全文获取类型
收费全文 | 891篇 |
免费 | 87篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 979篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 33篇 |
2021年 | 128篇 |
2020年 | 47篇 |
2019年 | 44篇 |
2018年 | 38篇 |
2017年 | 42篇 |
2016年 | 49篇 |
2015年 | 37篇 |
2014年 | 55篇 |
2013年 | 66篇 |
2012年 | 87篇 |
2011年 | 61篇 |
2010年 | 41篇 |
2009年 | 50篇 |
2008年 | 45篇 |
2007年 | 27篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有979条查询结果,搜索用时 15 毫秒
81.
82.
Lev A. Slobozhanin Valentina M. Shevtsova J. Iwan D. Alexander José Meseguer José M. Montanero 《Microgravity science and technology》2012,24(2):65-77
This paper reviews the dynamics of breaking or oscillating axisymmetric liquid bridges, and estimates of the energy which
is needed to break a liquid bridge. We consider a liquid bridge spanning two coaxial equal disks with sharp edges and held
by surface-tension forces. The liquid volume is assumed to be conserved under perturbations, and the contact lines are pinned
to the disk edges. The perturbations are finite and axisymmetric. An analysis is based on the one-dimensional models previously
used in capillary jet theory and last several decades for study a liquid bridge dynamics. According to the scientific project
JEREMI (Japanese and European Research Experiment on Marangoni Instabilities), the first stage of the space experiment on
ISS will involve an isothermal liquid bridge with a gas blowing parallel to the axial direction of the bridge. The geometry
corresponds to a cylindrical volume liquid bridge coaxially placed into an outer cylinder with solid walls. The gas enters
the annular duct bounded by the outer cylinder and the internal system consisting of supporting vertical rods and the liquid
bridge. Considering that the bridge is small (the rod’s radii are 3 mm) and the gas velocity is typically (0.25 ÷ 0.37) m/s,
the perturbations cannot be considered small. Thus, one may assume that the amplitude of the liquid bridge perturbations is
sufficiently large that departures from linearity must be considered. 相似文献
83.
Carlo Ricciardi Giancarlo Canavese Riccardo Castagna Gabriella Digregorio Ivan Ferrante Simone L. Marasso Alessandro Ricci Valentina Alessandria Kalliopi Rantsiou Luca S. Cocolin 《Food and Bioprocess Technology》2010,3(6):956-960
The micro- and nano-technologies coupled with a deep knowledge of organic/inorganic interfaces guarantee an exceptional sensitivity
and specificity of the sensor, while the lab-on-a-chip platform reduces assay times and limits sampling and/or sample preparation,
providing compact and portable objects. Therefore, the development of innovative biosensors such as antibody-immobilized microcantilevers
can overcome the evident limits of nowadays technologies, such as time consuming, expensiveness, difficult automation, low
sensitivity, accuracy, and precision for quantitative methods. The present study proposes two device designs for the detection
of food pathogens, exploiting an antibody-immobilized microcantilever biosensors, a novel class of mass detectors. For the
first one, we integrated the mechanical sensors on a microfluidic platform (lab-on-a-chip) to perform online analysis, directly
in liquid environment. We showed that our portable biosensors could easily detect the presence of pathogenic bacteria such
as Salmonella enterica serotype enteritidis in concentration 105 cfu/mL in just 40 min, without any enrichment and/or sample preparation. To increase the mass sensitivity of our analysis,
we also fabricated microstructures optimized for vibrating in vacuum environment. Using a dip-and-dry technique, we showed
that, in such configuration, the experimental limit of detection is as low as 103 cfu/mL. Due to the extremely small volumes needed, our biosensors operating in vacuum have the potentiality of detecting
the presence or absence of a single cell. 相似文献
84.
