首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   479篇
  免费   6篇
  国内免费   2篇
电工技术   12篇
化学工业   93篇
金属工艺   20篇
机械仪表   7篇
建筑科学   8篇
能源动力   12篇
轻工业   20篇
水利工程   1篇
无线电   56篇
一般工业技术   104篇
冶金工业   120篇
原子能技术   27篇
自动化技术   7篇
  2022年   7篇
  2021年   3篇
  2018年   4篇
  2017年   5篇
  2016年   5篇
  2015年   4篇
  2014年   10篇
  2013年   14篇
  2012年   9篇
  2011年   16篇
  2010年   16篇
  2009年   12篇
  2008年   11篇
  2007年   10篇
  2006年   8篇
  2005年   10篇
  2004年   15篇
  2003年   11篇
  2002年   15篇
  2001年   4篇
  2000年   16篇
  1999年   14篇
  1998年   59篇
  1997年   15篇
  1996年   13篇
  1995年   13篇
  1994年   11篇
  1993年   15篇
  1992年   11篇
  1991年   2篇
  1990年   5篇
  1989年   7篇
  1988年   8篇
  1987年   11篇
  1986年   7篇
  1985年   9篇
  1984年   5篇
  1983年   11篇
  1982年   10篇
  1981年   2篇
  1980年   7篇
  1979年   5篇
  1978年   6篇
  1977年   4篇
  1976年   10篇
  1975年   2篇
  1974年   7篇
  1973年   3篇
  1970年   3篇
  1939年   2篇
排序方式: 共有487条查询结果,搜索用时 15 毫秒
111.
The authors have observed the relationship between waveform of electromagnetic noise and change of surface for opening Ag-Pd electric contacts. In case of Ag-Pd electrodes, continuous noise is observed in the whole period of arc discharge in both current polarities. Fluctuations of are voltage and noise are large in the middle part of arc discharge duration. The noise decreases in the later half. The authors proposed a classification of noise waveforms and pattern of surface changes. As a result, patterns of noise waveform and changes of electrode surface at various circuit conditions are classified into three categories. In this paper, the authors showed the correlation between pattern of noise waveform and the change of electrode surface  相似文献   
112.
113.
This paper proposes a CTI client/server coordination system exclusively for use with a smart phone. The system makes use of a CTI client, performing combined functions of a SIP phone and a Web browser. The proposed CTI client/server coordination system comprises SIP servers and Web servers, both of which are installed in enterprises, and CTI clients that run on smart phones in a mobile environment. Furthermore, the CTI clients perform the function of SIP phone by communicating with SIP servers. In addition, CTI clients can display telephone directories and logging of phone calls stored in Web servers. They can display screens of ordinary Web browsers. Here, one might switch between a SIP phone function and a Web communication screen with merely a single touch of the tab key. Consequently, smart phones in the mobile environment make it possible to conduct telephone meetings while browsing with a Web screen.  相似文献   
114.
Converter slag contains free lime (CaO) and unstable iron oxides (FeO, FeOOH) that may lead to expansive self-destruction. A typical industry practice for converter slag has been stabilization by steam curing and autoclaving; however, the stabilization can only reach the surface, and not the inside, of slag particles. A new method is proposed in this study to stabilize the converter slag by heating at a low temperature. After magnetic separation, specimens of converter slag were subjected to heating for 2 h at a temperature of 500°C, resulting in a decrease of free lime content irrespective of the particle size. This effect was attributed to the formation of Ca2Fe9O13 and complicated apatite groups owing to the heating. The iron oxides in the converter slag were analyzed by X-ray photoelectron spectra. It was found that after heating, the unstable FeO (wustite) content decreased and an oxidized α-Fe2O3 (hematite) increased. This led to the prevention of the iron-induced expansion. The rate of heat liberation by the free lime in converter slag was smaller than that of the reagent CaO. This suggests that the presumed free lime is in a different form based on the Ca bond energy in the surface of slag particles.  相似文献   
115.
Methionine (Met) is considered the most toxic amino acid in mammals. Here, we investigated biochemical and behavioral impacts of ad libitum one-week feeding of high-Met diets on mice. Adult male mice were fed the standard rodent diet that contained 0.44% Met (1×) or a diet containing 16 graded Met doses (1.2×–13×). High-Met diets for one-week induced a dose-dependent decrease in body weight and an increase in serum Met levels with a 2.55 mM peak (versus basal 53 µM) on the 12×Met diet. Total homocysteine (Hcy) levels were also upregulated while concentrations of other amino acids were almost maintained in serum. Similarly, levels of Met and Hcy (but not the other amino acids) were highly elevated in the cerebrospinal fluids of mice on the 10×Met diet; the Met levels were much higher than Hcy and the others. In a series of behavioral tests, mice on the 10×Met diet displayed increased anxiety and decreased traveled distances in an open-field test, increased activity to escape from water soaking and tail hanging, and normal learning/memory activity in a Y-maze test, which were reflections of negative/positive symptoms and normal cognitive function, respectively. These results indicate that high-Met ad libitum feeding even for a week can induce bipolar disorder-like disease models in mice.  相似文献   
116.
