全文获取类型
收费全文 | 428篇 |
免费 | 22篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 95篇 |
金属工艺 | 17篇 |
机械仪表 | 6篇 |
建筑科学 | 3篇 |
能源动力 | 17篇 |
轻工业 | 9篇 |
无线电 | 130篇 |
一般工业技术 | 103篇 |
冶金工业 | 25篇 |
原子能技术 | 1篇 |
自动化技术 | 36篇 |
出版年
2023年 | 11篇 |
2022年 | 11篇 |
2021年 | 19篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 18篇 |
2011年 | 24篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 22篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 25篇 |
1984年 | 8篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有450条查询结果,搜索用时 15 毫秒
1.
Manesh K.M. Gopalan A.I. Kwang-Pill Lee Santhosh P. Kap-Duk Song Duk-Dong Lee 《Nanotechnology, IEEE Transactions on》2007,6(5):513-518
A nanofibrous sensor for ammonia gas is fabricated by electrospinning the composite of poly(diphenylamine) (PDPA) with poly(methyl methacrylate) (PMMA) onto the patterned interdigit electrode. The composite electrospun membrane shows interconnected fibrous morphology. Functional groups in PDPA and the high active surface area of the fibrous membrane make the device detect a lower concentration of ammonia with a good reproducibility. The sensing capability of the device is studied by monitoring the changes in resistance of the membrane with different concentrations of ammonia. The changes in resistance of the membrane shows linearity with the concentration of ammonia in the limit of 10 and 300 ppm. UV-visible spectroscopy reveals the mechanism of sensing ammonia by the membrane. 相似文献
2.
T. M. Rice S. Gopalan M. Sigrist F. C. Zhang 《Journal of Low Temperature Physics》1994,95(1-2):299-308
The key elements in all known cuprate superconductors are lightly doped CuOi-planes. Recently a new homologous series of compounds Srn–1Cun+1O2n have been reported in which the planes contain a parallel array of line defects which form a trellis lattice with ladder-segments of the square lattice weakly coupled through triangular line defects. The width of the ladder segments is determined by the parameter n and varies from single chains to arbitrarily wide ladders. The magnetic properties of undoped compounds will be dominated by the properties of the ladders. Heisenberg s = 1/2 ladders can have a spin liquid groundstate with a spin gap if the number of rungs is odd so that a short range RVB groundstate is predicted for such trellis lattices. Using a t-J model to describe the doped material leads to the prediction of a d-wave RVB superconducting groundstate with a large spin gap. 相似文献
3.
M. K. Gopalan 《Materials and Structures》1995,28(4):235-240
Four grades of concrete with and without fly ash were devised and tested for compressive strength. The concretes were cured in three different curing regimes. The skin strength of concretes under inadequate curing was calculated by assuming a linear model for the variation of strength, and the strength difference between cement and fly ash concretes has been worked out. The skin strength of cement concretes was found to be higher than that of fly ash concretes. The test results were found to be affected by the size of the test specimen, when proper curing was not provided. The difference in sorptivity of fly ash and cement concretes cured for four days and not provided with any initial curing has been included. For all grades of concrete, the sorptivity of fly ash concrete was found to be marginally higher. The difference in sorptivity between fly ash and cement concretes was observed to increase as the strength of the mix decreased. The effect of initial curing was found to be highly significant. The sorptivity of samples with no curing was twice as much as those with four days initial curing. Besides the material properties, the age and strength of a fly ash concrete were also found to be important factors in determining the cementing efficiency of the fly ash. 相似文献
4.
