全文获取类型
收费全文 | 19023篇 |
免费 | 2507篇 |
国内免费 | 2095篇 |
专业分类
电工技术 | 2240篇 |
综合类 | 3109篇 |
化学工业 | 1109篇 |
金属工艺 | 485篇 |
机械仪表 | 1240篇 |
建筑科学 | 795篇 |
矿业工程 | 306篇 |
能源动力 | 331篇 |
轻工业 | 624篇 |
水利工程 | 391篇 |
石油天然气 | 469篇 |
武器工业 | 252篇 |
无线电 | 2726篇 |
一般工业技术 | 1887篇 |
冶金工业 | 270篇 |
原子能技术 | 204篇 |
自动化技术 | 7187篇 |
出版年
2024年 | 30篇 |
2023年 | 225篇 |
2022年 | 369篇 |
2021年 | 441篇 |
2020年 | 563篇 |
2019年 | 587篇 |
2018年 | 529篇 |
2017年 | 751篇 |
2016年 | 807篇 |
2015年 | 802篇 |
2014年 | 1156篇 |
2013年 | 1591篇 |
2012年 | 1444篇 |
2011年 | 1523篇 |
2010年 | 1200篇 |
2009年 | 1271篇 |
2008年 | 1208篇 |
2007年 | 1352篇 |
2006年 | 1087篇 |
2005年 | 1022篇 |
2004年 | 864篇 |
2003年 | 735篇 |
2002年 | 650篇 |
2001年 | 525篇 |
2000年 | 455篇 |
1999年 | 366篇 |
1998年 | 266篇 |
1997年 | 283篇 |
1996年 | 234篇 |
1995年 | 203篇 |
1994年 | 190篇 |
1993年 | 147篇 |
1992年 | 129篇 |
1991年 | 120篇 |
1990年 | 101篇 |
1989年 | 76篇 |
1988年 | 53篇 |
1987年 | 40篇 |
1986年 | 20篇 |
1985年 | 19篇 |
1984年 | 33篇 |
1983年 | 36篇 |
1982年 | 25篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1975年 | 4篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
José M. León Blanco Pedro L. González-R Carmen Martina Arroyo García María José Cózar-Bernal Marcos Calle Suárez David Canca Ortiz 《Drug development and industrial pharmacy》2018,44(1):135-143
This work was aimed at determining the feasibility of artificial neural networks (ANN) by implementing backpropagation algorithms with default settings to generate better predictive models than multiple linear regression (MLR) analysis. The study was hypothesized on timolol-loaded liposomes. As tutorial data for ANN, causal factors were used, which were fed into the computer program. The number of training cycles has been identified in order to optimize the performance of the ANN. The optimization was performed by minimizing the error between the predicted and real response values in the training step. The results showed that training was stopped at 10?000 training cycles with 80% of the pattern values, because at this point the ANN generalizes better. Minimum validation error was achieved at 12 hidden neurons in a single layer. MLR has great prediction ability, with errors between predicted and real values lower than 1% in some of the parameters evaluated. Thus, the performance of this model was compared to that of the MLR using a factorial design. Optimal formulations were identified by minimizing the distance among measured and theoretical parameters, by estimating the prediction errors. Results indicate that the ANN shows much better predictive ability than the MLR model. These findings demonstrate the increased efficiency of the combination of ANN and design of experiments, compared to the conventional MLR modeling techniques. 相似文献
32.
Xuan-Wei Lei Jun-Biao Liu Yue Wang Rong-Bo Yang 《Materials Science & Technology》2020,36(15):1655-1662
Simple closed-form expression of the generalised temperature integral in the basic equation to describe kinetic reactions for solid materials in linear heating process is always suitable for use in determining parameters. Many developed solutions only can give high accuracies on the general conditions. A new analytical approximate solution was deduced in this work. The deviations of this solution from the true value are fully analysed. This solution takes advantage in broader application conditions than other known solutions. The application of the new analytical approximate solution in austenite kinetic reaction in this work reinforces that austenite reaction rate is feasible to be given a priori. 相似文献
33.
研制了一种用于KDP晶体加工的平面飞切机床,该机床直线轴基于直线电动机驱动、液体静压导轨支承;刀具旋转轴采用高刚度气浮主轴+高刚度主轴旋转机构。基于高精度分辨率位置反馈+线性驱动器+PID控制算法,直线轴获得了1 mm/min速度下,0.018 mm/min的低速波动以及±0.01μm的位置精度;刀具微进给装置采用差动螺纹进给来实现,最终获得了进给分辨率1μm、锁紧后位置移动量小于1μm高精度进给。在优化工艺参数后,金刚石飞切机床加工100 mm×100 mm×10mm的KDP晶体后获得表面粗糙度Rq优于2 nm高精度指标;加工400 mm×400 mm×30 mm的铝镜后获得面形PV值优于3μm的高精度指标。 相似文献
34.
