全文获取类型
收费全文 | 237篇 |
免费 | 17篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 53篇 |
金属工艺 | 1篇 |
机械仪表 | 4篇 |
建筑科学 | 18篇 |
能源动力 | 12篇 |
轻工业 | 22篇 |
水利工程 | 5篇 |
无线电 | 21篇 |
一般工业技术 | 42篇 |
冶金工业 | 19篇 |
原子能技术 | 2篇 |
自动化技术 | 47篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 18篇 |
2012年 | 20篇 |
2011年 | 30篇 |
2010年 | 16篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有254条查询结果,搜索用时 46 毫秒
41.
TW Breen T Shapiro B Glass D Foster-Payne NE Oriol 《Canadian Metallurgical Quarterly》1993,77(5):919-924
The effectiveness of two epidural analgesic regimens on the ability to ambulate was compared in women in labor by a prospective, randomized, double-blind design. One group of patients received epidural fentanyl, a 75-micrograms bolus and an infusion of fentanyl 2.5 micrograms/mL at 15 mL/h (FENT, n = 53). A second group received ultra low-dose bupivacaine (0.04%), epinephrine (1.7 micrograms/mL), and fentanyl (1.7 micrograms/mL) (BEF, n = 77), a 15-mL bolus followed by an infusion at 15 mL/h. Adequate analgesia was rapidly obtained in 90.6% of patients in the FENT group and 92.2% of patients in the BEF group (P = 0.89). Seventy percent of patients in the FENT group ambulated versus 68% in the other group. The BEF mixture provided analgesia of longer duration (287 +/- 171 min versus 156 +/- 72 min, P = 0.0001). The number of patients delivering during administration of only their study drug (without needing higher doses of local anesthetics) was 52% for BEF and 21% for FENT (P = 0.0005). Hip flexion weakness precluding ambulation occurred in 17% (P = 0.002) of BEF patients and orthostatic hypotension in 9% (P = 0.08). Neither problem occurred in FENT patients. Neonatal outcome was similar in both groups. Approximately 70% of women receiving epidural analgesia with fentanyl or ultra low-dose bupivacaine, epinephrine, and fentanyl may ambulate safely during labor. 相似文献
42.
Rivet B. Souloumiac A. Attina V. Gibert G. 《IEEE transactions on bio-medical engineering》2009,56(8):2035-2043
A brain-computer interface (BCI) is a communication system that allows to control a computer or any other device thanks to the brain activity. The BCI described in this paper is based on the P300 speller BCI paradigm introduced by Farwell and Donchin. An unsupervised algorithm is proposed to enhance P300 evoked potentials by estimating spatial filters; the raw EEG signals are then projected into the estimated signal subspace. Data recorded on three subjects were used to evaluate the proposed method. The results, which are presented using a Bayesian linear discriminant analysis classifier, show that the proposed method is efficient and accurate. 相似文献
43.
Andreas P. Kyriacou Leonel Muinelo-Gallo Oriol Roca-Sagalés 《Papers in Regional Science》2015,94(1):89-107
In this paper we consider how government quality mediates the relationship between fiscal decentralization and regional disparities. Previous work has argued that fiscal decentralization has the potential to reduce income differences across regions but that this potential may not be realized because of governance problems associated with sub-national authorities. Our empirical evidence based on a sample of 24 OECD countries over the period 1984 to 2006 lends a measure of support to this idea. We find that fiscal decentralization promotes regional convergence in high government quality settings but, worryingly, it leads to wider regional disparities in countries with poor governance. 相似文献
44.
Matthias Schulz Frank Balzer Dorothea Scheunemann Oriol Arteaga Arne Lützen Stefan C. J. Meskers Manuela Schiek 《Advanced functional materials》2019,29(16)
A facile route to soft matter self‐powered bulk heterojunction photodiode detectors sensitive to the circular polarization state of light is shown based on the intrinsic excitonic circular dichroism of the photoactive layer blend. As light detecting materials, enantiopure semiconducting small molecular squaraine derivates of opposite handedness are employed. Via Mueller matrix ellipsometry, the circular dichroism is proven to be of H‐type excitonic nature and not originating from mesoscopic structural ordering. Within the green spectral range, the photodiodes convert circular polarized light into a handedness‐dependent photocurrent with a maximum dissymmetry factor of ±0.1 corresponding to 5% overall efficiency for the polarization discrimination under short circuit conditions. On the basis of transfer matrix optical simulations, it is rationalized that the optical dissymmetry fully translates into a photocurrent dissymmetry for ease of device design. Thereby, the photodiode's ability to efficiently distinguish between left and right circularly polarized light without the use of external optical elements and voltage bias is demonstrated. This allows a straightforward and sustainable future design of flexible, lightweight, and compact integrated platforms for chiroptical imaging and sensing. 相似文献
45.
