全文获取类型
收费全文 | 107926篇 |
免费 | 12964篇 |
国内免费 | 5352篇 |
专业分类
电工技术 | 7953篇 |
技术理论 | 3篇 |
综合类 | 7511篇 |
化学工业 | 17662篇 |
金属工艺 | 4956篇 |
机械仪表 | 6379篇 |
建筑科学 | 16377篇 |
矿业工程 | 3937篇 |
能源动力 | 2859篇 |
轻工业 | 9474篇 |
水利工程 | 4318篇 |
石油天然气 | 5484篇 |
武器工业 | 1666篇 |
无线电 | 8870篇 |
一般工业技术 | 10821篇 |
冶金工业 | 4668篇 |
原子能技术 | 1219篇 |
自动化技术 | 12085篇 |
出版年
2024年 | 317篇 |
2023年 | 1621篇 |
2022年 | 3788篇 |
2021年 | 5538篇 |
2020年 | 3706篇 |
2019年 | 3340篇 |
2018年 | 3407篇 |
2017年 | 4455篇 |
2016年 | 5808篇 |
2015年 | 6457篇 |
2014年 | 8010篇 |
2013年 | 7526篇 |
2012年 | 7539篇 |
2011年 | 7040篇 |
2010年 | 5471篇 |
2009年 | 5445篇 |
2008年 | 4978篇 |
2007年 | 6678篇 |
2006年 | 6525篇 |
2005年 | 5601篇 |
2004年 | 4111篇 |
2003年 | 3614篇 |
2002年 | 2910篇 |
2001年 | 2256篇 |
2000年 | 1887篇 |
1999年 | 1389篇 |
1998年 | 1063篇 |
1997年 | 825篇 |
1996年 | 836篇 |
1995年 | 673篇 |
1994年 | 551篇 |
1993年 | 388篇 |
1992年 | 341篇 |
1991年 | 242篇 |
1990年 | 257篇 |
1989年 | 199篇 |
1988年 | 122篇 |
1987年 | 101篇 |
1986年 | 91篇 |
1985年 | 79篇 |
1984年 | 85篇 |
1983年 | 52篇 |
1981年 | 55篇 |
1980年 | 100篇 |
1979年 | 61篇 |
1965年 | 47篇 |
1964年 | 68篇 |
1962年 | 82篇 |
1959年 | 56篇 |
1955年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators 总被引:3,自引:0,他引:3
An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM
plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness
direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback
control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented
for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence
of feedback control gain on the static and dynamic responses of the FGM plates are examined.
Received: 13 March 2002 / Accepted: 5 March 2003
The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special
Administrative Region, China (Project No. CityU 1024/01E). 相似文献
182.
183.
A three-dimensional FE analysis of large deformations for impact loadings using tetrahedral elements
A three-dimensional dynamic program for the anaysis of large deformations in contact-penetration problems is developed using
the finite element Lagrangian method with explicit time integration. By incorporating a tetrahedral element, which allows
a single-point integration without a special hourglass control scheme, this program can be more effective to the present problem.
The position code algorithm is used to search contact surface. Eroding surfaces are also considered. The defense node algorithm
was slightly modified for the calculation of contact forces. A study of obliquity effects on metallic plate perforation and
ricochet processes in thin plates impacted by a sphere was conducted. It is well simulated that on separation of two parts
of the sphere, the portion still within the crater tends to perforate, while the portion in contact with the plate surface
ricochets. This deformation pattern is observed in experiments, especially at high obliquities. A long rod that impacts an
oblique steel plate at high impact velocity was also simulated in order to study the dynamics of the rod caused by the three
dimensional asymmetric contact. The agreement between simulated and experimental results is quite good. Fracture phenomena
occuring at high obliquity deserves further investigations.
Received: 20 February 2002 / Accepted: 20 September 2002 相似文献
184.
185.
As we approach 100 nm technology the interconnect issues are becoming one of the main concerns in the testing of gigahertz system-on-chips. Voltage distortion (noise) and delay violations (skew) contribute to the signal integrity loss and ultimately functional error, performance degradation and reliability problems. In this paper, we first define a model for integrity faults on the high-speed interconnects. Then, we present a BIST-based test methodology that includes two special cells to detect and measure noise and skew occurring on the interconnects of the gigahertz system-on-chips. Using an inexpensive test architecture the integrity information accumulated by these special cells can be scanned out for final test and reliability analysis. 相似文献
186.
187.
Erik Jan Marinissen 《Journal of Electronic Testing》2002,18(4-5):435-454
Modular testing is an attractive approach to testing large system ICs, especially if they are built from pre-designed reusable embedded cores. This paper describes an automated modular test development approach. The basis of this approach is that a core or module test is dissected into a test protocol and a test pattern list. A test protocol describes in detail how to apply one test pattern to the core, while abstracting from the specific test pattern stimulus and response values. Subsequent automation tasks, such as the expansion from core-level tests to system-chip-level tests and test scheduling, all work on test protocols, thereby greatly reducing the amount of compute time and data involved. Finally, an SOC-level test is assembled from the expanded and scheduled test protocols and the (so far untouched) test patterns. This paper describes and formalizes the notion of test protocols and the algorithms for test protocol expansion and scheduling. A running example is featured throughout the paper. We also elaborate on the industrial usage of the concepts described. 相似文献
188.
游梁式抽油机二次平衡分析 总被引:1,自引:0,他引:1
为解决游梁式抽油机能耗大、效率低的问题,设计了二次平衡装置。这种装置通过是挂在抽油机后端的平衡重的平衡作用,降低一次平衡曲柄轴净扭矩的两个峰值,达到减少能耗提高效率的目的。对抽油机的二次平衡作了较详尽的理论分析,给出了实行二次平衡后曲柄轴净扭矩的计算公式和安装二次平衡装置前后曲柄轴净扭矩曲线图。在大庆油田两口井上进行的现场试验结果表明,安装二次平衡装置后,两口井年节约电费分别为0.25万元和1.17万元,经济效益明显。 相似文献
189.
190.
本文从小卫星、星座飞速发展以及对测控通信系统新的要求出发,介绍了综合基带、连续波多波束相控阵天线的功能、特点及工作原理,提出了建立新型多功能智能化测控通信站的设想。 相似文献