全文获取类型
收费全文 | 3673篇 |
免费 | 122篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 176篇 |
综合类 | 3篇 |
化学工业 | 981篇 |
金属工艺 | 75篇 |
机械仪表 | 93篇 |
建筑科学 | 93篇 |
能源动力 | 137篇 |
轻工业 | 397篇 |
水利工程 | 19篇 |
石油天然气 | 3篇 |
无线电 | 298篇 |
一般工业技术 | 648篇 |
冶金工业 | 427篇 |
原子能技术 | 138篇 |
自动化技术 | 319篇 |
出版年
2023年 | 26篇 |
2022年 | 48篇 |
2021年 | 90篇 |
2020年 | 30篇 |
2019年 | 47篇 |
2018年 | 80篇 |
2017年 | 63篇 |
2016年 | 118篇 |
2015年 | 61篇 |
2014年 | 107篇 |
2013年 | 198篇 |
2012年 | 179篇 |
2011年 | 216篇 |
2010年 | 157篇 |
2009年 | 175篇 |
2008年 | 208篇 |
2007年 | 153篇 |
2006年 | 132篇 |
2005年 | 129篇 |
2004年 | 119篇 |
2003年 | 98篇 |
2002年 | 110篇 |
2001年 | 73篇 |
2000年 | 65篇 |
1999年 | 78篇 |
1998年 | 190篇 |
1997年 | 128篇 |
1996年 | 86篇 |
1995年 | 68篇 |
1994年 | 66篇 |
1993年 | 59篇 |
1992年 | 38篇 |
1991年 | 33篇 |
1990年 | 35篇 |
1989年 | 38篇 |
1988年 | 24篇 |
1987年 | 23篇 |
1986年 | 28篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 17篇 |
1976年 | 25篇 |
1975年 | 11篇 |
1974年 | 7篇 |
排序方式: 共有3807条查询结果,搜索用时 15 毫秒
71.
We present a method to control the phase of an optical lattice according to an external trigger signal. The method has a latency of less than 30 μs. Two phase locked digital synthesizers provide the driving signal for two acousto-optic modulators which control the frequency and phase of the counter-propagating beams which form a standing wave (optical lattice). A micro-controller with an external interrupt function is connected to the desired external signal, and updates the phase register of one of the synthesizers when the external signal changes. The standing wave (period λ/2 = 390 nm) can be moved by units of 49 nm with a mean jitter of 28 nm. The phase change is well known due to the digital nature of the synthesizer, and does not need calibration. The uses of the scheme include coherent control of atomic matter-wave dynamics. 相似文献
72.
High concentrations of manganese and iron in the Saigon River are major problems for the water supply in Ho Chi Minh City (HCMC), Viet Nam. To identify their sources and leaching processes, we surveyed water quality along the Saigon River and ran batch leaching tests using soil and sediment samples. Two important leaching processes were identified: acidic leaching from acid sulfate soil (ASS) in the middle reaches of the river, and Mn dissolution and Fe reduction from sediments in the downstream reaches. Low pH caused the concurrent release of Fe and Mn from the ASS. In contrast, anoxia caused the release of Fe but not Mn from the sediments, whereas low pH facilitated Mn dissolution. Sediments are a more important source of Mn because of their higher Mn contents (10 times) and release rates (14 times) than those from ASS. 相似文献
73.
