全文获取类型
收费全文 | 615篇 |
免费 | 14篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 44篇 |
综合类 | 2篇 |
化学工业 | 180篇 |
金属工艺 | 21篇 |
机械仪表 | 18篇 |
建筑科学 | 13篇 |
能源动力 | 35篇 |
轻工业 | 51篇 |
水利工程 | 3篇 |
无线电 | 37篇 |
一般工业技术 | 114篇 |
冶金工业 | 34篇 |
原子能技术 | 31篇 |
自动化技术 | 51篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 38篇 |
2012年 | 25篇 |
2011年 | 29篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 47篇 |
2007年 | 34篇 |
2006年 | 23篇 |
2005年 | 31篇 |
2004年 | 31篇 |
2003年 | 29篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 20篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有634条查询结果,搜索用时 31 毫秒
21.
Quality of an SEM image is strongly influenced by the extent of noise. As a well-known method in the field of SEM, the covariance is applied to measure the signal-to-noise ratio (SNR). This method has potential ability for highly accurate measurement of the SNR, which is hardly known until now. If the precautions discussed in this article are adopted, that method can demonstrate its real ability. These precautions are strongly related to "proper acquisition of two images with the identical view," "alignment of an aperture diaphragm," "reduction of charging phenomena," "elimination of particular noises," and "accurate focusing," As necessary, characteristics in SEM signal and noise are investigated from a few standpoints. When using the maximum performance of this measurement, SNR of many SEM images obtained in a variety of the SEM operating conditions and specimens can be measured accurately. 相似文献
22.
Nariaki Sakaba Kazuhiko Iigaki Masaaki Kondo Koichi Emori 《Nuclear Engineering and Design》2004,233(1-3):135
The containment structures of the HTTR consist of the reactor containment vessel, the service area, and the emergency air purification system, which minimise the release of fission products in postulated accidents, which lead to fission product release from the reactor facilities. The reactor containment vessel is designed to withstand the temperature and pressure transients and to be leak-tight in the case of a rupture of the primary concentric hot-gas duct, etc. The pressure inside the service area is maintained at a negative pressure by the emergency air purification system. The emergency air purification system will also remove airborne radioactivity and will maintain a correct pressure in the service area.The leak-tightness characteristics of the containment structures are described in this paper. The measured leakage rates of the reactor containment vessel were enough less than the specified leakage limit of 0.1%/d confirmed during the commissioning tests and annual inspections. The service area was kept in a way that the design pressure becomes well below its allowable limitation by the emergency air purification system, which filters efficiency of particle removal and iodine removal well over the limited values.The obtained data demonstrate that the reactor containment structures were fabricated to minimise the release of fission products in the postulated accidents with fission product release from the reactor facilities. 相似文献
23.
JAERI established the safety design philosophy of the HTTR based on that of current reactors such as LWR in Japan, considering inherent safety features of the HTTR. The strategy of defense in depth was implemented so that the safety engineering functions such as control of reactivity, removal of residual heat and confinement of fission products shall be well performed to ensure safety. However, unlike the LWR, the inherent design features of the high-temperature gas-cooled reactor (HTGR) enables the HTTR meet stringent regulatory criteria without much dependence on active safety systems. On the other hand, the safety in an accident typical to the HTGR such as the depressurization accident initiated by a primary pipe rupture shall be ensured. The safety design philosophy of the HTTR considers these unique features appropriately and is expected to be the basis for future Japanese HTGRs.This paper describes the safety design philosophy and safety evaluation procedure of the HTTR especially focusing on unique considerations to the HTTR. Also, experiences obtained from an HTTR safety review and R&D needs for establishing the safety philosophy for the future HTGRs are reported. 相似文献
24.
The thermal behavior of polyacrylonitrile (PAN) has been investigated using X-ray diffraction, differential scanning calorimetry (DSC), and ultrafast DSC. In conventional DSC, it is difficult to prevent the concurrent occurrence of the exothermic reactions of PAN with melting. However, in the ultrafast DSC curve, the exothermic peak due to these reactions disappears over the temperature range 0–400 °C at heating rates above 250 °C s−1. Alternatively, the glass transition and the melting of PAN are observed over the temperature range 109–129 °C and 335–362 °C, respectively. Moreover, upon cooling from the molten state at a rate of −7500 °C s−1, PAN crystallization is observed at 204 °C. These findings were observed repeatedly during heating and cooling measurements. From the extrapolation analysis, the zero-entropy-production melting temperature of PAN is found to lie in the temperature range 320–350 °C. Finally, the equilibrium melting temperature of PAN is estimated to be ca. 465 °C. 相似文献
25.
Lixin Xiao Koichi Kitazawa Kazuhiko Saigo 《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(6):531-543
Abstract A series of [60]fullerene pearl-necklace polyamides, consisting of equatorial-[60]fullerenobisacetic acid and various chromophoric aromatic diamines, were synthesized by a phosphorylation route using large amounts of triphenyl phosphite and pyridine as condensing reagents with stepwise addition of the condensing reagents. In the present polymers, [60]fullerene pearls and diamine linkers were attached to one another by cyclopropane connectors. The polyamides had weight-average molecular weights (Mw)of 4.5-5.0×104 g/mol and inherent viscosities (n inh) of 0.3-0.4 dL/g in N, N-dimethylacetamide (DMAc) at 30 °C. They had glass transition temperatures at 30-125 °C and decomposition temperatures at 300-310 °C. The UV-VIS spectra in DMAc exhibited broad absorption with λmax at 310-390 nm tailing to longer wavelengths. 相似文献
26.
