全文获取类型
收费全文 | 23261篇 |
免费 | 4156篇 |
国内免费 | 3242篇 |
专业分类
电工技术 | 3459篇 |
技术理论 | 3篇 |
综合类 | 3582篇 |
化学工业 | 859篇 |
金属工艺 | 454篇 |
机械仪表 | 1475篇 |
建筑科学 | 1129篇 |
矿业工程 | 908篇 |
能源动力 | 575篇 |
轻工业 | 336篇 |
水利工程 | 586篇 |
石油天然气 | 622篇 |
武器工业 | 629篇 |
无线电 | 4152篇 |
一般工业技术 | 1816篇 |
冶金工业 | 512篇 |
原子能技术 | 98篇 |
自动化技术 | 9464篇 |
出版年
2024年 | 160篇 |
2023年 | 509篇 |
2022年 | 808篇 |
2021年 | 865篇 |
2020年 | 1062篇 |
2019年 | 961篇 |
2018年 | 848篇 |
2017年 | 1028篇 |
2016年 | 1097篇 |
2015年 | 1192篇 |
2014年 | 1580篇 |
2013年 | 1801篇 |
2012年 | 1854篇 |
2011年 | 1992篇 |
2010年 | 1498篇 |
2009年 | 1558篇 |
2008年 | 1544篇 |
2007年 | 1614篇 |
2006年 | 1443篇 |
2005年 | 1224篇 |
2004年 | 1007篇 |
2003年 | 811篇 |
2002年 | 661篇 |
2001年 | 583篇 |
2000年 | 522篇 |
1999年 | 412篇 |
1998年 | 330篇 |
1997年 | 303篇 |
1996年 | 261篇 |
1995年 | 218篇 |
1994年 | 161篇 |
1993年 | 152篇 |
1992年 | 136篇 |
1991年 | 91篇 |
1990年 | 92篇 |
1989年 | 63篇 |
1988年 | 49篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 7篇 |
1984年 | 25篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1963年 | 4篇 |
1960年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Denis Rodrigue 《加拿大化工杂志》2002,80(2):289-292
Recently, the author (Rodrigue, 2001 a, b) proposed a generalized correlation for the steady rise of gas bubbles in uncontaminated viscous Newtonian fluids of infinite extent. It is the purpose of this note to show that this model can be modified for inelastic non‐Newtonian power‐law fluids. Using data taken from six different studies, it is shown that the modified model can predict quite nicely the bubble velocity for these non‐Newtonian inelastic fluids. 相似文献
82.
Ramon R. Costa Liu Hsu 《International Journal of Adaptive Control and Signal Processing》1992,6(1):19-33
A variable structure model reference adaptive controller (VS-MRAC) using only input and output measurements was recently proposed and shown to be globally asymptotically stable with superior transient behaviour and disturbance rejection properties. In this paper a singular perturbation approach is used in order to establish the robustness of the controller in the presence of unmodelled dynamics (parasitics) and disturbances. We develop a new Lyapunov-based technique to analyse the overall system and show that for sufficiently small parasitics the system remains stable and the output error is small in some sense. 相似文献
83.
Zhang Sheng-ming Yangtze River Scientific Research Institute Wuhan Hubei P. R. China 《水动力学研究与进展(B辑)》1992,(2)
Through a series of model tests of five scales for 2-D free hydraulic jump, the da-ta of fluctuating pressure acting on the floor level within the hydraulic jump were obtained. Dur-ing the experiments, Froude number varied from 2.94 to 8.61, and Reynolds number rangedfrom 2×10~4 to 6×10~5. Experiment results indicate that the amplitude scale of fluctuating pres-sure is the length scale of model, i. e. P'=L, which agrees with gravity similarity law: Thefrequency scale of the fluctuating pressure is a unity i. e., f=1, which does not satisfy thegravity similarity law. 相似文献
84.
具有Hammerstein形式的非线性系统广义预测控制 总被引:14,自引:2,他引:12
本文提出了具有Hammerstein形式的非线性系统广义预测控制方法,分析了当控制水平等于1时闭环系统的稳定性,同时还提出了使用线性估计器的非线性自适应广义预测控制算法。仿真结果表明了算法的有效性。 相似文献
85.
