全文获取类型
收费全文 | 1405篇 |
免费 | 63篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 83篇 |
化学工业 | 438篇 |
金属工艺 | 35篇 |
机械仪表 | 27篇 |
建筑科学 | 19篇 |
矿业工程 | 2篇 |
能源动力 | 52篇 |
轻工业 | 157篇 |
水利工程 | 3篇 |
石油天然气 | 5篇 |
无线电 | 89篇 |
一般工业技术 | 294篇 |
冶金工业 | 79篇 |
原子能技术 | 45篇 |
自动化技术 | 145篇 |
出版年
2023年 | 12篇 |
2022年 | 27篇 |
2021年 | 54篇 |
2020年 | 16篇 |
2019年 | 29篇 |
2018年 | 31篇 |
2017年 | 21篇 |
2016年 | 42篇 |
2015年 | 35篇 |
2014年 | 44篇 |
2013年 | 92篇 |
2012年 | 76篇 |
2011年 | 100篇 |
2010年 | 74篇 |
2009年 | 75篇 |
2008年 | 84篇 |
2007年 | 70篇 |
2006年 | 70篇 |
2005年 | 52篇 |
2004年 | 45篇 |
2003年 | 51篇 |
2002年 | 49篇 |
2001年 | 31篇 |
2000年 | 25篇 |
1999年 | 27篇 |
1998年 | 44篇 |
1997年 | 32篇 |
1996年 | 24篇 |
1995年 | 24篇 |
1994年 | 16篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1473条查询结果,搜索用时 15 毫秒
11.
OBJECTIVE: To determine the distribution and severity of arterial lesions of intracranial and extracranial arteries in stroke patients in Chinese. METHODS: We studied 120 consecutive autopsy cases including 100 cases of stroke (50-80 years) and 20 cases of cancer as controls (50-80 years). Medium intracranial arteries and their primary branches, small intracerebral arteries, arterioles and extracranial carotid arteries (from 16 cases only) were examined with light microscopy. RESULTS: The stroke patients had significantly lower mean LA-VA ratios of the medium sized intracranial arteries and their primary branches, small intracerebral arteries and arterioles than the controls (P < 0.001). The stroke patients had higher mean VW-VR ratios of these arteries than the controls (P < 0.001). Atherosclerotic narrowing of the medium sized intracranial arteries and their primary branch were more severe than those of the extracranial caotid arteries. Moreover, the proximal portion of the primary branch arteries was much more severe than that of extracranial caotid arteries (P < 0.01, P < 0.05) in the stroke patients. CONCLUSION: Stroke patients had atherosclerotic lesions of the intracranial medium sized arteries and their primary branches and sclerotic lesions of the small intracerebral arteries and arterioles. These pathological changes resulted in thickening arterial walls and narrowing arterial lumens. 相似文献
12.
Nishihori K. Kitaura Y. Hirose M. Mihara M. Nagaoka M. Uchitomi N. 《Electron Devices, IEEE Transactions on》1998,45(7):1385-1392
This paper describes a newly developed GaAs metal semiconductor field-effect transistor (MESFET)-termed p-pocket MESFET-for use as a linear power amplifier in personal handy-phone systems. Conventional buried p-layer technology, the primary technology for microwave GaAs power MESFET's, has a drawback of low power efficiency for linear power applications. The low power efficiency of the buried p-layer MESFET is ascribed to the I-V kink which is caused by holes collected in the buried p-layer under the channel. In order to overcome this problem, we have developed the self-aligned gate p-pocket MESFET which incorporates p-layers not under the channel but under the source and drain regions. This new MESFET exhibited high transconductance and uniform threshold voltage. The problematic I-V kink was successfully removed and an improved power efficiency of 48% was achieved under bias conditions, which resulted in adjacent channel leakage power at 600-kHz offset as low as -59 dBc for 1.9-GHz π/4-shift QPSK modulated input 相似文献
13.
A dc brushless motor is a kind of synchronous motor driven by an inverter and requires sensors to detect the rotor position. As one of the methods, the induced voltages of a brushless motor have been utilized in practice. However, there are some problems in this method, e.g., the motor can obtain insufficient torque due to the low induced voltages in a low-speed range. This paper proposes a new method which controls the inverter angular frequency ω1 by using inherent characteristics wherein the torque current ir is almost proportional to the internal phase angle φ where the primary flux of a synchronous motor is controlled to be constant. If the parameters of a motor are given exactly, the speed regulation is quite small and the transient characteristics with high response and high starting torque are obtained. Furthermore, it is possible to operate a synchronous motor in the field-weakening range. Here, the principle of the control method and the performance characteristics of a dc brushless motor having no position sensors are discussed. The simulation and the experimental results of the tested machine show that the proposed method is very useful for practical applications. 相似文献
14.
Tsukasa Kinjo Naoki Saito Makoto Omodani 《Journal of the Society for Information Display》2012,20(10):559-565
Projected image on a screen is not always vivid enough when it is projected in a bright room. We generally have to choose either vivid image in a dark room or dull image in a bright room. We have suggested a new projection system which can realize high contrast image projection in a bright room. It is consisted of electronic paper screen, projector, and light‐emitting diode room light. The electronic paper (e‐Paper) screen alternates its whole surface white/black with 120 Hz. Room lights are controlled with the same frequency of 120 Hz with the opposite phase as that of the e‐Paper screen. We have confirmed that our new system has achieved higher contrast than the conventional projection system and also enough readability of paper documents in the room simultaneously. We have thus confirmed that our new system can bring an ideal condition, for audience, which can realize a vivid image projection in a bright room. 相似文献
15.
