全文获取类型
收费全文 | 1722篇 |
免费 | 45篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 28篇 |
化学工业 | 317篇 |
金属工艺 | 78篇 |
机械仪表 | 31篇 |
建筑科学 | 24篇 |
能源动力 | 74篇 |
轻工业 | 40篇 |
水利工程 | 5篇 |
石油天然气 | 7篇 |
无线电 | 254篇 |
一般工业技术 | 374篇 |
冶金工业 | 287篇 |
原子能技术 | 13篇 |
自动化技术 | 242篇 |
出版年
2023年 | 15篇 |
2022年 | 22篇 |
2021年 | 36篇 |
2020年 | 37篇 |
2019年 | 31篇 |
2018年 | 51篇 |
2017年 | 32篇 |
2016年 | 42篇 |
2015年 | 36篇 |
2014年 | 29篇 |
2013年 | 102篇 |
2012年 | 64篇 |
2011年 | 90篇 |
2010年 | 55篇 |
2009年 | 69篇 |
2008年 | 84篇 |
2007年 | 85篇 |
2006年 | 53篇 |
2005年 | 49篇 |
2004年 | 31篇 |
2003年 | 29篇 |
2002年 | 29篇 |
2001年 | 20篇 |
2000年 | 22篇 |
1999年 | 35篇 |
1998年 | 61篇 |
1997年 | 59篇 |
1996年 | 42篇 |
1995年 | 38篇 |
1994年 | 38篇 |
1993年 | 35篇 |
1992年 | 18篇 |
1991年 | 25篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 13篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 22篇 |
1975年 | 6篇 |
1974年 | 12篇 |
排序方式: 共有1774条查询结果,搜索用时 31 毫秒
121.
The steady flow of an incompressible micropolar fluid between a rotating and a stationary disc is studied when a uniform suction is applied on the stationary disc. The nonlinear coupled equations involving velocity and microrotation components have been solved numerically using quasilinearisation technique. The pressure coefficient at any radius r of the rotating disc varies linearly with micropolar parameter R. The three velocities and microrotation components have been displayed graphically. It is observed that for low suction and high rotation, both radial and axial flows are of cellular type for small R but turn unidirectional for large values of R. The flow regimes are completely reversed in the case of blowing. 相似文献
122.
In this paper, the thermodynamic properties of lithium nitrate-ammonia mixtures are presented. The vapour pressure-temperature correlations are developed by fitting the experimental P-T-x data. The enthalpy of solution, the latent heat of vaporization, the integral heat of solution and the differential heat of solution are presented in appropriate tabular and graphical forms. 相似文献
123.
Savaria Y. Hayes J. Rumin N. Agarwal V. 《Selected Areas in Communications, IEEE Journal on》1986,4(1):15-23
Soft errors caused by ionizing radiation will be a limiting factor in the reliability of VLSI circuits with submicron-feature sizes. A new approach to the design of soft-error-tolerant digital integrated circuits'is presented. It is based on the filtering of transients at register inputs, and it incurs a lower area overhead than known techniques. The method, called soft-error filtering (SEF), is derived on the basis of the analogy between a noise-sensitive finite-state machine and a noisy communication channel. The necessary characteristics of the register are examined and a design is presented for the associated filter. It is shown that SEF can be used to reduce the associated error rate to insignificant levels. 相似文献
124.
In this paper, we propose a novel concept called Hitch-hiking in order to reduce the energy consumption of broadcast application for wireless networks. Hitch-hiking takes advantage of
the physical layer design that facilitates the combining of partial signals to obtain the complete information. The concept
of combining partial signals using maximal ratio combiner [15] has been used to improve the reliability of the communication link but has never been exploited to reduce energy consumption
in broadcasting over wireless ad hoc networks. We study the advantage of Hitch-hiking for the scenario when the transmission
power level of nodes is fixed as well as the scenario when the nodes can adjust their power level. For both scenarios, we
show that Hitch-hiking is advantageous and have proposed algorithms to construct broadcast tree with Hitch-hiking taken into
consideration. For fixed transmission power case, we propose and analyze a centralized heuristic algorithm called SPWMH (Single
Power Wireless Multicast with Hitch-hiking) to construct a broadcast tree with minimum forwarding nodes. For the latter case,
we propose a centralized heuristic algorithm called Wireless Multicast with Hitch-hiking (WMH) to construct an energy efficient
tree using Hitch-hiking and also present a distributed version of the heuristic. We also evaluate the proposed heuristics
through simulation. Simulation results show that Hitch-hiking can reduce the transmission cost of broadcast by as much as
50%. Further, we propose and evaluate a protocol called Power Saving with Broadcast Tree (PSBT) that reduces energy consumption
of broadcast by eliminating redundancy in receive operation. Finally, we propose an algorithm that takes advantage of both
Hitch-hiking and PSBT in conserving energy.
