全文获取类型
收费全文 | 2782篇 |
免费 | 150篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 40篇 |
综合类 | 8篇 |
化学工业 | 574篇 |
金属工艺 | 80篇 |
机械仪表 | 169篇 |
建筑科学 | 72篇 |
矿业工程 | 5篇 |
能源动力 | 113篇 |
轻工业 | 204篇 |
水利工程 | 28篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 437篇 |
一般工业技术 | 549篇 |
冶金工业 | 174篇 |
原子能技术 | 32篇 |
自动化技术 | 454篇 |
出版年
2024年 | 2篇 |
2023年 | 57篇 |
2022年 | 82篇 |
2021年 | 149篇 |
2020年 | 100篇 |
2019年 | 132篇 |
2018年 | 102篇 |
2017年 | 97篇 |
2016年 | 126篇 |
2015年 | 84篇 |
2014年 | 152篇 |
2013年 | 203篇 |
2012年 | 185篇 |
2011年 | 212篇 |
2010年 | 133篇 |
2009年 | 135篇 |
2008年 | 126篇 |
2007年 | 127篇 |
2006年 | 97篇 |
2005年 | 62篇 |
2004年 | 64篇 |
2003年 | 55篇 |
2002年 | 30篇 |
2001年 | 47篇 |
2000年 | 33篇 |
1999年 | 38篇 |
1998年 | 63篇 |
1997年 | 44篇 |
1996年 | 35篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 6篇 |
排序方式: 共有2945条查询结果,搜索用时 15 毫秒
1.
To prevent post-transfusional hepatitis B and C, two epidemiologic studies were performed. The first, based on the frequencies distribution of hepatitis B virus serological markers versus sex and classes of age, has permitted the assessment of the profile of the infection in a population composed of 573 north vietnamese blood donors. There is no significant difference between men and women frequencies of HBs antigen (11.5%), anti-HBs antibody (70.2%) and anti-HBc antibody alone (3.8%), but a significant difference of no-marker frequencies: 7.8% and 17.9% in men and women respectively (X2 = 9.11; p = 0.010). The percentage of no-marker decreases when the mean age of each class increases. The second, using the increase of the serum alanine aminotransferase (ALAT) activity as an indirect marker of non-A, non-B hepatitis for determining in a population of more than 25,000 parisian blood donors, the percentage of donors eliminated. They are between 0.70 and 0.76 in women and 2.26 and 2.46 in men. These investigations can be applied to prevent the hepatitis B transmission in a population of 102 south vietnamese women in age to procreate or to determine the percentage of blood donors eliminated (3.12%) in a population of 2,950 Parisians composed in majority (50.9%) of new donors. The hemobiologist will have an important role to elaborate strategies for orientation of blood gifts with hepatitis B and C virus markers. 相似文献
2.
3.
During the 1997 winter season, shipborne polarimetric backscatter measurements of Great Lakes (freshwater) ice types using the Jet Propulsion Laboratory C-band scatterometer, together with surface-based ice physical characterization measurements and environmental parameters, were acquired concurrently with Earth Resource Satellite 2 (ERS-2) and RADARSAT Synthetic Aperture Radar (SAR) data. This polarimetric data set, composed of over 20 variations of different ice types measured at incident angles from 0° to 60° for all polarizations, was processed to radar cross-section to establish a library of signatures (look-up table) for different ice types. The library is used in the computer classification of calibrated satellite SAR data. Computer analysis of ERS-2 and RADARSAT ScanSAR images of Great Lakes ice cover using a supervised classification technique indicates that different ice types in the ice cover can be identified and mapped, and that wind speed and direction can have an influence on the classification of water as ice based on single frequency, single polarization data. Once satellite SAR data are classified into ice types, the ice map provides important and necessary input for environmental protection and management, ice control and ice breaking operations, and ice forecasting and modeling efforts. 相似文献
4.
Thai Binh Wan Rachel Seneviratne Aruna Rakotoarivelo Thierry 《Mobile Networks and Applications》2003,8(1):27-36
The high expectations and demand for users to access the Internet from anywhere at anytime has made user mobility an important part of the design and development of the next generation mobile communications and computing. Traditionally user mobility has been divided into two areas: Terminal Mobility and Personal Mobility. In recent years terminal mobility has focused on the movement of the terminal and developed extensions to IP protocols such as Mobile IP. In contrast, personal mobility has only received limited attention, and is somewhat lagging behind. This research has either focussed on personal mobility in communications or personalisation of operating environments. As a result, to date no framework for providing true personal mobility has emerged. In this paper, we introduce a new personal mobility framework called IPMoA (Integrated Personal Mobility Architecture), which integrates both aspects of personal mobility to provide a complete personal mobility solution, and illustrate the viability of this approach through a proof-of-concept implementation. 相似文献
5.
