全文获取类型
收费全文 | 512篇 |
免费 | 26篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 100篇 |
金属工艺 | 12篇 |
机械仪表 | 26篇 |
建筑科学 | 23篇 |
能源动力 | 10篇 |
轻工业 | 64篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 38篇 |
一般工业技术 | 105篇 |
冶金工业 | 81篇 |
原子能技术 | 2篇 |
自动化技术 | 69篇 |
出版年
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 10篇 |
2014年 | 16篇 |
2013年 | 36篇 |
2012年 | 51篇 |
2011年 | 46篇 |
2010年 | 16篇 |
2009年 | 28篇 |
2008年 | 28篇 |
2007年 | 22篇 |
2006年 | 22篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 36篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 14篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有538条查询结果,搜索用时 109 毫秒
91.
Sanità Di Toppi L Musetti R Vattuone Z Pawlik-Skowrońska B Fossati F Bertoli L Badiani M Favali MA 《Microscopy research and technique》2005,66(5):229-238
In this work, we tried to go deeper inside distribution and toxicity of cadmium (Cd) in the macrolichen Xanthoria parietina (L.) Th. Fr. Thalli of this species were treated with 0 (control), 4.5, 9, 18, or 36 muM Cd for 24 or 48 hours. Transmission electron microscopy, X-ray microanalysis, and electron energy loss spectroscopy were exploited to study distribution and ultrastructural effects of Cd in thalli; spectrophotometric techniques were utilized for measuring Cd effects on chlorophyll (Chl) content; light fluorescence microscopy was used to evaluate Chl autofluorescence. The highest Cd concentration caused ultrastructural alterations both in the mycobiont and in the photobiont, more severe in the latter, decreased total Chl content and progressively quenched Chl autofluorescence. Cell wall immobilization was observed in both bionts, and evidence pointing to a Cd-binding ability by the concentric bodies in the mycobiont was also obtained. Lower Cd concentrations led to slight or even no effects on thallus structures and on Chl content and autofluorescence. The results obtained suggest that: (1) among the two bionts, the algal partner appears to be more susceptible to Cd stress, probably because of the presence of delicate and sensitive components such as the chloroplast and photosynthetic pigments; (2) a concentration threshold exists for the occurrence of evident structural and functional damage in X. parietina thalli exposed to Cd. 相似文献
92.
Ciofi C Scandurra G Merlino R Cannatà G Giusi G 《The Review of scientific instruments》2007,78(11):114702
The properties of a differential transconductance amplifier coupled with a four channel measurement system are exploited in order to reach a very high sensitivity in current noise measurements. In particular, it is demonstrated that, in proper conditions, the noise contributions coming from the active and passive devices that make up the transresistance amplifier can be virtually eliminated. Moreover, the proposed measurement method allows the evaluation of the impedance of the device under test from noise measurement data. Actual measurement results are also reported that demonstrate the effectiveness of the proposed approach. 相似文献
93.
Rojo L Borzacchiello A Parra J Deb S Vázquez B San Román J 《Journal of materials science. Materials in medicine》2008,19(4):1467-1477
Copolymeric systems bearing eugenol covalently linked to the macromolecular chains have been prepared and characterised in
terms of thermal, rheological and in vitro behaviour. Eugenyl methacrylate (EgMA) and ethoxyeugenyl methacrylate (EEgMA) were
polymerized and copolymerized with ethyl methacrylate (EMA) in a wide range of feed composition by bulk at high conversion.
Glass transition temperature (Tg) increased with the content of EgMA in the copolymer whereas Tg decreased with the content of EEgMA. The presence of any of the eugenyl monomers in the copolymer increased the thermal stability
of the materials. Rheological analysis showed that EMA-co-EgMA copolymers present a higher density of crosslinking or entanglements
among the chains compared with EMA-co-EEgMA materials, and copolymers containing more than 40% EgMA exhibited a pseudo-solid
like behaviour with G′ relatively independent of the frequency. The average molecular weight between cross-links (Mc) for the latter copolymers was in the order of 104 Da. For EEgMA copolymers, tan δ was lower than unity and G′ showed a gradual and slight dependency with frequency over the
whole range of composition. In vitro behaviour showed a higher hydrophilicity of the EEgMA containing copolymers manifested
in higher water sorption values, lower water contact angle values and higher surface free energy due to an increase in polarity.
