全文获取类型
收费全文 | 1310篇 |
免费 | 37篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 62篇 |
化学工业 | 339篇 |
金属工艺 | 30篇 |
机械仪表 | 15篇 |
建筑科学 | 28篇 |
能源动力 | 47篇 |
轻工业 | 135篇 |
水利工程 | 2篇 |
无线电 | 97篇 |
一般工业技术 | 248篇 |
冶金工业 | 180篇 |
原子能技术 | 61篇 |
自动化技术 | 108篇 |
出版年
2023年 | 7篇 |
2022年 | 25篇 |
2021年 | 36篇 |
2020年 | 16篇 |
2019年 | 35篇 |
2018年 | 27篇 |
2017年 | 25篇 |
2016年 | 32篇 |
2015年 | 24篇 |
2014年 | 37篇 |
2013年 | 90篇 |
2012年 | 79篇 |
2011年 | 96篇 |
2010年 | 72篇 |
2009年 | 61篇 |
2008年 | 71篇 |
2007年 | 60篇 |
2006年 | 58篇 |
2005年 | 41篇 |
2004年 | 42篇 |
2003年 | 35篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 23篇 |
1999年 | 16篇 |
1998年 | 72篇 |
1997年 | 41篇 |
1996年 | 40篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 13篇 |
1968年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1352条查询结果,搜索用时 31 毫秒
41.
42.
ABSTRACT: Forming electrodes on opposite sides of an individual bismuth nanowire was attempted to prepare for Hall measurements. Although a 1-mm-long bismuth nanowire which is completely covered with a quartz template has been successfully fabricated to prevent oxidation, it is very difficult to attach Hall electrodes on the opposite sides of the nanowire due to the quartz covering. One side of the cylindrical quartz template was removed by polishing without exposure of the nanowire to the atmosphere; the thickness between the polished template surface and the nanowire was estimated to be several micrometers. Focused ion beam processing was successfully employed to expose both surfaces of the nanowire under high vacuum by removing part of the quartz template. A carbon thin film was then deposited in situ on the wire surface to fabricate an electrical contact on the bismuth nanowire sample. Furthermore, the energy dispersive X-ray analysis was performed to the area processed by focused ion beam, and the bismuth component of the nanowire was successfully detected. It was confirmed that the focused ion beam processing was applicable to attach electrodes to bismuth nanowire for Hall measurement. 相似文献
43.
High‐temperature latent heat storage technology to utilize exergy of solar heat and industrial exhaust heat 下载免费PDF全文
Latent heat storage (LHS) using phase change materials is quite attractive for utilization of the exergy of solar energy and industrial exhaust heat because of its high‐heat storage capacity, heat storage and supply at constant temperature, and repeatable utilization without degradation. In this article, general LHS technology is outlined, and then recent advances in the uses of LHS for high‐temperature applications (over 100 °C) are discussed, with respect to each type of phase change material (e.g., sugar alcohol, molten salt, and alloy). The prospects of future LHS systems are discussed from a principle of exergy recuperation. In addition, the technologies to minimize exergy loss in the future LHS system are discussed on the basis of the thermodynamic analysis by ‘thermodynamic compass’. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
44.
Ryuta Shigefuku Hideaki Takahashi Hiroyasu Nakano Tsunamasa Watanabe Kotaro Matsunaga Nobuyuki Matsumoto Masaki Kato Ryo Morita Yousuke Michikawa Tomohiro Tamura Tetsuya Hiraishi Nobuhiro Hattori Yohei Noguchi Kazunari Nakahara Hiroki Ikeda Toshiya Ishii Chiaki Okuse Shigeru Sase Fumio Itoh Michihiro Suzuki 《International journal of molecular sciences》2016,17(9)
The progression of chronic liver disease differs by etiology. The aim of this study was to elucidate the difference in disease progression between chronic hepatitis C (CHC) and nonalcoholic fatty liver disease (NAFLD) by means of fibrosis markers, liver function, and hepatic tissue blood flow (TBF). Xenon computed tomography (Xe-CT) was performed in 139 patients with NAFLD and 152 patients with CHC (including liver cirrhosis (LC)). The cutoff values for fibrosis markers were compared between NAFLD and CHC, and correlations between hepatic TBF and liver function tests were examined at each fibrosis stage. The cutoff values for detection of the advanced fibrosis stage were lower in NAFLD than in CHC. Although portal venous TBF (PVTBF) correlated with liver function tests, PVTBF in initial LC caused by nonalcoholic steatohepatitis (NASH-LC) was significantly lower than that in hepatitis C virus (C-LC) (p = 0.014). Conversely, the liver function tests in NASH-LC were higher than those in C-LC (p < 0.05). It is important to recognize the difference between NAFLD and CHC. We concluded that changes in hepatic blood flow occurred during the earliest stage of hepatic fibrosis in patients with NAFLD; therefore, patients with NAFLD need to be followed carefully. 相似文献
45.
Masaki Saito Marina Hirano Tomohiro Izumi Yu Mori Kentaro Ito Yurika Saitoh Nobuo Terada Takeya Sato Jun Sukegawa 《International journal of molecular sciences》2022,23(4)
The primary cilium is a hair-like immotile organelle with specific membrane receptors, including the receptor of Hedgehog signaling, smoothened. The cilium organized in preosteoblasts promotes differentiation of the cells into osteoblasts (osteoblast differentiation) by mediating Hedgehog signaling to achieve bone formation. Notably, 4.1G is a plasma membrane-associated cytoskeletal protein that plays essential roles in various tissues, including the peripheral nervous system, testis, and retina. However, its function in the bone remains unexplored. In this study, we identified 4.1G expression in the bone. We found that, in the 4.1G-knockout mice, calcium deposits and primary cilium formation were suppressed in the trabecular bone, which is preosteoblast-rich region of the newborn tibia, indicating that 4.1G is a prerequisite for osteoblast differentiation by organizing the primary cilia in preosteoblasts. Next, we found that the primary cilium was elongated in the differentiating mouse preosteoblast cell line MC3T3-E1, whereas the knockdown of 4.1G suppressed its elongation. Moreover, 4.1G-knockdown suppressed the induction of the cilia-mediated Hedgehog signaling and subsequent osteoblast differentiation. These results demonstrate a new regulatory mechanism of 4.1G in bone formation that promotes the primary ciliogenesis in the differentiating preosteoblasts and induction of cilia-mediated osteoblast differentiation, resulting in bone formation at the newborn stage. 相似文献
46.