Manish Agarwal is an engineer at Microsoft, Redmond. He received his Masters degree in Electrical and Computer Engineering from University
of Massachusetts, Amherst in 2004. He received his undergraduate degree from Indian Institute of Technology, Guwahati. His
research interest lies in the field of mobile ad hoc networks.
Lixin Gao is an associate professor of Electrical and Computer Engineering at the University of Masschusetts, Amherst. She received
her Ph.D. degree in computer science from the University of Massachusettes at Amherst in 1996. Her research interests include
multimedia networking and Internet routing. Between May 1999 and January 2000, she was a visiting researcher at AT&T Research
Labs and DIMACS. She is an Alfred P. Sloan Fellow and received an NSF CAREER Award in 1999. She is a member of IEEE, ACM,
and Sigma Xi.
Joon Ho Cho received the B.S. degree (summa cum laude) in electrical engineering from Seoul National University, Seoul, Korea, in 1995
and the M.S.E.E. and Ph.D. degrees in electrical and computer engineering from Purdue University, West Lafayette, IN, in 1997
and 2001, respectively. From 2001 to 2004, he was with the University of Massachusetts at Amherst as an Assistant Professor.
Since July 2004, he has been with Pohang University of Science and Technology (POSTECH), Pohang, Korea, where he is presently
an Assistant Professor in the Department of Electronic and Electrical Engineering. His research interests include wideband
systems, multiuser communications, adaptive signal processing, packet radio networks, and information theory. Dr. Cho is currently
an Associate Editor for the IEEE Transactions on Vehicular Technology.
Jie Wu is a Professor at Department of Computer Science and Engineering, Florida Atlantic University. He has published over 300
papers in various journal and conference proceedings. His research interests are in the area of mobile computing, routing
protocols, fault-tolerant computing, and interconnection networks. Dr. Wu served as a program vice chair for 2000 International
Conference on Parallel Processing (ICPP) and a program vice chair for 2001 IEEE International Conference on Distributed Computing
Systems (ICDCS). He is a program co-chair for the IEEE 1st International Conference on Mobile Ad-hoc and Sensor Systems (MASS'04).
He was a co-guest-editor of a special issue in IEEE Computer on “Ad Hoc Networks”. He also editored several special issues
in Journal of Parallel and Distributing Computing (JPDC) and IEEE Transactions on Parallel and Distributed Systems (TPDS).
He is the author of the text “Distributed System Design” published by the CRC press. Currently, Dr. Wu serves as an Associate
Editor in IEEE Transactions on Parallel and Distributed Systems and three other international journals. Dr. Wu is a recipient
of the 1996–97 and 2001–2002 Researcher of the Year Award at Florida Atlantic University. He served as an IEEE Computer Society
Distinguished Visitor. Dr. Wu is a Member of ACM and a Senior Member of IEEE. 相似文献
125.
Over the past few years, hydrogen has been recognized as a suitable substitute for present vehicular fuels. This paper covers the economic analysis of one of the most promising hydrogen production methods—using wind energy for producing hydrogen through electrolysis of seawater—with a concentration on the Indian transport sector. The analysis provides insights about several questions such as the advantages of offshore plants over coastal installations, economics of large wind-machine clusters, and comparison of cost of producing hydrogen with competing gasoline. Robustness of results has been checked by developing several scenarios such as fast/slow learning rates for wind systems for determining future trends. Results of this analysis show that use of hydrogen for transportation is not likely to be attractive before 2012, and that too with considerable learning in wind, electrolyzer and hydrogen storage technology. 相似文献
126.