All systems presented a good cytocompatibility with human fibroblasts assessed through direct and indirect assays. 相似文献
94.
Santamariña-Rubio E Pérez K Ricart I Arroyo A Castellà J Borrell C 《Accident; analysis and prevention》2007,39(1):1-5
The objective is to describe injuries of road traffic deaths in Barcelona and identify injury profiles by road user type, through a cross-sectional study including road traffic deaths for the period 1997-2004. The data source was the Institut de Medicina Legal de Catalunya. Diagnoses were coded using the International Classification of Diseases, 9th revision, Clinical Modification, and classified using the Barell Matrix. Of the 719 deaths studied, 45% were pedestrians, 32% two wheel motor vehicle users, and 23% car occupants. The injury profile of the road traffic deaths in Barcelona is internal injuries and fractures to the torso and to the head/neck. This profile is repeated in all the road user groups, although pedestrians present higher frequencies of fractures and contusions to extremities and contusions to the head/neck, and fewer internal torso injuries than car occupants or two wheel motor vehicle users. 相似文献
95.
Magalhães LM Segundo MA Reis S Lima JL Estela JM Cerdà V 《Analytical chemistry》2007,79(10):3933-3939
In the present work, a chemiluminometric automatic flow methodology for the in vitro determination of hypochlorous acid scavenging capacity, under pH and concentration conditions similar to those found in vivo, is proposed. As the pH found in physiological conditions (7.4) and the pH required for the chemiluminescence detection reaction (>10) are different, the multisyringe flow injection analysis features were exploited to perform the in-line reaction of HOCl and the scavenger molecule at physiological pH prior to reaction of the remaining HOCl with luminol at alkaline conditions. These two reactions were carried out in about 3 s, allowing the determination of fast reacting antioxidants, in a time frame closer to in vivo generation of HOCl when compared to previously described methods. The developed method was applied to nonsteroidal antiinflammatory drugs of different chemical families, and positive controls (cysteine, gallic acid, lipoic acid). The HOCl scavenging capacity was evaluated at pH 7.4 and 10.0; different results were found for oxicam derivatives, providing evidence that the pH of in vitro methods should be carefully selected to allow assumptions about putative in vivo effects. 相似文献
96.
The effects of a high hydrostatic pressure (HHP) treatment (450MPa, 15min at 20°C) on both the microbiological quality and the functional properties of plasma from biopreserved porcine blood were evaluated. Blood was inoculated with Enterococcus raffinosus-PS99 (10(7)ufcmL(-1)) and stored at 5°C. After 72-h storage, bacterial counts in inoculated samples decreased by 52, 70, 81 and more than 99% for coliforms, Pseudomonas spp, hemolytic and proteolytic bacteria, respectively. Counts of these bacterial groups were undetectable in the final product after pressurization, whereas total lactic acid bacteria were detected at levels up to 10(2)ufcmL(-1). Gelling, foaming and emulsifying properties of the plasma proteins were not noticeably affected by HHP. The results show that it is possible to obtain high-quality and microbiologically stable blood derivatives as functional ingredients, by combining biopreservation and HHP. 相似文献
97.
