全文获取类型
收费全文 | 2587篇 |
免费 | 57篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 192篇 |
综合类 | 1篇 |
化学工业 | 520篇 |
金属工艺 | 69篇 |
机械仪表 | 60篇 |
建筑科学 | 52篇 |
能源动力 | 101篇 |
轻工业 | 218篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 283篇 |
一般工业技术 | 415篇 |
冶金工业 | 404篇 |
原子能技术 | 111篇 |
自动化技术 | 226篇 |
出版年
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 35篇 |
2020年 | 16篇 |
2019年 | 23篇 |
2018年 | 38篇 |
2017年 | 34篇 |
2016年 | 40篇 |
2015年 | 28篇 |
2014年 | 54篇 |
2013年 | 130篇 |
2012年 | 85篇 |
2011年 | 127篇 |
2010年 | 73篇 |
2009年 | 122篇 |
2008年 | 128篇 |
2007年 | 99篇 |
2006年 | 94篇 |
2005年 | 78篇 |
2004年 | 88篇 |
2003年 | 97篇 |
2002年 | 64篇 |
2001年 | 69篇 |
2000年 | 44篇 |
1999年 | 75篇 |
1998年 | 198篇 |
1997年 | 110篇 |
1996年 | 85篇 |
1995年 | 69篇 |
1994年 | 52篇 |
1993年 | 47篇 |
1992年 | 32篇 |
1991年 | 32篇 |
1990年 | 21篇 |
1989年 | 26篇 |
1988年 | 23篇 |
1987年 | 22篇 |
1986年 | 26篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 22篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 30篇 |
1973年 | 7篇 |
1970年 | 10篇 |
排序方式: 共有2657条查询结果,搜索用时 31 毫秒
1.
To enhance chemical stability and suppress of aggregation of magnetite nanoparticles (MNPs), which are used as a support for thermoresponsive copolymer immobilization, silica coating of the MNPs is applied via the electrooxidation method. Although the resulting silica coated-MNPs also formed aggregates, the size distribution of the aggregate shifted to smaller size range. Because of that, the surface area available for copolymer immobilization increased approximately 6.7 times at maximum as compared with that of the uncoated MNPs. It contributed to the increase of the amount of the immobilized copolymer on the silica-coated MNPs, which is approximately four times larger than that on the uncoated MNPs. Fe3O4 dissolution test confirmed enhancement of chemical stability of MNPs. The thermoresponsive copolymer immobilized on the silica-coated MNPs shows the ability to recycle Cu(II) ion from Cu(II) containing solution by changing temperature with significantly shorter time than those in other thermoresponsive adsorbents in gel form. 相似文献
2.
Hitoshi Muta 《Journal of Nuclear Science and Technology》2019,56(5):367-368
Recent activities in the field of Nuclear Operational Management and Nuclear Safety Engineering, the studies related to risk analysis methodology, design, and operational management, physical phenomena, and emergency preparedness and nuclear security, have been progressed. Especially, ‘risk analysis methodology’ and ‘design and operational management’ are the main categories of the field, in which more than half of published articles on Journal of Nuclear Science and Technology are related to these categories. 相似文献
3.
Tuning-current splitting network for three-section DBR lasers 总被引:1,自引:0,他引:1
A simple current-splitting network for DBR-laser frequency tuning is proposed that distributes a single control current among two tuning sections and can adjust the current distribution without yielding impedance mismatching. The nonlinear characteristics of the tuning sections realise the non-proportional current splitting suitable for continuous tuning; 470 GHz (3.8 nm) tuning range is achieved 相似文献
4.
Iwao Shimizu Yuji Naito Iwao Yamaguchi Katsuyuki Kaiho Hitoshi Mizoguchi Satoru Yanabu 《Electrical Engineering in Japan》2008,164(1):52-61
Using conventional high‐temperature superconducting wire, a model superconducting fault current limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series to it. A conventional reactor coil is connected in parallel. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 52–61, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20315 相似文献
5.
