全文获取类型
收费全文 | 87297篇 |
免费 | 7468篇 |
国内免费 | 4190篇 |
专业分类
电工技术 | 4968篇 |
技术理论 | 8篇 |
综合类 | 6569篇 |
化学工业 | 14508篇 |
金属工艺 | 4440篇 |
机械仪表 | 5381篇 |
建筑科学 | 7063篇 |
矿业工程 | 2222篇 |
能源动力 | 2520篇 |
轻工业 | 7176篇 |
水利工程 | 1674篇 |
石油天然气 | 5041篇 |
武器工业 | 740篇 |
无线电 | 9825篇 |
一般工业技术 | 9935篇 |
冶金工业 | 3669篇 |
原子能技术 | 1089篇 |
自动化技术 | 12127篇 |
出版年
2024年 | 385篇 |
2023年 | 1342篇 |
2022年 | 2391篇 |
2021年 | 3318篇 |
2020年 | 2525篇 |
2019年 | 2142篇 |
2018年 | 2420篇 |
2017年 | 2718篇 |
2016年 | 2482篇 |
2015年 | 3289篇 |
2014年 | 4204篇 |
2013年 | 5079篇 |
2012年 | 5560篇 |
2011年 | 6126篇 |
2010年 | 5363篇 |
2009年 | 5183篇 |
2008年 | 5259篇 |
2007年 | 4857篇 |
2006年 | 4883篇 |
2005年 | 4139篇 |
2004年 | 2950篇 |
2003年 | 2792篇 |
2002年 | 3005篇 |
2001年 | 2578篇 |
2000年 | 2180篇 |
1999年 | 2275篇 |
1998年 | 1724篇 |
1997年 | 1454篇 |
1996年 | 1384篇 |
1995年 | 1132篇 |
1994年 | 913篇 |
1993年 | 693篇 |
1992年 | 523篇 |
1991年 | 383篇 |
1990年 | 283篇 |
1989年 | 258篇 |
1988年 | 241篇 |
1987年 | 137篇 |
1986年 | 110篇 |
1985年 | 61篇 |
1984年 | 47篇 |
1983年 | 31篇 |
1982年 | 33篇 |
1981年 | 29篇 |
1980年 | 28篇 |
1979年 | 18篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1971年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
Local residence time,residence revolution,and residence volume distributions in twin‐screw extruders
Xian‐Ming Zhang Lian‐Fang Feng Sandrine Hoppe Guo‐Hua Hu 《Polymer Engineering and Science》2008,48(1):19-28
This work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co‐rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in‐line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19–28, 2008. © 2007 Society of Plastics Engineers 相似文献
33.
数控车床的回转刀架故障发生频繁,影响零部件的加工.通过对电动回转刀架的电气控制原理分析,结合实际的维修经验,提出相应的维修方法及措施. 相似文献
34.
Haijun Fang Zongli Lin 《Automatic Control, IEEE Transactions on》2006,51(7):1177-1184
In this note, we revisit the problem of global practical stabilization for planar linear systems subject to actuator saturation and input additive disturbances. A parameterized linear state feedback law is designed such that, by tuning the value of the parameter, all trajectories of the closed-loop system converge to an arbitrarily small neighborhood of the origin in a finite time and remain in there. 相似文献
35.
Bin Xie Shi X.Q. Han Ding 《Components and Packaging Technologies, IEEE Transactions on》2008,31(2):361-369
In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles used in the ACA assembly are with cracks in the metal coating of the particles after the ACA bonding. This paper introduced the fracture analysis by applying the cohesive elements in the numerical model of the nickel-coated polymer particle and further simulating the cracks initiation and propagation in the nickel coating during the ACA bonding. The simulation results showed that the stress distribution on the nickel-coated particle with cracks was significantly different from that on the nickel-coated particle without crack, indicating that the stress analysis by taking the crack into consideration is very important for the reliability assessment of the ACA interconnection. The stress analysis of cohesive elements indicated that the cracks initiated at the central area of the nickel coating and propagated to the polar area. Furthermore, by the introduction of a new parameter of the virtual resistance, a mathematical model was established to describe the electrical characteristics of the nickel-coated particle with cracks. The particle resistance of the nickel-coated particle with cracks was found to be much higher than that of the particle without crack in the optimized bonding pressure range, indicating that it is necessary to take the crack into consideration for the particle conduction analysis as well. Therefore, the fracture analysis on the conductive particle by taking the crack into consideration could accurately evaluate the reliability of ACA interconnection and avoid serious reliability issues. 相似文献
36.
Bingyong Yan Zuohua Tian Songjiao Shi 《International Journal of Electrical Power & Energy Systems》2008,30(5):343-360
In this paper, we propose a novel distributed robust fault detection and identification (RFDI) scheme for a class of nonlinear systems. Firstly, a detection and identification estimator—robust fault tracking approximator (RFTA) is designed for online health monitoring. A novel feature of the RFTA is that it can simultaneously detect and accurately identify the shape and magnitude of the fault and disturbance. Moreover, it takes less online training time compared with the traditional neural network based fault diagnosis schemes. For some distributed systems, a network of distributed estimators is constructed where the RFTA is embedded into each estimator. Then we use consensus filter to filter the outputs of each estimator. One of the most important merits of the consensus filter is that its outputs can dramatically improve the accuracy of fault detection and identification. Next, the stability of the distributed RFDI scheme is rigorously investigated. Finally, two numerical examples are given to illustrate the feasibility and effectiveness of the proposed approach. 相似文献
37.
日本落叶松是适合在北半球广泛种植的早期速生树种 ,在我国的生长适应范围比较广 ,如今在我国华北、西北、西南和华中亚热带山区的部分地区已有种植。它在造纸领域中的应用研究已经开始 ,而且已经证实是一种很有潜力的造纸木材 相似文献
38.
沸石孔结构对1-己烯异构化性能的影响 总被引:1,自引:0,他引:1
采用1-己烯为原料,对硅铝比相近、不同孔结构的沸石在脉冲微反装置上进行了评价试验,考察了FCC条件下沸石孔结构对烯烃异构化性能的影响。结果表明,大孔径的Y型沸石具有良好的异构化性能,异构化能力由强到弱的排列顺序为Y>β>ZRP>丝光沸石>镁碱沸石。 相似文献
39.
Mixtures of Cr and Mo elemental powders, with the nominal compositions Cr25Mo75, Cr50Mo50, and Cr75Mo25, are processed by high-energy ball milling at ambient temperature. Milling is observed to force the mixing of the immiscible
bcc elements Cr and Mo into solid solutions. The lattice parameter of these solid solutions, measured by X-ray diffraction
(XRD), displays the expected positive deviation from Vegard’s law. These deviations are compared to the ones predicted by
Eshelby’s inclusion model for dilute alloys. The conventional Williamson-Hall approach is shown to fail to determine the grain
size in as-milled samples, probably due to the high density of dislocations. Annealing at 700 °C for 10 hours under argon
leads to a large reduction in structural defect density, without inducing any significant decomposition. The mixing measured
in Cr-Mo is discussed in the broader context of the mechanical mixing forced by ball milling in moderately immiscible systems. 相似文献
40.