全文获取类型
收费全文 | 391852篇 |
免费 | 5440篇 |
国内免费 | 2414篇 |
专业分类
电工技术 | 7555篇 |
技术理论 | 1篇 |
综合类 | 1512篇 |
化学工业 | 56919篇 |
金属工艺 | 16995篇 |
机械仪表 | 12091篇 |
建筑科学 | 9470篇 |
矿业工程 | 2289篇 |
能源动力 | 9704篇 |
轻工业 | 33260篇 |
水利工程 | 4074篇 |
石油天然气 | 8139篇 |
武器工业 | 126篇 |
无线电 | 46716篇 |
一般工业技术 | 76854篇 |
冶金工业 | 75318篇 |
原子能技术 | 8791篇 |
自动化技术 | 29892篇 |
出版年
2021年 | 3393篇 |
2019年 | 2916篇 |
2018年 | 5081篇 |
2017年 | 5082篇 |
2016年 | 5347篇 |
2015年 | 3967篇 |
2014年 | 6408篇 |
2013年 | 17132篇 |
2012年 | 10219篇 |
2011年 | 13741篇 |
2010年 | 11336篇 |
2009年 | 12896篇 |
2008年 | 13239篇 |
2007年 | 13203篇 |
2006年 | 11711篇 |
2005年 | 10566篇 |
2004年 | 9776篇 |
2003年 | 9331篇 |
2002年 | 9045篇 |
2001年 | 9144篇 |
2000年 | 8602篇 |
1999年 | 9047篇 |
1998年 | 23566篇 |
1997年 | 16712篇 |
1996年 | 12945篇 |
1995年 | 9395篇 |
1994年 | 8470篇 |
1993年 | 8285篇 |
1992年 | 5946篇 |
1991年 | 5871篇 |
1990年 | 5658篇 |
1989年 | 5498篇 |
1988年 | 5297篇 |
1987年 | 4369篇 |
1986年 | 4406篇 |
1985年 | 5018篇 |
1984年 | 4702篇 |
1983年 | 4267篇 |
1982年 | 4050篇 |
1981年 | 4168篇 |
1980年 | 3942篇 |
1979年 | 3791篇 |
1978年 | 3817篇 |
1977年 | 4415篇 |
1976年 | 5935篇 |
1975年 | 3411篇 |
1974年 | 3254篇 |
1973年 | 3256篇 |
1972年 | 2826篇 |
1971年 | 2601篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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
72.
In this work it is presented a study on the residence time distribution (RTD) of particles in a co-current pilot-plant spray dryer operated with a rotary atomization system. A nuclear technique is applied to investigate the RTD responses of spray dryers. The methodology is based on the injection of a radioisotope tracer in the feed stream followed by the monitoring of its concentration at the outlet stream. The experiments were performed during the drying of aqueous suspensions of gadolinium oxide. The RTD responses obtained experimentally presented good reproducibility, indicating that the technique applied is well suited to investigating fluid-dynamics of spray dryers. In addition to the experimental investigation, a mathematical model was used to describe the RTD experimental curves. 相似文献
73.
Scale Up from Small Oven-Drying Tests of Mineral Concentrate to Pilot-Scale Drying with a Heated Pad
While Fickian diffusion models are commonly used in other applications, there are few reports of them being applied to the batch drying of a mineral concentrate. Diffusion coefficients estimated from small-scale oven-drying tests were used to predict the drying behavior of a concentrate sample 1 m × 1 m in area and 50 cm deep, with a heated bottom pad. These pilot-scale tests included both daily turning of the sample and turning every three days. The excellent quantitative agreement between the predicted and observed pilot-scale behavior gives a high level of confidence in the model predictions and suggests that a Fickian diffusion model is adequate to predict the behavior of mineral concentrates at the low moisture contents used here. 相似文献
74.
75.
G. Murali Dhar B. N. Srinivas M. S. Rana Manoj Kumar S. K. Maity 《Catalysis Today》2003,86(1-4):45-60
Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al2O3 containing mixed oxide supports, TiO2 containing mixed oxide supports, ZrO2 containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO2 containing mixed oxides received maximum attention, especially TiO2–Al2O3 supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication. 相似文献
76.
Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
M. Kawasaki T. Tsukamoto Y. Kimura T. Iwasaki H. Yamane 《Journal of Materials Science》2003,38(4):739-745
The damage imposed on SiO
x
deposited nylon 6 films as a result of abrasion with a cotton cloth and Gelboflex testing was examined by evaluating the rate at which copper plates, which were enveloped by the damaged films, were corroded by H2S. Abrasion with a cotton cloth caused some micro-cracking of the SiO
x
layer and the permeation rate of H2S approached that of the uncoated nylon 6 film. Damage to the SiO
x
layer by twisting and crushing progressed gradually with the number of Gelboflex test cycles and correspondingly the corrosion rate of the copper plates increased. Comparison of the corrosion rates of the copper plates kept in the pouches made of various commercial films with those obtained for the damaged SiO
x
deposited nylon 6 films showed a clear relationship between the H2 permeation rate of the films and the corrosion rate of the copper plates by H2S. 相似文献
78.
79.
J. B. Quinn G. E. Schumacher L. W. Schultheis 《Journal of Failure Analysis and Prevention》2004,4(1):41-46
Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage,
recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist
during placement of a breathing tube at the start of surgery.
In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture
characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be
described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken
by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken
canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied
during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing
tube during recovery was the likely cause of fracture.
This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic
analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing. 相似文献
80.
Mathematical models of thermomechanical processes which are based on the laws of rational thermodynamics of irreversible processes are treated. Singular features of the unsteady-state behavior of a continuous medium are demonstrated within different models, such as a medium with internal parameters of state, a medium with memory, and a medium of the velocity type. 相似文献