全文获取类型
收费全文 | 20045篇 |
免费 | 1108篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 221篇 |
综合类 | 48篇 |
化学工业 | 4134篇 |
金属工艺 | 423篇 |
机械仪表 | 389篇 |
建筑科学 | 901篇 |
矿业工程 | 48篇 |
能源动力 | 590篇 |
轻工业 | 1757篇 |
水利工程 | 154篇 |
石油天然气 | 57篇 |
武器工业 | 1篇 |
无线电 | 1480篇 |
一般工业技术 | 3847篇 |
冶金工业 | 3399篇 |
原子能技术 | 175篇 |
自动化技术 | 3558篇 |
出版年
2023年 | 166篇 |
2022年 | 211篇 |
2021年 | 627篇 |
2020年 | 417篇 |
2019年 | 428篇 |
2018年 | 569篇 |
2017年 | 534篇 |
2016年 | 624篇 |
2015年 | 563篇 |
2014年 | 704篇 |
2013年 | 1218篇 |
2012年 | 1122篇 |
2011年 | 1338篇 |
2010年 | 985篇 |
2009年 | 892篇 |
2008年 | 966篇 |
2007年 | 917篇 |
2006年 | 735篇 |
2005年 | 613篇 |
2004年 | 488篇 |
2003年 | 507篇 |
2002年 | 446篇 |
2001年 | 339篇 |
2000年 | 297篇 |
1999年 | 329篇 |
1998年 | 574篇 |
1997年 | 438篇 |
1996年 | 357篇 |
1995年 | 277篇 |
1994年 | 245篇 |
1993年 | 242篇 |
1992年 | 178篇 |
1991年 | 123篇 |
1990年 | 185篇 |
1989年 | 170篇 |
1988年 | 114篇 |
1987年 | 135篇 |
1986年 | 147篇 |
1985年 | 134篇 |
1984年 | 124篇 |
1983年 | 117篇 |
1982年 | 141篇 |
1981年 | 130篇 |
1980年 | 108篇 |
1979年 | 115篇 |
1978年 | 100篇 |
1977年 | 149篇 |
1976年 | 155篇 |
1975年 | 78篇 |
1974年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
D. Spemann K. Schindler P. Esquinazi M. Diaconu H. Schmidt R. Hhne A. Setzer T. Butz 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2006,250(1-2):303-308
In this study, ferromagnetic microstructures in highly oriented pyrolytic graphite and superparamagnetic spots in polyimide foils were created by 2.25 MeV proton microbeam irradiation and characterized using atomic and magnetic force microscopy. For this purpose, graphite samples were irradiated with cross-like patterns of 15 μm × 15 μm size using ion fluences in the range of (0.003–2.5) × 1018 cm−2. The irradiated crosses showed strong magnetic signals and a complex domain structure in the magnetic images depending on the geometrical dimensions of the crosses. Furthermore, polyimide foils were irradiated with microspots and fluences in the range of (0.016–3.1) × 1019 cm−2. Magnetic force microscopy shows very strong phase shifts in these irradiated areas. 相似文献
102.
ABSTRACT: One of the major growth segments in the food retail industry is fresh and minimally processed fruits and vegetables. This new market trend has thus increased the demands to the food industry for seeking new strategies to increase storability and shelf life and to enhance microbial safety of fresh produce. The technology of edible coatings has been considered as one of the potential approaches for meeting this demand. Edible coatings from renewable sources, including lipids, polysaccharides, and proteins, can function as barriers to water vapor, gases, and other solutes and also as carriers of many functional ingredients, such as antimicrobial and antioxidant agents, thus enhancing quality and extending shelf life of fresh and minimally processed fruits and vegetables. This review discusses the rationale of using edible coatings on fresh and minimally processed produce, the challenges in developing effective coatings that meet the specific criteria of fruits and vegetables, the recent advances in the development of coating technology, the analytical techniques for measuring some important coating functionalities, and future research needs for supporting a broad range of commercial applications. 相似文献
103.
Many analyses of boxed microstrip discontinuities require the location of large numbers of high-order modes. Using Sturm-Liouville theory, this letter derives a relationship between microstrip modes and slab-loaded guide modes, leading to an efficient mode location algorithm for microstrip, including microstrip with finite strip thickness.<> 相似文献
104.
105.
A microbubble-powered bioparticle actuator 总被引:4,自引:0,他引:4
Maxwell R.B. Gerhardt A.L. Toner M. Gray M.L. Schmidt M.A. 《Journal of microelectromechanical systems》2003,12(5):630-640
We present the results of a device that uses controllable microbubble actuation to manipulate bioparticles. In order to create a useful device for controlling the position of bioparticles, predictable microfluidic actuation is crucial. The goal of this project was to develop fundamental technology that can be used to manipulate single bioparticles (e.g., cells). We use a thermal bubble actuation method to accomplish this goal. Microbubbles have the advantages of relatively simple electronics and fabrication but can be difficult to control. In this paper, we describe two specific accomplishments: the use of micromachined nucleation cavities to precisely localize thermal bubbles and to achieve controllable bubble formation temperatures and bubble dissipation and the demonstration of controllable microbubbles in a new device for particle sorting. 相似文献
106.
107.
Measurement of Energy Expenditure in Elite Athletes Using MEMS-Based Triaxial Accelerometers 总被引:1,自引:0,他引:1
Andrew J. Wixted David V. Thiel Allan G. Hahn Christopher J. Gore David B. Pyne Daniel A. James 《IEEE sensors journal》2007,7(4):481-488
Fitness development and performance assessment of elite athletes requires an understanding of many physiological factors, many of these are direct and indirect measures of athlete energy expenditure. Many methods are physiological factor assessments and require the athlete to be constrained by laboratory equipment or periodic interruption of activity to take measurements such as blood samples are required to be taken. This paper presents a method that is entirely ambulatory and noninvasive, using microelectromechanical systems (MEMS) accelerometers. The commonly used output of commercial accelerometer-based devices (known as "counts") cannot discriminate activity intensity for the activities of interest. This, in conjunction with variability in output from different systems and lack of commonality across manufacturers, limits the usefulness of commercial devices. This paper identifies anthropometric and kinematic sources of inter-athlete variability in accelerometer output, leading to an alternate energy expenditure estimator based mainly on step frequency modified by anthropometric measures. This energy expenditure estimator is more robust and not influenced by many sources of variability that affect the currently used estimator. In this system, low-power signal processing was implemented to extract both the energy estimator and other information of physiological and statistical interest 相似文献
108.
109.
Shuman Daniel W.; Cunningham Mark D.; Connell Mary A.; Reid William H. 《Canadian Metallurgical Quarterly》2003,34(3):233
Forensic psychology has made important gains in professional recognition and stature in the courts, resulting in increasing demands for mobility of expertise. Current regulations regarding the interjurisdictional temporary forensic practice of psychology, however, are characterized by variability of regulations, ambiguity and inaccessibility, and continuing total barriers. A uniform, well-reasoned policy is needed. A conceptual basis for such a policy is provided by a discussion of licensing rationales and the application of these to forensic practice. Uniformity, public and professional protection, and practicability are identified as fundamental regulatory criteria. A Model Rule Regarding the Temporary Forensic Practice of Psychology is proposed for adoption by state licensing boards on a nationwide basis. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
110.