Dr. Daisuke Fujiwara Kousuke Mihara Ryo Takayama Yusuke Nakamura Prof. Mitsuhiro Ueda Prof. Takeshi Tsumuraya Prof. Ikuo Fujii 《Chembiochem : a European journal of chemical biology》2021,22(24):3406-3409
Conformationally constrained peptides hold promise as molecular tools in chemical biology and as a new modality in drug discovery. The construction and screening of a target-focused library could be a promising approach for the generation of de novo ligands or inhibitors against target proteins. Here, we have prepared a protein kinase-focused library by chemically modifying helix-loop-helix (HLH) peptides displayed on phage and subsequently tethered to adenosine. The library was screened against aurora kinase A (AurA). The selected HLH peptide Bip - 3 retained the α-helical structure and bound to AurA with a KD value of 13.7 μM. Bip - 3 and the adenosine-tethered peptide Bip - 3 - Adc provided IC50 values of 103 μM and 7.7 μM, respectively, suggesting that Bip - 3 - Adc bivalently inhibited AurA. In addition, the selectivity of Bip - 3 - Adc to several protein kinases was tested, and was highest against AurA. These results demonstrate that chemical modification can enable the construction of a kinase-focused library of phage-displayed HLH peptides. 相似文献
16.
Koki Murano Tomoyoshi Shimobaba Atsushi Sugiyama Naoki Takada Takashi Kakue Minoru Oikawa Tomoyoshi Ito 《Computer Physics Communications》2014
We report fast computation of computer-generated holograms (CGHs) using Xeon Phi coprocessors, which have massively x86-based processors on one chip, recently released by Intel. CGHs can generate arbitrary light wavefronts, and therefore, are promising technology for many applications: for example, three-dimensional displays, diffractive optical elements, and the generation of arbitrary beams. CGHs incur enormous computational cost. In this paper, we describe the implementations of several CGH generating algorithms on the Xeon Phi, and the comparisons in terms of the performance and the ease of programming between the Xeon Phi, a CPU and graphics processing unit (GPU). 相似文献
17.
The interface area between the bubble and emulsion phases in a fluidized catalyst bed is one of the important parameters used to analyze and design the fluidized bed reactor. We used a fast‐scanning X‐ray CT system to observe the bubble shape and structure. We then obtained the transient 2‐dimensional cross sectional gas‐phase distribution in a fluidized catalyst bed. Using image‐processing techniques, pseudo 3‐dimensional images of the bubbles were reconstructed. The bubble structure was studied based on the 3‐dimensional images and the previously obtained results in a 2‐dimensional fluidized bed. It was found that the bubble shape was not spherical but complicated, and that the bubbles ascending in a fluidized catalyst bed consisted of some smaller bubbles. 相似文献
18.
Effects of Annealing on Dielectric Loss and Microstructure of Aluminum Nitride Ceramics 总被引:1,自引:0,他引:1
Shoichi Kume Masaki Yasuoka Naoki Omura Koji Watari 《Journal of the American Ceramic Society》2005,88(11):3229-3231
The effect of annealing on tan δ and microstructures of aluminum nitride (AlN) ceramics were explored. Yttria was added as a sintering additive to AlN powders, and the powders were pressureless-sintered at 1900°C for 2 h in a nitrogen flow atmosphere. In succession to sintering, AlN samples were annealed at 720, 970 and 1210°C for 2 and 4 h. Very low tan δ values between 2.6 and 6.0 × 10−4 at 28 GHz were obtained when the AlN samples were annealed for 4 h at all the annealing temperatures. 相似文献
19.
Yu-Ping Zeng Jian-Feng Yang Naoki Kondo Tatsuki Ohji Hideki Kita Shuzo Kanzaki 《Journal of the American Ceramic Society》2005,88(6):1622-1624
The fracture energies of the tape-cast silicon nitride with and without 3 wt% rod-like β-Si3 N4 seed addition were investigated by a chevron-notched-beam technique. The material was doped with Lu2 O3 –SiO2 as sintering additives for giving rigid grain boundaries and good heat resistance. The seeded and tape-cast silicon nitride has anisotropic microstructure, where the fibrous grains grown from seeds were preferentially aligned parallel to the casting direction. When a stress was applied parallel to the fibrous grain alignment direction, the strength measured at 1500°C was 738 MPa, which was almost the same as room temperature strength 739 MPa. The fracture energy of the tape-cast Si3 N4 without seed addition was 109 and 454 J/m2 at room temperature and 1500°C, respectively. On the contrary, the fracture energy of the seeded and tape-cast Si3 N4 was 301 and 781 J/m2 at room temperature and 1500°C, respectively, when a stress was applied parallel to the fibrous gain alignment. The large fracture energies were attributable primarily to the unidirectional alignment fibrous Si3 N4 grains. 相似文献
20.
NO
x
reduction with a combination of catalysts, Pd catalyst, NO
x
storage reduction (NSR) catalyst and Cu/ZSM-5 in turn, was investigated to elucidate for the high NO
x
reduction activity of this catalyst combination under oxidative atmosphere with periodic deep rich operation. The catalytic
activity was evaluated using the simulated exhaust gases with periodically fluctuation between oxidative and reductive atmospheres,
and it was found that the NO
x
reduction activity with this catalyst combination was apparently higher than that of the solely accumulation of these individual
activities, which was caused by the additional synergic effect by this combination. The Pd catalyst upstream of the NSR catalyst
improved NO
x
storage ability by NO2 formation under oxidative atmosphere. The stored NO
x
was reduced to NH3 on the NSR catalyst, and the generated NH3 was adsorbed on Cu/ZSM-5 downstream of the NSR catalyst under the reductive atmosphere, and subsequently reacted with NO
x
on the Cu/ZSM-5 under the oxidative atmosphere. 相似文献