全文获取类型
收费全文 | 287605篇 |
免费 | 3066篇 |
国内免费 | 817篇 |
专业分类
电工技术 | 5031篇 |
综合类 | 162篇 |
化学工业 | 45417篇 |
金属工艺 | 11896篇 |
机械仪表 | 8605篇 |
建筑科学 | 6849篇 |
矿业工程 | 1835篇 |
能源动力 | 6734篇 |
轻工业 | 25905篇 |
水利工程 | 3190篇 |
石油天然气 | 7087篇 |
武器工业 | 16篇 |
无线电 | 31449篇 |
一般工业技术 | 56934篇 |
冶金工业 | 51362篇 |
原子能技术 | 7532篇 |
自动化技术 | 21484篇 |
出版年
2021年 | 2101篇 |
2018年 | 3672篇 |
2017年 | 3623篇 |
2016年 | 3905篇 |
2015年 | 2466篇 |
2014年 | 4230篇 |
2013年 | 12020篇 |
2012年 | 6829篇 |
2011年 | 9214篇 |
2010年 | 7568篇 |
2009年 | 8643篇 |
2008年 | 8931篇 |
2007年 | 8813篇 |
2006年 | 7826篇 |
2005年 | 7310篇 |
2004年 | 6800篇 |
2003年 | 6553篇 |
2002年 | 6627篇 |
2001年 | 6498篇 |
2000年 | 6176篇 |
1999年 | 6229篇 |
1998年 | 14750篇 |
1997年 | 11029篇 |
1996年 | 8566篇 |
1995年 | 6523篇 |
1994年 | 5915篇 |
1993年 | 5787篇 |
1992年 | 4479篇 |
1991年 | 4441篇 |
1990年 | 4284篇 |
1989年 | 4302篇 |
1988年 | 4255篇 |
1987年 | 3598篇 |
1986年 | 3595篇 |
1985年 | 4161篇 |
1984年 | 3965篇 |
1983年 | 3620篇 |
1982年 | 3422篇 |
1981年 | 3558篇 |
1980年 | 3422篇 |
1979年 | 3365篇 |
1978年 | 3445篇 |
1977年 | 3923篇 |
1976年 | 5037篇 |
1975年 | 3158篇 |
1974年 | 3007篇 |
1973年 | 3024篇 |
1972年 | 2651篇 |
1971年 | 2473篇 |
1970年 | 2104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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
72.
73.
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
74.
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
75.
I. I. Abramov I. A. Goncharenko S. A. Ignatenko A. V. Korolev E. G. Novik A. I. Rogachev 《Russian Microelectronics》2003,32(2):97-104
The concept and structure of the NANODEV simulation software are described. NANODEV deals with nanoelectronic devices that exploit single-electron tunneling, resonant tunneling, or quantum interference. It can use both simplified and sophisticated models and enables one to evaluate a wide variety of devices and configurations. The capabilities of NANODEV are illustrated by examples. 相似文献
76.
Low supply voltage high-performance CMOS current mirror with low input and output voltage requirements 总被引:1,自引:0,他引:1
Ramirez-Angulo J. Carvajal R.G. Torralba A. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2004,51(3):124-129
This paper presents a scheme for the efficient implementation of a low supply voltage continuous-time high-performance CMOS current mirror with low input and output voltage requirements. This circuit combines a shunt input feedback and a regulated cascode output stage to achieve low input resistance and very high output resistance. It can be used as a high-precision current mirror in analog and mixed signal circuits with a power supply close to a transistor's threshold voltage. The proposed current mirror has been simulated and a bandwidth of 40 MHz has been obtained. An experimental chip prototype has been sent for fabrication and has been experimentally verified, obtaining 0.15-V input-output voltage requirements, 100-/spl Omega/ input resistance, and more than 200-M/spl Omega/ (G/spl Omega/ ideally) output resistance with a 1.2-V supply in a standard CMOS technology. 相似文献
77.
Managing sewerage systems is a highly complex task due to the dynamic nature of the facilities. Their performance strongly depends on the know-how applied by the operators. In order to define optimal operational settings, two decision support tools based on mathematical models have been developed. Moreover, easy-to-use interfaces have been created as well, aiding operators who presumably do not have the necessary skills to use modelling software. The two developed programs simulate the behaviour of both wastewater treatment plants (WWTP) and sewer network systems, respectively. They have essentially the same structure, including raw data management and statistical analysis, a simulation layer using the application programming interface of the applied software and a layer responsible for the representation of the obtained results. Four user modes are provided in the two software including the simulation of historical data using the applied and novel operational settings, as well as modes concerning prediction of possible operation periods and updates. Concerning the WWTP software, it was successfully installed in Nantes (France) in June 2004. Moreover, the one managing sewer networks has been deployed in Saint-Malo (France) in January 2005. This paper presents the structure of the developed software and the first results obtained during the commissioning phase. 相似文献
78.
The use of gratings written in tin-doped silica fibres as a thermometer for high-temperature applications is described. Measurements up to ~800°C show a significant advantage over conventional fibre gratings. A considerable blue-shift has been observed at high temperatures. If corrections for blue-shift are taken into account, the errors are smaller than ~2°C 相似文献
79.
Exact pairwise error probability of space-time codes 总被引:9,自引:0,他引:9
Taricco G. Biglieri E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(2):510-513
We describe a simple technique for the numerical calculation, within any desired degree of accuracy, of the pairwise error probability (PEP) of space-time codes over fading channels. This method applies also to the calculation of E[Q(√ξ)] for any nonnegative random variable ξ whose moment-generating function Φξ(s)=E[exp(-sξ)] is known. Its application to the multiple antenna independent Rayleigh-fading channel and to the Rayleigh block fading channel is discussed, and illustrated by two simple examples 相似文献
80.