全文获取类型
收费全文 | 774篇 |
免费 | 32篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 60篇 |
综合类 | 2篇 |
化学工业 | 216篇 |
金属工艺 | 25篇 |
机械仪表 | 23篇 |
建筑科学 | 13篇 |
能源动力 | 26篇 |
轻工业 | 40篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 68篇 |
一般工业技术 | 177篇 |
冶金工业 | 86篇 |
原子能技术 | 14篇 |
自动化技术 | 59篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 15篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 23篇 |
2015年 | 13篇 |
2014年 | 26篇 |
2013年 | 41篇 |
2012年 | 16篇 |
2011年 | 41篇 |
2010年 | 22篇 |
2009年 | 39篇 |
2008年 | 42篇 |
2007年 | 28篇 |
2006年 | 34篇 |
2005年 | 36篇 |
2004年 | 24篇 |
2003年 | 19篇 |
2002年 | 19篇 |
2001年 | 12篇 |
2000年 | 24篇 |
1999年 | 22篇 |
1998年 | 34篇 |
1997年 | 38篇 |
1996年 | 20篇 |
1995年 | 27篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有812条查询结果,搜索用时 140 毫秒
131.
The stable ranges concerning the composition and temperature have been experimentally de-termined for the intermetallic compounds in system Fe-Cr-Mo at high-temperatures. Theisothermal section of the Fe-Cr-Mo ternary phase diagram at 1250℃ and the formation re-actions for the intermetallic compounds, which are different in part from those shown in theliterature, have been proposed. 相似文献
132.
Yoshikazu Suzuki Peter E. D. Morgan Koichi Niihara 《Journal of the American Ceramic Society》1998,81(12):3141-3149
Additions of 1-20 mol% Sc2 O3 or Y2 O3 to MoSi2 eliminate glassy SiO2 , which improves mechanical properties at both ambient and high temperatures. In particular, only 1 mol% ScO3 additions dramatically enhance three-point bending strength from 521 to 1081 MPa. Vickers hardness, Young's modulus, fracture toughness, and high-temperature strength are also improved by this low level of additive. The improvement of mechanical properties is attributed to the formation of crystalline silicates: Sc2 Si2 O7 , Y2 Si2 O7 , Y2 SiO5 , and Y4 Si3 O12 , which are analyzed by XRD, SEM-EDS, and TEM-EDS methods. 相似文献
133.
134.
Tanaka Takanori; Miwa Naofumi; Kawamura Satoru; Sohma Hitoshi; Nitta Katsutoshi; Matsushima Norio 《Protein engineering, design & selection : PEDS》1999,12(5):395-405
P26olf from olfactory tissue of frog, which may be involvedin olfactory transduction or adaptation, is a Ca2+-binding proteinwith 217 amino acids. The p26olf molecule contains two homologousparts consisting of the N-terminal half with amino acids 1109and the C-terminal half with amino acids 110217. Eachhalf resembles S100 protein with about 100 amino acids and containstwo helixloophelix Ca2+-binding structural motifsknown as EF-hands: a normal EF-hand at the C-terminus and apseudo EF-hand at the N-terminus. Multiple alignment of thetwo S100-like domains of p26olf with 18 S100 proteins indicatedthat the C-terminal putative EF-hand of each domain containsa four-residue insertion when compared with the typical EF-handmotifs in the S100 protein, while the N-terminal EF-hand ishomologous to its pseudo EF-hand. We constructed a three-dimensionalmodel of the p26olf molecule based on results of the multiplealignment and NMR structures of dimeric S100B(ßß)in the Ca2+-free state. The predicted structure of the p26olfsingle polypeptide chain satisfactorily adopts a folding patternremarkably similar to dimeric S100B(ßß). Each domainof p26olf consists of a unicornate-type four-helix bundle andthey interact with each other in an antiparallel manner formingan X-type four-helix bundle between the two domains. The twoS100-like domains of p26olf are linked by a loop with no sterichindrance, suggesting that this loop might play an importantrole in the function of p26olf. The circular dichroism spectraldata support the predicted structure of p26olf and indicatethat Ca2+-dependent conformational changes occur. Since theC-terminal putative EF-hand of each domain fully keeps the helixloophelixmotif having a longer Ca2+-binding loop, regardless of the four-residueinsertion, we propose that it is a new, novel EF-hand, althoughit is unclear whether this EF-hand binds Ca2+. P26olf is a newmember of the S100 protein family. 相似文献
135.