G. Agarwal H. Gao M. Amirthalingam M.J.M. Hermans 《Science & Technology of Welding & Joining》2018,23(2):134-139
In situ strain evolution during laser welding has been measured by means of digital image correlation to assess the susceptibility of an advanced high strength automotive steel to solidification cracking. A novel method realised using auxiliary illumination and optical narrow bandpass filter allowed strain measurements as close as 1.5?mm from the fusion boundary with good spatial and temporal resolution. A finite-element thermomechanical model of the welding process supports the experimentally measured transverse strain. The validated finite-element numerical model can be used to assess the local strain and associated stress conditions which influences weldability and in particular, solidification cracking. 相似文献
127.
Wireless mesh networks (WMNs) are considered as cost effective, easily deployable and capable of extending Internet connectivity.
However, one of the major challenges in deploying reliable WMNs is preventing their nodes from malicious attacks, which is
of particular concern as attacks can severely degrade network performance. When a DoS attack is targeted over an entire communication
path, it is called a path-based DoS attack. We study the performance impact of path-based DoS attacks by considering attack
intensity, medium errors, physical diversity, collusion and hop count. We setup a wireless mesh testbed and configure a set
of experiments to gather realistic measurements, and assess the effects of different factors. We find that medium errors have
significant impact on the performance of WMNs when a path-based DoS attack is carried out, and the impact is exacerbated by
the MAC layer retransmissions. We show that due to physical diversity, a far attacker can lead to an increased performance
degradation than a close-by attacker. Additionally, we demonstrate that the joint impact of two colluding attackers is not
as severe as the joint result of individual attacks. We also discuss a strategy to counter path-based DoS attacks which can
potentially alleviate the impact of the attack significantly. 相似文献
128.
Double gate FinFETs are shown to be better candidates for subthreshold logic design than equivalent bulk devices. However it is not so clear which configuration of DG FinFETs will be more optimal for subthreshold logic. In this paper, we compare the different device and circuit level performance metrics of DG FinFETs with symmetric, asymmetric, tied and independent gate options for subthreshold logic. We observe that energy delay product (EDP) shows a better subthreshold performance metric than power delay product (PDP) and it is observed that the tied gate symmetric option has ≈78% lower EDP value than that of independent gate option for subthreshold logic. The asymmetry in back gate oxide thickness adds to further reduction in EDP for tied gate and has no significant effect on independent gate option. The robustness (measured in terms of % variation in device/circuit performance metrics for a ±10% variation in design parameters) of DG FinFETs with various options has also been investigated in presence of different design parameter variations such as silicon body thickness, channel length, threshold voltage, supply voltage and temperature, etc. Independent gate option has been seen to be more robust (≈40% less) than that of tied gate option for subthreshold logic. Comparison of logic families for subthreshold regime with DG FinFET options shows that for tied gate option, sub-CMOS, sub-Domino and sub-DCVSL have almost similar and better energy consumption and robustness characteristics with respect to PVT variations than other families. 相似文献
129.
The protective potential of protective devices such as respirators, suits, gloves, and overboots is widely evaluated using the standard colorimetric test (spot disc breakthrough time test, also called SD BTT) involving sulfur mustard (SM) as the challenge chemical. The vesicant nature of SM makes the test inconvenient and poses stringent safety demands. Moreover, such tests are allowed only at a limited number of facilities, causing delay in product development and supply. This prompted the present study on the search for suitable SM simulant responsive to SD BTT test. The diffusivities at BTT (DBTT) of 10 commercially available thiocompounds through butyl rubber (IIR) were compared vis‐a‐vis DBTT of SM. For three representative thiocompounds, namely methyl (phenyl thio)acetate, 2‐chloroethyl phenyl sulfide (2‐CEPS) and phenyl‐n‐propyl sulfide (PNPS), the transport parameters through IIR were obtained. PNPS and 2‐CEPS were further compared with respect to DBTT in elastomers such as IIR, ethylene–propylene–diene methylene rubber, polydimethylsiloxane, nitrile rubber, polybutadiene, and natural rubber. 2‐CEPS showed generally same order of DBTT as SM implying its potential use as a simulant. The transport parameters for various 2‐CEPS/elastomer systems were also determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
130.