6.
D. Xu T. Enoki T. Suemitsu Y. Umeda H. Yokoyama Y. Ishii 《Journal of Electronic Materials》1998,27(7):L51-L53
We have achieved a self-controlled asymmetrical etching in metalorganic chemical vapor deposition-grown InAlAs/InGaAs heterostructures,
which can be suitable for fabricating modulation-doped field-effect transistors (MODFETs) with gate-groove profiles for improved
performance. The technology is based on electrochemical etching phenomena, which can be effectively controlled by using different
surface metals for ohmic electrodes. When surface metals of Pt and Ni are deposited on the source and the drain, respectively,
the higher electrode potential of Pt results in slower etching on the source side than on the drain side. Thus, asymmetry
of gate grooves can be formed by wet-chemical etching with citric-acid-based etchant. This represents a new possibility to
conduct “recess engineering” for InAlAs/InGaAs MODFETs. 相似文献
7.
For the first time, the surface metal on nonalloyed ohmic electrodes is found to significantly change the profiles of gate grooves, when resist openings are employed to monitor drain current during wet-chemical gate recess for sub-micron InAlAs/lnGaAs heterojunction field-effect transistors (HFETs). The surface metal of Ni enhances the etching rate in comparison with that in the absence of electrodes by a factor of 4 and 10, laterally and vertically, which is favorable to fabricate deep gate grooves with small side etching. The Pt surface metal, however, leads to preferential etching of InGaAs over InAlAs, which can be useful to realize large side etching. The existence of an electrochemistry-related etching component, which arises when the ohmic electrodes are present during recess etching, is considered to be responsible for these behaviors 相似文献
8.
A design for composite-channel structures consisting of an InGaAs channel and an InP subchannel for use as heterostructure field-effect transistors is presented for the first time. This novel channel structure takes advantage of both the high drift velocity and low impact ionization of InP at high electric fields as well as the high electron mobility of InGaAs at low electric fields. It is shown that the doping density of the InP subchannel is the key parameter to realize the advantages of the composite channel. A very high transconductance of 1.29 S/mm and a current gain cutoff frequency of 68.7 GHz are achieved with 0.6 and 0.7 /spl mu/m gates, respectively. The average velocity of electrons in the composite channel is 2.9/spl times/10/sup 7/ cm/s. The devices have no kink phenomena in their I-V characteristics possibly due to low impact ionization in the InP subchannel.<> 相似文献
9.
The inhibitory effect of alpha-tocopherol on methemoglobin formation in normal and acatalasemic mice was studied by exposing their hemolysates to nitric oxide. Methemoglobin formation in normal and acatalasemic mouse hemolysates exposed to nitric oxide were significantly inhibited by the addition of alpha-tocopherol at final concentrations ranging from 1.2 to 5.8 mM. Negative correlations were observed between the logarithm of alpha-tocopherol concentration and the methemoglobin formation. The formation of methemoglobin in acatalasemic mouse hemolysates was greater than that in normal mouse hemolysates with or without added alpha-tocopherol. The methemoglobin formation in acatalasemic mice was also significantly inhibited by addition of more than 500 units/ml of catalase, and the methemoglobin formation in normal and acatalasemic mice was also inhibited with sodium diethyldithiocarbamate at a final concentration of 1 M. 相似文献
10.
Hitoshi Furuta Jianhong He Eiichi Watanabe 《Computer-Aided Civil and Infrastructure Engineering》1996,11(1):37-45
Abstract: An efficient knowledge-acquisition support method is required for improvement and maintenance of the knowledge base in durability evaluation of an RC bridge deck. Such a method is proposed in this paper to automatically acquire fuzzy production rules. This method makes joint use of genetic algorithms and a neural network. Using a neural network as a subsystem, the evaluation function of genetic algorithms can be provided with the weights of the neural network. Introducing a neural network into genetic algorithms, it is possible to acquire new knowledge so that the method is useful when it is difficult to acquire knowledge in the field. 相似文献