全文获取类型
收费全文 | 2920篇 |
免费 | 50篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 127篇 |
综合类 | 3篇 |
化学工业 | 591篇 |
金属工艺 | 99篇 |
机械仪表 | 80篇 |
建筑科学 | 36篇 |
能源动力 | 145篇 |
轻工业 | 136篇 |
水利工程 | 11篇 |
石油天然气 | 7篇 |
无线电 | 371篇 |
一般工业技术 | 475篇 |
冶金工业 | 681篇 |
原子能技术 | 51篇 |
自动化技术 | 168篇 |
出版年
2023年 | 19篇 |
2022年 | 29篇 |
2021年 | 55篇 |
2020年 | 19篇 |
2019年 | 21篇 |
2018年 | 29篇 |
2017年 | 28篇 |
2016年 | 45篇 |
2015年 | 34篇 |
2014年 | 52篇 |
2013年 | 125篇 |
2012年 | 83篇 |
2011年 | 117篇 |
2010年 | 100篇 |
2009年 | 99篇 |
2008年 | 108篇 |
2007年 | 104篇 |
2006年 | 77篇 |
2005年 | 63篇 |
2004年 | 64篇 |
2003年 | 109篇 |
2002年 | 77篇 |
2001年 | 69篇 |
2000年 | 48篇 |
1999年 | 84篇 |
1998年 | 319篇 |
1997年 | 178篇 |
1996年 | 110篇 |
1995年 | 73篇 |
1994年 | 83篇 |
1993年 | 75篇 |
1992年 | 39篇 |
1991年 | 35篇 |
1990年 | 47篇 |
1989年 | 36篇 |
1988年 | 25篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 33篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 21篇 |
1975年 | 10篇 |
1974年 | 10篇 |
排序方式: 共有2981条查询结果,搜索用时 15 毫秒
101.
Toshihiko Yamaguchi Ovidiu Mihalache 《Journal of Nuclear Science and Technology》2017,54(11):1201-1214
A new design has been adopted for the steam generator (SG) tubes of the Japan Sodium-cooled Fast Reactor (JSFR) using double-wall tubes. This paper estimates and assesses the effectiveness of detecting defects in SG double-wall tubes of the JSFR by using combined high-frequency eddy current testing (ECT) and low-frequency remote field eddy current sensors. We confirm that the proposed hybrid ECT sensor is highly sensitive to small defects, fatigue cracks, and other defects even when located under support plates of tubes. The parameters of the hybrid ECT sensor are designed and optimized to detect small defects using accurate numerical simulations based on the finite element method, using an in-house developed code. The sensitivity and high performance of the hybrid ECT sensor was validated with experimental measurements. 相似文献
102.
Autonomous control of vehicles has recently attracted considerable attention. In this sense, vehicle merging has become an important topic in this field of research. However, in conventional studies, the controlled vehicle must calculate the movement of other surrounding vehicles to complete the merge, requiring high computational costs. In this paper, we focus on dragonfly behavior to solve this issue. Indeed, insects can behave adaptively in the complex real world in spite of the limited size of their brains. They reduce the computational requirements of their brain by relying on different properties of their surroundings, basing their intelligent behaviors on simple strategies. The behavior of a dragonfly when chasing a prey is an example of these strategies. In this study, we address the vehicle merging maneuver by applying dragonfly’s strategies to control the movement of the merging vehicle. We propose a simple control method inspired by the aforementioned strategies and, finally, we present simulation results that were conducted to demonstrate the effectiveness of this method. 相似文献
103.
Koji Honda Ikuo Yamamoto Masamichi Morita Hiroki Yamaguchi Hiroshi Arita Ryohei Ishige Yuji Higaki Atsushi Takahara 《Polymer》2014
The effect of α-substituent on the molecular motion and wetting behavior of poly{2-(perfluorobutyl)ethyl acrylate} [PFA-C4], poly{2-(perfluorobutyl)ethyl methacrylate} [PFMA-C4], poly{2-(perfluorobutyl)ethyl α-fluoroacrylate} [PFFA-C4], and poly{2-(perfluorobutyl)ethyl α-chloroacrylate} [PFClA-C4] films were characterized by dynamic contact angle measurement, lateral force microscopy (LFM), wide angle X-ray diffraction (WAXD), and X-ray photoelectron spectroscopy (XPS). WAXD of oriented PFClA-C4 fiber suggested the presence of rod-like chain due to the presence of bulky α-substituent. The glass transition temperature (Tg) of PFFA-C4 and PFClA-C4 were well above the room temperature. The water repellencies of PFFA-C4 and PFClA-C4 were as high as that of PFMA-C4 and their oil repellency of PFFA-C4 and PFClA-C4 was higher than the PFMA-C4. This result was originated from the low main chain mobility of PFFA-C4 and PFClA-C4 due to the presence of bulky α-substituents. The effect of molecular motion on water repellency was clarified by the results of temperature dependence studies of dynamic contact angle, LFM, and surface chemical composition measured by XPS. 相似文献
104.
105.
106.
