全文获取类型
收费全文 | 104239篇 |
免费 | 27006篇 |
国内免费 | 3624篇 |
专业分类
电工技术 | 13064篇 |
技术理论 | 1篇 |
综合类 | 5250篇 |
化学工业 | 27726篇 |
金属工艺 | 2812篇 |
机械仪表 | 4433篇 |
建筑科学 | 6246篇 |
矿业工程 | 1622篇 |
能源动力 | 3841篇 |
轻工业 | 9130篇 |
水利工程 | 2197篇 |
石油天然气 | 3506篇 |
武器工业 | 558篇 |
无线电 | 14231篇 |
一般工业技术 | 21272篇 |
冶金工业 | 2955篇 |
原子能技术 | 1355篇 |
自动化技术 | 14670篇 |
出版年
2024年 | 235篇 |
2023年 | 750篇 |
2022年 | 1501篇 |
2021年 | 2181篇 |
2020年 | 4776篇 |
2019年 | 7111篇 |
2018年 | 6499篇 |
2017年 | 7407篇 |
2016年 | 7332篇 |
2015年 | 7283篇 |
2014年 | 8218篇 |
2013年 | 8803篇 |
2012年 | 8142篇 |
2011年 | 8007篇 |
2010年 | 6210篇 |
2009年 | 5985篇 |
2008年 | 5798篇 |
2007年 | 5990篇 |
2006年 | 5545篇 |
2005年 | 4506篇 |
2004年 | 3995篇 |
2003年 | 3680篇 |
2002年 | 3314篇 |
2001年 | 2796篇 |
2000年 | 2464篇 |
1999年 | 1700篇 |
1998年 | 852篇 |
1997年 | 641篇 |
1996年 | 562篇 |
1995年 | 479篇 |
1994年 | 470篇 |
1993年 | 315篇 |
1992年 | 264篇 |
1991年 | 211篇 |
1990年 | 176篇 |
1989年 | 149篇 |
1988年 | 120篇 |
1987年 | 81篇 |
1986年 | 71篇 |
1985年 | 58篇 |
1984年 | 44篇 |
1983年 | 26篇 |
1982年 | 38篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1959年 | 8篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
11.
L.J. Espinoza-Pérez S. Esquivel-Medina E. López-Honorato 《Ceramics International》2021,47(11):15527-15532
The influence of the microstructure on the corrosion rate of three monolithic SiC samples in FLiNaK salt at 900 °C for 250 h was studied. The SiC samples, labeled as SiC-1, SiC-2, and SiC-3, had corrosion rates of 0.137, 0.020, and 0.043 mg/cm2h, respectively. Compared with grain size and the presence of special grain boundaries (i.e., Σ3), the content of high-angle grain boundaries (HAGBs) appeared to have the strongest influence on the corrosion rate of SiC in FLiNaK salt, since the corrosion rate increased six times as the concentration of high-angle grain boundaries increased from 19 to 32% for SiC-2 and SiC-1, respectively. These results stress the importance of controlling the content of HAGBs during the production process of SiC. 相似文献
12.
《Ceramics International》2022,48(15):21600-21609
Stereolithography (SL) shows advantages for preparing alumina-based ceramics with complex structures. The effects of the particle size distribution, which strongly influence the sintering properties in ceramic SL, have not been systematically explored until now. Herein, the influence of the particle size distribution on SL-manufactured alumina ceramics was investigated, including bending strength at room temperature, post-sintering shrinkage, porosity, and microstructural morphology. Seven particle size distributions of alumina ceramics were studied (in μm/μm: 30/5, 20/3, 10/2, 5/2, 5/0.8, 3/0.5, and 2/0.3); a coarse:fine particle ratio of 6:4 was maintained. At the same sintering temperature, the degree of sintering was greater for finer particle sizes. The particle size distribution had a larger influence on flexural strength, porosity and shrinkage than sintering temperature when the particle size distribution difference reached 10-fold but was weaker for 10 μm/2 μm, 5 μm/2 μm and 5 μm/0.8 μm. The sintering shrinkage characteristics of cuboid samples with different particle sizes were studied. The use of coarse particles influenced the accuracy of small-scale samples. When the particle size was comparable to the sample width, such as 30 μm/5 μm and 5 mm, the width shrinkage was consistent with the height shrinkage. When the particle size was much smaller than the sample width, such as 2 μm/0.3 μm and 5 mm, the width shrinkage was consistent with the length shrinkage. The results of this study provide meaningful guidance for future research on applications of SL and precise control of alumina ceramics through particle gradation. 相似文献
13.
Structural health monitoring system based on multi-agent coordination and fusion for large structure
In practical applications of structural health monitoring technology, a large number of distributed sensors are usually adopted to monitor the big dimension structures and different kinds of damage. The monitored structures are usually divided into different sub-structures and monitored by different sensor sets. Under this situation, how to manage the distributed sensor set and fuse different methods to obtain a fast and accurate evaluation result is an important problem to be addressed deeply. In the paper, a multi-agent fusion and coordination system is presented to deal with the damage identification for the strain distribution and joint failure in the large structure. Firstly, the monitoring system is adopted to distributedly monitor two kinds of damages, and it self-judges whether the static load happens in the monitored sub-region, and focuses on the static load on the sub-region boundary to obtain the sensor network information with blackboard model. Then, the improved contract net protocol is used to dynamically distribute the damage evaluation module for monitoring two kinds of damage uninterruptedly. Lastly, a reliable assessment for the whole structure is given by combing various heterogeneous classifiers strengths with voting-based fusion. The proposed multi-agent system is illustrated through a large aerospace aluminum plate structure experiment. The result shows that the method can significantly improve the monitoring performance for the large-scale structure. 相似文献
14.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018)
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
15.
This paper proposes a method for the coordinated control of power factor by means of a multiagent approach. The proposed multiagent system consists of two types of agent: single feeder agent (F_AG) and bus agent (B_AG). In the proposed system, an F_AG plays as an important role, which decides the power factors of all distributed generators by executing the load flow calculations repeatedly. The voltage control strategies are implemented as the class definition of Java into the system. In order to verify the performance of the proposed method, it has been applied to a typical distribution model system. The simulation results show that the system is able to control very violent fluctuation of the demands and the photovoltaic (PV) generations. 相似文献
16.
Fabiana Piscitelli Roberto Coccurello Antonio Totaro Alessandro Leuti Giacomo Giacovazzo Roberta Verde Emanuela Rossi Michele Podaliri Vulpiani Nicola Ferri Roberto Giacominelli Stuffler Vincenzo Di Marzo Sergio Oddi Tiziana Bisogno Mauro Maccarrone 《European Journal of Lipid Science and Technology》2019,121(10)
17.
18.
Yasoub Eghbali Mahmoud Ferdosizade Naeiny 《International Journal of Communication Systems》2020,33(14)
In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals. 相似文献
19.
20.
SPEEK/cSMM membrane for simultaneous electricity generation and wastewater treatment in microbial fuel cell
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)