A new multivariable adaptive nonlinear predictive controller is designed using a general nonlinear input-output model and variable transformations. The controller is similar in form to typical linear predictive controllers can be tuned analogously or by specifying a single parameters for each controlled variable. In addition, the design procedure is computationally efficient. The new controller is compared to a multi-loop proportional-integral (PI) controller with one-way static decoupling and to an adaptive linear predictive controller through tests on a simulated nonlinear distillation column. The new controller performed well in an experimental application to a multicomponent distillation column. 相似文献
86.
Giuseppe Ferri 《Analog Integrated Circuits and Signal Processing》2002,33(3):249-262
In this paper the author will present the working principle and the applications of a novel adaptive biasing topology, designed to decrease the stand-by power dissipation without affecting the transient performance of low-power amplifiers. The proposed circuit, whose principle and circuit topology can be implemented both in CMOS and in bipolar standard technologies, gives a biasing current whose value depends on the applied input differential voltage and can be set according to the requested transient performance constraints. The adaptive architecture can be utilized in the design of high-efficient low-power operational amplifiers, for the biasing of both the input stage (where the input source current is dynamically increased) and the output stage (where the output current can be controlled and limited). These amplifiers show a very good behaviour, evaluated in terms of two efficiency factors, if compared with those of other adaptive solutions and class-AB topologies, proposed in the literature. Simulation results and also measurements on a chip prototype, fabricated in a standard CMOS technology, are finally presented. 相似文献
87.
The equilibrium CO2 sorption isotherms and isobars for rubbery EVA containing various amounts of vinyl acetate (VA) over a wide pressure range 10-340 atm and 25-52 °C were investigated. The normalized CO2 sorption concentration (in cm3 (STP) CO2/mole VA) isotherms of these polymers as a function of pressure consisted of two distinct regions turning at near Pc. The normalized sorption isotherms in these two distinct regions could be fairly described by two respective power laws: C=KaPna for above Pc and C=kbPnb for below Pc. The normalized CO2 sorption isotherms were found to be about the same for four EVA samples having different VA contents for below Pc, suggesting that the sorption process at below Pc may be mainly driven by the presence of carbonyl groups. At above Pc, the degree of crystallinity of the polymer appeared to be a major factor to affect the sorption process, with the higher the degree of crystallinity, the lower the normalized CO2 sorption concentration in the polymer. The sorption isobars of the polymer as a function of temperature were governed by the interplay of density, viscosity, and diffusivity of CO2 depending on the pressure studied. 相似文献
88.
Diedrichsen J?rn; Ivry Richard B.; Hazeltine Eliot; Kennerley Steven; Cohen Asher 《Canadian Metallurgical Quarterly》2003,29(1):64
Four experiments were conducted to identify the locus of interference observed during the preparation of bimanual reaching movements. Target locations were specified by color, and the right-hand and left-hand targets could be either the same or a different color. Movements of different amplitudes (Experiment 1) or different directions (Experiment 2) to targets of the same color were initiated more quickly than symmetric movements to targets of different colors. These results indicate that costs observed during bimanual movements arise during target selection rather than during motor programming. Experiments 3 and 4 further examined the interference associated with target selection. Reaction time costs were found with unimanual movements when the target was presented among distractors associated with responses for the other hand. Interference observed during bimanual reaching appears to reflect difficulty in segregating the response rules assigned to each hand. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
89.
A generalized diffusion coefficient correlation for a binary system of liquids has been developed to represent the data for a wide range of temperatures. Detailed analysis shows that the proposed correlation fits the experimental measurements of diffusivity with the corresponding calculated values with an acceptable percentage error. 相似文献
90.
实际图像处理中当视场的变化引起目标变形时,固定大小的形态学算子很难达到较好的处理效果。研究了利用距离变换自适应地调整结构元大小的方法,即根据图像的不同位置来调整结构元素的大小,从而实现图像的形态学运算,并由此推导出了快速计算方法,最后测试了这种新算法的有效性。实验结果表明,该算法取得了较为理想的效果。 相似文献