Polymer foams are commonly used in the protective packaging of fragile products. Cushion curves are commonly used within the packaging industry to characterize a foam's impact performance. These curves are two-dimensional representations of the deceleration of an impacting mass versus static stress. Cushion curves are currently generated from exhaustive experimental test data. This study represents the first time that the physics of the mass-cushion impact have been analysed by modelling the foam as nonlinear, continuous rod. Using a single mode of vibration and excluding the effects of damping, the maximum displacement during the impact can be obtained from a polynomial describing the maximum elastic energy in the foam. The displacements can be used to recover the amplitude of the deceleration shock pulse. Numerical and analytical analysis of the model with damping is considered in its ability to predict the shock pulse shape, duration, and amplitude at various static stresses, foam thickness, and drop heights as compared with experimental data. Furthermore, both the analytical and numerical results agree and are primarily within the expected lab-to-lab variability of 18% documented in ASTM D1596 - Standard Test Method for Dynamic Shock Cushioning Characteristics of Packaging Material. 相似文献
46.
Davide Blasi Nerea Gonzalez-Pato Xavier Rodriguez Rodriguez Iñigo Diez-Zabala Sumithra Yasaswini Srinivasan Núria Camarero Oriol Esquivias Mònica Roldán Judith Guasch Anna Laromaine Pau Gorostiza Jaume Veciana Imma Ratera 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(32):2370250
Ratiometric fluorescent nanothermometers with near-infrared emission play an important role in in vivo sensing since they can be used as intracellular thermal sensing probes with high spatial resolution and high sensitivity, to investigate cellular functions of interest in diagnosis and therapy, where current approaches are not effective. Herein, the temperature-dependent fluorescence of organic nanoparticles is designed, synthesized, and studied based on the dual emission, generated by monomer and excimer species, of the tris(2,4,6-trichlorophenyl)methyl radical (TTM) doping organic nanoparticles (TTMd-ONPs), made of optically neutral tris(2,4,6-trichlorophenyl)methane (TTM-αH), acting as a matrix. The excimer emission intensity of TTMd-ONPs decreases with increasing temperatures whereas the monomer emission is almost independent and can be used as an internal reference. TTMd-ONPs show a great temperature sensitivity (3.4% K−1 at 328 K) and a wide temperature response at ambient conditions with excellent reversibility and high colloidal stability. In addition, TTMd-ONPs are not cytotoxic and their ratiometric outputs are unaffected by changes in the environment. Individual TTMd-ONPs are able to sense temperature changes at the nano-microscale. In vivo thermometry experiments in Caenorhabditis elegans (C. elegans) worms show that TTMd-ONPs can locally monitor internal body temperature changes with spatio-temporal resolution and high sensitivity, offering multiple applications in the biological nanothermometry field. 相似文献
47.
The production of a lead glaze with galena: Thermal transformations in the PbS–SiO2 system
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Roberta Di Febo Judit Molera Trinitat Pradell Joan C. Melgarejo Josep Madrenas Oriol Vallcorba 《Journal of the American Ceramic Society》2018,101(5):2119-2129
Galena, also known as PbS, was widely used in the production of lead glazes from the beginning of the 18th century to the second half of the 20th century. Although the PbO‐SiO2 system has been studied for years, the PbS–SiO2 phase diagram, involved in the formation of a glaze with galena, has not yet been investigated. Temperature transformations for the system 75 wt% PbS‐25 wt% SiO2 are investigated in a high‐temperature resolved X‐ray diffraction experiment with synchrotron radiation and compared to those of the equivalent system 70 wt% PbO‐30 wt% SiO2. Lanarkite, PbO·PbSO4, is the phase predominantly formed as soon as galena decomposes during the heating. The results show that the system melts at a temperature higher than the PbO–SiO2 system, but far lower than those expected for the PbO–PbSO4–PbS system. A historical misfired lead glaze produced with galena is also studied. The presence of galena, lanarkite, and mattheddleite, Pb10(SiO4)3.5(SO4)2Cl2, is determined and discussed in terms of the composition of the galena mineral used and the firing conditions in light of the high‐temperature transformations previously obtained. 相似文献
48.
