全文获取类型
收费全文 | 1692篇 |
免费 | 47篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 116篇 |
综合类 | 2篇 |
化学工业 | 550篇 |
金属工艺 | 72篇 |
机械仪表 | 58篇 |
建筑科学 | 41篇 |
矿业工程 | 1篇 |
能源动力 | 110篇 |
轻工业 | 119篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 59篇 |
一般工业技术 | 333篇 |
冶金工业 | 61篇 |
原子能技术 | 38篇 |
自动化技术 | 184篇 |
出版年
2023年 | 7篇 |
2022年 | 34篇 |
2021年 | 45篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 36篇 |
2017年 | 22篇 |
2016年 | 29篇 |
2015年 | 16篇 |
2014年 | 31篇 |
2013年 | 85篇 |
2012年 | 67篇 |
2011年 | 125篇 |
2010年 | 73篇 |
2009年 | 83篇 |
2008年 | 89篇 |
2007年 | 65篇 |
2006年 | 60篇 |
2005年 | 64篇 |
2004年 | 49篇 |
2003年 | 53篇 |
2002年 | 45篇 |
2001年 | 37篇 |
2000年 | 27篇 |
1999年 | 36篇 |
1998年 | 48篇 |
1997年 | 42篇 |
1996年 | 32篇 |
1995年 | 37篇 |
1994年 | 45篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 20篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1974年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有1752条查询结果,搜索用时 734 毫秒
991.
This paper proposes a new concept of an electric power delivery system for future decades. The power delivery network consists of a set of meshed networks spread over every demand-side block (city or town). On the end point of the power line network, quality improvement facilities (referred to as “quality improvement centers”) are installed, and each consumer can select an arbitrary quality of electricity. Thus the system can achieve multi-menu-services and uninterrupted power supply. The system contains small-scale energy storage and dispersed small-scale power generation systems. The main circuit breakers consist of power electronics devices, and communication networks are fully installed so as to control the power electronics devices or power flow according to system situations or the fault situations. The communication network also controls the demand-side management. From the above, the proposed power delivery network is flexible and reliable. The intelligent facilities (computers) are installed in the control centers as well as in the quality improvement centers. They keep the system as the most energy-conservative form. In this paper, the system is named FRIENDS (Flexible, Reliable and Intelligent Electrical eNergy Delivery system). The conclusion of this paper summarizes the major research areas that must be completed to realize the system. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(1): 26–34, 1997 相似文献
992.
993.
Ken-ichi Tajima † Hae Jin Hwang Mutsuo Sando Koichi Niihara 《Journal of the American Ceramic Society》2000,83(3):651-653
Hard lead zirconate titanate (PZT) and PZT/Al2 O3 composites were prepared and the alternating-electric-field-induced crack growth behavior of a precrack above the coercive field was evaluated via optical and scanning electron microscopy. The crack extension in the 1.0 vol% Al2 O3 composite was significantly smaller than that in monolithic PZT and the 0.5 vol% Al2 O3 composite. Secondary-phase Al2 O3 dispersoids were found both at grain boundaries and within grains in the composites. A large number of dispersoids were observed at the grain boundaries in the 1.0 vol% Al2 O3 composite. It appears that the Al2 O3 dispersoids reinforce the grain boundaries of the PZT matrix as well as act as effective pins against microcrack propagation. 相似文献
994.
Takaaki Nagaoka Yuji Iwamoto Koichi Kikuta Shin-ichi Hirano 《Journal of the American Ceramic Society》2000,83(7):1613-1616
Two types of barium aluminate binders were prepared by heat treatment of barium aluminate precursors, synthesized by using solution processes, at low temperatures ( T < 500°C). One was barium monoaluminate (BaAl2 O4 ), and the other was barium aluminate binder (BAH binder) composed of amorphous phase, barium aluminate monohydrate (BaAl2 O4 ·H2 O), and BaAl2 O4 . The setting time of the BAH binder was controlled by adjusting the heat-treatment temperature of the BAH binder precursor. The addition of the synthesized BaAl2 O4 powders to Al2 O3 powders improved the bending strength of Al2 O3 matrix green bodies. The synthesized BaAl2 O4 powders led to the in situ forming of barium hexaaluminate (BaO· x Al2 O3 , x = 6.9: BA6) platelets in the matrix by reacting with Al2 O3 during sintering. The formed BA6 platelets inhibited the grain growth of the matrix Al2 O3 grains. 相似文献
995.
An approach based on the finite element method (FEM) with the rectangular-parallelepipd edge element is proposed for the analysis of electromagnetic waveguide bends. Here, to be permissible for analysis of various electromagnetic waveguides, the analytical relations in the uniform waveguide are constructed numerically by using the FEM with the rectangular edge element. To confirm the validity and versatility of this approach, bends of a hollow waveguide, a half-filled dielectric waveguide, and a finline are analyzed. © 1996 John Wiley & Sons, Inc. 相似文献
996.
