全文获取类型
收费全文 | 1980篇 |
免费 | 164篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 24篇 |
综合类 | 2篇 |
化学工业 | 542篇 |
金属工艺 | 44篇 |
机械仪表 | 33篇 |
建筑科学 | 79篇 |
能源动力 | 72篇 |
轻工业 | 239篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 211篇 |
一般工业技术 | 394篇 |
冶金工业 | 51篇 |
原子能技术 | 36篇 |
自动化技术 | 415篇 |
出版年
2024年 | 1篇 |
2023年 | 18篇 |
2022年 | 38篇 |
2021年 | 65篇 |
2020年 | 51篇 |
2019年 | 45篇 |
2018年 | 62篇 |
2017年 | 73篇 |
2016年 | 68篇 |
2015年 | 78篇 |
2014年 | 104篇 |
2013年 | 160篇 |
2012年 | 137篇 |
2011年 | 221篇 |
2010年 | 147篇 |
2009年 | 135篇 |
2008年 | 126篇 |
2007年 | 86篇 |
2006年 | 88篇 |
2005年 | 79篇 |
2004年 | 58篇 |
2003年 | 63篇 |
2002年 | 45篇 |
2001年 | 24篇 |
2000年 | 20篇 |
1999年 | 29篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 23篇 |
1995年 | 6篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有2150条查询结果,搜索用时 46 毫秒
251.
Delgorge C Rosenberger C Poisson G Vieyres P 《IEEE transactions on medical imaging》2006,25(11):1502-1509
This paper presents a new tool for the evaluation of ultrasound image compression. The goal is to measure the image quality as easily as with a statistical criterion, and with the same reliability as the one provided by the medical assessment. An initial experiment is proposed to medical experts and represents our reference value for the comparison of evaluation criteria. Twenty-one statistical criteria are selected from the literature. A cumulative absolute similarity measure is defined as a distance between the criterion to evaluate and the reference value. A first fusion method based on a linear combination of criteria is proposed to improve the results obtained by each of them separately. The second proposed approach combines different statistical criteria and uses the medical assessment in a training phase with a support vector machine. Some experimental results are given and show the benefit of fusion. 相似文献
252.
Fatigue crack monitoring of riveted aluminium strap joints by Lamb wave analysis and acoustic emission measurement techniques 总被引:3,自引:0,他引:3
Sbastien Grondel Christophe Delebarre Jamal Assaad Jean-Pierre Dupuis Livier Reithler 《NDT & E International》2002,35(3)
Statistics show that fatigue crack development comes first and foremost as a damage source in aerospace metallic structures. Currently, widespread methods are available to inspect these structures, but they are quite time-consuming, costly and require the structural system to be idle. Next, attempts to develop damage detection integrated systems are paramount for the safety and cost of such structures. This paper describes an investigation into the feasibility of using an integrated system based on Lamb waves in order to assess the integrity of riveted aluminium joints during cyclical loading. In this experimental analysis, Lamb waves are excited and received outside the joint area using piezoelectric transducers coupled onto the plates. The detected damage is cracks in joint resulting from fatigue loading. The collected signals on the piezoelectric transducers are analysed using Hilbert transform and time–frequency analysis. It is shown that the final interpretation of Lamb wave analysis may provide a means of sizing the defects and following the crack development. In addition to that, an acoustic emission system is used jointly with the Lamb wave analysis in order to discuss results and damage development. Finally, it is demonstrated that both methods can work together and the results obtained are in good agreement. 相似文献
253.
99Tc- and 239Pu-Doped Glass Leaching Experiments: Residual Alteration Rate and Radionuclide Behavior
Séverine Rolland Magaly Tribet Christophe Jégou Véronique Broudic Magali Magnin Sylvain Peuget Thierry Wiss Arne Janssen Antoine Blondel Pierre Toulhoat 《International Journal of Applied Glass Science》2013,4(4):295-306
The long-term behavior of high-level nuclear glass subjected to alpha/beta radiation by long-life radionuclides must be investigated with respect to geological disposal. This study focuses on the effects of alpha and beta radiations on the chemical reactivity of R7T7 glass with pure water, mainly on the residual alteration rate regime. Glass specimens doped with 0.85 wt% 239PuO2 (α emitter) and 0.24 wt% 99TcO2 (β emitter) that simulate alpha and beta dose rate corresponding to long-term disposal conditions are leached under static conditions in argon atmosphere at 90°C, in initially pure water and at a high surface-area-to-volume ratio (S/V = 20/cm). The alteration rate is monitored by the release of glass alteration tracer elements (B, Na, and Li). Radiation effects on the leached glass and its gel network are characterized by SEM and TEM analyses. Plutonium and technetium releases are also measured by radiometry, and their chemical oxidation state is assessed by measuring the pH and reduction–oxidation potential of the leachates. The results do not highlight any significant effect of alpha/beta radiation on the residual alteration of these doped glasses. These observations are consistent with solid characterizations, which show that a protective layer can be formed under such irradiation fields. Under our experimental conditions (Eh~380 mV/SHE, pH90°C = 8–8.6), very low concentrations of soluble plutonium are measured in the leachate, indicating strong plutonium retention, whereas technetium performs as a soluble element and is not retained in the altered layer. 相似文献
254.
Maurin B Bayle B Piccin O Gangloff J de Mathelin M Doignon C Zanne P Gangi A 《IEEE transactions on bio-medical engineering》2008,55(10):2417-2425
In this paper, we present a novel robotic assistant dedicated to medical interventions under computed tomography scan guidance. This compact and lightweight patient-mounted robot is designed so as to fulfill the requirements of most interventional radiology procedures. It is built from an original 5 DOF parallel structure with a semispherical workspace, particularly well suited to CT-scan interventional procedures. The specifications, the design, and the choice of compatible technological solutions are detailed. A preclinical evaluation is presented, with the registration of the robot in the CT-scan. 相似文献
255.