Kwang‐Pill Lee Anantha Iyengar Gopalan See‐Hee Lee Ali Md Showkat Young Chang Nho 《应用聚合物科学杂志》2006,102(4):3912-3918
Conducting polydiphenylamine was used to encapsulate silica nanoparticles through the oxidative polymerization of diphenylamine in the presence of ultrasonic irradiation. The polymerization was performed in the presence of sodium lauryl sulfate as a surfactant. Experiments performed in the absence of ultrasound clearly demonstrated that the application of ultrasonication played multiple roles in the preparation of a composite of polydiphenylamine with silica nanoparticles. Ultrasonication dispersed the silica nanoparticles, converted sodium lauryl sulfate to lauryl alcohol, and augmented the dispersion of the silica‐nanoparticle/polydiphenylamine composite in an organic medium. Silica‐nanoparticle/polydiphenylamine composites were also prepared in the absence of ultrasound and/or sodium lauryl sulfate. The silica‐nanoparticle/polydiphenylamine composites were characterized with Fourier trans form infrared spectroscopy, ultraviolet–visible/near‐infrared spectroscopy, and thermogravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3912–3918, 2006 相似文献
5.
A novel method for the preparation of electrically conducting fibers through chemical grafting of electrically conducting polymer onto poly(propylene) (PP) fiber is described. The graft copolymerization of aniline (ANI) was performed in aqueous acidic medium by using a chemical oxidant such as peroxydisulfate (PDS). Grafting occurred with simultaneous homopolymer formation. The content of polyaniline in the backbone fiber was found to vary by varying [monomer], [initiator], and amount of PP fiber. Various graft parameters such as rate of grafting (Rg), % grafting, and % grafting efficiency were evaluated. The rate of homopolymerization (Rh) was also determined. Both Rh and Rg showed first‐order dependency on [ANI], [PDS], and amount of PP fiber variation. The chemical grafting was confirmed by use of cyclic voltammetry and conductivity measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3827–3834, 2003 相似文献
6.
Ali Md Showkat Kwang‐Pill Lee Anantha Iyengar Gopalan Sang‐Ho Kim Seong‐Ho Choi Sang‐Ho Sohn 《应用聚合物科学杂志》2006,101(6):3721-3729
Composites based on poly(diphenyl amine) (PDPA) and multiwall carbon nanotubes (MWNTs) were prepared by chemical oxidative polymerization through two different approaches: in situ polymerization and intimate mixing. In in situ polymerization, DPA was polymerized in the presence of dispersed MWNTs in sulfuric acid medium for different molar composition ratios of MWNT and DPA. Intimate mixing of synthesized PDPA with MWNT was also used for the preparation of PDPA/MWNT composites. Transmission electron microscopy revealed that the diameter of the tubular structure for the composite was 10–20 nm higher than the diameter of pure MWNT. Scanning electron microscopy provided evidence for the differences in the morphology between the MWNTs and the composites. Raman and Fourier transform IR (FTIR) spectroscopy, thermogravimetric analysis, X‐ray diffraction, and UV–visible spectroscopy were used to characterize the composites and reveal the differences in the molecular level interactions between the components in the composites. The Raman and FTIR spectral results revealed doping‐type molecular interactions and coordinate covalent‐type interactions between MWNT and PDPA in the composite prepared by in situ polymerization and intimate mixing, respectively. The backbone structure of PDPA in the composite decomposed at a higher temperature (>340°C) than the pristine PDPA (~300°C). This behavior also favored the molecular level interactions between MWNT and PDPA in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3721–3729, 2006 相似文献
7.
8.
9.
10.
Gopalan R Taheri S Turaga P Chellappa R 《IEEE transactions on pattern analysis and machine intelligence》2012,34(6):1220-1226
Understanding the effect of blur is an important problem in unconstrained visual analysis. We address this problem in the context of image-based recognition by a fusion of image-formation models and differential geometric tools. First, we discuss the space spanned by blurred versions of an image and then, under certain assumptions, provide a differential geometric analysis of that space. More specifically, we create a subspace resulting from convolution of an image with a complete set of orthonormal basis functions of a prespecified maximum size (that can represent an arbitrary blur kernel within that size), and show that the corresponding subspaces created from a clean image and its blurred versions are equal under the ideal case of zero noise and some assumptions on the properties of blur kernels. We then study the practical utility of this subspace representation for the problem of direct recognition of blurred faces by viewing the subspaces as points on the Grassmann manifold and present methods to perform recognition for cases where the blur is both homogenous and spatially varying. We empirically analyze the effect of noise, as well as the presence of other facial variations between the gallery and probe images, and provide comparisons with existing approaches on standard data sets. 相似文献