全文获取类型
收费全文 | 1818篇 |
免费 | 55篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 27篇 |
综合类 | 2篇 |
化学工业 | 402篇 |
金属工艺 | 80篇 |
机械仪表 | 43篇 |
建筑科学 | 29篇 |
矿业工程 | 1篇 |
能源动力 | 103篇 |
轻工业 | 88篇 |
水利工程 | 17篇 |
石油天然气 | 8篇 |
无线电 | 227篇 |
一般工业技术 | 365篇 |
冶金工业 | 184篇 |
原子能技术 | 21篇 |
自动化技术 | 279篇 |
出版年
2023年 | 14篇 |
2022年 | 24篇 |
2021年 | 31篇 |
2020年 | 18篇 |
2019年 | 35篇 |
2018年 | 41篇 |
2017年 | 36篇 |
2016年 | 42篇 |
2015年 | 35篇 |
2014年 | 42篇 |
2013年 | 110篇 |
2012年 | 65篇 |
2011年 | 103篇 |
2010年 | 84篇 |
2009年 | 78篇 |
2008年 | 78篇 |
2007年 | 78篇 |
2006年 | 67篇 |
2005年 | 55篇 |
2004年 | 29篇 |
2003年 | 46篇 |
2002年 | 40篇 |
2001年 | 33篇 |
2000年 | 30篇 |
1999年 | 36篇 |
1998年 | 71篇 |
1997年 | 60篇 |
1996年 | 35篇 |
1995年 | 34篇 |
1994年 | 43篇 |
1993年 | 26篇 |
1992年 | 36篇 |
1991年 | 37篇 |
1990年 | 21篇 |
1989年 | 24篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 26篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有1876条查询结果,搜索用时 15 毫秒
101.
Summary The present paper describes the grafting of vinyl monomers onto cellulose nitrate in non-aqueous medium using benzoyl peroxide as a catalyst. The complete separation of the homopolymers and graft copolymer was carried out by selective solvent extraction. The graft copolymer was characterized by IR spectra. The GPC was used as a technique to differentiate between homopolymer, polymer mixture, polyblend, and graft copolymer. 相似文献
102.
103.
104.
Srinivasan S. DeLiang Wang 《IEEE transactions on audio, speech, and language processing》2007,15(7):2130-2140
Recently, several algorithms have been proposed to enhance noisy speech by estimating a binary mask that can be used to select those time-frequency regions of a noisy speech signal that contain more speech energy than noise energy. This binary mask encodes the uncertainty associated with enhanced speech in the linear spectral domain. The use of the cepstral transformation smears the information from the noise dominant time-frequency regions across all the cepstral features. We propose a supervised approach using regression trees to learn the nonlinear transformation of the uncertainty from the linear spectral domain to the cepstral domain. This uncertainty is used by a decoder that exploits the variance associated with the enhanced cepstral features to improve robust speech recognition. Systematic evaluations on a subset of the Aurora4 task using the estimated uncertainty show substantial improvement over the baseline performance across various noise conditions. 相似文献
105.
Containerless tube extrusion has been investigated with commerically pure titanium at room temperature and a strain rate of 0.07 s-1 using 20 conical dies of five different strains and four different angles with MoS2 lubricant. Theoretical punch pressures have been calculated using appropriate equations from slab analysis of the process and compared with experimentally determined punch pressures. It is found that there exists an optimum angle at which the punch pressure is the least at a given strain. 相似文献
106.
P.-Y. Chen R. Srinivasan G. Fedosejevs J. R. Kiniry 《International journal of remote sensing》2013,34(17):3403-3412
Normalized Difference Vegetation Index (NDVI) data derived from Advanced Very High Resolution Radiometer (AVHRR) data are influenced by cloud contamination, which is common in individual AVHRR scenes. Maximum value compositing (MVC) of NDVI data has been employed to minimize cloud contamination. Two types of weekly NDVI composites were built for crop seasons in summer: one from all available AVHRR data (named the traditional NDVI composite) and the other from solely cloud-free AVHRR data (named the conditional NDVI composite). The MVC method was applied to both composites. The main objective of this study was to compare the two types of NDVI composites using Texas data. The NDVI seasonal profiles produced from the conditional NDVI composites agreed with the field measured leaf area index (LAI) data, reaching maximum values at similar times. However, the traditional NDVI composites showed irregular patterns, primarily due to cloud contamination. These study results suggest that cloud detection for individual AVHRR scenes should be strongly recommended before producing weekly NDVI composites. Appropriate AVHRR data pre-processing is important for composite products to be used for short-term vegetation condition and biomass studies, where the traditional NDVI composite data do not eliminate cloud-contaminated pixels. In addition, this study showed that atmosphere composition affected near-infrared reflectance more than visible reflectance. The near-infrared reflectance was increasingly adjusted through atmospheric correction. 相似文献
107.
