全文获取类型
收费全文 | 548691篇 |
免费 | 50756篇 |
国内免费 | 30737篇 |
专业分类
电工技术 | 35188篇 |
技术理论 | 56篇 |
综合类 | 67389篇 |
化学工业 | 69146篇 |
金属工艺 | 24042篇 |
机械仪表 | 32458篇 |
建筑科学 | 73986篇 |
矿业工程 | 25189篇 |
能源动力 | 15654篇 |
轻工业 | 34355篇 |
水利工程 | 22569篇 |
石油天然气 | 22536篇 |
武器工业 | 5844篇 |
无线电 | 43692篇 |
一般工业技术 | 52201篇 |
冶金工业 | 26634篇 |
原子能技术 | 5966篇 |
自动化技术 | 73279篇 |
出版年
2024年 | 2049篇 |
2023年 | 6650篇 |
2022年 | 14031篇 |
2021年 | 15846篇 |
2020年 | 14990篇 |
2019年 | 12826篇 |
2018年 | 12586篇 |
2017年 | 15685篇 |
2016年 | 18322篇 |
2015年 | 20172篇 |
2014年 | 32756篇 |
2013年 | 30483篇 |
2012年 | 37538篇 |
2011年 | 39008篇 |
2010年 | 30721篇 |
2009年 | 32137篇 |
2008年 | 30139篇 |
2007年 | 38510篇 |
2006年 | 35740篇 |
2005年 | 30876篇 |
2004年 | 25473篇 |
2003年 | 22655篇 |
2002年 | 18751篇 |
2001年 | 15585篇 |
2000年 | 13376篇 |
1999年 | 10987篇 |
1998年 | 8384篇 |
1997年 | 7299篇 |
1996年 | 6411篇 |
1995年 | 5556篇 |
1994年 | 4920篇 |
1993年 | 3527篇 |
1992年 | 3163篇 |
1991年 | 2377篇 |
1990年 | 2070篇 |
1989年 | 1787篇 |
1988年 | 1400篇 |
1987年 | 886篇 |
1986年 | 683篇 |
1985年 | 553篇 |
1984年 | 508篇 |
1983年 | 386篇 |
1982年 | 355篇 |
1981年 | 262篇 |
1980年 | 249篇 |
1979年 | 173篇 |
1978年 | 100篇 |
1977年 | 100篇 |
1962年 | 97篇 |
1959年 | 97篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
3.
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
4.
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
5.
6.
本文以云杉八齿小蠹Ips typographus Linnaeus为例,经标本选取,观察虫体整体形态,绘制整体结构草图,电子显微镜观察局部、得到局部数字图像,分别建立虫体每一部分的高精度细节。把模型每部分拼装在一起组成整体模型,构建出了云杉八齿小蠹三维虚拟昆虫数字化模型。 相似文献
7.
The aim of the research is evaluating the classification performances of eight different machine-learning methods on the antepartum cardiotocography (CTG) data. The classification is necessary to predict newborn health, especially for the critical cases. Cardiotocography is used for assisting the obstetricians’ to obtain detailed information during the pregnancy as a technique of measuring fetal well-being, essentially in pregnant women having potential complications. The obstetricians describe CTG shortly as a continuous electronic record of the baby's heart rate took from the mother's abdomen. The acquired information is necessary to visualize unhealthiness of the embryo and gives an opportunity for early intervention prior to happening a permanent impairment to the embryo. The aim of the machine learning methods is by using attributes of data obtained from the uterine contraction (UC) and fetal heart rate (FHR) signals to classify as pathological or normal. The dataset contains 1831 instances with 21 attributes, examined by applying the methods. In the paper, the highest accuracy displayed as 99.2%. 相似文献
8.
Energy bands, effective mass of carriers, absolute band edge positions and optical properties of tetragonal AgInS2 were calculated using a first-principles approach with the exchange correlation described by B3LYP hybrid functional. The results indicate that tetragonal AgInS2 has a direct band gap of 1.93 eV, which reproduce well experimental value. Calculated effective masses of electrons and holes are both small which are beneficial to separation and migration of electron and hole pairs. This implies that AgInS2 has good photocatalytic performance. The calculated optical characteristics indicate that AgInS2 has a slight anisotropy for both the real and imaginary parts of the dielectric function and exhibits large optical absorption in the visible light region. Furthermore, the calculated band edge positions in (100), (010) and (001) surfaces indicate that tetragonal AgInS2 is beneficial to the reduction and oxidation of water to hydrogen and oxygen under visible light irradiation. 相似文献
9.
大型综合室内亲子乐园属于高大空间,设有游乐设施和游戏的特殊性使得对空间的舒适性要求一致,但是送风气流遇阻严重,室内存在较多气流死角,影响室内空气质量和儿童健康。因此其空调设计不仅需要考虑温度、风速的空间均匀度,还要考虑各点的空气龄和PMV-PPD指标。以天津某亲子乐园为研究对象,利用scSTREAM软件对适用于该房间的辐射供冷加新风、置换通风、混合通风三种空调方式的送风效果进行数值模拟分析,从流场的均匀性、人员的热舒适性等方面对模拟结果进行探讨,研究结果表明辐射供冷加新风方式的空间均匀性和PMV指标最佳,混合通风方式的空气龄最小。 相似文献
10.