全文获取类型
收费全文 | 609篇 |
免费 | 14篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 162篇 |
金属工艺 | 19篇 |
机械仪表 | 12篇 |
建筑科学 | 8篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 14篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 89篇 |
一般工业技术 | 148篇 |
冶金工业 | 17篇 |
原子能技术 | 8篇 |
自动化技术 | 124篇 |
出版年
2023年 | 4篇 |
2022年 | 23篇 |
2021年 | 25篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 28篇 |
2013年 | 56篇 |
2012年 | 42篇 |
2011年 | 59篇 |
2010年 | 31篇 |
2009年 | 30篇 |
2008年 | 38篇 |
2007年 | 20篇 |
2006年 | 22篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1974年 | 1篇 |
1969年 | 5篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有623条查询结果,搜索用时 31 毫秒
1.
Since the discovery in 1922 of 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl stable free radical (DPPH·), the chemistry of such open-shell compounds has developed continuously, allowing for both theoretical and practical advances in the free radical chemistry area. This review presents the important, general and modern aspects of the chemistry of hydrazyl free radicals and the science behind it. 相似文献
2.
Petre Badica Dan Batalu Mihail Burdusel Mihai A. Grigoroscuta Gheorghe V. Aldica Monica Enculescu Raluca A. Gabor Zhiyong Wang Ruoxuan Huang Peifeng Li 《Ceramics International》2018,44(9):10181-10191
Pristine and (SiC+Te)-added MgB2 powders, green and spark plasma sintered (SPS) compacts were investigated from the viewpoint of quasi-static and dynamic (Split-Hopkinson Pressure Bar, SHPB) compressive mechanical properties The amount of the additive (SiC+Te) was selected to be the optimum one for maximization of the superconducting functional parameters. Pristine and added MgB2 show very similar compressive parameters (tan δ, fracture strength, Vickers hardness, others) and fragment size in the SHPB test. However, for the bulk SPSed samples the ratio of intergranular to transgranular fracturing changes, the first one being stronger in the added sample. This is reflected in the quasi-static KIC that is higher for the added sample. Despite this result, sintered samples are brittle and have roughly similar fragmentation behavior as for brittle engineering ceramics. In the fragmentation process, the composite nature of our samples should be considered with a special focus on MgB2 blocks (colonies) that show the major contribution to fracturing. The Glenn-Chudnovsky model of fracturing under dynamic load provides the closest values to our experimental fragment size data. 相似文献
3.
This paper considers the estimation of the parameters of a linear discrete-time system from noise-perturbed input and output measurements. The conditions imposed on the system are fairly general. In particular, the input and output noises are allowed to be auto-correlated and they may be cross-correlated as well. The proposed method makes use of an instrumental variable (IV)-vector to produce a covariance matrix that is pre- and postmultiplied by some prechosen weights. The singular vectors of the so-obtained matrix possess complete information on the system parameters. A weighted subspace fitting (WSF) method is then applied to the aforementioned singular vectors to consistently estimate the parameters of the system. The IV-WSF technique suggested herein is noniterative and easy to implement, and has a small computational burden. The asymptotic distribution of its estimation errors is derived and the result is used to motivate the choice of the weighting matrix in the WSF step and also to predict the estimation accuracy. Numerical examples are included to illustrate the performance achievable by the method.This work has been supported by the Swedish Research Council of Engineering Sciences under contract 93-669 and by the Göran Gustafsson Foundation. 相似文献
4.
5.
Mats Cedervall Petre Stoica Randolph Moses 《Circuits, Systems, and Signal Processing》1997,16(3):349-362
We propose a new algorithm for estimating the parameters of damped, undamped, or explosive sinusoidal signals. The algorithm resembles the MODE algorithm, which is commonly used for direction of arrival estimation in the array signal processing field. It is derived as a natural approximation to an asymptotically (high-SNR) optimal parameter estimator and has excellent statistical accuracy. Nevertheless, it is computationally simple and easy to implement. Numerical examples are included to illustrate the performance of the proposed method.This work has been supported by the Swedish Research Council for Engineering Sciences (TFR). 相似文献
6.
