全文获取类型
收费全文 | 13806篇 |
免费 | 1920篇 |
国内免费 | 1553篇 |
专业分类
电工技术 | 653篇 |
技术理论 | 5篇 |
综合类 | 2240篇 |
化学工业 | 1235篇 |
金属工艺 | 180篇 |
机械仪表 | 292篇 |
建筑科学 | 2046篇 |
矿业工程 | 176篇 |
能源动力 | 467篇 |
轻工业 | 243篇 |
水利工程 | 312篇 |
石油天然气 | 362篇 |
武器工业 | 53篇 |
无线电 | 2587篇 |
一般工业技术 | 1037篇 |
冶金工业 | 201篇 |
原子能技术 | 169篇 |
自动化技术 | 5021篇 |
出版年
2024年 | 37篇 |
2023年 | 273篇 |
2022年 | 415篇 |
2021年 | 516篇 |
2020年 | 581篇 |
2019年 | 467篇 |
2018年 | 403篇 |
2017年 | 521篇 |
2016年 | 585篇 |
2015年 | 652篇 |
2014年 | 1034篇 |
2013年 | 980篇 |
2012年 | 1204篇 |
2011年 | 1166篇 |
2010年 | 983篇 |
2009年 | 956篇 |
2008年 | 946篇 |
2007年 | 1096篇 |
2006年 | 878篇 |
2005年 | 719篇 |
2004年 | 546篇 |
2003年 | 473篇 |
2002年 | 385篇 |
2001年 | 326篇 |
2000年 | 205篇 |
1999年 | 170篇 |
1998年 | 141篇 |
1997年 | 105篇 |
1996年 | 88篇 |
1995年 | 90篇 |
1994年 | 67篇 |
1993年 | 47篇 |
1992年 | 44篇 |
1991年 | 26篇 |
1990年 | 33篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 4篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1961年 | 5篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
为了有效降低因驾驶员紧急换道行为而诱发的交通事故,提高道路交通事故链阻断效率,提出一种基于高斯混合隐马尔科夫模型(GMM-HMM)和人工神经网络(ANN)的紧急换道行为预测方法。首先利用GMM-HMM对车辆行驶状态以及驾驶行为连续观察序列进行换道意图辨识,采用ANN预测下一时段的驾驶行为,再预测换道过程中的横向加速度变化率,从而判断紧急换道的危险程度。驾驶员在环仿真实验及实车实验结果表明,该方法预测避险成功率达92.83%,实验避险成功率达90.32%。该方法能有效地对紧急换道行为进行提前警告与干预。 相似文献
12.
Jorge Humberto Luna-Domínguez Héctor Téllez-Jiménez Heriberto Hernández-Cocoletzi Margarita García-Hernández José Aaron Melo-Banda Håkan Nygren 《Ceramics International》2018,44(18):22583-22591
Biomaterials that meet the requirements to stimulate bone tissue formation play a vital role in orthopedics and dentistry. In this work, chitosan and a biphasic, non-cytotoxic material hydroxyapatite/whitlockite were obtained from natural sources, which are available as organic waste. The osteogenic activity was assessed using a rabbit model animal with a chitosan barrier membrane in combination with a bone-filling graft substitute composed of hydroxyapatite/whitlockite. FT-IR results showed the typical absorption bands of the chitosan and hydroxyapatite. Moreover, the X-ray diffraction pattern revealed a typical hexagonal phase of hydroxyapatite and rhombohedral structures related to whitlockite. Masson's trichrome stain showed an early formation of extracellular matrix mineralized, in accord with the surface morphology of a cortical mature bond observed by Scanning Electron Microscopy. The immunocytochemistry results showed a significant increase of positive immunoreactive cells to osteonectin in the treated defects in comparison with the control defects 6 and 8 weeks postoperatively. Overall, the results confirm that the use of this low-cost and versatile biomaterial as a barrier membrane and a bone substitute graft are useful for bone tissue engineering. 相似文献
13.
Computational continua for linear elastic heterogeneous solids on unstructured finite element meshes
《International journal for numerical methods in engineering》2018,115(4):501-530
The computational continua framework, which is a variant of higher‐order computational homogenization theories that is free of scale separation, does not require higher‐order finite element continuity, and is free of higher‐order boundary conditions, has been generalized to unstructured meshes. The salient features of the proposed generalization are (i) a nonlocal quadrature scheme for distorted elements that accounts for unit cell distortion in the parent element domain and (ii) an approximate variant of the nonlocal quadrature that eliminates the cost of computing positions of the quadrature points in the preprocessing stage. The performance of the computational continua framework on unstructured meshes has been compared to the first‐order homogenization theory and the direct numerical simulation. 相似文献
14.
