全文获取类型
收费全文 | 500篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 16篇 |
化学工业 | 180篇 |
金属工艺 | 9篇 |
机械仪表 | 12篇 |
建筑科学 | 2篇 |
能源动力 | 27篇 |
轻工业 | 16篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 45篇 |
一般工业技术 | 98篇 |
冶金工业 | 38篇 |
原子能技术 | 9篇 |
自动化技术 | 64篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 17篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 26篇 |
2012年 | 29篇 |
2011年 | 32篇 |
2010年 | 32篇 |
2009年 | 24篇 |
2008年 | 18篇 |
2007年 | 19篇 |
2006年 | 21篇 |
2005年 | 22篇 |
2004年 | 20篇 |
2003年 | 21篇 |
2002年 | 14篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有518条查询结果,搜索用时 15 毫秒
51.
Grain boundaries (GBs) together with their associated impurity segregation often affect or alter properties of many polycrystalline materials. However, their atomic-scale structures remain difficult to resolve spatially, especially for those with an orientation misalignment. Here, we apply a bicrystal technique to fabricate the near-Σ5 GBs of MgO with a misalignment angle from the exact Σ5 orientation relationship and show an unexpected selective impurity segregation behavior at this GB. We find that the near-Σ5 GB comprises an alternating array of five exact Σ5 GB structural units and one deformed Σ17 GB unit, and interestingly that the Ca and Ti impurities are co-segregated to the Σ5 GB structural units, yet are not to the deformed Σ17 GB structural units. The findings are important for the understanding of GBs with a misalignment and impurity segregation and for correlating structures with properties in polycrystalline materials. 相似文献
52.
Qixin Guo Masaki Nada Katsuhiko Saito Mitsuhiro Nishio 《Materials Research Bulletin》2011,46(4):551-554
The effect of gas flow rate on surface morphology and crystal quality of ZnTe layers grown on the (1 0 0) GaAs substrates by atmospheric pressure metalorganic vapor phase epitaxy with dimethylzinc and diethyltelluride as the source materials was investigated. The surface morphology of the ZnTe epilayers is significantly improved with increasing the total gas flow rate. X-ray rocking curve and photoluminescence measurements indicate that the total gas flow rate plays a vital role in the growth characteristics of the ZnTe epilayers, and the ZnTe epilayer with best crystal quality is obtained at the total gas flow rate around 300 standard cubic centimeters per minute (sccm) in this work. 相似文献
53.
K Hayashi M Tamura T Shimozuru S Kasamo K Hirahara K Kadota T Asakura 《Canadian Metallurgical Quarterly》1994,34(5):295-299
A 13-year-old boy presented with a very unusual ependymoma extending extra-axially. Computed tomography demonstrated a tumor with a cyst and calcification adjacent to the dura and extending over the right occipital and parietal lobes. The cyst wall and solid tumor were enhanced postcontrast. Magnetic resonance imaging revealed that the solid tumor was isointense on T1-weighted images and a mixed iso- and high-intensity on T2-weighted images. The solid tumor and tissue surrounding the cyst were enhanced markedly by gadolinium-diethylenetriaminepentaacetic acid. Sagittal and coronal images demonstrated a multilocular tumor shadow. Cerebral angiography demonstrated a tumor fed by a posterior branch of the right middle meningeal artery but no feeders from the internal carotid and vertebral arteries. The tumor was removed en bloc. The histological diagnosis was clear cell-type ependymoma. 相似文献
54.
A method of data analysis for dynamic light scattering is proposed to evaluate the weight fraction, w(Rh), of a small amount of large aggregates in a dilute solution, where Rh is the hydrodynamic radius. We examined the time-correlation function of scattering intensity for model multi-modal systems, i.e., mixtures of latex solutions having different particle sizes and of polystyrene standard solutions having different molecular weights, by properly taking into account the unknown fractions, w(Rh), and scattering intensities of individual components. We derived an equation to evaluate the weight fractions of the components. The validity of this method was verified by successfully reconstructing the observed correlation functions having fast and slow modes. As a demonstration, the fraction of aggregates in a thermosensitive polymer solution in water was evaluated as a function of temperature. 相似文献
55.
