to an end in the late seventies, coinciding with major changes
in economic activity. This paper shows how these factors appear to have provoked a regionally differentiated response which,
though significant, did not, in all likelihood, exacerbate the decrease in regional inequalities. 相似文献
87.
88.
Duraiswami Divakar Dhanagopal Manikandan Valentine Rupa Esther Leena Preethi Revathi Chandrasekar Thiripuranthagan Sivakumar 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(3):253-258
Palladium nanoparticles were generated in the interlamellar region of swelling 2:1 type vermiculite clay using an adsorption excess isotherm. An adsorption excess isotherm was constructed for vermiculite after exchanging the exchangeable Na+ ions in the interlamellar region using a binary liquid mixture (ethanol:toluene). Based on adsorption excess isotherm, 1% w/w palladium was intercalated into the interlamellar space of vermiculite. The Pd‐intercalated vermiculite was characterized by X‐ray diffraction, transmission electron microscopy and atomic absorption spectroscopy. The 1% w/w Pd‐intercalated vermiculite was tested for its catalytic activity towards selective hydrogenation reactions involving some α,β‐unsaturated carbonyl compounds using a pulse reactor and its catalytic activity was compared with commercial 1% Pd/C. The intercalated catalyst was found to be very selective towards the desired product of unsaturated alcohols. Copyright © 2007 Society of Chemical Industry 相似文献
89.
Herta Aidoo Esther Sakyi-Dawson Kwaku Tano-Debrah Firibu Kwesi Saalia 《Food research international (Ottawa, Ont.)》2010,43(1):79-85
This study explored the feasibility of producing peanut–cowpea milk for use in vegetable milk chocolates. Development of the vegetable milk followed a 3 × 2 factorial design, with peanut–cowpea ratio (1:1, 1:2 and 1:3), and treatment with enzyme (i.e. enzyme hydrolyzed and non-hydrolyzed milk) as the factors. The milk was dehydrated and then milled using a hammer mill (mesh size 40). It was then used in recipes to produce chocolates and evaluated sensorially based on ranking for preference. Skimmed milk powder was used to produce the control chocolate. The ratio of cowpea to peanut affected the chemical and functional characteristics of the vegetable milk. Vegetable milk made from 1:2 ratios of peanuts:cowpea produced the most preferred chocolates. The successful application of this by industry will improve the utilization of the legume crops and enhance their market value. 相似文献
90.