The current approach of the biological treatment of acid mine drainage by means of a passive remediation system involves the choice of an appropriate organic substrate as electron donor for sulphate reducers. Nowadays this selection is one of the critical steps in the performance of such treatment, as this depends to a great extent on the degradability of the organic substrate. Thus, a prior characterisation of the organic substrate predicting its biodegradability would be desirable before embarking on an extensive large-scale application. The aim of this study was to correlate the chemical composition (lignin content) of four different natural organic substrates (compost, sheep and poultry manures, oak leaf) and their capacity to sustain bacterial activity in an attempt to predict biodegradation from chemical characterisation. The results showed that the lower the content of lignin in the organic substrate, the higher its biodegradability and capacity for developing bacterial activity. Of the four organic materials, sheep and poultry manures and oak leaf evolved reducing conditions and sustained active sulphidogenesis, which coupled with the decrease in sulphate concentration indicated bacterial activity. Sheep manure was clearly the most successful organic material as electron donor (sulphate removal >99%), followed by poultry manure and oak leaf (sulphate removal of 80%). Compost appeared to be too poor in carbon to promote sulphate-reducing bacteria activity by itself. Column experiments emphasised the importance of considering the residence time as a key factor in the performance of continuous systems. With a residence time of 0.73 days, sheep manure did not promote sulphidogenesis. However, extending residence time to 2.4 and 9.0 days resulted in an increase in the sulphate removal to 18% and 27%, respectively. 相似文献
49.
Johnson AC Aerni HR Gerritsen A Gibert M Giger W Hylland K Jürgens M Nakari T Pickering A Suter MJ Svenson A Wettstein FE 《Water research》2005,39(1):47-58
The effluent of 17 sewage treatment works (STW) across Norway, Sweden, Finland, The Netherlands, Belgium, Germany, France and Switzerland was studied for the presence of estradiol (E2), estrone (E1), ethinylestradiol (EE2) and nonylphenol (NP). Treatment processes included primary and chemical treatment only, submerged aerated filter, oxidation ditch, activated sludge (AS) and combined trickling filter with activated sludge. The effluent strength ranged between 87 and 846 L/PE (population equivalent), the total hydraulic retention time (HRT) ranged between 4 and 120 h, sludge retention time (SRT) between 3 and 30 d, and water temperature ranged from 12 to 21 °C. The highest estrogen values were detected in the effluent of the STW which only used primary treatment (13 ng/L E2 and 35 ng/L E1) and on one occasion in one of the STW using the AS system (6.5 ng/L E2, 50.5 ng/L E1, but on three other occasions the concentrations in this STW were at least a factor of 6 lower). For the 16 STW employing secondary treatment E2 was only detected in the effluent of six works during the study period (average 0.7-5.7 ng/L). E1 was detected in the effluent of 13 of the same STW. The median value for E1 for the 16 STW with secondary treatment was 3.0 ng/L. EE2 was only detected in two STW (1.1, <0.8-2.8 ng/L). NP could be detected in the effluent of all 14 STW where this measurement was attempted, with a median of 0.31 μg/L and values ranging from 0.05 to 1.31 μg/L. A comparison of removal performance for E1 was carried out following prediction of the probable influent concentration. A weak but significant (α<5%) correlation between E1 removal and HRT or SRT was observed. 相似文献
50.
Dynamics of solutes and dissolved oxygen in shallow urban groundwater below a stormwater infiltration basin 总被引:4,自引:0,他引:4
Artificial recharge of urban aquifers with stormwater has been used extensively in urban areas to dispose of stormwater and compensate for reduced groundwater recharge. However, stormwater-derived sediments accumulating in infiltration beds may act as a source of dissolved contaminants for groundwater. Concentrations of hydrocarbons, heavy metals, nutrients and dissolved oxygen (DO) were monitored at multiple depths in shallow groundwater below a stormwater infiltration basin retaining large amounts of contaminated organic sediments. Multilevel wells and multiparameter loggers were used to examine changes in groundwater chemistry occurring over small spatial and temporal scales. Rainfall events produced a plume of low-salinity stormwater in the first 2 m below the groundwater table, thereby generating steep vertical physico-chemical gradients that resorbed during dry weather. Heavy metals and hydrocarbons were below reference concentrations in groundwater and aquifer sediments, indicating that they remained adsorbed onto the bed sediments. However, mineralization of organic sediments was the most probable cause of elevated concentrations of phosphate and DOC in groundwater. DO supply in groundwater was severely limited by bed respiration which increased with temperature. Cold winter stormwater slightly re-oxygenated groundwater, whereas warm summer stormwater lowered DO concentrations in groundwater. Among several results provided by this study, it is recommended for management purposes that infiltration practices should minimize the contact between inflow stormwater and organic sediments retained in infiltration basins. 相似文献