全文获取类型
收费全文 | 3238篇 |
免费 | 133篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 53篇 |
综合类 | 59篇 |
化学工业 | 561篇 |
金属工艺 | 109篇 |
机械仪表 | 100篇 |
建筑科学 | 86篇 |
矿业工程 | 10篇 |
能源动力 | 147篇 |
轻工业 | 190篇 |
水利工程 | 15篇 |
石油天然气 | 15篇 |
武器工业 | 2篇 |
无线电 | 474篇 |
一般工业技术 | 709篇 |
冶金工业 | 402篇 |
原子能技术 | 15篇 |
自动化技术 | 459篇 |
出版年
2023年 | 24篇 |
2022年 | 55篇 |
2021年 | 72篇 |
2020年 | 39篇 |
2019年 | 43篇 |
2018年 | 52篇 |
2017年 | 58篇 |
2016年 | 66篇 |
2015年 | 51篇 |
2014年 | 91篇 |
2013年 | 245篇 |
2012年 | 177篇 |
2011年 | 185篇 |
2010年 | 150篇 |
2009年 | 173篇 |
2008年 | 151篇 |
2007年 | 140篇 |
2006年 | 152篇 |
2005年 | 114篇 |
2004年 | 98篇 |
2003年 | 81篇 |
2002年 | 73篇 |
2001年 | 69篇 |
2000年 | 69篇 |
1999年 | 75篇 |
1998年 | 112篇 |
1997年 | 101篇 |
1996年 | 117篇 |
1995年 | 70篇 |
1994年 | 63篇 |
1993年 | 51篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 25篇 |
1986年 | 30篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1977年 | 12篇 |
1976年 | 15篇 |
1975年 | 5篇 |
1972年 | 6篇 |
1970年 | 2篇 |
排序方式: 共有3406条查询结果,搜索用时 15 毫秒
1.
Scientometrics - The article published on 5 July 2021 is well-written and of interest. However, some improvements could be made, such as ten Tables/Figures can be shortened to highlight the focused... 相似文献
2.
3.
4.
Chou Y.C. Leung D. Lai R. Grundbacher R. Barsky M. Kan Q. Tsai R. Wojtowicz M. Eng D. Tran L. Block T. Liu P.H. Nishimoto M. Oki A. 《Electron Device Letters, IEEE》2003,24(6):378-380
The authors have investigated the reliability performance of G-band (183 GHz) monolithic microwave integrated circuit (MMIC) amplifiers fabricated using 0.07-/spl mu/m T-gate InGaAs-InAlAs-InP HEMTs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel on 3-in wafers. Life test was performed at two temperatures (T/sub 1/ = 200 /spl deg/C and T/sub 2/ = 215 /spl deg/C), and the amplifiers were stressed at V/sub ds/ of 1 V and I/sub ds/ of 250 mA/mm in a N/sub 2/ ambient. The activation energy is as high as 1.7 eV, achieving a projected median-time-to-failure (MTTF) /spl ap/ 2 /spl times/ 10/sup 6/ h at a junction temperature of 125 /spl deg/C. MTTF was determined by 2-temperature constant current stress using /spl Delta/G/sub mp/ = -20% as the failure criteria. The difference of reliability performance between 0.07-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel and 0.1-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with In/sub 0.6/Ga/sub 0.4/As channel is also discussed. The achieved high-reliability result demonstrates a robust 0.07-/spl mu/m pseudomorphic InGaAs-InAlAs-InP HEMT MMICs production technology for G-band applications. 相似文献
5.
BACKGROUND: The enterococci have become important nosocomial pathogens. They can cause multiple site infections and enterococcal bacteremia becomes more frequently associated with a high mortality rate. Previous studies of enterococcal bacteremia showed a variety of results. To establish the significance and importance of enterococci as nosocomial pathogens in this hospital, to characterize their clinical pictures and to search for the risk factors for mortality, this retrospective study was performed. METHODS: There were 208 cases of enterococcal bacteremia which occurred from 1988 to 1992. Twenty-seven cases had no medical charts, dismissing possibility of evaluation. Finally, 181 cases of enterococcal bacteremia were analysed. RESULTS: One hundred and eighteen episodes were nosocomial infections. Polymicrobial bacteremia occurred in 68.5% of the patients and the most common co-isolate was Pseudomonas aeruginosa. Those patients (78.5%) with underlying diseases and malignancies were the most common underlying problems. The portal of entry could be found in 69.6 percent of patients, with the gastrointestinal tract the most common sources. Antimicrobial susceptibility testing showed high gentamicin resistance rate (89.5%), and ampicillin still had about 80 percent sensitivity rate. The group who received specific antibiotic therapy for enterococcus showed lower mortality (36.4% versus 47.6%). Only one case had infective endocarditis. Forty-nine patients suffered from septic shock, the cause of 30 deaths. Totally 75 patients died during hospitalization. Besides sepsis, another major cause of death was their underlying diseases itself. CONCLUSIONS: Enterococci have no doubt become important nosocomial pathogens and enterococcal bacteremia were associated with high mortality, especially in elderly patients with underlying diseases such as malignancy or diabetes. When clinically dealing with sepsis from the gastrointestinal or biliary tract, especially when previous cephalosporins therapy showed no response, the possibility of enterococcal bacteremia should always be considered. 相似文献
6.