Bioequivalence of Docosahexaenoic Acid from Different Algal Oils in Capsules and in a DHA-Fortified Food 总被引:4,自引:0,他引:4
Arterburn LM Oken HA Hoffman JP Bailey-Hall E Chung G Rom D Hamersley J McCarthy D 《Lipids》2007,42(11):1011-1024
Docosahexaenoic acid (DHA), a long-chain omega-3 fatty acid, is important for eye and brain development and ongoing visual, cognitive, and cardiovascular health. Unlike fish-sourced oils, the bioavailability of DHA from vegetarian-sourced (algal) oils has not been formally assessed. We assessed bioequivalence of DHA oils in capsules from two different algal strains versus bioavailability from an algal-DHA-fortified food. Our 28-day randomized, placebo-controlled, parallel group study compared bioavailability of (a) two different algal DHA oils in capsules ("DHASCO-T" and "DHASCO-S") at doses of 200, 600, and 1,000 mg DHA per day (n = 12 per group) and of (b) an algal-DHA-fortified food (n = 12). Bioequivalence was based on changes in plasma phospholipid and erythrocyte DHA levels. Effects on arachidonic acid (ARA), docosapentaenoic acid-n-6 (DPAn-6), and eicosapentaenoic acid (EPA) were also determined. Both DHASCO-T and DHASCO-S capsules produced equivalent DHA levels in plasma phospholipids and erythrocytes. DHA response was dose-dependent and linear over the dose range, plasma phospholipid DHA increased by 1.17, 2.28 and 3.03 g per 100 g fatty acid at 200, 600, and 1,000 mg dose, respectively. Snack bars fortified with DHASCO-S oil also delivered equivalent amounts of DHA on a DHA dose basis. Adverse event monitoring revealed an excellent safety and tolerability profile. Two different algal oil capsule supplements and an algal oil-fortified food represent bioequivalent and safe sources of DHA. 相似文献
98.
The use of mechanical processes, such as calendering, is an interesting method to disperse carbon nanofibres because this technique avoids the use of organic solvents needed in chemical methods. Variations of the process are used by researchers, and further study of the effect of the calendering parameters is still needed. For this reason, the effectiveness of the dispersion of several percentages of carbon nanofibres (0.5–3 wt.%) in epoxy resin using different parameters of the calendering process has been studied in this work. Carbon nanofibres/epoxy nanocomposites and non-cured nanoreinforced mixtures have been characterised. This study showed that the dispersion was enhanced with a Sequential method. Density and thermomechanical properties of nanocomposites manufactured by the selected calendering method were evaluated. The viscosity of the CNF/epoxy mixtures at different percentages of nanoreinforcement was adequate to use them as a matrix in multiscale reinforced composites. 相似文献
99.
Odacir Almeida Neves Estaner Claro Romão João Batista Campos Silva 《Numerical Heat Transfer, Part A: Applications》2013,63(10):730-748
This work presents a numerical study of the tri-dimensional convection-diffusion equation by the control-volume-based on finite-element method using quadratic hexahedral elements. Considering that the equation governing this problem in its main variable may represent several properties, including temperature, turbulent kinetic energy, viscous dissipation rate of the turbulent kinetic energy, specific dissipation rate of the turbulent kinetic energy, or even the concentration of a contaminant in a given medium, among others, the wide applicability of this problem is thus evidenced. Three cases of temperature distributions will be studied specifically in this work, in addition to one case of pollutant dispersion upon analysis of the concentration of a contaminant in a fixed flow point. Some comparisons will be carried out against works found in the open literature, while others will be done according to each phenomenon characteristics. 相似文献
100.
A new, multisyringe flow injection setup was designed to develop the first completely automated flow methodology for the expeditious, accurate in-line determination of halogenated organic compounds (HOCs) in water. The target compounds are preconcentrated and isolated by solid-phase extraction. Following elution, previously organically bound halogens are released as free hydrogen halides by the combined action of UV light and a chemical oxidant for their subsequent spectrophotometric determination by reaction with Hg(SCN) 2 and Fe(3+). Optimizing the major hydrodynamic and chemical variables resulted in improved performance. Recovery of various HOCs was assessed, and potential interferents were examined. Under the selected operating conditions, the proposed method exhibits variable analytical performance depending on the particular sample volume used (e.g., a sample volume of 5 mL provides a linear working range of 140-2000 microg L(-1), a LOD of 100 microg L(-1), and a throughput of 9 samples h(-1)). The method was successfully used to determine total adsorbable organic halogens (AOX) in well water and leachates, and the results validated against an AOX reference method. The role of the proposed system in the environmental analytical field is critically discussed. 相似文献