Keiji Nagatani Seiga Kiribayashi Yoshito Okada Kazuki Otake Kazuya Yoshida Satoshi Tadokoro Takeshi Nishimura Tomoaki Yoshida Eiji Koyanagi Mineo Fukushima Shinji Kawatsuma 《野外机器人技术杂志》2013,30(1):44-63
On March 11, 2011, a massive earthquake (magnitude 9.0) and accompanying tsunami hit the Tohoku region of eastern Japan. Since then, the Fukushima Daiichi Nuclear Power Plants have been facing a crisis due to the loss of all power that resulted from the meltdown accidents. Three buildings housing nuclear reactors were seriously damaged from hydrogen explosions, and, in one building, the nuclear reactions became out of control. It was too dangerous for humans to enter the buildings to inspect the damage because radioactive materials were also being released. In response to this crisis, it was decided that mobile rescue robots would be used to carry out surveillance missions. The mobile rescue robots needed could not be delivered to the Tokyo Electric Power Company (TEPCO) until various technical issues were resolved. Those issues involved hardware reliability, communication functions, and the ability of the robots' electronic components to withstand radiation. Additional sensors and functionality that would enable the robots to respond effectively to the crisis were also needed. Available robots were therefore retrofitted for the disaster reponse missions. First, the radiation tolerance of the electronic componenets was checked by means of gamma ray irradiation tests, which were conducted using the facilities of the Japan Atomic Energy Agency (JAEA). The commercial electronic devices used in the original robot systems operated long enough (more than 100 h at a 10% safety margin) in the assumed environment (100 mGy/h). Next, the usability of wireless communication in the target environment was assessed. Such tests were not possible in the target environment itself, so they were performed at the Hamaoka Daiichi Nuclear Power Plants, which are similar to the target environment. As previously predicted, the test results indicated that robust wireless communication would not be possible in the reactor buildings. It was therefore determined that a wired communication device would need to be installed. After TEPCO's official urgent mission proposal was received, the team mounted additional devices to facilitate the installation of a water gauge in the basement of the reactor buildings to determine flooding levels. While these preparations were taking place, prospective robot operators from TEPCO trained in a laboratory environment. Finally, one of the robots was delivered to the Fukushima Daiichi Nuclear Power Plants on June 20, 2011, where it performed a number of important missions inside the buildings. In this paper, the requirements for the exploration mission in the Fukushima Daiichi Nuclear Power Plants are presented, the implementation is discussed, and the results of the mission are reported. 相似文献
74.
Ken-ichi Kohichi Hiroyuki Shiro Satoshi Hitoshi Atsushi 《Sensors and actuators. B, Chemical》2008,130(2):707-712
Pt-loaded metal oxides [WO3/ZrO2, MOx/TiO2 (MOx = WO3, MoO3, V2O5), WO3 and TiO2] equipped with interdigital Au electrodes have been tested as a NOx (NO and NO2) gas sensor at 500 °C. The impedance value at 4 Hz was used as a sensing signal. Among the samples tested, Pt-WO3/TiO2 showed the highest sensor response magnitude to NO. The sensor was found to respond consistently and rapidly to change in concentration of NO and NO2 in the oxygen rich and moist gas mixture at 500 °C. The 90% response and 90% recovery times were as short as less than 5–10 s. The impedance at 4 Hz of the present device was found to vary almost linearly with the logarithm of NOx (NO or NO2) concentration from 10 to 570 ppm. Pt-WO3/TiO2 showed responses to NO and NO2 of the same algebraic sign and nearly the same magnitude, while Pt/WO3 and WO3/TiO2 showed higher response to NO than NO2. The impedance at 4 Hz in the presence of NO for Pt-WO3/TiO2 was almost equal at any O2 concentration examined (1–99%), while in the case of Pt/WO3 and WO3/TiO2 the impedance increased with the oxygen concentration. The features of Pt-WO3/TiO2 are favorable as a NOx sensor that can monitor and control the NOx concentration in automotive exhaust. The effect of WO3 loading of Pt-WO3/ZrO2-based sensor is studied to discuss the role of surface W-OH sites on the NOx sensing. 相似文献
75.