S. Yamada K. Fukutani K. Yamaguchi H. Funahashi S. Watanabe K. Ebata 《Polymer-Plastics Technology and Engineering》2016,55(15):1577-1585
An intermeshing corotating twin-screw extruder is often used for producing polymer composites. In this study, we discussed mixing performance of special rotor segments in molten zone. These rotor segments have several tip clearances for achievement of self-cleaning and effective mixing, and these are named various clearance mixing technology. We studied about dispersive mixing performance of configuration, which consists of various clearance mixing technologys (various clearance mixing technology configuration) using numerical analyses and experiments. For the analytical evaluation of mixing performance, we have adopted a particle tracking method. As evaluation indices of dispersive mixing performance, we focused on following three values (1) maximum value in a history of first principal stress of each particle, (2) time-integrated shear rate of each particle, and (3) time-integrated first principal stress of each particle. And we made the probability distributions of the indices. We adopted weighted probability as approximation of volume probability in each region. The results were compared with those of kneading disk segments configuration (kneading disk configuration). Furthermore, we validated the accuracy of the analytical evaluation by performing experiments under same conditions as those of numerical analyses. For the experimental evaluation of mixing performance, we used twin-screw extruder. Polypropylene was selected as suspending media. And CaCO3 was selected as filler. To compare just the mixing performance of various clearance mixing technology configuration with that of kneading disk configuration, side feeding and screw configuration which had third mixing segments zone were adopted. From the experimental result, it is found that various clearance mixing technology configuration dispersed better than kneading disk configuration. And from the comparison between the experimental evaluation and the analytical evaluation, it is found that the first principal stress is more appropriate for evaluation index of dispersive mixing. Finally, it can be mentioned that various clearance mixing technology configuration has better mixing performance than kneading disk configuration, and large stress is important for dispersive mixing. 相似文献
107.
108.
MicroRNA-331-3p Suppresses Cervical Cancer Cell Proliferation and E6/E7 Expression by Targeting NRP2
Tomomi Fujii Keiji Shimada Aya Asano Yoshihiro Tatsumi Naoko Yamaguchi Masaharu Yamazaki Noboru Konishi 《International journal of molecular sciences》2016,17(8)
Aberrant expression of microRNAs (miRNAs) is involved in the development and progression of various types of cancers. In this study, we investigated the role of miR-331-3p in cell proliferation and the expression of keratinocyte differentiation markers of uterine cervical cancer cells. Moreover, we evaluated whether neuropilin 2 (NRP2) are putative target molecules that regulate the human papillomavirus (HPV) related oncoproteins E6 and E7. Cell proliferation in the human cervical cancer cell lines SKG-II, HCS-2, and HeLa was assessed using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay. Cellular apoptosis was measured using the TdT-mediated dUTP nick end labeling (TUNEL) and Annexin V assays. Quantitative RT-PCR was used to measure the messenger RNA (mRNA) expression of the NRP2, E6, E7, p63, and involucrin (IVL) genes. A functional assay for cell growth was performed using cell cycle analyses. Overexpression of miR-331-3p inhibited cell proliferation, and induced G2/M phase arrest and apoptosis in SKG-II, HCS-2 and HeLa cells. The luciferase reporter assay of the NRP2 3′-untranslated region revealed the direct regulation of NRP2 by miR-331-3p. Gene expression analyses using quantitative RT-PCR in SKG-II, HCS-2, and HeLa cells overexpressing miR-331-3p or suppressing NRP2 revealed down-regulation of E6, E7, and p63 mRNA and up-regulation of IVL mRNA. Moreover, miR-331-3p overexpression was suppressed NRP2 expression in protein level. We showed that miR-331-3p and NRP2 were key effectors of cell proliferation by regulating the cell cycle, apoptosis. NRP-2 also regulates the expression of E6/E7 and keratinocyte differentiation markers. Our findings suggest that miR-331-3p has an important role in regulating cervical cancer cell proliferation, and that miR-331-3p may contribute to keratinocyte differentiation through NRP2 suppression. miR-331-3p and NRP2 may contribute to anti-cancer effects. 相似文献
109.
Tsukaho Yahagi Daisuke Kawai Takuma Takahashi Motoyuki Iijima Junichi Tatami 《Journal of the American Ceramic Society》2022,105(3):2046-2057
Si3N4 ceramics with excellent mechanical properties are used for heat dissipation substrates and so on. In order to improve their reliability and expand their application fields, it is desirable to understand and control the electrical properties of Si3N4 ceramics. In this study, the electrical resistivity of Si3N4 ceramics with Yb2O3 additive was investigated by applying various voltages at temperatures ranging from 25°C to 300°C. When Yb2O3 was added as a sintering aid to Si3N4 ceramics, a crystalline J-phase (Yb4Si2O7N2) was formed and their electrical resistivity was significantly lower than that of Y2O3 additive. The electrical resistivity of the Yb2O3-added ceramics decreased with an increase in temperature and applied voltage. Yb existed in multiple valence states, Yb2+ and Yb3+, in the Si3N4 ceramics and the decrease in the electrical resistivity can be attributed hopping conduction through the J-phase. The J-phase in the Si3N4 ceramics was observed to be continuous, and percolation analysis suggested that the J-phase formed an infinite cluster. Therefore, the decrease in the electrical resistivity of the Yb2O3-added Si3N4 ceramics was found mainly to result from the formation of an infinite cluster of J-phase, which exhibits hopping conduction. 相似文献
110.
Poly(3-hexylthiophene-2,5-diyl) is among the most widely used conjugated polymers for opto-electronic applications. To enhance its properties, researchers have attempted to nanostructure this polymer using various processes including breath figure arrays, nanolithography and elaborated organic synthesis. We here demonstrate a simple process to nanostructure the conjugated polymer using self-assembly with polystyrene and selective removal of one of the phases. The influence of the molecular weight of each polymer on the thin film morphology was systematically studied by atomic force microscopy. Using this approach, we observe two types of nanostructure, namely, nanoporous and nanoisland structures, of which the dimensions can be tuned by modifying the molecular weight of each polymer in the blend. This simple process introduces a cost-effective alternative to produce thin films of conjugated polymer with average nano-features from 100 nm up to 500 nm which could be used in a wide range of applications. 相似文献