Pijush Kanti Chattopadhyay Srinivasan Praveen Narayan Chandra Das Santanu Chattopadhyay 《Polymer Engineering and Science》2013,53(5):923-930
Influence of organic modifying agent of clay on dispersion, distribution, hybrid microstructure formation, and associated performance properties of epoxidized natural rubber‐based composites was evaluated. Binary and ternary composites of carbon black (CB) and two organomodified layered silicates (i.e., nanomer I30E and Cloisite 30B) were prepared and characterized based on small angle X‐ray scattering, transmission electron microscopy, hydrodynamic swelling, tensile measurement, and dynamic mechanical analyses. Greater extent of exfoliation and “nanounit” formation was noted in ternary composites containing nanomer I30E, which was reflected in higher interfacial roughness (ds = 2.82) and lower radius of gyration (Rg = 205 Å). Morphological observations suggested higher nanomer I30E–CB interactions than that of Cloisite 30B–CB. The interplatelet distance in Cloisite 30B (d = 1.83 nm) stacks was lower than that of nanomer I30E (d = 2.26 nm). These two factors jointly contributed in higher breakdown of nanomer I30E stacks by CB than that of Cloisite 30B stacks. Greater exfoliation and nanounit formation in I30E–CB‐filled nanocomposite was also reflected in increased degree of crosslinking (n = 20 × 10?5%), tensile modulus/strength, half height width of damping peak (20.3°C), and filler effectiveness (C = 0.33). POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers 相似文献
108.
Packed‐bed reactor experimentation is a key tool used in order to formulate chemical kinetics. The chemical species equation and overall methodology are described for a one‐dimensional pseudo‐homogeneous packed‐bed reactor model useful for experimental calibration of chemical kinetics. Over the history of simulation development for this equation there exist numerous different effective diffusivity correlations. The included historical review and parametric study of these correlations help to determine the correct choice based on numerical simplicity and model outcomes. A subsequent review paper describes the energy equation and effective thermal conductivity correlations while coming to a generalized conclusion regarding modeling efforts. 相似文献
109.
Chandrasekar Saravanan Srinivasan Palaniappan Valaboju Akhila Sunkara Sakunthala Madhavendra Prakriti Ranjan Bangal 《应用聚合物科学杂志》2011,120(4):2421-2427
Sulfonated‐p‐cresol (SPC) was used as novel dopant for the first time in the synthesis of polyaniline in 3D nanofiber networks (PANI‐3D). Polyaniline in 3D nanofiber network was prepared using organic solvent soluble benzoyl peroxide as oxidizing agent in presence of SPC and sodium lauryl sulfate (SLS) surfactant via inverted emulsion polymerization pathway. The influence of synthesis conditions such as the concentration of the reactants, stirring/static condition, and temperature etc., on the properties and formation of polyaniline nanofiber network were investigated. Polyaniline in 3D nanofiber network with 40–160 nm (diameter), high yield (134 wt % with respect to aniline used), and reasonably good conductivity (0.1 S/cm) was obtained in 24 h time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
110.
A micromechanically motivated model is proposed to capture nonlinear effects and switching phenomena present in ferroelectric
polycrystalline materials. The changing remnant state of the ferroelectric crystal is accounted for by means of so-called
back fields—such as back stresses—to resist or assist further switching processes in the crystal depending on the local loading
history. To model intergranular effects present in ferroelectric polycrystals, the computational model elaborated is embedded
into a mixed polygonal finite element approach, whereby an individual ferroelectric grain is represented by one single irregular
polygonal finite element. This computationally efficient coupled simulation framework is shown to reproduce the specific characteristics
of the responses of ferroelectric polycrystals under complex electromechanical loading conditions in good agreement with experimental
observations. 相似文献