Hiroshi Mukawa Katsuyuki Akutsu Ikuo Matsumura Satoshi Nakano Takuji Yoshida Mieko Kuwahara Kazuma Aiki 《Journal of the Society for Information Display》2009,17(3):185-193
Abstract— A full‐color eyewear display with over 85% see‐through transmittance with a 16° horizontal field of view was developed. Very low color crosstalk, less than 0.008 Δu′v′ uniformity, and 120% NTSC color gamut were achieved. Waveguides with two in‐ and out‐coupling reflection volume hologram elements enabled a simple configuration that has an optical engine beside the user's temples. The reflection volume hologram elements used on the waveguides realized a small thickness of 1.4 mm for each waveguide, and an out‐coupling reflection volume hologram used as an optical combiner contributed a high see‐through transmittance of 85% due to its wavelength selectivity. However, there are technical challenges in achieving a reasonable screen size and quality color images with optics that utilize holographic waveguides because holograms have large chromatic dispersions compared to conventional optical elements such as lenses and mirrors. Approaches to overcome these issues are described. 相似文献
76.
Masahiro Nakagawa Tadashi Kondo Tsuyosi Kudo Shoichiro Takao Junji Ueno 《Artificial Life and Robotics》2009,14(2):118-122
In this study, we propose a revised radial basis function (RBF) neural network algorithm and apply this algorithm to computer-aided diagnosis (CAD) of the liver. First, the revised RBF neural network algorithm is applied to recognition of the liver regions, and the recognition results are compared with those obtained using the conventional RBF neural network and the conventional multilayered neural network trained using the back-propagation algorithm. It is shown that the revised RBF neural network is accurate, and is a useful method because the parameters are automatically determined. Then, the revised RBF neural network is applied to CAD of the liver cancer called hepatocellular carcinoma (HCC). 相似文献
77.
G. -H. Oh Y. Ishimoto T. Kawae M. Nakagawa O. Ishikawa T. Hata T. Kodama S. Ikehata 《Journal of Low Temperature Physics》1994,95(3-4):525-546
We have cooled a3He-4He dilute solution down to 97 K, which is the lowest temperature ever been achieved in a dilute mixture. However, there is no sign of the superfluid transition of3He quasiparticles in the solution. In the sub-millikelvin region, we have measured the thermal boundary resistance between the solutions and sintered metal powder as a function of temperature T. We find that the thermal boundary resistence is proportional to T–2 below 1 mK and that the resistance shows a strong dependence on magnetic fields below 0.1 T. These results suggest that the magnetic coupling is dominant in this temperature region. We have also estimated the heat leak into the dilute solution. It is found that the heat leak is proportional to the power of one third of inverse time, and the main source of the heat leak is ascribed to the viscous movement of3He quasiparticles. 相似文献
78.
Zilong Zhang Wen Zhao Guo Chen Masaya Toda Satoshi Koizumi Yasuo Koide Meiyong Liao 《Advanced functional materials》2023,33(27):2300805
Electrically integrable, high-sensitivity, and high-reliability magnetic sensors are not yet realized at high temperatures (500 °C). In this study, an integrated on-chip single-crystal diamond (SCD) micro-electromechanical system (MEMS) magnetic transducer is demonstrated by coupling SCD with a large magnetostrictive FeGa film. The FeGa film is multifunctionalized to actuate the resonator, self-sense the external magnetic field, and electrically readout the resonance signal. The on-chip SCD MEMS transducer shows a high sensitivity of 3.2 Hz mT−1 from room temperature to 500 °C and a low noise level of 9.45 nT Hz−1/2 up to 300 °C. The minimum fluctuation of the resonance frequency is 1.9 × 10−6 at room temperature and 2.3 × 10−6 at 300 °C. An SCD MEMS resonator array with parallel electric readout is subsequently achieved, thus providing a basis for the development of magnetic image sensors. The present study facilitates the development of highly integrated on-chip MEMS resonator transducers with high performance and high thermal stability. 相似文献
79.
Artificial Life and Robotics - In recent years, unspecified messages posted on social media have significantly affected the price fluctuations of online-traded products, such as stocks and virtual... 相似文献
80.
Computational Economics - It is possible to model trust as an investment game, where a player in order to receive a reward or a better outcome, accepts a certain risk of defection by another... 相似文献