Takashi Taya Akira Yoshida Nobusuke Yamaoka Shuichi Matsumoto Yoshikazu Yoshida 《Electrical Engineering in Japan》1998,125(2):35-43
In a large-scale broadband communication system, thousands of high-speed serial data interconnections are used and a bit synchronization circuit (a clock and data recovery circuit) is required in each of the receiver side interconnection circuits. In this paper, the requirements and the implementation of a bit synchronization circuit for the interconnection are considered, and one solution is proposed. In the proposed circuit, the oscillation phase of a VCO is directly controlled by the trigger signal extracted from the input data. Synchronization capture is quick and the circuit is applicable to burst signals. The circuit tolerates jitter and phase variation of the incoming data. The circuit requires no external components, and is suitable for an integrated circuit. The circuit was implemented using a 0.5 μm CMOS process and the data recovery operation from a 440 Mbps pseudo-random pattern was confirmed. Data acquisition is accomplished within three clock periods from 440 Mbps burst data. © 1998 Scripta Technica, Electr Eng Jpn, 125(2): 35–43, 1998 相似文献
136.
In this paper, a new application of superconducting magnetic energy storage (SMES) for diagnosis of power systems is proposed. Basic experiments for measurement of damping coefficient of power systems by use of SMES are carried out in an experimental system with a small generator, artificial transmission lines, and a small SMES. The SMES produces small power disturbances in the power system without affecting its operating conditions. The small power oscillations in the power system due to continuous power disturbances generated by SMES are observed. The relations among the damping coefficient, the power disturbances, and the power change of SMES are discussed for a one-machine infinite-bus system. The damping coefficients of the power system are obtained by investigating the oscillations due to the sinusoidal power changes of the SMES. The possibility of estimation of the steady-state power system stability by monitoring the damping coefficients of an operating power system by the use of SMES can be shown experimentally. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(3): 40–48, 1997 相似文献
137.
One-pot polymerization of polyimide from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) was examined. The equilibrium in the polyimide with water was examined in detail in p-chlorophenol solution during the polymerization. The equilibrium constant was expressed by log K = 1.50 + 1433 (1/T). The polymerization reaction is exothermic. The molecular weight increased with decrease of temperature. © 1996 John Wiley & Sons, Inc. 相似文献
138.
Various copolymides were prepared from two acid dianhydrides (BPDA, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride; PMDA, pyromelitic dianhydride) and two diamines (PPD, p-phenylene diamine; ODA, 4,4′-oxydianiline). The thermal and mechanical properties of these polyimides were examined in detail. By appropriately selecting the ratios of the acid dianhydride component and the diamine component, polyimide films having desirable mechanical and thermal characteristics can be obtained. Further, it was proved that there is a correlation between the properties and the compositions of the copolyimides and that the properties could be estimated from the compositions by the use of multiple regression analysis. © 1996 John Wiley & Sons, Inc. 相似文献
139.
Kazuo Tomita Taisuke Nagasawa Yoshikazu Kuwahara Seiji Torii Kento Igarashi Mehryar Habibi Roudkenar Amaneh Mohammadi Roushandeh Akihiro Kurimasa Tomoaki Sato 《International journal of molecular sciences》2021,22(15)
In cancer therapy, radioresistance or chemoresistance cells are major problems. We established clinically relevant radioresistant (CRR) cells that can survive over 30 days after 2 Gy/day X-ray exposures. These cells also show resistance to anticancer agents and hydrogen peroxide (H2O2). We have previously demonstrated that all the CRR cells examined had up-regulated miR-7-5p and after miR-7-5p knockdown, they lost radioresistance. However, the mechanism of losing radioresistance remains to be elucidated. Therefore, we investigated the role of miR-7-5p in radioresistance by knockdown of miR-7-5p using CRR cells. As a result, knockdown of miR-7-5p increased reactive oxygen species (ROS), mitochondrial membrane potential, and intracellular Fe2+ amount. Furthermore, miR-7-5p knockdown results in the down-regulation of the iron storage gene expression such as ferritin, up-regulation of the ferroptosis marker ALOX12 gene expression, and increases of Liperfluo amount. H2O2 treatment after ALOX12 overexpression led to the enhancement of intracellular H2O2 amount and lipid peroxidation. By contrast, miR-7-5p knockdown seemed not to be involved in COX-2 and glycolysis signaling but affected the morphology of CRR cells. These results indicate that miR-7-5p control radioresistance via ROS generation that leads to ferroptosis. 相似文献
140.
A three-dimensional (3D) digital holographic display system with image processing is presented. By use of phase-shifting digital holography, we obtain the complex amplitude of a 3D object at a recording plane. Image processing techniques are introduced to improve the quality of the reconstructed 3D object or manipulate 3D objects for elimination and addition of information by modifying the complex amplitude. The results show that the information processing is effective in such manipulations of 3D objects. We also show a fast recording system of 3D objects based on phase-shifting digital holography for display with image processing. The acquisition of 3D object information at 500 Hz is demonstrated experimentally. 相似文献