Makoto Tanaka Mikio Taguchi Tsuysohi Takahama Toru Sawada Shigeru Kuroda Takao Matsuyama Shinya Tsuda Akio Takeoka Shoichi Nakano Hiroshi Hanafusa Yukinori Kuwano 《Progress in Photovoltaics: Research and Applications》1993,1(2):85-92
A new solar cell structure named HIT (Heterojunction with Intrinsic Thin layer) has been developed based on new artificially constructed junction (ACJ) technology. In this structure a non-doped a-Si thin layer was inserted between the p(a-Si)/n(c-Si) heterojunction, improving the output characteristics and achieving a conversion efficiency of 18.1%. This structure was applied to cast polycrystalline silicon solar cells of a practical size. A high conversion efficeincy of 13.6% was obtained with a cell size of 10 cm × 10 cm using various technologies, including hydrogen plasma passivation. 相似文献
47.
48.
Experiments were carried out on the flow pattern, heat transfer, and pressure drop of flow boiling of pure CO2 and CO2‐oil mixtures in horizontal smooth and micro‐fin tubes. The smooth tube is a stainless steel tube with an inner diameter of 3.76 mm. The micro‐fin tube is a copper tube with a mean inner diameter of 3.75 mm. The experiments were carried out at mass velocities from 100 to 500 kg/(m2·s), saturation temperature of 10 °C, and the circulation ratio of lubricating oil (PAG) was from 0 to 1.0 mass%. Flow pattern observations mainly showed slug and wavy flow for the smooth tube, but annular flow for the micro‐fin tube. Compared with the flow patterns in the case of pure CO2, an increase in frequency of slug occurrence in the slug flow region, and a decrease in the quantity of liquid at the top of the tube in the annular flow region were observed in the case of CO2‐oil mixtures. With pure CO2, the flow boiling heat transfer was dominated by nucleate boiling in the low vapor quality region, and the heat transfer coefficients for the micro‐fin tube were higher than those of the smooth tube. With CO2‐oil mixtures, the flow boiling heat transfer was dominated by convective evaporation, especially in the high vapor quality region. In addition, the heat transfer coefficient decreased significantly when the oil circulation ratio was larger than 0.1 mass%. For the pressure drop characteristics, in the case of pure CO2, the homogeneous flow model agreed with the experimental results within ±30% for the smooth tube. The pressure drops of the micro‐fin tube were 0–70% higher than those predicted with the homogeneous flow model, and the pressure drops increased for the high oil circulation ratio and high vapor quality conditions. The increases in the pressure drops were considered to be due to the increase in the thickness of the oil film and the decrease in the effective flow cross‐sectional area. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20287 相似文献
49.
Soichiro Ogi Tomohiro Ikeda Masayuki Takeuchi 《Journal of Inorganic and Organometallic Polymers and Materials》2013,23(1):193-199
New rotary molecular machines (1 and 2) were synthetically constructed from two distinct porphyrin-based rotors, a cerium(IV) bis(porphyrinate)s double-decker (CeDD) and a porphyrinatorhodium(III)-based rotor. These rotors are adjacently mounted on rotational axes aligned to near vertical as resembling the bevel-gear-shaped structure. Structural study using NMR analysis reveals that these distinct rotors are connected through a coordination bond between rhodium(III) and a pyridyl group. At temperature from 193 to 393 K, each rotor represents rotational motion driven by heat fluctuation without decomposition into the corresponding precursors in dichloromethane-d 2 and tetrachloroethane-d 4. Importantly, the mechanical interaction between the teeth of these rotors is strongly dependent on the central metal atom in a DD rotor and the teeth structure in a porphyrinatorhodium(III)-based rotor. Understanding such relationship between the chemical structures and mechanical interaction is of importance for generating cooperative motion in the hybrid machinery system. 相似文献
50.
Polyacene capacitors 总被引:2,自引:0,他引:2
Shizukuni Yata Eiji Okamoto Hisashi Satake Hidekazu Kubota Masanori Fujii Tomohiro Taguchi Hajime Kinoshita 《Journal of power sources》1996,60(2):207-212
We fabricated two types of polyacene capacitor with extremely stable polyacenic semiconductor (PAS) as the positive and negative electrodes. The first one is a coin-type PAS capacitor (six different sizes), which possesses large capacity with high reliability. Its capacity is much larger than that of the conventional electric double-layer capacitor which uses activated carbon as electrode. PAS capacitor can maintain more than 70% of the initial capacity even after 100 000 cycles. Moreover, this capacitor can be charged and discharged in a few minutes as well as at low rate. The second one is a cylinder-type PAS capacitor (diameter: 18 mm, height: 65 mm) which shows high capacity of 100 F and can discharge at the extremely high rate of 80 C. The coin-type PAS capacitor is currently used for memory back-up of electrical and communication equipment, and the cylinder-type is considered to be useful as power back-up for starting drive parts of electric equipment which needs high power density. 相似文献