Pai H. Chou Jinfeng Liu Dexin Li Nader Bagherzadeh 《Design Automation for Embedded Systems》2002,7(3):205-232
Power-aware systems are those that must exploit a widerange of power/performance trade-offs in order to adapt to the power availabilityand application requirements. They require the integration of many novel powermanagement techniques, ranging from voltage scaling to subsystem shutdown.However, those techniques do not always compose synergistically with eachother; in fact, they can combine subtractively and often yield counterintuitive,and sometimes incorrect, results in the context of a complete system. Thiscan become a serious problem as more of these power aware systems are beingdeployed in mission critical applications.To address the problem of technique integration for power-aware embedded systems, we propose a new design tool framework called IMPACCT and the associated design methodology. The system modeling methodology includes application model for capturing timing/powerconstraints and mode dependencies at the system level. The tool performs power-awarescheduling and mode selection to ensure that all timing/power constraintsare satisfied and that all overhead is taken into account. IMPACCT then synthesizesthe implementation targeting a symmetric multiprocessor platform. Experimentalresults show that the increased dynamic range of power/performance settingsenabled a Mars rover to achieve significant acceleration while using lessenergy. More importantly, our tool correctly combines the state-of-the-arttechniques at the system level, thereby saving even experienced designersfrom many pitfalls of system-level power management. 相似文献
7.
The minimum energy required to transmit one bit of information through a network characterizes the most economical way to communicate in a network. In this paper, we show that, under a layered model of wireless networks, the minimum energy-per-bit for multicasting in a mobile ad hoc network can be found by a linear program; the minimum energy-per-bit can be attained by performing network coding. Compared with conventional routing solutions, network coding not only allows a potentially lower energy-per-bit to be achieved, but also enables the optimal solution to be found in polynomial time, in sharp contrast with the NP-hardness of constructing the minimum-energy multicast tree as the optimal routing solution. We further show that the minimum energy multicast formulation is equivalent to a cost minimization with linear edge-based pricing, where the edge prices are the energy-per-bits of the corresponding physical broadcast links. This paper also investigates minimum energy multicasting with routing. Due to the linearity of the pricing scheme, the minimum energy-per-bit for routing is achievable by using a single distribution tree. A characterization of the admissible rate region for routing with a single tree is presented. The minimum energy-per-bit for multicasting with routing is found by an integer linear program. We show that the relaxation of this integer linear program, studied earlier in the Steiner tree literature, can now be interpreted as the optimization for minimum energy multicasting with network coding. In short, this paper presents a unifying study of minimum energy multicasting with network coding and routing. 相似文献
8.
Dynamic Programming (DP) applies to many signal and image processing applications including boundary following, the Viterbi algorithm, dynamic time warping, etc. This paper presents an array processor implementation of generic dynamic programming. Our architecture is a SIMD array attached to a host computer. The processing element of the architecture is based on an ASIC design opting for maximum speed-up. By adopting a torus interconnection network, a dual buffer structure, and a multilevel pipeline, the performance of the DP chip is expected to reach the order of several GOPS. The paper discusses both the dedicated hardware design and the data flow control of the DP chip and the total array.This work was supported in part by the NATO, Scientific and Environmental Affairs Division, Collaborative Research Grant SA.5-2-05(CRG.960201)424/96/JARC-501. 相似文献
9.
Magnesiumandmagnesiumalloyshavebeenin vestigatedashydrogenstoragematerialsforseveralde cadesbecausefarmorehydrogenbyweightcanbestoredinthemthaninmostoftheothercurrentlyknownhydrogenstoragealloys .Moreover ,thehighnaturalabundanceofMg ,itslightmassandenviron mentalcompatibilitypotentiallymakemagnesiumoneofthemostprospectivecandidatesforfuturehydrogenstoragematerials .Unfortunately ,thepracticalappli cationofMganditsalloyshasbeenlimitedonlytocertainstoragedevicebecauseoftheirpoorhydriding dehydr… 相似文献
10.
Chun-Yuan Huang Tzu-Min Ou Shu-Ting Chou Meng-Chyi Wu Shih-Yen Lin Jim-Yong Chi 《Nanotechnology, IEEE Transactions on》2007,6(6):589-594
In this paper, we report that low-density InAs/GaAs quantum dots (QDs) can be formed by postgrowth annealing the samples with 1.5-monolayer (ML) InAs coverage, which is thinner than the critical layer thickness for the Stranski-Krastanov growth. The annealing procedure was performed immediately after the deposition of the InAs layer. The effects of annealing time and annealing temperature on the dot density, dot size, and optical characteristics of the QDs were investigated. The optimum annealing conditions to obtain low-density QDs are longer than 60 s and higher than 500degC . Meanwhile, no luminescence can be observed for the wetting-layer, which may suggest that the postgrowth annealing will make the wetting layer thinner and thus reduce the effects of wetting layer on carrier relaxation and recombination. On the other hand, we observe that a decrease of the PL intensity at the annealing conditions of 60 s and 515degC , which is possibly due to the increasing surface dislocations resulted from the In adatom desorption at higher annealing temperature. 相似文献