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排序方式: 共有750条查询结果,搜索用时 15 毫秒
651.
Charlet L Kang M Bardelli F Kirsch R Géhin A Grenèche JM Chen F 《Environmental science & technology》2012,46(9):4869-4876
A nanopyrite/greigite composite was synthesized by reacting FeCl(3) and NaHS in a ratio of 1:2 (Wei et al. 1996). Following this procedure, the obtained solid phases consisted of 30-50 nm sized particles containing 28% of greigite (Fe(2+)Fe(3+)(2)S(4)) and 72% pyrite (FeS(2)). Batch reactor experiments were performed with selenite or selenate by equilibrating suspensions containing the nanosized pyrite-greigite solid phase at different pH-values and with or without the addition of extra Fe(2+). XANES-EXAFS spectroscopic techniques revealed, for the first time, the formation of ferroselite (FeSe(2)) as the predominant reaction product, along with elemental Se. In the present experimental conditions, at pH 6 and in equilibrium with Se(0), the solution is oversaturated with respect to ferrosilite. Furthermore, thermodynamic computations show that reaction kinetics likely played a significant role in our experimental system. 相似文献
652.
The particular interest in supplementing human foods with n-3 fatty acids has arisen from the findings that this series of polyunsaturated fatty acids (PUFA) have an impact on neuronal functions. Indeed vertebrates, including humans, preferentially use docosahexaenoic acid (DHA, 22:6n-3) over other long-chain n-3 PUFA for the genesis of their neuronal and retinal membranes. The grey mouse lemur is a nocturnal prosimian primate originating from Madagascar. The increased use of this omnivorous primate in nutritional studies (chronic caloric restriction, n-3 fatty acids supplementation), justifies the interest of determining their fatty acids body composition. In the present study, we report the fatty acid composition in lipid classes from the main target tissues (brain, retina, liver and adipose tissue) of six adult mouse lemurs raised under laboratory nutritional conditions. Among the main findings, n-6-docosapentaenoic acid (n-6-DPA; 22:5n-6) is very low in the brain cortex and retina, whereas there is a very high accumulation of docosahexaenoic acid (DHA, 22:6n-3) in the neural tissues compared to liver and plasma. In particular, DHA accounts for about one half of the total fatty acids in the retina ethanolamine glycerophospholipids. This high concentration clearly indicates that DHA is efficiently transferred from blood lipids to the outer segment of the mouse lemur retina. We conclude that the mouse lemur n-3 PUFA metabolism efficiently drives DHA to neural tissues, through the blood-brain barrier and the blood-retina barrier. 相似文献
653.
Dawber M Lichtensteiger C Paruch P Triscone JM 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(12):2261-2269
Understanding the behavior of ferroelectrics on the nanoscale level requires the production of materials of the highest quality and advanced characterization techniques for probing the fascinating properties of these systems with reduced dimensions. Here we give an overview of our recent achievements in this area, which includes the detailed study of the suppression of ferroelectricity in PbTiO3 thin films, the fabrication of PbTiO3/SrTiO3 superlattices in which ferroelectricity shows some surprising behavior, and finally the manipulation of nanoscale ferroelectric domains using the atomic force microscope which leads to the precise analysis of domain wall creep and roughness in Pb(Zr,Ti)O3 thin films. 相似文献
654.
Costantini A Luciani G Annunziata G Silvestri B Branda F 《Journal of materials science. Materials in medicine》2006,17(4):319-325
A novel hydrogel based on 2-hydroxyethyl- methacrilate and SiO2 nanoparticles was prepared. The filler was added at a concentration of 30% w/w of silica nanoparticles to the mass of polymer.
The composite material was characterised as far as concerns swelling behaviour in comparison to pHEMA. Swelling ratio of modified
pHEMA was higher. Bioactivity of both SiO2 nanoparticles and the modified hydrogel was evaluated by soaking samples into a simulated body fluid (SBF). FT-IR spectroscopy,
scanning electron microscopy (SEM) and energy dispersive system (EDS) results suggest silica nanoparticles keep bioactive
in the polymer. SiO2 filler in a p(HEMA) matrix makes the composite bioactive. Therefore, these composites can be used to make bioactive scaffold
for bone engineering. 相似文献
655.
Sheathless capillary electrophoresis-mass spectrometry (CE-MS), using a porous tip sprayer, is proposed for the first time for highly sensitive metabolic profiling of human urine. A representative metabolite mixture and human urine were used for evaluation of the sheathless CE-MS platform. For test compounds, relative standard deviations (RSDs) for migration times and peak areas were below 2% and 12%, respectively, and an injection volume of only ~8 nL resulted in detection limits between 11 and 120 nM. Approximately 900 molecular features were detected in human urine by sheathless CE-MS whereas about 300 molecular features were found with classical sheath-liquid CE-MS. This difference can probably be attributed to an improved ionization efficiency and increased sensitivity at low flow-rate conditions. The integration of transient-isotachophoresis (t-ITP) as an in-capillary preconcentration procedure in sheathless CE-MS further resulted in subnanomolar limits of detection for compounds of the metabolite mixture, and more than 1300 molecular features were observed in urine. Compared to the classical CE-MS approaches, the integration of t-ITP combined with the use of a sheathless interface provides up to 2 orders of magnitude sensitivity improvement. Hence, sheathless CE-MS can be used for in-depth metabolic profiling of biological samples, and we anticipate that this approach will yield unique information in the field of metabolomics. 相似文献
656.
