全文获取类型
收费全文 | 158670篇 |
免费 | 20073篇 |
国内免费 | 13564篇 |
专业分类
电工技术 | 21724篇 |
技术理论 | 12篇 |
综合类 | 16890篇 |
化学工业 | 7947篇 |
金属工艺 | 4640篇 |
机械仪表 | 9420篇 |
建筑科学 | 16147篇 |
矿业工程 | 4934篇 |
能源动力 | 3972篇 |
轻工业 | 4469篇 |
水利工程 | 5292篇 |
石油天然气 | 5763篇 |
武器工业 | 2333篇 |
无线电 | 24895篇 |
一般工业技术 | 9281篇 |
冶金工业 | 3895篇 |
原子能技术 | 909篇 |
自动化技术 | 49784篇 |
出版年
2024年 | 1121篇 |
2023年 | 2984篇 |
2022年 | 5786篇 |
2021年 | 6515篇 |
2020年 | 6835篇 |
2019年 | 4994篇 |
2018年 | 4357篇 |
2017年 | 5403篇 |
2016年 | 5707篇 |
2015年 | 6404篇 |
2014年 | 10696篇 |
2013年 | 9438篇 |
2012年 | 12278篇 |
2011年 | 12666篇 |
2010年 | 9629篇 |
2009年 | 9933篇 |
2008年 | 9808篇 |
2007年 | 11194篇 |
2006年 | 9690篇 |
2005年 | 8572篇 |
2004年 | 7124篇 |
2003年 | 6111篇 |
2002年 | 4923篇 |
2001年 | 4205篇 |
2000年 | 3363篇 |
1999年 | 2744篇 |
1998年 | 2057篇 |
1997年 | 1632篇 |
1996年 | 1439篇 |
1995年 | 1125篇 |
1994年 | 848篇 |
1993年 | 584篇 |
1992年 | 438篇 |
1991年 | 280篇 |
1990年 | 252篇 |
1989年 | 204篇 |
1988年 | 130篇 |
1987年 | 78篇 |
1986年 | 71篇 |
1985年 | 68篇 |
1984年 | 47篇 |
1983年 | 37篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 68篇 |
1979年 | 54篇 |
1964年 | 34篇 |
1959年 | 36篇 |
1956年 | 29篇 |
1955年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
41.
Because the oceanaut plays a significant role in safety and capability during manned deep-diving scientific tasks, preventing oceanaut performance decline is of paramount importance. However, the factors responsible for oceanaut performance are almost entirely unexplored. To address the preceding issues, a quantitative method of fuzzy integrated Bayesian network (FIBN) was modeled within the limits of oceanaut operating procedures. To quantify the probabilities of the influencing factors, the probability of each node in the FIBN was calculated using integrated expert judgement, fuzzy logic theory, and Bayesian network. By considering a total of 28 factors related to oceanaut performance in the “Jiaolong” manned submersible, this study found that difficult sampling, long sampling times, cabin equipment failure, oceanaut physical decline, and declining decision-making ability are important factors that affect oceanaut performance. The FIBN proposed in our study fused the qualitative and quantitative methods and can be developed into a versatile tool for analysis of comprehensive systems that contain both static and dynamic factors.Relevance to industryThe results provide a powerful basis for the design of manned submersible and assignment of tasks to oceanauts, while the fuzzy integrated Bayesian network (FIBN) method proposed can be effectively applied to various quantitative assessment fields which direct researchers to deal with analysis problems of complex systems. 相似文献
42.
In group assessment, the focus is on finding high‐authority experts to improve the reliability of assessment results. In this study, we propose an authority updating algorithm while considering the power and judgement reliability of an expert on the basis of social networks and post‐evaluations. A network power index is established and used to reflect the power of an expert while considering social networks. The measurement of the judgement reliability of an expert considers the post‐evaluation of the objects selected by experts, thereby more scientifically reflecting the reliability of experts. The analysis shows the following: although the social‐network structure influences the authority of experts, the influence weakens when the assessment group is a highly or even fully connected group; the network effect may increase the authority of some experts and reduce that of others, and it will weaken as the network connectivity increases; moreover, the judgement reliability and authority of an expert while considering post‐evaluation can encourage him/her to make fair assessments and strive to reduce his/her motivation and cognitive biases. 相似文献
43.
