全文获取类型
收费全文 | 10545篇 |
免费 | 951篇 |
国内免费 | 626篇 |
专业分类
电工技术 | 554篇 |
综合类 | 811篇 |
化学工业 | 804篇 |
金属工艺 | 196篇 |
机械仪表 | 497篇 |
建筑科学 | 554篇 |
矿业工程 | 162篇 |
能源动力 | 398篇 |
轻工业 | 139篇 |
水利工程 | 102篇 |
石油天然气 | 131篇 |
武器工业 | 128篇 |
无线电 | 760篇 |
一般工业技术 | 852篇 |
冶金工业 | 587篇 |
原子能技术 | 71篇 |
自动化技术 | 5376篇 |
出版年
2024年 | 37篇 |
2023年 | 286篇 |
2022年 | 410篇 |
2021年 | 507篇 |
2020年 | 505篇 |
2019年 | 295篇 |
2018年 | 247篇 |
2017年 | 303篇 |
2016年 | 326篇 |
2015年 | 350篇 |
2014年 | 523篇 |
2013年 | 553篇 |
2012年 | 491篇 |
2011年 | 709篇 |
2010年 | 551篇 |
2009年 | 675篇 |
2008年 | 642篇 |
2007年 | 675篇 |
2006年 | 576篇 |
2005年 | 498篇 |
2004年 | 421篇 |
2003年 | 394篇 |
2002年 | 289篇 |
2001年 | 214篇 |
2000年 | 180篇 |
1999年 | 169篇 |
1998年 | 170篇 |
1997年 | 122篇 |
1996年 | 113篇 |
1995年 | 103篇 |
1994年 | 129篇 |
1993年 | 81篇 |
1992年 | 73篇 |
1991年 | 62篇 |
1990年 | 52篇 |
1989年 | 48篇 |
1988年 | 46篇 |
1987年 | 24篇 |
1986年 | 27篇 |
1985年 | 32篇 |
1984年 | 13篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1966年 | 12篇 |
1965年 | 9篇 |
1964年 | 11篇 |
1955年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
61.
62.
An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore hole. Therefore, suitable simulation models are necessary to evaluate new tool designs and optimize drilling processes. In this paper the coolant distribution during helical deep hole drilling is analyzed with high-speed microscopy. Micro particles are added to the cutting fluid circuit by a developed high-pressure mixing vessel. After the evaluation of suitable particle size, particle concentration and coolant pressure, a computational fluid dynamics (CFD) simulation is validated with the experimental results. The comparison shows a very good model quality with a marginal difference for the flow velocity of 1.57% between simulation and experiment. The simulation considers the kinematic viscosity of the fluid. The results show that the fluid velocity in the chip flutes is low compared to the fluid velocity at the exit of the coolant channels of the tool and drops even further between the guide chamfers. The flow velocity and the flow pressure directly at the cutting edge decrease to such an extent that the fluid cannot generate a sufficient cooling or lubrication. With the CFD simulation a deeper understanding of the behavior and interactions of the cutting fluid is achieved. Based on these results further research activities to improve the coolant supply can be carried out with great potential to evaluate new tool geometries and optimize the machining process.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00383-w 相似文献
63.
64.
In the present work, the derivation of two surrogate models (SMs) for modelling the flow around a propeller for small aircrafts is presented. Both methodologies use derived functions based on computations with the detailed propeller geometry. The computations were performed using k–ω shear stress transport for modelling turbulence. In the SMs, the modelling of the propeller was performed in a computational domain of disk-like geometry, where source terms were introduced in the momentum equations. In the first SM, the source terms were polynomial functions of swirl and thrust, mainly related to the propeller radius. In the second SM, regression analysis was used to correlate the source terms with the velocity distribution through the propeller. The proposed SMs achieved faster convergence, in relation to the detail model, by providing also results closer to the available operational data. The regression-based model was the most accurate and required less computational time for convergence. 相似文献
65.
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
66.
Some studies have discussed the potential and challenges related to the use of artificial intelligence (AI) in government. However, there are few empirical studies that have examined factors that influence the use of AI in government. By collecting policy documents and empirical data from the government, IT enterprises, and the public in China, we identified the influencing factors in the three stages of government adoption, implementation, and decision-making. The research results show that the influencing factors of government application of AI are different at different stages and with different stakeholders’ backgrounds. 相似文献
67.