Heemskerk AA Busnel JM Schoenmaker B Derks RJ Klychnikov O Hensbergen PJ Deelder AM Mayboroda OA 《Analytical chemistry》2012,84(10):4552-4559
The potential benefits of ultra-low flow electrospray ionization (ESI) for the analysis of phosphopeptides in proteomics was investigated. First, the relative flow dependent ionization efficiency of nonphosphorylated vs multiplyphosphorylated peptides was characterized by infusion of a five synthetic peptide mix with zero to four phophorylation sites at flow rates ranging from 4.5 to 500 nL/min. Most importantly, similar to what was found earlier by Schmidt et al., it has been verified that at flow rates below 20 nL/min the relative peak intensities for the various peptides show a trend toward an equimolar response, which would be highly beneficial in phosphoproteomic analysis. As the technology to achieve liquid chromatography separation at flow rates below 20 nL/min is not readily available, a sheathless capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) strategy based on the use of a neutrally coated separation capillary was used to develop an analytical strategy at flow rates as low as 6.6 nL/min. An in-line preconcentration technique, namely, transient isotachophoresis (t-ITP), to achieve efficient separation while using larger volume injections (37% of capillary thus 250 nL) was incorporated to achieve even greater sample concentration sensitivities. The developed t-ITP-ESI-MS strategy was then used in a direct comparison with nano-LC-MS for the detection of phosphopeptides. The comparison showed significantly improved phosphopeptide sensitivity in equal sample load and equal sample concentration conditions for CE-MS while providing complementary data to LC-MS, demonstrating the potential of ultra-low flow ESI for the analysis of phosphopeptides in liquid based separation techniques. 相似文献
657.
Fluorescent (rhodamine), folate decorated and doxorubicin charged, PEGylated nanoparticles synthesis
Silvestri B Guarnieri D Luciani G Costantini A Netti PA Branda F 《Journal of materials science. Materials in medicine》2012,23(7):1697-1704
PEGylated silica nanoparticles, giving very stable aqueous sols, were successfully functionalised with rhodamine, one of the more stable fluorophore; they were also decorated with the targeting agent folic acid (FA) and charged with the well known drug doxorubicin. Rhodamine functionalization required a modification of the synthesis route of the nanoparticles (NP). Functionalization with FA required activation with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. Folate decorated NP were easily charged with doxorubicin. The experimental results proved the successfulness of the functionalization. The bond to the NP does not reduce the therapeutic efficacy of the drug. The calculated encapsulation efficiency (32?%) was only a little lower than the value (47?%) reported for the very popular PEGylated PLGA NP. 相似文献
658.
Spatially resolved spectroscopic optical coherence tomography (OCT) has been demonstrated to be a convenient tool for spectral analysis in turbid media. For a full-field OCT configuration using a Mirau objective in the visible range, we found that the effective numerical aperture varies over the field of view, leading to field-dependent spectral shifts in the reconstructed spectra. Interferograms recorded with quasi-monochromatic lights are theoretically fitted with a general Mirau interference formula, and we propose a numerical correction method for white-light spectroscopy. The method is then tested successfully for the measure of the reflectivity of a plane gold sample. 相似文献
659.
Beatrice Bocca Giovanni Forte Sergio Costantini 《The Science of the total environment》2009,407(7):2183-2190
The aim of this study was to quantify metals contained in and leached from different types of rubber granulates used in synthetic turf areas. To investigate the total content of metals, ca 0.5 g of material was added with HNO3, HF and HClO4 and microwave digested with power increasing from 250 W to 600 W. Leachates were prepared by extraction of about 5.0 g of material at room temperature for 24 h in an acidic environment (pH 5). Leaching with deionized water was also performed for comparison. Aluminium, As, Ba, Be, Cd, Co, Cr, Cu, Hg, Fe, Li, Mg, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Tl, V, W and Zn were quantified by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) and ICP optical emission spectrometry (ICP-OES).Results indicated that the developed method was accurate and precise for the multi-element characterization of rubber granulates and leachates. The total amount and the amount leached during the acidic test varied from metal to metal and from granulate to granulate. The highest median values were found for Zn (10,229 mg/kg), Al (755 mg/kg), Mg (456 mg/kg), Fe (305 mg/kg), followed by Pb, Ba, Co, Cu and Sr. The other elements were present at few units of mg/kg. The highest leaching was observed for Zn (2300 μg/l) and Mg (2500 μg/l), followed by Fe, Sr, Al, Mn and Ba. Little As, Cd, Co, Cr, Cu, Li, Mo, Ni, Pb, Rb, Sb and V leached, and Be, Hg, Se, Sn, Tl and W were below quantification limits. Data obtained were compared with the maximum tolerable amounts reported for similar materials, and only the concentration of Zn (total and leached) exceeded the expected values. 相似文献
660.
The purpose of this study was to measure radon concentration in public primary schools located in priority investigation areas, with the aim of decreasing occupants' exposure to radon in public buildings where concentrations exceed the Canadian Federal guidelines (i.e. 200 Bq m(-3)). In addition, the association between radon levels, substratum geological characteristics and schools' structural characteristics were investigated. The results showed that radon concentrations measured in the 65 investigated schools are generally below the Federal guideline levels. Eleven schools (17 %) had at least one measurement above the Federal guideline, while one had a level above 600 Bq m(-3). On average, targeted schools' occupants are exposed to radon concentrations of 56 Bq m(-3). Although statistical analysis, which was limited by the sample size, did not show any link between aggregated radon measurements and geochemical or radiological signatures of investigated sites, the geological evidence that led to the choice of the studied regions remains relevant. 相似文献