A network of powerful personal computers, linked by a high-speed local area network, is being seen increasingly as an alternative to a traditional centralized time-sharing operating system. The PULSE project is investigating how such a system may be constructed to give the benefits of a self-sufficient personal computer to each user without losing the facilities for communication and sharing of data inherent in centralized systems. In particular, a distributed file system has been built which provides a single global UNIX 1 UNIX is a trademark of Bell Laboratories. -like hierarchy, with a consistent appearance when accessed from any machine. Replicated copies of files are maintained to improve reliability, increase performance, and enable each machine to run stand-alone, albeit with reduced facilities. 相似文献
44.
近年来,国际上标准参考物质的种类与数量急剧增加,一些重要的领域,象地球化学、环境科学、生物学等都有了相应的SRM。国内研制SRM的工作也十分活跃。 标准样品必须均匀,故在分析定值和样品发行前,需要先作均匀性检验。由于均匀性是一个相对的概念,它与各个元素在SRM中的分布紧密相关。取样量直接影响均匀性的好坏。因此,当给出SRM中某元素的均匀性数值时,必须注明相应的取样量。由于仪器中子活化分析法(INAA)具有灵敏度高、不破坏试样、且可同时测定多种元素等特点,因此可在较小的取样量情况下,实现对SRM中多种痕量元素的均匀性检验。 相似文献
45.
The constrained blister test is investigated through finite element analysis to determine the applicabilities and the limitations of the new technique. Numerical results confirm that the strain energy release rate asymptotically approaches a constant value. These results also show that the test technique and the approximate solution for strain energy release rate are applicable for some practical cases. 相似文献
46.
J.Dougherty S.Ziebold 《硫酸工业》2005,(3):8-13
开发了一种用于布朗扩散型纤维除雾器的便携式现场测试装置,用这套装置可在现场测定纤维床阻力,从而对元件制造水平进行评价和比较,或在维修期间预测清洗后元件的操作性能。介绍便携式现场测试装置的设备布局、安装和运行,并对整体充填、平行缠绕、斜交叉缠绕纤维床及同心组合纤维床进行比较。此外,论述了硫酸装置工艺气体压降的价值。 相似文献
47.
以己二异氰酸酯(HDI)改性聚酯树脂与氨基树脂配制成家电用卷材涂料。阐述了氨酯键对涂膜性能的贡献。探讨了HDI用量对涂膜性能的影响。 相似文献
48.
介绍了聚烯烃成核剂合成反应所用助剂选择,反应条件的确立,利用均匀设计实现最佳配比实验,对不同侧基苯甲醛缩合反应进行了研究。 相似文献
49.
《Expert systems with applications》2014,41(13):5858-5869
A new architecture of intelligent audio emotion recognition is proposed in this paper. It fully utilizes both prosodic and spectral features in its design. It has two main paths in parallel and can recognize 6 emotions. Path 1 is designed based on intensive analysis of different prosodic features. Significant prosodic features are identified to differentiate emotions. Path 2 is designed based on research analysis on spectral features. Extraction of Mel-Frequency Cepstral Coefficient (MFCC) feature is then followed by Bi-directional Principle Component Analysis (BDPCA), Linear Discriminant Analysis (LDA) and Radial Basis Function (RBF) neural classification. This path has 3 parallel BDPCA + LDA + RBF sub-paths structure and each handles two emotions. Fusion modules are also proposed for weights assignment and decision making. The performance of the proposed architecture is evaluated on eNTERFACE’05 and RML databases. Simulation results and comparison have revealed good performance of the proposed recognizer. 相似文献
50.
E brahim Mahdipour Amir Masoud Rahmani Saeed Setayeshi 《International journal of systems science》2014,45(3):373-383
Importance sampling is a technique that is commonly used to speed up Monte Carlo simulation of rare events. However, little is known regarding the design of efficient importance sampling algorithms in the context of queueing networks. The standard approach, which simulates the system using an a priori fixed change of measure suggested by large deviation analysis, has been shown to fail in even the simplest network settings. Estimating probabilities associated with rare events has been a topic of great importance in queueing theory, and in applied probability at large. In this article, we analyse the performance of an importance sampling estimator for a rare event probability in a Jackson network. This article carries out strict deadlines to a two-node Jackson network with feedback whose arrival and service rates are modulated by an exogenous finite state Markov process. We have estimated the probability of network blocking for various sets of parameters, and also the probability of missing the deadline of customers for different loads and deadlines. We have finally shown that the probability of total population overflow may be affected by various deadline values, service rates and arrival rates. 相似文献