全文获取类型
收费全文 | 199374篇 |
免费 | 23736篇 |
国内免费 | 17973篇 |
专业分类
电工技术 | 15272篇 |
技术理论 | 12篇 |
综合类 | 24969篇 |
化学工业 | 20059篇 |
金属工艺 | 6091篇 |
机械仪表 | 13125篇 |
建筑科学 | 16383篇 |
矿业工程 | 6528篇 |
能源动力 | 11061篇 |
轻工业 | 10650篇 |
水利工程 | 9747篇 |
石油天然气 | 11876篇 |
武器工业 | 2496篇 |
无线电 | 16302篇 |
一般工业技术 | 16987篇 |
冶金工业 | 8010篇 |
原子能技术 | 1993篇 |
自动化技术 | 49522篇 |
出版年
2024年 | 960篇 |
2023年 | 2988篇 |
2022年 | 5734篇 |
2021年 | 6492篇 |
2020年 | 7031篇 |
2019年 | 6026篇 |
2018年 | 5687篇 |
2017年 | 6937篇 |
2016年 | 7756篇 |
2015年 | 8072篇 |
2014年 | 11819篇 |
2013年 | 12743篇 |
2012年 | 14362篇 |
2011年 | 15329篇 |
2010年 | 12185篇 |
2009年 | 12466篇 |
2008年 | 12342篇 |
2007年 | 14250篇 |
2006年 | 12675篇 |
2005年 | 11158篇 |
2004年 | 9153篇 |
2003年 | 7980篇 |
2002年 | 6482篇 |
2001年 | 5362篇 |
2000年 | 4657篇 |
1999年 | 3665篇 |
1998年 | 2993篇 |
1997年 | 2437篇 |
1996年 | 2263篇 |
1995年 | 1942篇 |
1994年 | 1614篇 |
1993年 | 1112篇 |
1992年 | 970篇 |
1991年 | 750篇 |
1990年 | 618篇 |
1989年 | 538篇 |
1988年 | 337篇 |
1987年 | 219篇 |
1986年 | 150篇 |
1985年 | 153篇 |
1984年 | 136篇 |
1983年 | 94篇 |
1982年 | 92篇 |
1981年 | 60篇 |
1980年 | 75篇 |
1979年 | 61篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1959年 | 19篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
The eutectic 80Au/20Sn solder alloy is widely used in high power electronics and optoelectronics packaging. In this study, low cycle fatigue behavior of a eutectic 80Au/20Sn solder alloy is reported. The 80Au/20Sn solder shows a quasi-static fracture characteristic at high strain rates, and then gradually transforms from a transgranular fracture (dominated by fatigue damage) to intergranular fracture (dominated by creep damage) at low strain rates with increasing temperature. Coffin-Manson and Morrow models are proposed to evaluate the low cycle fatigue behavior of the 80Au/20Sn solder. Besides, the 80Au/20Sn solder has enhanced fatigue resistance compared to the 63Sn/37Pb solder. 相似文献
33.
Wireless Body Area Networks (WBANs) are envisaged to play crucial role in psychological, medical and non-medical applications. This paper presents iM-SIMPLE; a reliable, and power efficient routing protocol with high throughput for WBAN. We deploy sensor nodes on human body to measure the physiological parameters such as blood pressure, temperature, glucose, lactic acid, EMG, acceleration, pressure, and position. Data from sensors is forwarded to intermediate node, from where it is transmitted to sink. An end user can access the required information available at sink via internet. To minimize energy consumption of the network, we utilize multi-hop mode of communication. A cost function is introduced to select the forwarder; node with high residual energy and least distance to sink has minimum cost function value and is selected. Residual energy parameter balances the energy consumption among the sensor nodes, and least distance improves packet delivery to sink because of reduced less path loss. We formulate the minimum energy consumption and high throughput problems as an Integer Linear Program. In order to support mobility, we also consider two body postures. Simulation results confirm the performance advantage of iM-SIMPLE compared to contemporary schemes in terms of maximizing stability period and throughput of the network. 相似文献
34.
