全文获取类型
收费全文 | 2732篇 |
免费 | 26篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 89篇 |
综合类 | 3篇 |
化学工业 | 532篇 |
金属工艺 | 96篇 |
机械仪表 | 77篇 |
建筑科学 | 36篇 |
能源动力 | 142篇 |
轻工业 | 125篇 |
水利工程 | 11篇 |
石油天然气 | 6篇 |
无线电 | 346篇 |
一般工业技术 | 443篇 |
冶金工业 | 661篇 |
原子能技术 | 49篇 |
自动化技术 | 153篇 |
出版年
2023年 | 15篇 |
2022年 | 17篇 |
2021年 | 42篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 17篇 |
2017年 | 25篇 |
2016年 | 31篇 |
2015年 | 28篇 |
2014年 | 47篇 |
2013年 | 115篇 |
2012年 | 71篇 |
2011年 | 109篇 |
2010年 | 91篇 |
2009年 | 91篇 |
2008年 | 100篇 |
2007年 | 98篇 |
2006年 | 74篇 |
2005年 | 60篇 |
2004年 | 63篇 |
2003年 | 105篇 |
2002年 | 71篇 |
2001年 | 64篇 |
2000年 | 44篇 |
1999年 | 82篇 |
1998年 | 310篇 |
1997年 | 173篇 |
1996年 | 108篇 |
1995年 | 69篇 |
1994年 | 83篇 |
1993年 | 71篇 |
1992年 | 38篇 |
1991年 | 35篇 |
1990年 | 45篇 |
1989年 | 33篇 |
1988年 | 23篇 |
1987年 | 26篇 |
1986年 | 25篇 |
1985年 | 31篇 |
1984年 | 23篇 |
1983年 | 30篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 21篇 |
1975年 | 10篇 |
1974年 | 10篇 |
排序方式: 共有2769条查询结果,搜索用时 15 毫秒
31.
Araki T. Nishima H. Hata H. Yamaguchi H. Yamauchi T. Miyashita M. 《Power Delivery, IEEE Transactions on》1998,13(3):718-727
Technologies for the after-laying test of long-distance SF6 gas insulated transmission line (GIL) have been developed for the detection of partial discharge (PD) and contact defects. We constructed a long (168 m) test line in a deep tunnel and clarified the propagation characteristics of PD signals through the GIL as well as the spatial sensitivity and S/N characteristics of PD sensors for locating metallic particles. We have also proposed the application of a fiber-optic temperature distribution sensor for locating contact defects and confirmed the validity of this sensor for the GIL test line 相似文献
32.
Boerner W.-M. Yan W.-L. Xi A.-Q. Yamaguchi Y. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1991,79(10):1538-1550
Basic principles of radar polarimetry are introduced. The target characteristic polarization state theory is developed first for the coherent case using the three stage, the basis transformation, and the power (Mueller) matrix optimization procedures. Kennaugh's and Huynen's theories of radar target polarimetry are verified for the monostatic reciprocal case. It is shown that there exist, in total, five unique pairs of characteristic polarization states for the symmetric scattering matrix of which two pairs, the cross-polarization null and copolarization max pairs, are identical, whereas the cross-pol max and the cross-pol saddlepoint pairs are distinct. The theory is verified by an example for which next to the polarization fork the copolarized and cross-polarized power density plots are also presented. The partially polarized case for completely polarized wave incidence is presented and compared with the results for the coherent and the partially coherent cases, the latter of which is still unresolved 相似文献
33.
Rabinzohn P.D. Usagawa T. Mizuta H. Yamaguchi K. 《Electron Devices, IEEE Transactions on》1991,38(2):222-231
The bipolar/FET characteristics of the 2DEG-HBT are analyzed extensively by a two-dimensional numerical simulator based on a drift-diffusion model. For bipolar operations at high collector current densities, it is confirmed that the cutoff frequency f T is determined mainly by the collector transit time of holes and by the charging time of the extrinsic base-collector capacitance C bcEXT. The charging times of the emitter and base regions and the base transit time are shown to be negligible. A high cutoff frequency F T (88 GHz) and current gain h FE (760) are obtained for an emitter size of 1×10 μm2, and undoped collector thickness of 150 nm, and a collector current density J c of 105 A/cm2. The FET operation of the same 2DEG-HBT structure shows a threshold voltage V th of 0.74 V, the transconductance G mmax of 80 mS/mm, and maximum cutoff frequency F Tmax of 15 GHz. The dependence of the device performance on material parameters is analyzed extensively from a device design point of view 相似文献
34.
The effect of particle agglomeration on sintering has been studied by slipcasting suspensions with pH values ranging from 2 to 11. The rate of densification has been found to depend on the degree of agglomeration. Complete dispersion of alumina primary particles has not been attained through adjustment of pH of suspensions, and agglomerates also remained in the best-dispersed suspension. Elimination of the agglomerates by sedimentation lowered the densification temperature of slip-cast compacts. The grain size-density curve is a function of temperature. High-density and small-grained sintered bodies were obtained by low-temperature long-time firing. 相似文献
35.