Atsuko Kimura Kazuhiko Namekata Xiaoli Guo Chikako Harada Takayuki Harada 《International journal of molecular sciences》2016,17(9)
Neurotrophic factors play key roles in the development and survival of neurons. The potent neuroprotective effects of neurotrophic factors, including brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), glial cell-line derived neurotrophic factor (GDNF) and nerve growth factor (NGF), suggest that they are good therapeutic candidates for neurodegenerative diseases. Glaucoma is a neurodegenerative disease of the eye that causes irreversible blindness. It is characterized by damage to the optic nerve, usually due to high intraocular pressure (IOP), and progressive degeneration of retinal neurons called retinal ganglion cells (RGCs). Current therapy for glaucoma focuses on reduction of IOP, but neuroprotection may also be beneficial. BDNF is a powerful neuroprotective agent especially for RGCs. Exogenous application of BDNF to the retina and increased BDNF expression in retinal neurons using viral vector systems are both effective in protecting RGCs from damage. Furthermore, induction of BDNF expression by agents such as valproic acid has also been beneficial in promoting RGC survival. In this review, we discuss the therapeutic potential of neurotrophic factors in retinal diseases and focus on the differential roles of glial and neuronal TrkB in neuroprotection. We also discuss the role of neurotrophic factors in neuroregeneration. 相似文献
27.
Kenji Hirota Kazuhiko Kitamura Yoshihiko Ukai Keiichi Matsunaga 《Journal of Materials Processing Technology》2014,214(10):2095-2101
In this paper, a new assembling method of spline joints that enables tight fitting in a simple manner by allowing slight plastic deformation at the spline teeth was introduced. Experiments were carried out for the spline joints of medium carbon steel varying the overlap zone between the male and the female spline teeth. Axial joining strength was increased with increase in the overlap length due to the residual compressive stress by forming. The joint by the proposed method also showed higher torsional strength than the conventional joint. Improvement in the torsional strength was explained based on the deformation and hardness distribution around the spline teeth. With respect to the shape of overlap zone, better results were obtained when using the specimen having a uniform overlap length along the axial direction. 相似文献
28.
Shinji Fukuda Kazuhiko Shimada Noriya Izu Hiroyuki Miyazaki Shoji Iwakiri Kiyoshi Hirao 《Journal of Materials Science: Materials in Electronics》2018,29(14):11688-11698
We observed crack generation and structural changes in electroless nickel–phosphorus (Ni–P) plating layers formed on copper-metalized silicon nitride substrates both during thermal cycling from ? 40 to 250 °C and during storage (not cycling) at 250 °C in order to investigate the effect of the phosphorus contents on crack generation and growth in the Ni–P platings. The used platings contained phosphorus at three different contents: 2.1 wt% [Ni–P(low)], 6.5 wt% [Ni–P(med)], and 10.9 wt% [Ni–P(high)]. The generation time and the amount of cracks were strongly dependent on their phosphorus contents. More cracks appeared after thermal cycling than after storage at 250 °C. In Ni–P(low), cracks were generated after 200 thermal cycles, whereas no cracks were observed even after 250 h of storage at 250 °C. In Ni–P(med) and Ni–P(high), both during thermal cycling and storage at 250 °C, cracks formed during or after crystallization of the amorphous layers. These results suggest that the primary factors affecting the generation of cracks in electroless Ni–P platings are crystallization of the Ni–P platings and repeated changes in thermal stress. 相似文献
29.
Amnach Khawne Boonwat Attachoo Kazuhiko Hamamoto 《IEEJ Transactions on Electrical and Electronic Engineering》2015,10(2):149-156
To prevent unauthorized access to a person's medical images, it is widely acknowledged that the security features of confidentiality, availability and integrity should be in place. This paper proposes the watermarking of ultrasonic echo images together with optimal watermark detection, in which pseudorandom noise is added to the images for integrity. The optimum watermark detection is the integration of the generalized Gaussian distribution (ρ‐GGD) and the Cauchy distribution. The results show that the proposed method gives good detection performance. The proposed method not merely achieves optimum detection using the Rao test but also leads to the highest detection probability with JPEG2000 compression. Compared with other detection methods, our proposed method exhibits better watermark detection performance even when the watermark‐to‐document ratio (WDR) is −50 dB. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
30.
Joao Gari da Silva Fonseca Junior Takashi Oozeki Hideaki Ohtake Takumi Takashima Kazuhiko Ogimoto 《Progress in Photovoltaics: Research and Applications》2015,23(10):1203-1218
The development of methods to forecast photovoltaic (PV) power generation regionally is of utmost importance to support the spread of such power systems in current power grids. The objective of this study is to propose and to evaluate methods to forecast regional PV power 1 day ahead of time and to compare their performances. Four forecast methods were regarded, of which two are new ones proposed in this study. Together, they characterize a set of forecast methods that can be applied in different scenarios regarding availability of data and infrastructure to make the forecasts. The forecast methods were based on the use of support vector regression and weather prediction data. Evaluations were performed for 1 year of hourly forecasts using data of 273 PV systems installed in two adjacent regions in Japan, Kanto, and Chubu. The results show the importance of selecting the proper forecast method regarding the region characteristics. For Chubu, the region with a variety of weather conditions, the forecast methods based on single systems' forecasts and the one based on stratified sampling provided the best results. In this case, the best annual normalized root mean square error (RMSE) and mean absolute error (MAE) were 0.25 and 0.15 kWh/kWhavg, respectively. For Kanto, with homogeneous weather conditions, the four methods performed similarly. In this case, the lowest annual forecast errors were 0.33 kWh/kWhavg for the normalized RMSE and 0.202 kWh/kWhavg for the normalized MAE. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献