全文获取类型
收费全文 | 53081篇 |
免费 | 7103篇 |
国内免费 | 4511篇 |
专业分类
电工技术 | 6989篇 |
技术理论 | 8篇 |
综合类 | 7218篇 |
化学工业 | 1462篇 |
金属工艺 | 773篇 |
机械仪表 | 4746篇 |
建筑科学 | 8966篇 |
矿业工程 | 1106篇 |
能源动力 | 838篇 |
轻工业 | 954篇 |
水利工程 | 589篇 |
石油天然气 | 829篇 |
武器工业 | 809篇 |
无线电 | 6674篇 |
一般工业技术 | 3399篇 |
冶金工业 | 631篇 |
原子能技术 | 291篇 |
自动化技术 | 18413篇 |
出版年
2024年 | 268篇 |
2023年 | 715篇 |
2022年 | 1427篇 |
2021年 | 1599篇 |
2020年 | 1644篇 |
2019年 | 1436篇 |
2018年 | 1400篇 |
2017年 | 1667篇 |
2016年 | 2004篇 |
2015年 | 2354篇 |
2014年 | 3686篇 |
2013年 | 3151篇 |
2012年 | 4324篇 |
2011年 | 4682篇 |
2010年 | 3817篇 |
2009年 | 3947篇 |
2008年 | 3901篇 |
2007年 | 4424篇 |
2006年 | 3735篇 |
2005年 | 3058篇 |
2004年 | 2383篇 |
2003年 | 1871篇 |
2002年 | 1522篇 |
2001年 | 1258篇 |
2000年 | 1040篇 |
1999年 | 716篇 |
1998年 | 488篇 |
1997年 | 385篇 |
1996年 | 330篇 |
1995年 | 300篇 |
1994年 | 233篇 |
1993年 | 171篇 |
1992年 | 175篇 |
1991年 | 100篇 |
1990年 | 98篇 |
1989年 | 91篇 |
1988年 | 70篇 |
1987年 | 38篇 |
1986年 | 35篇 |
1985年 | 20篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
本文以云杉八齿小蠹Ips typographus Linnaeus为例,经标本选取,观察虫体整体形态,绘制整体结构草图,电子显微镜观察局部、得到局部数字图像,分别建立虫体每一部分的高精度细节。把模型每部分拼装在一起组成整体模型,构建出了云杉八齿小蠹三维虚拟昆虫数字化模型。 相似文献
2.
The aim of the research is evaluating the classification performances of eight different machine-learning methods on the antepartum cardiotocography (CTG) data. The classification is necessary to predict newborn health, especially for the critical cases. Cardiotocography is used for assisting the obstetricians’ to obtain detailed information during the pregnancy as a technique of measuring fetal well-being, essentially in pregnant women having potential complications. The obstetricians describe CTG shortly as a continuous electronic record of the baby's heart rate took from the mother's abdomen. The acquired information is necessary to visualize unhealthiness of the embryo and gives an opportunity for early intervention prior to happening a permanent impairment to the embryo. The aim of the machine learning methods is by using attributes of data obtained from the uterine contraction (UC) and fetal heart rate (FHR) signals to classify as pathological or normal. The dataset contains 1831 instances with 21 attributes, examined by applying the methods. In the paper, the highest accuracy displayed as 99.2%. 相似文献
3.
4.
AbstractIndustry 4.0 aims at providing a digital representation of a production landscape, but the challenges in building, maintaining, optimizing, and evolving digital models in inter-organizational production chains have not been identified yet in a systematic manner. In this paper, various Industry 4.0 research and technical challenges are addressed, and their present scenario is discussed. Moreover, in this article, the novel concept of developing experience-based virtual models of engineering entities, process, and the factory is presented. These models of production units, processes, and procedures are accomplished by virtual engineering object (VEO), virtual engineering process (VEP), and virtual engineering factory (VEF), using the knowledge representation technique of Decisional DNA. This blend of the virtual and physical domains permits monitoring of systems and analysis of data to foresee problems before they occur, develop new opportunities, prevent downtime, and even plan for the future by using simulations. Furthermore, the proposed virtual model concept not only has the capability of Query Processing and Data Integration for Industrial Data but also real-time visualization of data stream processing. 相似文献
5.
6.
