全文获取类型
收费全文 | 5153篇 |
免费 | 120篇 |
国内免费 | 79篇 |
专业分类
电工技术 | 236篇 |
综合类 | 226篇 |
化学工业 | 488篇 |
金属工艺 | 349篇 |
机械仪表 | 740篇 |
建筑科学 | 148篇 |
矿业工程 | 257篇 |
能源动力 | 240篇 |
轻工业 | 256篇 |
水利工程 | 57篇 |
石油天然气 | 194篇 |
武器工业 | 47篇 |
无线电 | 415篇 |
一般工业技术 | 398篇 |
冶金工业 | 105篇 |
原子能技术 | 44篇 |
自动化技术 | 1152篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 56篇 |
2021年 | 98篇 |
2020年 | 84篇 |
2019年 | 88篇 |
2018年 | 75篇 |
2017年 | 105篇 |
2016年 | 122篇 |
2015年 | 143篇 |
2014年 | 222篇 |
2013年 | 214篇 |
2012年 | 217篇 |
2011年 | 348篇 |
2010年 | 212篇 |
2009年 | 219篇 |
2008年 | 248篇 |
2007年 | 327篇 |
2006年 | 280篇 |
2005年 | 283篇 |
2004年 | 257篇 |
2003年 | 228篇 |
2002年 | 188篇 |
2001年 | 151篇 |
2000年 | 171篇 |
1999年 | 159篇 |
1998年 | 157篇 |
1997年 | 128篇 |
1996年 | 115篇 |
1995年 | 94篇 |
1994年 | 77篇 |
1993年 | 42篇 |
1992年 | 53篇 |
1991年 | 22篇 |
1990年 | 26篇 |
1989年 | 31篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有5352条查询结果,搜索用时 15 毫秒
91.
电梯是随着高层建筑的兴建而发展起来的一种垂直运输工具,其要求安全性、舒适性和经济性。在多年的实践之后,变频调速已经成为了电梯传动的主要控制方式。本文主要阐述了MM440变频器在电梯控制中的应用。 相似文献
92.
The paper presents a new sensorless parameter identification method for permanent magnet stepper motors. Current sensors are assumed available, but mechanical sensors are not. Data is obtained with open-loop commands at multiple speeds. A new frame is proposed that presents advantages similar to the d–q frame, but without the need for a position sensor. The method exploits derived linear parameterizations and least-squares algorithms. In some cases, overparameterization is resolved using elimination theory. The parameters identified using the new procedure are found to be very close to those obtained with sensors. The approach is potentially applicable to other types of synchronous motors. 相似文献
93.
94.
A test for the serial independence of errors in panel data models is proposed. The test is based on the difference between the joint empirical characteristic function of residuals at different lags and the product of their marginal empirical characteristic functions. The test is nuisance-parameter-free and powerful against any type of pairwise dependence at all lags. A simple random permutation procedure is used to approximate the limit distribution of the test. A Monte Carlo experiment illustrates the finite sample performance of the test, and supports that the test statistic based on the estimated residuals has the same asymptotic distribution as the corresponding statistic based on the unobservable true errors. 相似文献
95.
In previous works, it was verified that the discrete-time microstructure (DTMS) model, which is estimated by training dataset of a financial time series, may be effectively applied to asset allocation control on the following test data. However, if the length of test dataset is too long, prediction capability of the estimated DTMS model may gradually decline due to behavior change of financial market, so that the asset allocation result may become worse on the latter part of test data. To overcome the drawback, this paper presents a semi-on-line adaptive modeling and trading approach to financial time series based on the DTMS model and using a receding horizon optimization procedure. First, a long-interval identification window is selected, and the dataset on the identification window is used to estimate a DTMS model, which will be used to do asset allocation on the following short-term trading interval that is referred to as the trading window. After asset allocation is over on the trading window, the length-fixed identification window is then moved to a new window that includes the previous trading window, and a new DTMS model is estimated by using the dataset on the new identification window. Next, asset allocation continues on the next trading window that follows the previous trading window, and then the modeling and asset allocation process will go on according to the above steps. In order to enhance the flexibility and adaptability of the DTMS model, a comprehensive parameter optimization method is proposed, which incorporates particle swarm optimization (PSO) with Kalman filter and maximum likelihood method for estimating the states and parameters of DTMS model. Based on the adaptive DTMS model estimated on each identification window, an adaptive asset allocation control strategy is designed to achieve optimal control of financial assets. The parameters of the asset allocation controller are optimized by the PSO algorithm on each identification window. Case studies on Hang Seng Index (HSI) of Hong Kong stock exchange and S&P 500 index show that the proposed adaptive modeling and trading strategy can obtain much better asset allocation control performance compared with the parameters-fixed DTMS model. 相似文献
96.