Microstructure Development and Dielectric Properties of Potassium Strontium Niobate Ceramics 总被引:1,自引:0,他引:1
Toshio Kimura Seiji Miyamoto Takashi Yamaguchi 《Journal of the American Ceramic Society》1990,73(1):127-130
Sintering of a KSr2 Nb5 O15 powder compact at 1350°C resulted in a duplex structure. Prefiring of the compact between 1200° and 1300°C inhibited the abnormal grain growth responsible for the duplex structure. The Curie temperature and dielectric constant were dependent on the microstructure. 相似文献
36.
Yamaguchi M. Kambe S. Yamazaki K. Kobayashi M. 《IEEE transactions on bio-medical engineering》2005,52(10):1796-1798
In order to realize a noninvasive blood glucose monitor, we monitored the gingival cerevicular fluid (GCF). In this paper, the clinical evaluations were performed on not only normal subjects but also diabetic subjects using a GCF-glucose monitor to determine blood glucose levels. Meal load tests were carried out and the time-course changes in blood glucose level and GCF glucose level were measured continuously. A positive correlation of more than 0.9 was found between blood glucose level and GCF glucose level, necessitating the calibration of individual correlations for every subject. Finally, the performance of the GCF-glucose monitor was evaluated using Error Grid Analysis. As the results, significant information for the glucose level decision was obtained not only for normal subjects, but also for diabetic subjects. 相似文献
37.
Igarashi S Haraguchi M Aihara J Saito T Yamaguchi K Yamamoto H Hojou K 《Journal of electron microscopy》2004,53(3):223-228
The formation and the phase transitions of iron silicide by solid-phase epitaxy have been investigated by means of plan-view transmission electron microscopy, which enables us to observe a clean interface between Fe and Si. Layers of Fe were deposited on Si (100) at room temperature in an ultrahigh vacuum chamber. The sample was annealed in the electron microscope at a temperature between 673 and 1073 K. After annealing at 673 K, FeSi crystallites were formed with various orientations. When the annealing temperature was increased to 973 K, we found that the crystallites suddenly started to coalesce into grains of several hundreds of nanometers in size and polycrystalline beta-FeSi2 was formed. These phase transitions were also confirmed with electron energy-loss spectroscopy. 相似文献
38.
Modulator integrated DFB lasers with more than 600-km transmission capability at 2.5 Gb/s 总被引:2,自引:0,他引:2
M. Ishizaka M. Yamaguchi Y. Sakata Y. Inomoto J. Shimizu K. Komatsu 《Photonics Technology Letters, IEEE》1997,9(10):1406-1408
The modulator integrated DFB laser diodes with more than 600-km transmission capability over normal fiber at 2.5 Gb/s, have been reproducibly achieved. The longest transmission length obtained in the experiment is as long as 800 km. 相似文献
39.
Shibata H Takahashi M Yamaguchi I Kobayashi S 《Journal of Bioscience and Bioengineering》1999,88(3):244-249
Sulfides (S2),SH-) such as hydrogen sulfide belong to a class of sulfur compounds with unpleasant odors. In order to confer sulfide-oxidizing ability on the intestine-inhabiting bacteria, the sulfide-quinone oxidoreductase gene (sqr) in Rhodobacter capsulatus DSM-155 and genes for quinone biosynthesis (ubiC, ubiA and ispB) in Escherichia coli XL1 Blue-MRF' were transduced into E. coli BL21(DE3). Plasmids pT7-7 and pSTV were used as vectors of sqr, and ubiCA and ispB, respectively. The recombinants sqr-BL21(DE3) and ubiCA,ispB-sqr-BL21(DE3) were successfully constructed. The maximal sulfide-removing activities of the whole cells and membrane fractions of sqr-BL21(DE3) attained at pH 8.0 and 7.8, were 267 nmol/mg cells (dry weight)/min and 1250 nmol/mg membrane fraction (protein)/min, respectively. The molecular ratio of sulfide (S2-) oxidized and oxygen (O2) consumed was 2:1. SQR activity in the recombinant cells was positively restricted under anaerobic conditions and also by the addition of electron transfer inhibitors. Ubiquinone-8 (UQ-8) biosynthesis in the cells of ubiCA,ispB-sqr-BL21(DE3) increased as much as 2.2-fold compared with that of (pSTV)-sqr-BL21(DE3) during the 12-16 h incubation period. The maximal sulfide removal in the quinone-raised E. coli was attained slightly earlier, however, SQR activities thereafter were lower than those in (pSTV)-sqr-BL21(DE3). 相似文献
40.
Yamaguchi Y. Honda T. Sengoku M. 《Electromagnetic Compatibility, IEEE Transactions on》1995,37(1):88-93
The reduction of radio wave attenuation in rectangular tunnels is discussed. The attenuation of the dominant mode due to its field penetration into a lossy dielectric wall is reduced by means of the attachment of wire netting (mesh). First, a reflection coefficient from a mesh screen over a lossy surface is analytically evaluated. Then, based on a geometrical optical approach to the propagation model in tunnels, the attenuation of the dominant mode in a rectangular tunnel is derived using the reflection coefficient. The calculated attenuation constants are in good agreement with experimental ones obtained in a laboratory. Finally, the efficiency of attenuation reduction rate by the mesh shielding method is summarized as a function of spatial ratio of the mesh wire interval divided by the wavelength. It is shown that the efficiency of reduction rate by mesh is significant 相似文献