117.
LiFePO4 as a cathode material for rechargeable lithium batteries was prepared by hydrothermal process at 170 °C under inert atmosphere. The starting materials were LiOH, FeSO4, and (NH4)2HPO4. The particle size of the obtained LiFePO4 was 0.5 μm. The electrochemical properties of LiFePO4 were characterized in a mixed solvent of ethylene carbonate and diethyl carbonate (1:1 in volume) containing 1.0 mol dm−3 LiClO4. The hydrothermally synthesized LiFePO4 exhibited a discharge capacity of 130 mA h g−1, which was smaller than theoretical capacity (170 mA h g−1). The annealing of LiFePO4 at 400 °C in argon atmosphere was effective in increasing the discharge capacity. The discharge capacity of the annealed LiFePO4 was 150 mA h g−1.  相似文献   
118.
To study the operation of selective attention in a conflict situation with automatic processes, we trained 4 Japanese macaques; (Macaca fuscata) extensively on a manual go/no-go task. The monkey had to discriminate either the color, shape, motion direction, or location of a visual stimulus. In each trial, the behavioral meaning of the relevant feature (go or no-go) could either be congruent or incongruent with irrelevant features of the same stimulus. Reaction times were slowed, and error rates increased when irrelevant stimulus features were incongruent with the required response. The effects were obtained when the monkey attended to the color, shape, or motion direction, but not when it attended to the location of the stimulus. The effects were cumulative so that the interference from 1 incongruent feature was smaller than that from 2 incongruent features. We propose that the present paradigm provides a behavioral analogue of the human Stroop effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
119.
Diffusion of platinum element which increase protectivity of NiAl layer for hot corrosion and oxidation of Ni-base superalloys was investigated in NiAl compound with compositions of 43.7–51.9 at% Al at 1373–1673 K by the diffusion couple method. The diffusion coefficients, DPt, exhibit a large concentration dependence of valley type-shape; the DPt has the minimum value quite near the stoichiometric composition and it increases with deviation from the stoichiometry. On the other hand, the activation energy, Q, shows the maximum value near the stoichiometry. Q slightly decreases with Ni composition in Ni-rich side, while it decrease dramatically with Al composition in Al-rich side. Diffusion of platinum element in NiAl occurs mainly by the Triple defect mechanism at stoichiometry, by the anti-site atom bridge mechanism in considerably off-stoichiometry in Ni-rich side and by the next nearest neighbor-jump mechanism with constitutional Ni vacancies in quite off-stoichiometry in Al-rich side.  相似文献   
120.
Extrapolation of animal data to assess pharmacokinetic parameters in humans is an important tool in drug development. Allometric scaling has many proponents, and many different approaches and techniques have been proposed to optimise the prediction of pharmacokinetic parameters from animals to humans. The allometric approach is based on the power function Y = aWb, where the bodyweight of the species is plotted against the pharmacokinetic parameter of interest on a log-log scale. Clearance, volume of distribution and elimination half-life are the 3 most frequently extrapolated pharmacokinetic parameters. Clearance is not predicted very well (error between predicted and observed clearance > 30%) using the basic allometric equation in most cases. Thus, several other approaches have been proposed. An early approach was the concept of neoteny, where the clearance is predicted on the basis of species bodyweight and maximum life-span potential. A second approach uses a 2-term power equation based on brain and body weight to predict the intrinsic clearance of drugs that are primarily eliminated by phase I oxidative metabolism. Most recently, the use of the product of brain weight and clearance has been proposed. A literature review reveals different degrees of success of improved prediction with the different methods for various drugs. In a comparative study, the determining factor in selecting a method for prediction of clearance was found to be the value of the exponent. Integration of in vitro data into in vivo clearance to improve the predictive performance of clearance has also been suggested. Although there are proponents of using body surface area instead of bodyweight, no advantage has been noted in this approach. It has also been noted that the unbound clearance of a drug cannot be predicted any better than the total body clearance (CL). In general, there is a good correlation between bodyweight and volume of the central compartment (Vc); hence, Vc does not face the same complications as CL. The relationship between elimination half-life (t 1/2 beta) and bodyweight across species results in poor correlation, most probably because of the hybrid nature of this parameter. When a reasonable prediction of CL and Vc is made, t 1/2 beta may be predicted from the equation t 1/2 beta = 0.693 Vc/CL.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号