Hyukmin Son Sanghoon Lee 《Communications Letters, IEEE》2006,10(5):360-362
A cell planning technique termed BRD (bandwidth and region division) is presented for overcoming interference, maintaining QoS (quality of service) and improving channel capacity over OFDM (orthogonal frequency division multiplexing)-based broadband cellular networks. Through an optimal combination of sectorization and zero padding, bandwidth and region division is achieved that minimizes the outage probability for forward-link cell planning. In order to verify the effectiveness of the proposed algorithm, a Monte Carlo simulation is performed over multi-cell environments. 相似文献
6.
Problems related to unpopular housing are not new in Britain's social rented sector. In the past, however, these have generally been associated with housing provided directly by the state through local authorities. For many, the term 'difficult to let' has become synonymous with large, ageing, poor quality estates managed under a centralised framework and subject to a long period of low investment and indifferent management. There has also been a long-standing assumption that social housing allocations systems tend to channel the most vulnerable tenants into the least desirable housing. In fact, the problem of difficult to let property is now as pervasive in the not-for-profit sector managed by housing associations as it is within council housing. In many cases the developments affected are small in scale and, in a significant proportion of cases, recently constructed. In explaining why property becomes difficult to let, the local and regional context is clearly important. The balance between social, economic and housing demand circumstances and property and estate characteristics varies between regions. There is relatively little evidence that difficult to let housing association properties are occupied by disproportionate numbers of the most severely disadvantaged tenants and this suggests that something has happened to modify the segregating effects of allocations systems observed in earlier studies. Nevertheless, this apparent change must be seen within the context of the general trend towards a residual role for social housing in its entirety. The social class and income range of new social sector tenants now is much diminished by comparison with earlier decades with few distinctions between the occupiers of difficult to let and other housing. 相似文献
7.
A chimeric dopamine transporter (DAT) cDNA encoding mutant human DAT (hDAT) protein in which the intracellular carboxyl-terminal tail is replaced by that of the bovine dopamine transporter (bDAT) was constructed. The chimeric hDAT cDNA was expressed in COS-7 cells, and [3H]dopamine and [3H]MPP+ uptake and [3H]CFT binding capacities were assessed. Substrate transport and ligand binding of bDAT were reduced by 32-43% as a result of substitution of the carboxyl tail in hDAT, suggesting that the functional characteristics of bDAT arise from differences in the carboxyl tail between human and bovine DAT. Thus, it appears that the sequences encoded within the carboxyl terminal of DAT would be one of the important determinants for its functions. 相似文献
8.
Yurak Son Takuya Kamano Takashi Yasuno Takayuki Suzuki Hironobu Harada 《Electrical Engineering in Japan》2006,155(1):35-43
This paper describes the generation of adaptive gait patterns using new Central Pattern Generators (CPGs) including motor dynamic models for a quadruped robot under various environments. The CPGs act as the flexible oscillators of the joints and adjust joint angles to required values. The CPGs are interconnected with each other and sets of their coupling parameters are adjusted by a genetic algorithm so that the quadruped robot can realize stable and adequate gait patterns. Generation of gait patterns results in the formation of the CPG networks suitable for the formation of not only a straight walking pattern but also of rotating gait patterns. Experimental results demonstrate that the proposed CPG networks are effective for the automatic adjustment of the adaptive gait patterns for the tested quadruped robot under various environments. Furthermore, the target tracking control based on image processing is achieved by combining the general gait patterns. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 35–43, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20225 相似文献
9.
Analysis and implementation of a real-time predictive currentcontroller for permanent-magnet synchronous servo drives 总被引:1,自引:0,他引:1
Hoang Le-Huy Slimani K. Viarouge P. 《Industrial Electronics, IEEE Transactions on》1994,41(1):110-117
A real-time current controller for PWM inverter-fed permanent-magnet synchronous motor drives is presented and analyzed. The proposed current control scheme is based on predictive control with a parallel integral loop added to compensate for the inaccuracy of the motor model and for the variations of motor parameters and DC voltage source. The proposed current control scheme is analyzed and its performance is evaluated by computer simulation. An EPROM-based implementation is presented in which calculations and pulsewidth modulation are executed by lookup tables resulting in high-speed operation. The controller performance is evaluated using a prototype l kW PM synchronous servo drive. Experimental results are given and discussed 相似文献
10.
An experimental investigation under cold condition was made to study the effects of some operating/design parameters and non-mechanical L valve configuration on the solid circulation rate in a 4.5 m tall, 0.15 m diameter circulating fluidized bed with riser flow rate varying from 1400 litres/min to 2000 litres/min and bed inventory from 15 kg to 25 kg of sand of average sizes 200 μm, 400 μm and 500 μm. Solid circulation rate was estimated by measuring velocity of sand particle travelling through a vertical Perspex tube section at the bottom of the return leg. It was found to be in the range of 2.8 to 12.3kg/m2s, 0.07 to 9.1kg/m2s and 0.12 to 2.23kg/m2s for sand sizes of 200 μm, 400 μm and 500 μm, respectively for a horizontal L valve. Two mathematical correlations have been developed from the experimental results to predict solid circulation rate as a function of riser flow rate, aeration flow rate, total bed inventory and particle size used. 相似文献