全文获取类型
收费全文 | 850篇 |
免费 | 18篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 41篇 |
化学工业 | 194篇 |
金属工艺 | 16篇 |
机械仪表 | 30篇 |
建筑科学 | 16篇 |
能源动力 | 44篇 |
轻工业 | 66篇 |
无线电 | 81篇 |
一般工业技术 | 164篇 |
冶金工业 | 138篇 |
原子能技术 | 28篇 |
自动化技术 | 54篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 21篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 39篇 |
2012年 | 30篇 |
2011年 | 41篇 |
2010年 | 26篇 |
2009年 | 45篇 |
2008年 | 37篇 |
2007年 | 27篇 |
2006年 | 25篇 |
2005年 | 32篇 |
2004年 | 30篇 |
2003年 | 26篇 |
2002年 | 28篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 17篇 |
1998年 | 74篇 |
1997年 | 37篇 |
1996年 | 26篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 17篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有872条查询结果,搜索用时 15 毫秒
81.
Matsuda N 《Behaviormetrika》1986,13(19):41-53
"Multidimensional scaling technique was applied to the Brazilian migration matrix in order to identify the functional regions of the nation, using the 1970 census data for males. The results obtained from three types of proximity matrices confirmed the key roles of Minas Gerais and Mato Grosso as the core states in addition to Rio de Janeiro and Sao Paulo. Substantial circulation of migrants among the core states runs counter to the popular notion about the Northeastern states as the major source of labor in Rio de Janeiro and Sao Paulo. The Northeast [was] found to consist of three groups of states: Maranhao, Piaui and Ceara showed a stable clustering, but peripherally located, in all configurations; and, the other two groups failed to form persistent regions across configurations. Though limited in scope, the observed attraction of Espirito Santo and Goias violated the widely held negative effect of distance and deserves further investigation." 相似文献
82.
83.
Seiji Motojima Noriyuki Iwamori Tatsuhiko Hattori 《Journal of Materials Science》1986,21(11):3836-3842
Si3N4 layers were obtained on a quartz substrate from a gas mixture of Si2Cl6, NH3 and H2 under a reduced pressure in a temperature range of 800 to 1300‡ C. Amorphous Si3N4 layers that were dense and adherent to the substrate were obtained in a temperature range of 800 to 1100‡ C. On the other
hand,α-Si3N4 layers were obtained at 1200‡ C and a source-gas ratio (N/Si) of 1.33 to 1.77. The lowest deposition temperature of amorphous
Si3N4 was considered to be about 700‡ C. The microhardness of amorphous Si3N4 obtained in a temperature range of 800 to 1100‡ C was 2400 to 2600 kg mm−2 (load: 50 g), and that ofα-Si3N4 obtained at 1200‡ C was 3400 kg mm−2. Chlorine contents in the Si3N4 layer decreased with increasing deposition temperature and source-gas ratio (N/Si), and with decreasing total pressure. 相似文献
84.
Takai Y. Fujita M. Nagata K. Isa S. Nakazawa S. Hirobe A. Ohkubo H. Sakao M. Horiba S. Fukase T. Takaishi Y. Matsuo M. Komuro M. Uchida T. Sakoh T. Saino K. Uchiyama S. Takada Y. Sekine J. Nakanishi N. Oikawa T. Igeta M. Tanabe H. Miyamoto H. Hashimoto T. Yamaguchi H. Koyama K. Kobayashi Y. Okuda T. 《Solid-State Circuits, IEEE Journal of》2000,35(2):149-162
This paper describes three circuit technologies indispensable for high-bandwidth multibank DRAM's. (1) A clock generator based on a bidirectional delay (BDD) eliminates the output skew. The BDD measures the cycle time as the quantity charged or discharged of an analog quantity, and replicates it in the next cycle. This achieves a 0.18-mm 2, two-cycle-lock clock generator operating from 25 to 167 MHz with a 30-ps resolution. (2) A quad-coupled receiver eliminates the internal skew caused by the difference between a rise input and a fall input by 40%. (3) An interbank shared redundancy scheme (ISR) with a variable unit redundancy (VUR) efficiently increases yield in multibank DRAM's. The ISR allows redundancy match circuits to be shared with two or more banks. The VUR allows the number of units replaced to be variable. These circuit technologies achieved a 250-Mb/s/pin, 8-bank, 1-Gb double-data-rate synchronous DRAM 相似文献
85.