Valentina E. Smirnova Iosif V. Gofman Vladimir E. Yudin Irina P. Dobrovolskaya Alexander N. Shumakov Andrey L. Didenko Valentine M. Svetlichnyi Ellen Wachtel Rinat Shechter Hannah Harel Gad Marom 《Polymer Engineering and Science》2009,49(2):217-222
The solid state crystallization in drawn thermoplastic polyimide films is studied as a function of draw ratio (DR) under the effect of vapor grown carbon fiber nanoinclusions. The nucleating effect of the nanoinclusions coupled with the orientation effect of drawing generates a unique orientated layered lamellar structure, characteristic of smectic‐like mesophase. The degree of draw induced orientated crystallization increases with the content of nanoinclusions and with the DR, and is reflected in the mechanical behavior of the film. Generally, the Young's modulus and the yield point of the drawn crystalline films in the drawing direction are significantly higher compared with the noncrystalline counterparts. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers 相似文献
85.
Alessandro Bedini Valentina Zanolli Sandro Zanardi Ugo Bersellini Enrico Dalcanale Michele Suman 《Food Analytical Methods》2013,6(1):17-27
The food industry has a direct interest into bitter-tasting substances either for the identification of negative off-flavors or for the monitoring of a desired organoleptic quality. A rapid technique, based on Fourier transform-near infrared (FT-NIR) spectroscopy and able to detect taste molecular markers in bakery commodities, was developed, focusing the attention on biscuits category. Xanthines (caffeine, theobromine, and theophylline) and polyphenols (catechins and epicathechins), considered as mainly responsible for the bitter-taste of coffee\cocoa\chocolate based products, were firstly checked using a confirmatory liquid chromatography (LC)-ESI\mass spectrometry (MS)-MS procedure after hot methanol–water extraction. Correspondent data were used for the calibration of the FT-NIR through PLS regression. Values of the standard errors of prediction (lower than 10 %) were comparable to the values of the standard errors of cross-validation. Coefficients of determination indicated a good predictive power in the calibration model (R 2 xanthines?=?0.97, R 2 polyphenols?=?0.96) and a satisfying discriminating power among different contents in the validation models (R 2 xanthines?=?0.96, R 2 polyphenols?=?0.96). A testing phase on the generated model was executed by a comparison of LC-MS and sensory panel data with FT-NIR responses recorded on unknown biscuits: differences between found and predicted levels were generally below 5 % and the best predictability was achievable in chocolate-based biscuits. This methodology is able to work directly on solid products, has the potential to be expanded on other categories of gustative molecular markers (like sugars) and can be conceived as applicable for a routine control of a standardized bitter taste quality in a real industrial production. 相似文献
86.
Ilona BOBEK Dehua GONG Massimo DE CAL Dinna CRUZ Chang Y. CHIONH Mikko HAAPIO Sachin S. SONI Federico NALESSO Paolo LENTINI Francesco GARZOTTO Valentina CORRADI Claudio RONCO 《Hemodialysis international. International Symposium on Home Hemodialysis》2010,14(3):302-307
Neutrophil gelatinase‐associated lipocalin (NGAL) protein is an early biomarker for acute kidney injury (AKI). It is unknown if extracorporeal therapies (EC) have an effect on circulating NGAL levels. This study was designed to describe the kinetics of NGAL molecule in different EC techniques and to evaluate NGAL clearance in different operational conditions. A mock hemofiltration (HF) and hemoperfusion (HP) setup was used. NGAL was added to the blood reservoir and then measured at 30‐minute intervals from arterial, venous, and ultrafiltrate (UF) lines. Removal kinetics and NGAL sieving coefficient were calculated. In our experiments, baseline NGAL concentration averaged 452 μg/L. There was a consistent downward trend throughout the experiment. NGAL concentration in the UF was between 80 and 90 μg/L, though it showed a slight increase in the second hour. The sieving coefficient of NGAL ranged from 0.2 to 0.4 during HF and it appeared to increase with time, suggesting an initial effect of membrane adsorption. HP proved clearly that there was adsorption of NGAL by the membrane and the point of saturation occured at approximately 60 minutes from the start of circulation. Our evaluation demonstrates that NGAL can be adsorbed and ultrafiltrated with polysulfone membranes. This should be taken into consideration when using NGAL as an AKI biomarker in patients undergoing EC circulation. 相似文献
87.
