全文获取类型
收费全文 | 370357篇 |
免费 | 25924篇 |
国内免费 | 10908篇 |
专业分类
电工技术 | 16623篇 |
技术理论 | 37篇 |
综合类 | 19239篇 |
化学工业 | 61095篇 |
金属工艺 | 21580篇 |
机械仪表 | 22134篇 |
建筑科学 | 25002篇 |
矿业工程 | 10036篇 |
能源动力 | 9299篇 |
轻工业 | 20469篇 |
水利工程 | 6003篇 |
石油天然气 | 20614篇 |
武器工业 | 2237篇 |
无线电 | 41226篇 |
一般工业技术 | 50340篇 |
冶金工业 | 17793篇 |
原子能技术 | 3481篇 |
自动化技术 | 59981篇 |
出版年
2024年 | 3585篇 |
2023年 | 5628篇 |
2022年 | 8201篇 |
2021年 | 12042篇 |
2020年 | 9343篇 |
2019年 | 7430篇 |
2018年 | 21553篇 |
2017年 | 21660篇 |
2016年 | 17478篇 |
2015年 | 11929篇 |
2014年 | 14150篇 |
2013年 | 16733篇 |
2012年 | 20667篇 |
2011年 | 28198篇 |
2010年 | 24461篇 |
2009年 | 20973篇 |
2008年 | 21779篇 |
2007年 | 22455篇 |
2006年 | 16075篇 |
2005年 | 15293篇 |
2004年 | 10094篇 |
2003年 | 9006篇 |
2002年 | 7818篇 |
2001年 | 6575篇 |
2000年 | 7257篇 |
1999年 | 8545篇 |
1998年 | 6897篇 |
1997年 | 5852篇 |
1996年 | 5498篇 |
1995年 | 4516篇 |
1994年 | 3768篇 |
1993年 | 2640篇 |
1992年 | 2149篇 |
1991年 | 1623篇 |
1990年 | 1175篇 |
1989年 | 935篇 |
1988年 | 780篇 |
1987年 | 530篇 |
1986年 | 396篇 |
1985年 | 273篇 |
1984年 | 186篇 |
1983年 | 125篇 |
1982年 | 133篇 |
1981年 | 87篇 |
1980年 | 70篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 46篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
891.
结合嵌入式实时操作系统VxWorks实现某测控系统的实际应用,以其中的TCP通信为例,讨论了在VxWorks下实现C/S通信的关键技术。 相似文献
892.
针对倒立摆系统,提出了在结构上可生长的神经网络控制方案。网络利用细胞生长结构算法,在工作域中实现对状态变量的模式分类,并通过新神经元的插入实现网络规模的生长演化。在输出域中针对倒立摆控制任务采用强化Hebb学习机制,实现不同的神经元以最佳方式响应不同性质的信号刺激。仿真表明,通过神经网络自身的发育,该方案有效控制了倒立摆系统。 相似文献
893.
从两摆间无弹簧连接的平行双倒立摆系统特定物理结构出发,结合控制目标进行合理建模与分析,验证所建模型可行性,讨论系统能控性和参数间的关系,并设计了滑模变结构控制律.该文的理论和方法对平行单级双倒立摆的进一步研究工作具有重要意义. 相似文献
894.
A closed-loop system is developed to control the weld fusion, which Is specified by the top-side and back-side bead widths of the weld pool. Because in many applications only a top-side sensor is allowed, which is attached to and moves with the welding torch, an image processing algorithm and neurofuzzy model have been incorporated to measure and estimate the top-side and back-side bead widths based on an advanced top-side vision sensor. The welding current and speed are selected as the control variables. It is found that the correlation between any output and input depends on the value of another input. This cross coupling implies that a nonlinearity exists in the process being controlled. A neurofuzzy model is used to model this nonlinear dynamic process. Based on the dynamic fuzzy model, a predictive control system has been developed to control the welding process. Experiments confirmed that the developed control system is effective in achieving the desired fusion state despite the different disturbances 相似文献
895.
Lei Wang Xiaoqing Gong Yongqin Zhang Pengfei Xu Xiaojiang Chen Dingyi Fang Xia Zheng Jun Guo 《Multimedia Tools and Applications》2018,77(3):2973-2990
Chinese calligraphy is a unique visual art, and and is one of the material basis of China’s traditional cultural heritage. However, time had caused the old calligraphy works to weathering and damages, so it is necessary to utilize advanced technologies to protect those works. One of those technologies is digital imaging, and the obtained images by digital imaging can preserve the visual information of calligraphy works better, furthermore, they can be used in further researches. While the basic works for those researches are to extract the artistic features which include two elements, i.e., form and spirit. However, most of the existing methods only extract the form and ignore the characters’ spirit, especially they are insensitive to the slight variation in complex ink strokes. To solve these problems, this paper proposes an extraction method based on regional guided flter (RGF) with reference images, which is generated by KNN matting and used as the input image for RGF. Since RGF is sensitive to the slight variation of ink, so the detailed information of the inside of strokes can be detected better. Besides, unlike the past works, which filter the whole strokes, RGF filters the inside of strokes and edges in different windows respectively, which results in that the edges are preserved accurately. Results from a deployment of several famous Chinese calligraphy works demonstrate that our method can extract more accurate and complete form and spirit with lower error rate. 相似文献
896.
