全文获取类型
收费全文 | 5448篇 |
免费 | 798篇 |
国内免费 | 783篇 |
专业分类
电工技术 | 404篇 |
技术理论 | 2篇 |
综合类 | 712篇 |
化学工业 | 158篇 |
金属工艺 | 60篇 |
机械仪表 | 246篇 |
建筑科学 | 202篇 |
矿业工程 | 90篇 |
能源动力 | 57篇 |
轻工业 | 82篇 |
水利工程 | 98篇 |
石油天然气 | 59篇 |
武器工业 | 57篇 |
无线电 | 361篇 |
一般工业技术 | 377篇 |
冶金工业 | 112篇 |
原子能技术 | 14篇 |
自动化技术 | 3938篇 |
出版年
2024年 | 9篇 |
2023年 | 54篇 |
2022年 | 70篇 |
2021年 | 115篇 |
2020年 | 163篇 |
2019年 | 159篇 |
2018年 | 155篇 |
2017年 | 193篇 |
2016年 | 228篇 |
2015年 | 246篇 |
2014年 | 331篇 |
2013年 | 463篇 |
2012年 | 409篇 |
2011年 | 426篇 |
2010年 | 380篇 |
2009年 | 416篇 |
2008年 | 465篇 |
2007年 | 434篇 |
2006年 | 384篇 |
2005年 | 331篇 |
2004年 | 306篇 |
2003年 | 287篇 |
2002年 | 206篇 |
2001年 | 134篇 |
2000年 | 147篇 |
1999年 | 103篇 |
1998年 | 67篇 |
1997年 | 57篇 |
1996年 | 52篇 |
1995年 | 42篇 |
1994年 | 47篇 |
1993年 | 19篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1962年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7029条查询结果,搜索用时 46 毫秒
51.
52.
53.
54.
55.
剩余寿命估计是工程系统预测与健康管理的关键.目前,基于观测的系统退化数据进行剩余寿命估计得到了很大的关注.由于系统随机退化过程和测量误差的影响,测量数据中不可避免包含退化随机性和测量不确定性.然而,现有基于观测数据的剩余寿命估计研究中,没有将退化随机性和测量不确定性对估计的剩余寿命分布的影响同时考虑.鉴于此,提出了一种基于Wiener过程且同时考虑随机退化和不确定测量的退化建模方法,利用Kalman滤波技术,实现了潜在退化状态的实时估计.在退化状态估计的基础上,得到了同时考虑退化状态不确定性和测量不确定性的解析剩余寿命分布.此外,提出了一种基于极大似然方法的退化模型参数估计方法.最后,通过陀螺仪的退化测量数据验证了本文提出的方法优于不考虑测量不确定性的方法,可以提高剩余寿命估计的准确性. 相似文献
56.
Araliya Mosleh Kheirollah Sepahvand Humberto Varum José Jara Mehran S. Razzaghi Steffen Marburg 《Structure and Infrastructure Engineering》2018,14(10):1324-1338
This paper focuses on the stochastic response of concrete bridges considering uncertainty in bearing and abutment stiffness. A multi-span simply supported bridge with concrete girders is selected. A 3D-dimensional model is prepared, and nonlinear response history analyses are performed. For the numerical dynamic simulation, the non-sampling stochastic method based on generalized polynomial chaos (gPC) expansion is utilised. The uncertain parameters include the vertical and shear stiffness of bearings and the lateral stiffness of abutments are presented by the truncated gPC expansions. Furthermore, the system response such as base shear, acceleration, velocity and displacement in different columns is presented by gPC expansion with unknown deterministic coefficients. The stochastic Galerkin projection is employed to calculate a set of deterministic equations. A non-intrusive solution, as a set of collocation points, determines the unknown gPC coefficients of the system response and the results are compared with Monte Carlo simulations. The key advantage of spectral discretization is the combination of the mentioned method with the spatial discretization, e.g. finite element model. This study also emphasises the accuracy in results and time efficiency of the proposed non-sampling method for uncertainty quantification of stochastic systems comparing to sampling procedure (e.g. Monte Carlo simulation). 相似文献
57.