A double optimal projection method that involves projections for intra-cluster and inter-cluster dimensionality reduction are proposed for video fingerprinting. The video is initially set as a graph with frames as its vertices in a high-dimensional space. A similarity measure that can compute the weights of the edges is then proposed. Subsequently, the video frames are partitioned into different clusters based on the graph model. Double optimal projection is used to explore the optimal mapping points in a low-dimensional space to reduce the video dimensions. The statistics and geometrical fingerprints are generated to determine whether a query video is copied from one of the videos in the database. During matching, the video can be roughly matched by utilizing the statistics fingerprint. Further matching is thereafter performed in the corresponding group using geometrical fingerprints. Experimental results show the good performance of the proposed video fingerprinting method in robustness and discrimination. 相似文献
35.
Hashim A.
Hashim 《国际强度与非线性控制杂志
》2020,30(10):3848-3870
》2020,30(10):3848-3870
This paper introduces two novel nonlinear stochastic attitude estimators developed on the Special Orthogonal Group with the tracking error of the normalized Euclidean distance meeting predefined transient and steady‐state characteristics. The tracking error is confined to initially start within a predetermined large set such that the transient performance is guaranteed to obey dynamically reducing boundaries and decrease smoothly and asymptotically to the origin in probability from almost any initial condition. The proposed estimators produce accurate attitude estimates with remarkable convergence properties using measurements obtained from low‐cost inertial measurement units. The estimators proposed in continuous form are complemented by their discrete versions for the implementation purposes. The simulation results illustrate the effectiveness and robustness of the proposed estimators against uncertain measurements and large initialization error, whether in continuous or discrete form. 相似文献
36.
This study addresses the problem of choosing the most suitable probabilistic model selection criterion for unsupervised learning
of visual context of a dynamic scene using mixture models. A rectified Bayesian Information Criterion (BICr) and a Completed
Likelihood Akaike’s Information Criterion (CL-AIC) are formulated to estimate the optimal model order (complexity) for a given
visual scene. Both criteria are designed to overcome poor model selection by existing popular criteria when the data sample
size varies from small to large and the true mixture distribution kernel functions differ from the assumed ones. Extensive
experiments on learning visual context for dynamic scene modelling are carried out to demonstrate the effectiveness of BICr
and CL-AIC, compared to that of existing popular model selection criteria including BIC, AIC and Integrated Completed Likelihood
(ICL). Our study suggests that for learning visual context using a mixture model, BICr is the most appropriate criterion given
sparse data, while CL-AIC should be chosen given moderate or large data sample sizes. 相似文献
37.
分析了冶炼烟气制酸工艺的特点,介绍了由PROFIBUS-DP现场总线构建的冶炼厂烟气制酸监控系统,详细介绍了其硬件配置及相应的软件设计。 相似文献
38.
提出了对暴露在任意外场中的传输线进行时频分析的新方法,这种方法非常稳定,它能够与任意的传输线模型和电路仿真方法兼容,并且使用这种方法得到的仿真值和实际值之间的差别小于1%。 相似文献
39.
Reports an error in "Tradeoffs and Theory: The Double-Mediation Model" by Marc Scholten and Steven J. Sherman (Journal of Experimental Psychology: General, 2006 May, Vol 135[2], 237-261). This article was inadvertently printed with the incorrect title. The original title was "Tradeoffs and Conflict: The Double-Mediation Model." This title highlights the relation between tradeoffs and conflict as investigated by the authors and accounted for by their model. However, readers are asked to refer to the article by the title with which it was printed to facilitate its retrieval.. (The following abstract of the original article appeared in record 2006-06642-006.) Most theories of decision making suggest that, when options imply tradeoffs between their attributes, conflict increases as tradeoff size increases, because greater sacrifices are to be incurred in choosing one option instead of another. An alternative view is that conflict decreases as tradeoff size increases, because stronger arguments can be made for any decision. The authors propose a unified model, the double-mediation model, which combines the mediating effects of sacrifice and argumentation. Our model generally predicts an inverse U-shaped relation between tradeoff size and conflict. Results support this prediction. Also, when the decision situation increases the mediating effect of sacrifice relative to that of argumentation, the relation between tradeoff size and conflict changes in an upward direction; conversely, when the decision situation increases the mediating effect of argumentation relative to that of sacrifice, the relation changes in a downward direction. Results support these predictions as well. Commonalities and differences between our model and other formulations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.