The current work introduces an enhancement in the performance of the microbial fuel cell through estimating the optimal set of controlling parameters. The maximization of both power density (PD) and the percentage of chemical oxygen demand (COD) removal were considered as the enhancement in the cell's performance. Three main parameters in terms of performance as well as commercialization are the system's inputs; the Pt which takes the range of 0.1‐0.5 mg/cm2, the degree of sulphonation in sulfonated‐poly‐ether‐ether‐ketone that changes in the range of 20‐80%, and the rate of aeration of cathode which varies between 10 and 150 mL/min. From the experimental dataset, two robust adaptive neuro‐fuzzy inference system models based on the fuzzy logic technique have been constructed. The comparisons between the models' outputs and the experimental data showed well‐fitting in both training and testing datasets. The mean squared errors of the PD model, for testing and whole datasets, were found 2.575 and 0.909 while for the COD model it showed 19.242 and 6.791, respectively. Then, based on the two fuzzy models, a Particle Swarm Optimization algorithm has been used to determine the best parameters that maximize both of the PD and the COD removal of the cell. The optimization process was utilized for single and multi‐object optimization processes. In the single optimization, the resulting maximums of the PD and the COD removal were found 62.844 (mW/m2) and 99.99 (%), respectively. Whereas, in the multi‐object optimization, the values of 61.787 (mW/m2) and 96.21 (%) were reached as the maximums for the PD and COD, respectively. This implies that, in both cases of optimization processes, the adopted methodology can efficiently enhance the microbial fuel cell performances than the previous work. 相似文献
68.
近年来,伴随着现代信息技术的迅猛发展,以人工智能为代表的新兴技术在教育领域得到了广泛应用,引发了学习理念和方式的深刻变革.在这种大背景下,在线学习超越了时空的限制,为学习者“随时随地”学习提供了更多的可能性,从而得到了蓬勃发展.然而,在线学习中师生时间、空间分离的特征,导致教师无法及时掌握学生的学习状态,一定程度上制约了在线学习中教学质量的提升.面对多元化的学习需求及海量学习资源,如何迅速完成学习目标、降低学习成本、合理分配学习资源等问题成为限制个人和时代发展的重大问题.然而,传统的“一刀切”的教育模式已经不能满足人们获取知识的需求了,需要一个更高效、更科学的个性化教育模式,以帮助学习者以最小的学习成本最大限度地完成学习目标.基于以上背景,如何自动高效识别学习者特征,高效地组织和分配学习资源,为每一位学习者规划个性化路径,成为面向个体的精准化教育资源匹配机制研究中亟待解决的问题.系统地综述并分析了当前个性化学习路径推荐的研究现状,并从多学科领域的角度分析了对于同一问题的不同研究思路,同时也归纳总结了当前研究中最为主流的核心推荐算法.最后,强调当前研究存在的主要不足之处. 相似文献
69.
全国竞技二打一扑克锦标赛是国家体育总局棋牌运动管理中心推出的新兴项目,比赛采用复式赛赛制,然而这种赛制存在无法杜绝线上比赛作弊的问题,为此提出用同等牌力赛制来代替复式赛制进行比赛的设想。本文主要针对如何判定和选取具有同等牌力的初始手牌进行研究,提出用等级难度评估指标来计算初始手牌的难度,初始手牌难度相近的牌认定为同等牌力,并给出了同等牌力的选取方法;为保证一副牌所得等级难度评估指标的可靠性,提出用多个不同水平的“二打一AI程序”来代替真人打牌产生牌谱的方法。实验证明了同等牌力生成方法的有效性,本文提出的同等牌力方法应用于比赛是可行的。 相似文献
70.
Manufacturing and Industrial Robotics have reached a point where to be more useful to small and medium sized manufacturers, the systems must become more agile and must be able to adapt to changes in the environment. This paper describes the process for creating and the lessons learned over multiple years of the Agile Robotics for Industrial Automation Competition (ARIAC) being run by the National Institute of Standards and Technology. 相似文献