全文获取类型
收费全文 | 836篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 125篇 |
机械仪表 | 17篇 |
建筑科学 | 58篇 |
矿业工程 | 2篇 |
能源动力 | 17篇 |
轻工业 | 55篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 138篇 |
一般工业技术 | 154篇 |
冶金工业 | 124篇 |
原子能技术 | 4篇 |
自动化技术 | 151篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 24篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 20篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 25篇 |
2014年 | 20篇 |
2013年 | 59篇 |
2012年 | 22篇 |
2011年 | 41篇 |
2010年 | 44篇 |
2009年 | 43篇 |
2008年 | 32篇 |
2007年 | 56篇 |
2006年 | 37篇 |
2005年 | 30篇 |
2004年 | 36篇 |
2003年 | 23篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 31篇 |
1997年 | 23篇 |
1996年 | 23篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 3篇 |
排序方式: 共有879条查询结果,搜索用时 171 毫秒
101.
Incorporating Web Analysis Into Neural Networks: An Example in Hopfield Net Searching 总被引:1,自引:0,他引:1
Chau M. Chen H. 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2007,37(3):352-358
Neural networks have been used in various applications on the World Wide Web, but most of them only rely on the available input-output examples without incorporating Web-specific knowledge, such as Web link analysis, into the network design. In this paper, we propose a new approach in which the Web is modeled as an asymmetric Hopfield Net. Each neuron in the network represents a Web page, and the connections between neurons represent the hyperlinks between Web pages. Web content analysis and Web link analysis are also incorporated into the model by adding a page content score function and a link score function into the weights of the neurons and the synapses, respectively. A simulation study was conducted to compare the proposed model with traditional Web search algorithms, namely, a breadth-first search and a best-first search using PageRank as the heuristic. The results showed that the proposed model performed more efficiently and effectively in searching for domain-specific Web pages. We believe that the model can also be useful in other Web applications such as Web page clustering and search result ranking 相似文献
102.
In this paper, a new six-phase pole-changing induction motor drive is proposed to extend the constant-power operating range for electric vehicle application. The double Fourier series is newly employed to analyze the spectra of the motor phase voltage and current. Consequently, the harmonic expression of the inverter DC-link current can be derived. In order to reduce the DC-link harmonics, a new sinusoidal pulsewidth-modulation strategy is developed for the proposed six-phase inverter. Experimental results, particularly the spectra of the phase current and the DC-link current, are given to verify the theoretical analysis. 相似文献
103.
Lubin Deborah A.; Elliot Jay C.; Black Mitchell C.; Johns Josephine M. 《Canadian Metallurgical Quarterly》2003,117(2):195
Decreased oxytocin levels in the amygdalas of rat dams following chronic gestational cocaine exposure have been correlated with heightened maternal aggressive behavior. In this experiment, drug-naive dams were implanted with bilateral cannulas into the central nucleus of the amygdala (CNA) or control area and infused with 1,000 or 500 ng of an oxytocin antagonist (OTA) or buffer, 4 hr before testing. Behavior was compared among dams infused with OTA into target areas just outside the CNA and cocaine-treated dams (infused with buffer). Dams infused with 1,000 ng OTA attacked intruders significantly more often than buffer-infused dams. OTA did not affect other behaviors, suggesting that disruption of oxytocin activity in the CNA may be sufficient to selectively alter maternal aggressive behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
The effects of zirconia (ZrO2), yttria (Y2O3), and nickel (Ni) on poly(vinyl butyral) (PVB) thermal degradation were evaluated using kinetic analysis of TGA data and nonlinear heating rates. An exact solution derived from the Arrhenius equation in an integration form was used for the kinetic analysis. The kinetic parameters of the thermal degradation reaction were determined utilizing the solution and the isoconversional principle. Results show that the reaction pathway of the PVB thermal degradation was altered by the presence of these inorganic materials except ZrO2. The strong catalytic effects of Y2O3, and Ni on the PVB degradation were found and discussed according to the analytical results. The reaction rate was accelerated faster in lower temperatures in the presence of Y2O3, and Ni. The degradation period of the PVB/Ni sample appeared the shortest for these cases. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2552–2559, 2006 相似文献
105.
We propose a novel high-speed magnetooptic (MO) modulator based on the optical excitation of surface magneto-plasmon (SMP) waves in bismuth-substituted yttrium iron garnet (Bi-YIG). A model describing magnetization dynamics of the Bi-YIG film is used in conjunction with an SMP reflectivity model to evaluate the performance of the device. In developing the reflectivity model, the dispersion relation for the SMP waves at a Bi-YIG-metal interface is derived. The optical response of the device is modeled for various driving pulses, and the performance of the device is discussed in terms of response time, efficiency, and bandwidth. Using practical material parameters, it is found that the modulator has an improved efficiency over MO modulation devices relying on bulk propagation for comparable driving current pulse durations, as well as the added benefits of a miniature design, multigigahertz operation, and tunable bandwidth. The analysis presented here provides a useful framework for the design and development of magneto-plasmon photonic devices. 相似文献
106.
Determined the effectiveness of a 10-wk filial therapy training model as an intervention method for Chinese parents living in the US. Results of the analyses of covariance reveal that the Chinese parents in the experimental group had a significant increase in their level of empathic interactions with their children; a significant increase in their attitude of acceptance toward their children; and a significant reduction in their level of stress related to parenting. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
Laryngospasm occurring after tracheal extubation in children is potentially dangerous. This study uses acupuncture with bloodletting at the Shao Shang (L 11) or Shang Yang (Li 1) acupoints to investigate whether this technique can prevent or treat laryngospasm. Seventy-six patients were randomly divided into two groups. Patients in the acupuncture group (n = 38) were treated with bilateral Shao Shang acupunctures at the end of the operation. Patients in the control group (n = 38) were not. The incidence of laryngospasm in the acupuncture group (5.3%) was less than that in the control group (23.7%) (p < 0.05). If laryngospasm developed, patients were immediately treated with acupuncture at either the Shao Shang or Shang Yang acupoints. As judged by an increase in peripheral oxygen saturation, the laryngospasm was relieved within 1 min of acupuncture in all patients. It is concluded that acupuncture with bloodletting at the Shao Shang acupoint may prevent and treat laryngospasm occurring after tracheal extubation in children. 相似文献
108.
109.
110.
Very-high-performance common-emitter InP/InGaAs single heterojunction bipolar transistors (HBTs) grown by metalorganic molecular beam epitaxy (MOMBE) are reported. They exhibit a maximum oscillation frequency (f T) of 180 GHz at a current density of 1×105 A/cm2. this corresponds to an (R BC BC)eff=f T/(8πf 2max) delay time of 0.12 ps, which is the smallest value every reported for common-emitter InP/InGaAs HBTs. The devices have 11 μm2 total emitter area and exhibit current gain values up to 100 at zero base-collector bias voltage. The breakdown voltage of these devices is high with measured BV CEO and BV CEO of 8 and 17 V, respectively 相似文献