全文获取类型
收费全文 | 12789篇 |
免费 | 762篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 174篇 |
综合类 | 15篇 |
化学工业 | 2700篇 |
金属工艺 | 450篇 |
机械仪表 | 939篇 |
建筑科学 | 231篇 |
矿业工程 | 3篇 |
能源动力 | 438篇 |
轻工业 | 1103篇 |
水利工程 | 83篇 |
石油天然气 | 13篇 |
无线电 | 2356篇 |
一般工业技术 | 2753篇 |
冶金工业 | 718篇 |
原子能技术 | 167篇 |
自动化技术 | 1449篇 |
出版年
2024年 | 13篇 |
2023年 | 164篇 |
2022年 | 233篇 |
2021年 | 440篇 |
2020年 | 286篇 |
2019年 | 329篇 |
2018年 | 367篇 |
2017年 | 421篇 |
2016年 | 458篇 |
2015年 | 381篇 |
2014年 | 554篇 |
2013年 | 833篇 |
2012年 | 837篇 |
2011年 | 1020篇 |
2010年 | 737篇 |
2009年 | 783篇 |
2008年 | 723篇 |
2007年 | 572篇 |
2006年 | 496篇 |
2005年 | 447篇 |
2004年 | 413篇 |
2003年 | 369篇 |
2002年 | 384篇 |
2001年 | 293篇 |
2000年 | 262篇 |
1999年 | 245篇 |
1998年 | 367篇 |
1997年 | 238篇 |
1996年 | 180篇 |
1995年 | 124篇 |
1994年 | 112篇 |
1993年 | 92篇 |
1992年 | 66篇 |
1991年 | 57篇 |
1990年 | 52篇 |
1989年 | 57篇 |
1988年 | 31篇 |
1987年 | 39篇 |
1986年 | 19篇 |
1985年 | 30篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
ABSTRACT: Degrees of hydrolysis and emulsifying activity of casein hydrolysates were the highest at 4 h hydrolysis. The oil-off values of the mixture of hydrolysate (H) or supernatant (S) and traditional emulsifier (T) were not significantly different from the control made with traditional emulsifier, except for S + T = 3:1. Two other samples made with hydrolysate or supernatant only (H or S) showed higher oil-off value than the others (p < 0.05). In flavor property, no difference was found between samples made with traditional emulsifier and those made with the mixture of hydrolysate or supernatant at the ratio of 3 to 1. Therefore, these results indicated that a mixture of the hydrolysate or supernatant and traditional emulsifier might replace a traditional emulsifier in process cheese manufacturing. 相似文献
102.
Xinyu Zhu Wing-Kit Choi Shin-Tson Wu 《Electron Devices, IEEE Transactions on》2002,49(11):1863-1867
A simple method is demonstrated for measuring the cell gap of reflective twisted nematic (RTN) liquid crystal (LC) cells. This method utilizes a single laser beam and crossed polarizer configuration such that Fabry-Perot effect and surface reflection are eliminated. Experimental results agree well with theory. 相似文献
103.
Oishi Shigehiro; Diener Ed; Choi Dong-Won; Kim-Prieto Chu; Choi Incheol 《Canadian Metallurgical Quarterly》2007,93(4):685
The authors examined cultural and individual differences in the relation between daily events and daily satisfaction. In a preliminary study, they established cross-cultural equivalence of 50 daily events. In the main study, participants in the United States, Korea, and Japan completed daily surveys on the 50 events and daily satisfaction for 21 days. The multilevel random coefficient model analyses showed that (a) the within-person association between positive events and daily satisfaction was significantly stronger among Asian American, Korean, and Japanese participants than among European American participants and (b) the within-person association between positive events and daily satisfaction was significantly weaker among individuals high in global life satisfaction than among those low in global life satisfaction. The findings demonstrate a weaker effect of positive events on daily well-being among individuals and cultures high in global well-being. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
105.