Muhammad Aminur RAHAMAN Mahmood JASIM Md. Haider ALI Md. HASANUZZAMAN 《Frontiers of Computer Science》2020,14(3):143302-64
Because of using traditional hand-sign segmentation and classification algorithm,many diversities of Bangla language including joint-letters,dependent vowels etc.and representing 51 Bangla written characters by using only 36 hand-signs,continuous hand-sign-spelled Bangla sign language(BdSL)recognition is challenging.This paper presents a Bangla language modeling algorithm for automatic recognition of hand-sign-spelled Bangla sign language which consists of two phases.First phase is designed for hand-sign classification and the second phase is designed for Bangla language modeling algorithm(BLMA)for automatic recognition of hand-sign-spelled Bangla sign language.In first phase,we have proposed two step classifiers for hand-sign classification using normalized outer boundary vector(NOBV)and window-grid vector(WGV)by calculating maximum inter correlation coefficient(ICC)between test feature vector and pre-trained feature vectors.At first,the system classifies hand-signs using NOBV.If classification score does not satisfy specific threshold then another classifier based on WGV is used.The system is trained using 5,200 images and tested using another(5,200×6)images of 52 hand-signs from 10 signers in 6 different challenging environments achieving mean accuracy of 95.83%for classification with the computational cost of 39.972 milliseconds per frame.In the Second Phase,we have proposed Bangla language modeling algorithm(BLMA)which discovers all"hidden characters"based on"recognized characters"from 52 hand-signs of BdSL to make any Bangla words,composite numerals and sentences in BdSL with no training,only based on the result of first phase.To the best of our knowledge,the proposed system is the first system in BdSL designed on automatic recognition of hand-sign-spelled BdSL for large lexicon.The system is tested for BLMA using hand-sign-spelled 500 words,100 composite numerals and 80 sentences in BdSL achieving mean accuracy of 93.50%,95.50%and 90.50%respectively. 相似文献
58.
The way a model is designed to assist farmers in their decision-making may influence how it is understood and perceived by farmers and shape interactions between farmers and model users (researcher, advisor). This study compared the strengths and weaknesses of three types of whole farm models used by researchers to assist 18 crop-livestock farmers in Burkina Faso in planning the next agricultural season. Due to its simplicity, the static simulation tool of annual farm stocks and flows led to superior changes in the farmers' knowledge and practices. The rule-based dynamic simulation tool helped the researchers grasp farmers' decision-making processes but was difficult for farmers to understand due to the discrepancy between its multi-annual time step and the farmers' short-term planning horizon. The optimisation tool stimulated more strategic discussions regarding paths to improve farm income despite a design that was distant from the farmers' reality. 相似文献
59.
Rough set theory (RST) has been the subject of much study and numerous applications in many areas. However, most previous studies on rough sets have focused on finding rules where the decision attribute has a flat, rather than hierarchical structure. In practical applications, attributes are often organized hierarchically to represent general/specific meanings. This paper (1) determines the optimal decision attribute in a hierarchical level-search procedure, level by level, (2) merges the two stages, generating reducts and inducting decision rules, into a one-shot solution that reduces the need for memory space and the computational complexity and (3) uses a revised strength index to identify meaningful reducts and to improve their accuracy. The selection of a green fleet is used to validate the superiority of the proposed approach and its potential benefits to a decision-making process for transportation industry. 相似文献
60.
该文用“图”这一数学工具,通过定量分析来揭示语言系统中的隐性规律,设计了“赢家通吃”和“赢多输少”两种生成算法,将理想算法“步步竞争、择优而行”的博弈论思路贯彻到非理想状态。两种新算法都较前人有更好的概括能力。赢多输少算法更兼顾了充分概括和适度概括均衡。生成语图后,该设计着重准确率的最小简图和着重覆盖率的最大简图归纳算法,挖掘控制的主流规则、分析语言系统的语言学规律。在最小简图基础上提出控制度公式以评价语言系统。
相似文献
相似文献