The polynomial-time solvable k-hurdle problem is a natural generalization of the classical s-t minimum cut problem where we must select a minimum-cost subset S of the edges of a graph such that |p∩S|≥k for every s-t path p. In this paper, we describe a set of approximation algorithms for “k-hurdle” variants of the NP-hard multiway cut and multicut problems. For the k-hurdle multiway cut problem with r terminals, we give two results, the first being a pseudo-approximation algorithm that outputs a (k−1)-hurdle solution whose cost is at most that of an optimal solution for k hurdles. Secondly, we provide a
2(1-\frac1r)2(1-\frac{1}{r})-approximation algorithm based on rounding the solution of a linear program, for which we give a simple randomized half-integrality
proof that works for both edge and vertex k-hurdle multiway cuts that generalizes the half-integrality results of Garg et al. for the vertex multiway cut problem. We
also describe an approximation-preserving reduction from vertex cover as evidence that it may be difficult to achieve a better
approximation ratio than
2(1-\frac1r)2(1-\frac{1}{r}). For the k-hurdle multicut problem in an n-vertex graph, we provide an algorithm that, for any constant ε>0, outputs a ⌈(1−ε)k⌉-hurdle solution of cost at most O(log n) times that of an optimal k-hurdle solution, and we obtain a 2-approximation algorithm for trees. 相似文献
897.
It is common for subsidiaries of a group company to use the same types of components for producing similar products. Different subsidiary companies may well procure such components from the same suppliers. This paper studies two sourcing management models. One is the Subsidiary-Autonomous Sourcing Management (SD-ASM) where subsidiaries manage their inventories and place purchasing orders independent of each other. The other is the Headquarter-centered Common Sourcing Management (HQ-CSM) where purchasing orders of subsidiaries are processed centrally through some kind of headquarter coordination. In the SD-ASM model, each subsidiary places replenishment orders at a time interval corresponding to their economic order quantity (EOQ). In the HQ-CSM model, two purchasing order management policies are examined. One is the Order Coordination policy in which common replenishment epochs or time periods are proposed by the headquarter and the subsidiaries are encouraged to coordinate the timing of their orders based on the common replenishment epochs. The other is the Order Consolidation policy in which the subsidiaries combine the quantity of their orders and the headquarter places a combined order with the supplier. In the Order Coordination policy, classic RAND heuristic is used to find the best common replenishment epoch and the best replenishment timing of each subsidiary. In the Order Consolidation policy, the optimal order quantity of the combined order is obtained from a mathematical model. The combined order is then allocated to the subsidiaries according to a proportional allocation rule. A series of numerical studies is conducted to compare the costs of the SD-ASM and HQ-CSM policies. The results show that HQ-CSM outperforms SD-ASM in terms of cost and robustness against demand uncertainties. This achievement is largely due to the economies of process (synergistic ordering process), the economies of scale (large order quantity with price discount) and risk pooling effect (transshipments). The results also reveal that the Order Consolidation policy with a combined order always performs better than the Order Coordination policy with common replenishment epochs especially in face of high demand uncertainties and high service level in the global market. 相似文献
898.
Yan Chen Andrés F. Barrientos Ashwin Machanavajjhala Jerome P. Reiter 《Knowledge and Information Systems》2018,54(1):33-64
Linear and logistic regression are popular statistical techniques for analyzing multi-variate data. Typically, analysts do not simply posit a particular form of the regression model, estimate its parameters, and use the results for inference or prediction. Instead, they first use a variety of diagnostic techniques to assess how well the model fits the relationships in the data and how well it can be expected to predict outcomes for out-of-sample records, revising the model as necessary to improve fit and predictive power. In this article, we develop \(\epsilon \)-differentially private diagnostics tools for regression, beginning to fill a gap in privacy-preserving data analysis. Specifically, we create differentially private versions of residual plots for linear regression and of receiver operating characteristic (ROC) curves as well as binned residual plot for logistic regression. The residual plot and binned residual plot help determine whether or not the data satisfy the assumptions underlying the regression model, and the ROC curve is used to assess the predictive power of the logistic regression model. These diagnostics improve the usefulness of algorithms for computing differentially private regression output, which alone does not allow analysts to assess the quality of the posited model. Our empirical studies show that these algorithms can be effective tools for allowing users to evaluate the quality of their models. 相似文献
899.
Bankruptcy prediction has long time been an active research field in finance. One of the main approaches to this issue is
dealing with it as a classification problem. Among the range of instruments available, we focus our attention on the Evolutionary
Nearest Neighbor Classifier (ENPC). In this work we assess the performance of the ENPC comparing it to six alternatives. The
results suggest that this algorithm might be considered a good choice. 相似文献
900.
张新宇 《计算机与应用化学》1996,(2)
本文介绍了实现TLP-18型激光热常数测试仪计算机辅助测试与管理系统的设计方案、开发方法以及系统的主要功能操作步骤,为开发动态数据的采集、实时处理系统以及其它类似的物性测试仪计算机辅助测试系统提供了实践经验. 相似文献