A survey of heterosexually active college students gathered information about condom use, self-efficacy (SE), outcome expectancies, sexual attitudes, peer group influences, AIDS knowledge, and a perceived vulnerability to AIDS. On the basis of A. Bandura's (1986) social-cognitive theory, a structural model with SE as the central mediator was formulated and evaluated with LISREL. This model explained 46% of the variance in condom use from judgments of SE and effects attributable to peers and 53% of the variance in SE from outcome expectancies and peer group influences. Sexual attitudes, AIDS knowledge, and perceived vulnerability did not predict condom use. Most students were well-informed about HIV transmission but reported not feeling at risk, even though many engaged in risky sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
107.
In this paper, a mixed approach for probabilistic structural durability design of mechanical systems is proposed. In this approach, a deterministic design optimization that considers structural crack initiation and crack propagation lives at critical points of the structural component as design constraints is performed first. After an optimal design is obtained, a reliability analysis is performed to ascertain if the deterministic optimal design is reliable. If the probability of the failure of the deterministic optimal design is found to be acceptable, a reliability-based design approach that employs a set of interactive design steps, such as trade-off analysis and what-if study, is used to obtain a near-optimal design that is reliable with an affordable computational cost. A 3-D tracked vehicle roadarm is employed to demonstrate the feasibility of the proposed approach. 相似文献
108.
Analysis and characterization of traveling-wave electrode in electroabsorption modulator for radio-on-fiber application 总被引:1,自引:0,他引:1
Jiyoun Lim Young-Shik Kang Kwang-Seong Choi Jong-Hyun Lee Sung-Bock Kim Jeha Kim 《Lightwave Technology, Journal of》2003,21(12):3004-3010
Comparing with a lumped electroabsorption modulator (EAM), we show the merits of a long EAM with traveling-wave electrode with high radio-frequency (RF) gain that could be used in high-frequency analog application. By terminating the RF output port with the characteristic impedance of 30 /spl Omega/, the device exhibited a large enhancement of 6 dB above 10 GHz in the electrical-to-optical response and a wide fractional bandwidth as estimated from simulation. In addition, an input impedance matching circuit of stub embedded on the device chip was found to be very effective for improving RF characteristics in the narrow band of frequency. 相似文献
109.
Spectrally stable Er-fiber laser for application in phase-sensitive optical time-domain reflectometry 总被引:3,自引:0,他引:3
Kyoo Nam Choi H.F. Taylor 《Photonics Technology Letters, IEEE》2003,15(3):386-388
A high degree of frequency stability in an Er-fiber laser with the Fabry-Perot configuration was achieved using a long (25-km) optical-feedback loop. The frequency-drift rate was determined to be <1 MHz/min by observing temporal fringes in an unbalanced Mach-Zehnder interferometer. Instantaneous linewidth measured with a delayed self-heterodyne interferometer was less than the 3-kHz resolution limit. The laser was utilized in an optical time-domain reflectometry experiment to detect and locate a time-varying phase perturbation applied to an optical fiber. 相似文献
110.
Jinho Park Kiyong Choi Allstot D.J. 《IEEE transactions on circuits and systems. I, Regular papers》2004,51(10):1953-1966
RF circuit synthesis techniques based on particle swarm optimization and adaptive simulated annealing with tunneling are described, and comparisons of parasitic-aware designs of an RF distributed amplifier and a nonlinear power amplifier are presented. Synthesized in 0.35-/spl mu/m digital CMOS using a single 3.3-V power supply, the designs provide an 8-dB gain and 8-GHz bandwidth for a four-stage distributed amplifier, and 1.2-W output power with 55% drain efficiency at 900 MHz for a three-stage power amplifier. A standard circuit simulator, HSPICE or SPECTRE, embedded in an optimization loop is used to evaluate cost functions. The proposed design and optimization methodology is computationally efficient and robust in searching complex multidimensional design spaces. 相似文献