Ryo Koyama Koichi Iwata Yoshinori Hayashi Suzuro Hitomi Ikuko Shibuta Akihiko Furukawa Sayaka Asano Tadayoshi Kaneko Yoshiyuki Yonehara Masamichi Shinoda 《International journal of molecular sciences》2021,22(21)
Pain is one of the most severe concerns in tongue cancer patients. However, the underlying mechanisms of tongue cancer pain are not fully understood. We investigated the molecular mechanisms of tongue cancer-induced mechanical allodynia in the tongue by squamous cell carcinoma (SCC) inoculation in rats. The head-withdrawal threshold of mechanical stimulation (MHWT) to the tongue was reduced following SCC inoculation, which was inhibited by intracisternal administration of 10Panx, an inhibitory peptide for pannexin 1 (PANX1) channels. Immunohistochemical analyses revealed that the expression of PANX1 was upregulated in the trigeminal spinal subnucleus caudalis (Vc) following SCC inoculation. The majority of PANX1 immunofluorescence was merged with ionized calcium-binding adapter molecule 1 (Iba1) fluorescence and a part of it was merged with glial fibrillary acidic protein (GFAP) fluorescence. Spike frequencies of Vc nociceptive neurons to noxious mechanical stimulation were significantly enhanced in SCC-inoculated rats, which was suppressed by intracisternal 10Panx administration. Phosphorylated extracellular signal-regulated kinase (pERK)-immunoreactive (IR) neurons increased significantly in the Vc after SCC inoculation, which was inhibited by intracisternal 10Panx administration. SCC inoculation-induced MHWT reduction and increased pERK-IR Vc neuron numbers were inhibited by P2X7 purinoceptor (P2X7R) antagonism. Conversely, these effects were observed in the presence of P2X7R agonist in SCC-inoculated rats with PANX1 inhibition. SCC inoculation-induced MHWT reduction was significantly recovered by intracisternal interleukin-1 receptor antagonist administration. These observations suggest that SCC inoculation causes PANX1 upregulation in Vc microglia and adenosine triphosphate released through PANX1 sensitizes nociceptive neurons in the Vc, resulting in tongue cancer pain. 相似文献
997.
Koichi Unami Toshihiko Kawachi Gordana Kranjac-Berisavljevic Felix Kofi Abagale Shigeya Maeda Junichiro Takeuchi 《Canadian Metallurgical Quarterly》2009,135(7):539-553
The inland valleys of West Africa are strategic in terms of food security and poverty alleviation, but scientific studies on hydrologic processes happening in these environments have not been well documented. Modeling approaches presented in this paper are an attempt to better comprehend hydraulic phenomena occurring in inland valleys. An inland valley situated in the Northern Region of Ghana is set as the study site. The inland valley comprises well-drained uplands and hydromorphic valley bottoms. There are several earthen dams across the valley bottoms, which are at the same time seasonal wetlands cultivated to rice during the rainy season. A finite volume model for the shallow water equations is developed to numerically simulate surface runoff flows in the valley bottoms during flood events. Innovation is necessitated to handle a series of different hydraulic phenomena. Flux-splitting and data reconstruction techniques are used to achieve stable computation in the complex topography of the valley bottoms. Standard problems of oblique hydraulic jump and dam break flows are used to test the accuracy of the numerical model. The Manning’s roughness coefficient is determined from calibration in another Ghanaian watershed located in the Eastern Region. Using actually observed time series data of rainfall intensity, surface flows during the rainfall events are simulated in the computational domain representing the valley bottoms of the study area. Observed data of water levels in the dams are compared to predictions, and discrepancies between them are examined from the hydrological point of view. In the case of a hypothetical flood event, cascading collapses of the dams and flooding of cultivated fields are reproduced. 相似文献
998.
Characterization of porous silicon nitride ceramics using bentonite as binder and sintering additive
Guang-Peng Jiang Jian-Feng Yang Ji-Qiang Gao Koichi Niihara 《Materials Characterization》2009,60(5):456-460
The effect of bentonite addition on extrusion behavior, open porosity, microstructure, and mechanical properties was investigated. The results showed that paste with an appropriate amount of bentonite had a good extrusion behavior. The resultant microstructures consisted of rod-like silicon nitride grains and some intergranular amorphous phase. Furthermore, superior mechanical properties were obtained. Using cheap but effective bentonite as inorganic binder as well as sintering aid is a promising eco-friendly preparation route for cost-effective porous silicon nitride ceramics. 相似文献
999.
Kaoru Aoki Yuki Usui Nobuyo Narita Nobuhide Ogiwara Norio Iashigaki Koichi Nakamura Hiroyuki Kato Kenji Sano Naoko Ogiwara Kiyokazu Kametani Chan Kim Seiichi Taruta Yoong Ahm Kim Morinobu Endo Naoto Saito 《Small (Weinheim an der Bergstrasse, Germany)》2009,5(13):1540-1546
Due to the rapid progress being made in tissue regeneration therapy, biomaterials used as scaffolds are expected to play an important role in future clinical application. We report the development of a 3D web (sheet) consisting of high‐purity carbon fibers in a nanoscale structure. When the thin carbon‐fiber web (TCFW) and recombinant human bone morphogenetic protein 2 (rhBMP‐2) composite is implanted in the murine back muscle, new ectopic bone is formed, and the values of the bone mineral content and bone mineral density are significantly higher than those obtained with a collagen sheet. Observation of the interface between the carbon fibers and bone matrix reveal that the fibers are directly integrated into the bone matrix, indicating high bone‐tissue compatibility. Further, the rhBMP‐2/TCFW composite repairs a critical‐size bone defect within a short time period. These results suggest that the TCFW functions as an effective scaffold material and will play an important role in tissue regeneration in the future. 相似文献
1000.
Fabrication and efficient photocatalytic degradation of methylene blue over CuO/BiVO4 composite under visible-light irradiation 总被引:1,自引:0,他引:1
Hai-qing Jiang Hiromitsu Endo Hirotaka Natori Masayuki Nagai Koichi Kobayashi 《Materials Research Bulletin》2009,44(3):700-706
CuO/BiVO4 composite photocatalysts were prepared by solution combustion synthesis method and impregnation technique. X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scan electron microscopy and UV-vis diffusion reflectance spectra were used to identify the physical properties and photophysical properties of CuO/BiVO4 composite photocatalysts. The photocatalysts exhibit the enhanced photocatalytic properties for degradation of methylene blue under visible-light (λ > 420 nm). The mechanism of improved photocatalytic activity is also discussed. 相似文献