Camelia Betianu Florentina A Caliman Maria Gavrilescu Igor Cretescu Corneliu Cojocaru Ioannis Poulios 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(11):1454-1465
BACKGROUND: Heterogeneous photocatalysis is influenced by a number of parameters involving synergistic effects; hence, an experimental strategy design that considers interactions between the main variables is needed. The response surface methodology was applied for the investigation of photodegradation of 20 mg L?1 Orange II in aqueous solutions and for optimization of color removal efficiency. Preliminary studies were performed to identify the parameters to be selected for optimization. RESULTS: The input variables considered for experimental design were: solution initial pH, oxidizing agent (H2O2) initial concentration and UV‐A irradiation time. The multivariate experimental design allowed the development of a quadratic response surface model to be used for the prediction of color removal efficiency over the full range of the experimental region. Under the optimum conditions established in the region of experimentation (pH = 6.9, [H2O2]0 = 183 mg L?1 and t = 32 min), a 100% color removal efficiency was obtained in experiments. CONCLUSIONS: It was found that the variables considered have important effects on color removal efficiency. The results demonstrate that the use of experimental design strategy is indispensable for successful investigation and adequate modeling of the process because the interdependence of the reaction parameters cannot be neglected. Copyright © 2008 Society of Chemical Industry 相似文献
7.
Sinuo Liu Xiaokun Wang Xiaojuan Ban Yanrui Xu Jing Zhou Jií Kosinka Alexandru C. Telea 《Computer Graphics Forum》2021,40(1):54-67
A major issue in smoothed particle hydrodynamics (SPH) approaches is the numerical dissipation during the projection process, especially under coarse discretizations. High‐frequency details, such as turbulence and vortices, are smoothed out, leading to unrealistic results. To address this issue, we introduce a vorticity refinement (VR) solver for SPH fluids with negligible computational overhead. In this method, the numerical dissipation of the vorticity field is recovered by the difference between the theoretical and the actual vorticity, so as to enhance turbulence details. Instead of solving the Biot‐Savart integrals, a stream function, which is easier and more efficient to solve, is used to relate the vorticity field to the velocity field. We obtain turbulence effects of different intensity levels by changing an adjustable parameter. Since the vorticity field is enhanced according to the curl field, our method can not only amplify existing vortices, but also capture additional turbulence. Our VR solver is straightforward to implement and can be easily integrated into existing SPH methods. 相似文献
8.
Popa Iolanda V. Burlacu Alexandru Gavrilescu Otilia Dranga Mihaela Prelipcean Cristina Cijevschi Mihai Cătălina 《Neural computing & applications》2021,33(21):14133-14146
Neural Computing and Applications - Colonoscopy is the “gold” standard for evaluating disease activity in ulcerative colitis (UC). An important area of research is finding a... 相似文献
9.
Bianca Stoean Dumitrita Rugina Monica Focsan Ana-Maria Craciun MÎdÎlina Nistor Tamas Lovasz Alexandru Turza Ioan-Dan Porumb Emese Gl Castelia Cristea Luminita Silaghi-Dumitrescu Simion Astilean Luiza Ioana Gaina 《International journal of molecular sciences》2021,22(6)
We report here the synthesis and structural characterization of novel cationic (phenothiazinyl)vinyl-pyridinium (PVP) dyes, together with optical (absorption/emission) properties and their potential applicability as fluorescent labels. Convective heating, ultrasound irradiation and mechanochemical synthesis were considered as alternative synthetic methodologies proficient for overcoming drawbacks such as long reaction time, nonsatisfactory yields or solvent requirements in the synthesis of novel dye (E)-1-(3-chloropropyl)-4-(2-(10-methyl-10H-phenothiazin-3-yl)vinyl)pyridin-1-ium bromide 3d and its N-alkyl-2-methylpyridinium precursor 1c. The trans geometry of the newly synthesized (E)-4-(2-(7-bromo-10-ethyl-10H-phenothiazin-3-yl)vinyl)-1-methylpyridin-1-ium iodide 3b and (E)-1-methyl-4-(2-(10-methyl-10H-phenothiazin-3-yl)vinyl)pyridin-1-ium tetrafluoroborate 3a′ was confirmed by single crystal X-ray diffraction. A negative solvatochromism of the dyes in polar solvents was highlighted by UV-Vis spectroscopy and explanatory insights were supported by molecular modeling which suggested a better stabilization of the lowest unoccupied molecular orbitals (LUMO). The photostability of the dye 3b was investigated by irradiation at 365 nm in different solvents, while the steady-state and time-resolved fluorescence properties of dye 3b and 3a′ in solid state were evaluated under one-photon excitation at 485 nm. The in vitro cytotoxicity of the new PVP dyes on B16-F10 melanoma cells was evaluated by WST-1 assay, while their intracellular localization was assessed by epi-fluorescence conventional microscopy imaging as well as one- and two-photon excited confocal fluorescence lifetime imaging microscopy (FLIM). PVP dyes displayed low cytotoxicity, good internalization inside melanoma cells and intense fluorescence emission inside the B16-F10 murine melanoma cells, making them suitable staining agents for imaging applications. 相似文献
10.