ABSTRACT The value of social network analysis is critically dependent on the comprehensive and reliable identification of actors and their relationships. We compare regional knowledge networks based on different types of data sources, namely, co-patents, co-publications, and publicly subsidized collaborative R&D projects. Moreover, by combining these three data sources, we construct a multilayer network that provides a comprehensive picture of intraregional interactions. By comparing the networks based on the data sources, we address the problems of coverage and selection bias. We observe that using only one data source leads to a severe underestimation of regional knowledge interactions, especially those of private sector firms and independent researchers. 相似文献
15.
This paper deals with modeling of the phenomenon of fretting fatigue in
heterogeneous materials using the multi-scale computational homogenization technique
and finite element analysis (FEA). The heterogeneous material for the specimens consists
of a single hole model (25% void/cell, 16% void/cell and 10% void/cell) and a four-hole
model (25% void/cell). Using a representative volume element (RVE), we try to produce
the equivalent homogenized properties and work on a homogeneous specimen for the
study of fretting fatigue. Next, the fretting fatigue contact problem is performed for 3 new
cases of models that consist of a homogeneous and a heterogeneous part (single hole cell)
in the contact area. The aim is to analyze the normal and shear stresses of these models
and compare them with the results of the corresponding heterogeneous models based on
the Direct Numerical Simulation (DNS) method. Finally, by comparing the
computational time and % deviations, we draw conclusions about the reliability and
effectiveness of the proposed method. 相似文献
16.
17.
交通流预测作为信号协调和出行时间预测等任务的基础,成为了交通领域的研究点。对于交通流预测问题,研究人员提出了多种方法,但这些方法大多只使用交通流数据的时域信息进行交通流预测,忽略了空间相关性对于预测目标路段流的影响,导致预测精度不理想。基于组合模型的思想提出了一种称为LSTM-RF的交通流预测模型。在交通流预测过程中,首先使用LSTM模型提取预测目标路段的时序特征,再将其预测值与采集的相邻上下游路段信息同时作为随机森林模型的输入特征,进行交通流时空相关性分析,获得最终的预测结果。并通过贵阳市车牌识别系统采集的城区132条路段的交通流数据进行实验验证。结果表明:该方法在预测精度上优于单一模型,并且预测误差相比单一模型有明显减少。 相似文献
18.
Drunk drivers are a menace to themselves and to other road users, as drunk driving significantly increases the risk of involvement in road accidents and the probability of severe or fatal injuries. Although injuries and fatalities related to road accidents have decreased in recent decades, the prevalence of drunk driving among drivers killed in road accidents has remained stable, at around 25% or more during the past 10 years. Understanding drunk driving, and in particular, recidivism, is essential for designing effective countermeasures, and accordingly, the present study aims at identifying the differences between non-drunk drivers, drunk driving non-recidivists and drunk driving recidivists with respect to their demographic and socio-economic characteristics, road accident involvement and other traffic and non-traffic-related law violations. This study is based on register-data from Statistics Denmark and includes information from 2008 to 2012 for the entire population, aged 18 or older, of Denmark. The results from univariate and multivariate statistical analyses reveal a five year prevalence of 17% for drunk driving recidivism, and a significant relation between recidivism and the drunk drivers’ gender, age, income, education, receipt of an early retirement pension, household type, and residential area. Moreover, recidivists are found to have a higher involvement in alcohol-related road accidents, as well as other traffic and, in particular, non-traffic-related offences. These findings indicate that drunk driving recidivism is more likely to occur among persons who are in situations of socio-economic disadvantage and marginalisation. Thus, to increase their effectiveness, preventive measures aiming to reduce drunk driving should also address issues related to the general life situations of the drunk driving recidivists that contribute to an increased risk of drunk driving recidivism. 相似文献
19.
20.
Krishnasamy Ragavan Krishnan Venkatalakshmi Kandasamy Vijayalakshmi 《Computational Intelligence》2021,37(1):538-558
Road traffic congestion is a serious problem in today's world and it happens because of urbanization and population growth. The traffic reduces the transport efficiency in the city, increases the waiting time and travel time, and also increases the usage of fuel and air pollution. To overcome these issues this papers propose an intelligent traffic control system using the Internet of Vehicles (IoV). The vehicles or nodes present in the IoV can communicate between themselves. This technique helps in determining the traffic intensity and the best route to reach the destination. The area of study used in this paper is Vellore city in Tamilnadu, India. The city map is separated into many segments of equal size and Ant Colony Algorithm (AOC) is applied to the separated maps to find the optimal route to reach the destination. Further, Support Vector Machine (SVM) is used to calculate the traffic density and to model the heavy traffic. The proposed algorithm performs better in finding the optimal route when compared to that of the existing path selection algorithms. From the results, it is evident that the proposed IoV‐based route selection method provides better performance. 相似文献