For many-objective optimization problems, how to get a set of solutions with good convergence and diversity is a difficult and challenging work. In this paper, a new decomposition based evolutionary algorithm with uniform designs is proposed to achieve the goal. The proposed algorithm adopts the uniform design method to set the weight vectors which are uniformly distributed over the design space, and the size of the weight vectors neither increases nonlinearly with the number of objectives nor considers a formulaic setting. A crossover operator based on the uniform design method is constructed to enhance the search capacity of the proposed algorithm. Moreover, in order to improve the convergence performance of the algorithm, a sub-population strategy is used to optimize each sub-problem. Comparing with some efficient state-of-the-art algorithms, e.g., NSGAII-CE, MOEA/D and HypE, on six benchmark functions, the proposed algorithm is able to find a set of solutions with better diversity and convergence. 相似文献
7.
ABSTRACT The concept of digital game-based learning (DGBL) evolves rapidly together with technological enhancements of virtual reality (VR) and smart phones. However, the mental workload (MWL) that VR-training applications demand and motivational qualities originating from user experience (UX) should be identified in order to create effective and enjoyable training/learning challenges that fit with individual users’ capabilities. This study examined the effects of reality-based interaction (RBI) and VR on measures of student motivation and MWL, in a mental arithmetic game for secondary school pupils. In a randomised controlled trial with sixty school children, a mental arithmetic game was tested with three different interaction and two different presentation methods – VR RBI, VR head-mounted-display tapping and tablet flick-gesture. Results found a significant effect of RBI on MWL but no differences in enjoyment of training were found between VR-experience and tablet training-experience. In fact, adding the gaming-context to the mental arithmetic task created an enjoyable, motivating experience regardless of presentation or interaction-style. 相似文献
8.
The ensemble learning paradigm has proved to be relevant to solving most challenging industrial problems. Despite its successful application especially in the Bioinformatics, the petroleum industry has not benefited enough from the promises of this machine learning technology. The petroleum industry, with its persistent quest for high-performance predictive models, is in great need of this new learning methodology. A marginal improvement in the prediction indices of petroleum reservoir properties could have huge positive impact on the success of exploration, drilling and the overall reservoir management portfolio. Support vector machines (SVM) is one of the promising machine learning tools that have performed excellently well in most prediction problems. However, its performance is a function of the prudent choice of its tuning parameters most especially the regularization parameter, C. Reports have shown that this parameter has significant impact on the performance of SVM. Understandably, no specific value has been recommended for it. This paper proposes a stacked generalization ensemble model of SVM that incorporates different expert opinions on the optimal values of this parameter in the prediction of porosity and permeability of petroleum reservoirs using datasets from diverse geological formations. The performance of the proposed SVM ensemble was compared to that of conventional SVM technique, another SVM implemented with the bagging method, and Random Forest technique. The results showed that the proposed ensemble model, in most cases, outperformed the others with the highest correlation coefficient, and the lowest mean and absolute errors. The study indicated that there is a great potential for ensemble learning in petroleum reservoir characterization to improve the accuracy of reservoir properties predictions for more successful explorations and increased production of petroleum resources. The results also confirmed that ensemble models perform better than the conventional SVM implementation. 相似文献
9.
A new matching cost computation method based on nonsubsampled contourlet transform (NSCT) for stereo image matching is proposed in this paper. Firstly, stereo image is decomposed into high frequency sub-band images at different scales and along different directions by NSCT. Secondly, by utilizing coefficients in high frequency domain and grayscales in RGB color space, the computation model of weighted matching cost between two pixels is designed based on the gestalt laws. Lastly, two types of experiments are carried out with standard stereopairs in the Middlebury benchmark. One of the experiments is to confirm optimum values of NSCT scale and direction parameters, and the other is to compare proposed matching cost with nine known matching costs. Experimental results show that the optimum values of scale and direction parameters are respectively 2 and 3, and the matching accuracy of the proposed matching cost is twice higher than that of traditional NCC cost. 相似文献
10.
如今我国信息化技术全面发展,尤其对于工程测量工作领域来讲,不管是在工程建设和管理方面都产生不小的支撑引导效用。由此,笔者具体结合如今工程建设信息化测绘核心任何以及设备布置细节,进行结构整体安全管理周期和周边地理空间信息技术发展能效整理解析,试图将工程测量最新发展机遇和技术挑战问题处理完全。希望能够借此为日后一定时期范围内相关工程测量规划主体提供合理指导性建议内容,最终为我国各类工程事业可持续发展前景绽放奠定深刻适应基础。 相似文献