Christophe M Courtin Katrien Swennen Willem F Broekaert Quirine Swennen Johan Buyse Eddy Decuypere Christiaan W Michiels Bart De Ketelaere Jan A Delcour 《Journal of the science of food and agriculture》2008,88(14):2517-2522
BACKGROUND: Arabinoxylan (AX)‐derived preparations have raised particular interest by the suggestion that they exert prebiotic properties. Therefore an in vivo experiment was conducted to study the effects of xylooligosaccharides (XOS), arabinoxylooligosaccharides (AXOS) and soluble AX (S‐AX) on several groups of gut bacteria of chickens. Chickens were fed a control diet or the same diet supplemented with 2.5 g kg?1 of XOS (average degree of polymerisation (avDP) of 3, average degree of arabinose substitution (avDS) of 0.09), wheat bran‐derived AXOS (avDP 9, avDS 0.34) or wheat endosperm alkali‐solubilised AX (S‐AX, avDP > 6000, avDS 0.5). RESULTS: All treatment groups showed an increase in the number of caecal bifidobacteria after 2 weeks of feeding (P < 0.05), while the treatments did not impact numbers of Enterobacteriaceae and aerobic lactobacilli in the caeca relative to the control. XOS led to a tremendous increase in caecal bifidobacteria counts (108 g?1 for the XOS treatment versus 103 g?1 for the control treatment) after only 1 week of supplementation, while AXOS and S‐AX led to similar strong increases in bifidobacteria counts after 2 weeks of supplementation. Addition of S‐AX to the diet, but not of AXOS or XOS, led to a significantly decreased (P < 0.05) body weight gain after 2 weeks of feeding relative to animals on the control diet, consistent with its known viscosity‐related antinutritive effects in chickens. CONCLUSION: Similar to XOS, AXOS selectively stimulate the presence of bifidobacteria in the caeca of chickens, establishing their bifidogenic effect as a first indicator for prebiotic potential. Copyright © 2008 Society of Chemical Industry 相似文献
256.
A new time-domain two-dimensional (2D) electromagnetic (EM) physical modelling of non-linear distributed semiconductor devices
has been developed. It is based on a numerical procedure which solves in a self consistent manner both Maxwell’s equations
and a macroscopic transport model based on the drift-diffusion approximation. The software can be run on a parallel computer.
It is based on finite-difference time-domain (FDTD) explicit schemes associated to the domain decomposition method. The millimetre-wave
travelling-wave IMPATT diode or Distributed IMPact ionisation and Avalanche and Transit Time (DIMPATT) diode is the non linear
test structure chosen to validate the model. RF simulations under amplification and CW oscillation operating modes have been
performed. The results presented in this paper consist on the one hand of results that can be qualitatively compared to previously
published theoretical works and on the other hand of features especially pointed out thanks to the new electromagnetic physical
model capabilities. 相似文献
257.
Dr. Pierre-Yves Geant Dr. Malika Kaci Dr. Jean-Pierre Uttaro Prof. Christian Périgaud Prof. Christophe Mathé 《ChemMedChem》2019,14(5):522-526
The synthesis and anti-HIV evaluation of hitherto unknown 3′-fluoro-5′-norcarbocyclic nucleoside phosphonates bearing adenine with modifications at the 4′ position (ethynyl, vinyl, ethyl, hydroxymethyl) is described. One of the synthesized compounds was found to be an inhibitor of HIV-1 replication, but with moderate efficiency relative to (R)-9-(2-phosphonylmethoxypropyl)adenine ((R)-PMPA, tenofovir), with no concomitant cytotoxicity. 相似文献
258.
Van der Meulen R Camu N Van Vooren T Heymans C De Vuyst L 《International journal of food microbiology》2008,124(1):27-33
The carbohydrate and aromatic amino acid metabolism of several species related to the human colon was investigated into more detail. Therefore, in vitro fermentations were performed, with different carbohydrate sources, during which several aromatic amino acids were added to the fermentation medium. Shifts in end-product formation in response to the available nutrients were observed for all strains tested. The major part of amino acid degradation occurred after depletion of the carbohydrates. Moreover, it was shown that Bifidobacterium strains are capable of degrading aromatic amino acids in the absence of carbohydrates. The excretion of certain intermediates of the aromatic amino acid metabolism was observed for a strain of Clostridium clostridioforme, after which they were metabolized again during a later stage of fermentation. This implies that cross-feeding on degradation products of aromatic amino acids, albeit within the same species, can occur in the human colon. 相似文献
259.
The present study describes the effects of glycerol, relative humidity (RH) and the minor components of corn flour on mechanical and thermal properties of native flour, defatted flour, and starch‐based materials. The kinetic of retrogradation for these different materials were dissimilar. For all samples, strain at break shows a maximum value as a function of RH followed by a decrease, explained by the appearance of water and glycerol clusters. Starch controls the mechanical properties of corn flour‐based material and their variations with temperature and humidity. Lipid and protein have negative effect on mechanical properties of thermoplastic flour toward starch but they did not have a plasticizing effect on the physicochemical behavior of the matrix. Tgs decreased as a result of water content increase. 相似文献
260.
The literature is reviewed on the formation and the structure of β-lactoglobulin and whey protein isolate (WPI) aggregates in aqueous solution induced by heating. The focus is on the effects of the pH and added salt. The use of β-lactoglobulin and WPI aggregates in cold-set gels, foams and emulsions, encapsulation, and films and coatings is also reviewed. 相似文献