Antonio Cataliotti Valentina Cosentino Alessandro Lipari Salvatore Nuccio Danilo Serazio 《Measurement》2013
This paper is focused on the use of data acquisition boards (DAQs) for the development of high accuracy PC-based instruments for the measurements of electrical power. The proposed systems are simple, portable and low cost because they are based on commercial data acquisition boards (DAQs) connected to a common personal computer. Data processing is carried out by a commercial software based on an interpolating windowed FFT. In the paper it is shown how the voltage can be sensed directly, thanks to the DAQ input range, thus avoiding expensive voltage dividers. The set up of the DAQs-based solutions is described and the evaluation of their metrological features is made by means of a comparison with the Italian power primary standard, which was built at INRIM with a complex solution and expensive with two high precision digital voltmeters. 相似文献
88.
Giulio Giovannetti Francesca Frijia Simona Attanasio Luca Menichetti Valentina Hartwig Nicola Vanello Jan Henrik Ardenkjaer-Larsen Daniele De Marchi Vincenzo Positano Rolf Schulte Luigi Landini Massimo Lombardi Maria Filomena Santarelli 《Measurement》2013
Hyperpolarized 13C magnetic resonance spectroscopy in pig models enables cardiac metabolism assessment and provides a powerful tool for heart physiology studies, although the low molar concentration of derivate metabolites gives rise to technological limitations in terms of data quality. The design of dedicated coils capable of providing large field of view with high Signal-to-Noise Ratio (SNR) data is of fundamental importance. 相似文献
89.
Despite recent progress, the production costs for renewable electricity remain above those for conventional power. Expectations of continuous reductions in production costs, typically underpin governments' policies for financial support. They often draw on the technology-focused versions of the Experience Curve model. This paper discusses how national-contextual factors also have a strong influence on production costs, such as geographic, infrastructural, institutional, and resource factors. As technologies mature, and as they reach significant levels of diffusion nationally, sustained increases in production costs might be recorded, due to these nationally contextual factors, poorly accounted for in policy-making decisions for price support. The paper suggests an analytical framework for a more comprehensive understanding of production costs. Based on this, it recommends that the evolution of specific cost levels and factors be monitored to locate ‘sources of changes’. The paper also suggests policy instruments that governments may use to facilitate cost decreases, whenever possible. The application of the framework is illustrated for the diffusion of wind power in Spain during the past three decades. 相似文献
90.
Valentina M. Shevtsova D. E. Melnikov J. C. Legros 《Microgravity science and technology》2003,14(2):33-40
The effects of residual accelerations have been studied by using three-dimensional modeling of the flow in a rectangular cell
filled with a liquid, Pr=20, the walls of which were kept at different temperatures. The system was subjected to an acceleration
field, which can be decomposed into two parts: a steady component and another one which varies slowly with time, the frequency
is about f0≈10−3 Hz. The convective heat transport and flow characteristics are discussed for different parameters of g-jitter. The high and
low frequency modulation of a sinusoidal g-jitter is discussed. To capture many of the essential characteristics of buoyancy-induced
convection a new approach is suggested, which was developed based on the observation of the trajectories of tracer particles.
On the one hand, it is a typical way to record the flow in experiments. On the other hand, creating database of different
types of trajectories gives the possibility to solve the inverse problem. The shape of the trajectory depends on the g-jitter
parameters. It is shown that for slow convective motions the tracer particles perform loops along trajectory due to g-jitter
with low frequencies, and the additional high frequencies only cause trembling of the shape of these loops. Taking the experimentally
recorded trajectories of tracer particles and comparing with those in the database, one can draw a conclusion about the amplitude
and direction of the resulting gravity vector during the experiment. 相似文献