Thermal comfort is an important factor for the design of buildings. Although it has been well recognized that many physiological parameters are linked to the state of thermal comfort or discomfort of humans, how to use physiological signal to judge the state of thermal comfort has not been well studied. In this paper, the feasibility of continuously determining feelings of personal thermal comfort was discussed by using electroencephalogram (EEG) signals in private space. In the study, 22 subjects were exposed to thermally comfortable and uncomfortably hot environments, and their EEG signals were recorded. Spectral power features of the EEG signals were extracted, and an ensemble learning method using linear discriminant analysis or support vector machine as a sub-classifier was used to build the discriminant model. The results show that an average discriminate accuracy of 87.9% can be obtained within a detection window of 60 seconds. This study indicates that it is feasible to distinguish whether a person feels comfortable or too hot in their private space by multi-channel EEG signals without interruption and suggests possibility for further applications in neuroergonomics. 相似文献
35.
We propose a polylithic method for medium-term scheduling of a large-scale industrial plant operating in a continuous mode. The method combines a decomposition approach, a genetic algorithm (GA) and a constructive MILP-based heuristic. In the decomposition, decisions are made at two levels, using the rolling horizon approach. At the upper level, a reduced set of products and the time period is chosen to be considered in the lower level. At the lower level, a short-term scheduling MILP-model with event-based representation is used. A heuristic solution to the lower level problem is found using a constructive Moving Window heuristic guided by a genetic algorithm. The GA is applied for finding efficient utilisation of critical units in the lower level problem. For solving the one unit scheduling problem, a parallel dynamic programming algorithm is proposed. Implementation of the dynamic programming algorithm for a graphics processing unit (GPU) is incorporated in the GA for improving its performance. The experimental study of the proposed method on a real case of a large-scale plant shows a significant improvement of the solution quality and the solving time comparing to the pure decomposition algorithm proposed in the earlier study, and confirmed suitability of the proposed approach for the real-life production scheduling. In particular, the reduction of the number of changeovers and their duration in the obtained solution as well as the CPU time of solving the problem was about 60% using the new approach. 相似文献
36.
37.
38.
This article introduces a new class of functional-coefficient predictive regression models, where the regressors consist of auto-regressors and latent factor regressors, and the coefficients vary with certain index variable. The unobservable factor regressors are estimated through imposing an approximate factor model on high dimensional exogenous variables and subsequently implementing the classical principal component analysis. With the estimated factor regressors, a local linear smoothing method is used to estimate the coefficient functions (with appropriate rotation) and obtain a one-step ahead nonlinear forecast of the response variable, and then a wild bootstrap procedure is introduced to construct the prediction interval. Under regularity conditions, the asymptotic properties of the proposed methods are derived, showing that the local linear estimator and the nonlinear forecast using the estimated factor regressors are asymptotically equivalent to those using the true latent factor regressors. The developed model and methodology are further generalized to the factor-augmented vector predictive regression with functional coefficients. Finally, some extensive simulation studies and an empirical application to forecast the UK inflation are given to examine the finite-sample performance of the proposed model and methodology. 相似文献
39.
Michael
Pauley Christopher Mclean Jonathan H. Manton 《International Journal of Adaptive Control and Signal Processing》2020,34(7):813-838
A class of discrete-time random processes arising in engineering and econometrics applications consists of a linear state-space model whose parameters are modulated by the state of a finite-state Markov chain. Typical filtering approaches are collapsing methods, which approximate filtered distributions by mixtures of Gaussians, each Gaussian corresponding to one possibility of the recent history of the Markov chain, and particle methods. This article presents an alternative approach to filtering these processes based on keeping track of the values of the underlying filtered density and its characteristic function on grids. We prove that it has favorable convergence properties under certain assumptions. On the other hand, as a grid method, it suffers from the curse of dimensionality, and so is only suitable for low-dimensional systems. We compare our method to collapsing filters and a particle filter with examples, and find that it can outperform them on 1- and 2-dimensional problems, but loses its speed advantage on 3-dimensional systems. Meanwhile, our method has a proven theoretical convergence rate that is probably not achieved by collapsing and particle methods. 相似文献
40.
Yude Ji Yanping Guo Yuejuan Liu Yun Tian 《International Journal of Adaptive Control and Signal Processing》2020,34(3):283-297
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results. 相似文献