Haruki Uchiyama Kohei Maruyama Edward Chen Tomonori Nishimura Kosuke Nagashio 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(15):2207394
Achieving the direct growth of an ultrathin gate insulator with high uniformity and high quality on monolayer transition metal dichalcogenides (TMDCs) remains a challenge due to the chemically inert surface of TMDCs. Although the main solution for this challenge is utilizing buffer layers before oxide is deposited on the atomic layer, this method drastically degrades the total capacitance of the gate stack. In this work, we constructed a novel direct high-κ Er2O3 deposition system based on thermal evaporation in a differential-pressure-type chamber. A uniform Er2O3 layer with an equivalent oxide thickness of 1.1 nm was achieved as the gate insulator for top-gated MoS2 field-effect transistors (FETs). The top gate Er2O3 insulator without the buffer layer on MoS2 exhibited a high dielectric constant that reached 18.0, which is comparable to that of bulk Er2O3 and is the highest among thin insulators (< 10 nm) on TMDCs to date. Furthermore, the Er2O3/MoS2 interface (Dit ≈ 6 × 1011 cm−2 eV−1) is confirmed to be clean and is comparable with that of the h-BN/MoS2 heterostructure. These results prove that high-quality dielectric properties with retained interface quality can be achieved by this novel deposition technique, facilitating the future development of 2D electronics. 相似文献
86.
Y. Ogata S. Uchiyama M. Hayashi M. Yasuda F. Hine 《Journal of Applied Electrochemistry》1990,20(4):555-558
The pH on the surface of an ion-exchange membrane was measured with a microprobe in a laboratory scale chlor-alkali cell to study the leakage of OH– through the membrane. The solution pH in the vicinity of the membrane facing the anode was found to be considerably higher than that in the bulk solution because of penetration and leakage of OH–. The pH varied with the membrane type. This explains why the carboxylate membrane is not protonated and can be used as a separator in chlor-alkali cells.Deceased. 相似文献
87.
T. Fujimoto M. KanazawaT. Shirai Y. IwataH. Uchiyama K. Noda 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(24):2886-2890
A fast three-dimensional scanning irradiation method is under development at the Heavy Ion Medical Accelerator in Chiba (HIMAC) as the next stage of heavy ion cancer therapy. This method requires highly accurate control of the beam size, energy, and intensity. To improve the accelerated beam’s quality, a new scheme for the synchrotron RF system has been developed. The new system adopts a periodic time clock system (T-clock) instead of an ordinary B-clock system. The new T-clock system is synchronized with a power line frequency of 50 Hz for synchronization with the synchrotron power supply. An ordinary B-clock system results in error pulses owing to the small analog signal of the magnetic field of the main dipole magnet, and the errors cause dipole oscillation of the beam in the RF bucket. Using the new T-clock generator at 192 kHz, we have observed an improvement in the acceleration efficiency and bunch shape compared to the B-clock generator. 相似文献
88.
89.
Fukuda H. Uchiyama A. Kuramochi T. Hayashi T. Iwabuchi T. 《Electronics letters》1992,28(19):1781-1783
For the first time, it is demonstrated that in flash-type EEPROMs, the endurance properties are dramatically improved by heavy oxynitridation (RTONO) of the tunnel oxide. The layer composition evaluated by SIMS measurement indicates that large amounts of N atoms (>10/sup 20/ atom/cm/sup 3/) pile up at the SiO/sub 2/-Si interface, and are distributed in the bulk SiO/sub 2/. In addition, the RTONO film reduces the number of hydrogen atoms, which are the origin of electron traps. This oxynitridation causes a decrease of both electron and hole traps in the tunnel oxide, resulting in an improvement of the threshold voltage narrowing.<> 相似文献
90.
Terufumi Okumura Yasuhiro Kinoshita Hiroaki Uchiyama Hiroaki Imai 《Materials Chemistry and Physics》2008,111(2-3):486-490
Photoluminescence depending on nitrogen concentration was investigated using anatase-type TiO2 prepared by the calcination of a mixture of titanyl sulfate hydrate and urea. The substitutional ratio (x) of nitrogen in TiO2 was successfully varied from 0.004 to 0.022 by changing the molar ratio of the mixture. The absorbance at 380–560 nm due to the formation of mid-gap states was proportional to the substitutional ratio of nitrogen controlled by the preparation conditions. In contrast, the fluorescent intensity at 382 nm originating from the band-to-band transition monotonically decreased with an increase in the substitutional ratio with an expansion of the anatase lattice. On the other hand, the maximum intensity of photoluminescence at 560 nm excited at 350 nm, which could be associated with the transition from the conduction band to the mid-gap states, was observed at x = 0.01. The optimal substitutional ratio for the emission was almost agreed with that for the photocatalytic decomposition of methylene blue and acetaldehyde under visible-light illumination. The photoluminescence was fundamentally determined by the balance between photoexcitation originating from a sufficient number of mid-gap states and deactivation of excited electrons and holes due to lattice distortion or defective states induced with the nitrogen doping. 相似文献