Numerical Verifications of Solutions for Nonlinear Parabolic Equations in One-Space Dimensional Case
In this paper, we describe a numerical method to verify the solutions with guaranteed error bounds for nonlinear parabolic problems in one dimensional case. It is based on Plum's method for formulating the problem and weak formulation for estimating explicitly the inverse norm of the linearized operator. We introduce some weighted norms on time-dependent Sobolev spaces, which play an important role in the application of our method. We present detailed verification procedures by using this weighted norm and show some numerical examples. 相似文献
56.
57.
Nanoscale molecular cavity in crystalline polymer membranes studied by molecular dynamics simulation
The size, shape, and connectivity of cavities in the crystals of syndiotactic polystyrene were investigated by molecular dynamics simulation. Cluster analysis of the free volume in the crystals clearly reveals the cavity structures: large individual holes are in an orderly manner connected by narrow channels. We call such a cavity structure a ‘molecular cavity’. The diffusion behavior and solubility of gases in the molecular cavity were also simulated. The extremely high solubility of a larger gas and the controllable diffusion path in the narrow channels proved the applicability of the concept of the molecular cavity to high performance separation membranes. 相似文献
58.
H Hasegawa R Suzuki C Wakabayashi J Murata Y Tezuka I Saiki S Kadota 《Canadian Metallurgical Quarterly》1998,21(5):513-516
PURPOSE: Prosthodontic components for implant treatment have been developed with minimal reported scientific investigation. This paper aims to highlight a number of problems caused by this approach to the development and marketing of prosthodontic components and to suggest solutions. CONCLUSION: Prosthodontic components must be developed with a scientific approach that involves both laboratory and clinical testing so as to optimize treatment outcomes in the future. 相似文献
59.
Mitsuhiro Horade Sommawan Khumpuang Susumu Sugiyama 《Microsystem Technologies》2008,14(9-11):1695-1698
Microfabrication technique using SR ablation for 3-D polytetrafluoroethylene (PTFE) structure is reported in this work. First of all, we investigated necessary basic data for the fabricated structure like the processing depth and the etching rate, etc. And, the exposure energy distribution was given to the surface of polytetrafluoroethylene by using the plane pattern to cross-section transfer (PCT) technique, 3-D microstructures was fabricated. To establish three dimension of highly accurate PTFE processing technology, we are researching the application to the device. 相似文献
60.
Okamoto H. Wada M. Sakai Y. Hirono T. Kawaguchi Y. Kondo Y. Kadota Y. Kishi K. Itaya Y. 《Lightwave Technology, Journal of》1998,16(10):1881-1887
The device structure and performance of 1.3-μm narrow beam superluminescent diodes (NB-SLD's), which consist of a spot-size converter and a new type rear absorbing region, are reported. A butt-jointed selectively grown spot-size converter (SSC) is employed to realize the narrow beam characteristics. The rear absorbing region is designed as a taper structure with a part of the region is inclined from the active-stripe axes. In order to investigate the effects of both SSC length and active-region length on device performance, two types of NB-SLDs, whose SSC and active-region lengths differ, are fabricated. An electrode to sweep out photoexcited carriers in the absorption region is formed on one device. By comparing the characteristics of these devices, we clarify that a 500-μm-active-region device is suitable for high-output power operation, and a 400-μm-active-region device is suitable for realizing short coherent length. The light-output power is 13.9 mW at 200-mA-injection current for the former device, and the full-width at half-maximum (FWHM) of the spectrum is 62.6 nm (calculated coherence length is 26.5 μm) for the latter device. Very small spectral modulation index (0.015 at 5 mW-output power) is attained by grounding the absorption-region electrode. For the SSC length, a 300-μm SSC device shows very narrow far-field patterns (FFPs) and very good fiber-coupling characteristics. The FWHM of horizontal and vertical FFPs are 8.9 and 10.6°, respectively. Because of this narrow beam divergence, the coupling efficiency of -1.9 dB to a flat-end 4-μm spot-size fiber is obtained without lenses. The alignment tolerance of this device to the fiber for both horizontal and vertical direction is more than 3 μm at a loss of when -1 dB from the optimum coupling 相似文献