Noise discrepancies in multiple scales are utilized as indicators for image splicing forgery detection in this paper. Specifically, the test image is initially segmented into superpixels of multiple scales. In each individual scale, noise level function, which reflects the relation between noise level and brightness of each segment, is computed. Those segments not constrained by the noise level function are regarded as suspicious regions. In the final step, pixels appears in suspicious regions of each scale, after necessary morphological processing, are marked as spliced region(s). The Optimal Parameter Combination Searching (OPCS) Algorithm is proposed to determine the optimal parameters during the process. Two datasets are created for training the optimal parameters and to evaluate the proposed scheme, respectively. The experimental results show that the proposed scheme is effective, especially for the multi-objects splicing. In addition, the proposed scheme is proven to be superior to the existing state-of-the-art method. 相似文献
97.
Multi-dimensional rate control schemes have been recently utilized to adapt video streams to dynamic network conditions and heterogeneous devices. However, current multi-dimensional rate control methods, which estimate the model coefficients using fixed update duration, usually yield inaccurate parameters for dynamically changing video content. To address this problem, a content-adaptive parameters estimation scheme is proposed for multi-dimensional rate control. Firstly, we propose to estimate the parameters using dynamical update duration based on video content and the update duration of the model coefficients is determined by jointly considering the varying picture complexity and feedback information from the actual encoding results, which can improve the model parameter estimation accuracy. Secondly, a coarse-to-fine initial parameter calculation method is proposed to refine the initial frame rate according to the channel condition and the video sequence characteristics. Extensive experimental results show that the proposed solutions outperform the state-of-the-art schemes, especially for video sequences with high temporal and spatial complexity. Furthermore, our algorithm also slightly reduces the computational complexity as compared to related algorithms. 相似文献
98.
BackgroundAlthough cereals are used extensively in food products, ingestion of gluten-containing food has been associated with gluten-related disorders in susceptible individuals. Recently, the gluten-free (GF) products are one of the most dynamically growing branches of the food industry. However, many commercially available GF products provide lower level of proteins, dietary fibre, vitamins and minerals, compared with wheat products. To meet the growing demands of GF food consumers, efforts have been made to improve the overall quality of these products. Recently, inulin-type fructans (ITFs) were proposed as the beneficial ingredients of GF products.Scope and approachOver the last decade, the application of ITFs in GF products has been widely explored. Therefore, the aim of this review is to present the current application of ITFs as components of GF products by summarising the existing data concerning their effect on the technological properties and sensory quality of these products in the light of their physicochemical characteristics.Key findings and conclusionsITFs added to the GF products interact with other ingredients and additives. Generally, they have the potential to improve the technological properties and sensory perception of obtained products. The presented facts may provide an inspiration for further intensive work on the improvement of the quality of GF products for the growing number of people struggling with the problem of gluten intolerance. 相似文献
99.
Simulation is of primal importance in the prediction of the produced power and automatic fault detection in PV grid-connected systems (PVGCS). The accuracy of simulation results depends on the models used for main components of the PV system, especially for the PV module. The present paper compares two PV array models, the five-parameter model (5PM) and the Sandia Array Performance Model (SAPM). Five different algorithms are used for estimating the unknown parameters of both PV models in order to see how they affect the accuracy of simulations in reproducing the outdoor behavior of three PVGCS. The arrays of the PVGCS are of three different PV module technologies: Crystalline silicon (c-Si), amorphous silicon (a-Si:H) and micromorph silicon (a-Si:H/μc-Si:H).The accuracy of PV module models based on the five algorithms is evaluated by means of the Route Mean Square Error (RMSE) and the Normalized Mean Absolute Error (NMAE), calculated for different weather conditions (clear sky, semi-cloudy and cloudy days). For both models considered in this study, the best accuracy is obtained from simulations using the estimated values of unknown parameters delivered by the ABC algorithm. Where, the maximum error values of RMSE and NMAE stay below 6.61% and 2.66% respectively. 相似文献
100.
This research seeks to understand how people perceive and respond to structural factors and different types of disclosure on Facebook when evaluating the profile of someone they have never met offline. Using a 2 × 3 × 2 between-subjects experimental design, this research explored the relationship between friend adding (add; no add), levels of self-disclosure (low, medium, high), and sex of the Facebook profile owner (male; female) on feelings of interpersonal liking, future behavioral intentions to interact, and homophily. Results indicated that friend adding and higher levels of self-disclosure led to greater feelings of interpersonal liking and homophily amongst both male and female participants. In addition, males tended to view other male profiles with moderate amounts of disclosure and female profiles with the highest amount of disclosure most favorably. Theoretical and practical implications are discussed. 相似文献