全文获取类型
收费全文 | 2710篇 |
免费 | 115篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 58篇 |
综合类 | 4篇 |
化学工业 | 653篇 |
金属工艺 | 73篇 |
机械仪表 | 44篇 |
建筑科学 | 134篇 |
矿业工程 | 12篇 |
能源动力 | 46篇 |
轻工业 | 219篇 |
水利工程 | 15篇 |
石油天然气 | 6篇 |
无线电 | 246篇 |
一般工业技术 | 568篇 |
冶金工业 | 376篇 |
原子能技术 | 18篇 |
自动化技术 | 364篇 |
出版年
2023年 | 23篇 |
2022年 | 32篇 |
2021年 | 57篇 |
2020年 | 45篇 |
2019年 | 35篇 |
2018年 | 61篇 |
2017年 | 43篇 |
2016年 | 64篇 |
2015年 | 58篇 |
2014年 | 75篇 |
2013年 | 141篇 |
2012年 | 118篇 |
2011年 | 153篇 |
2010年 | 117篇 |
2009年 | 108篇 |
2008年 | 137篇 |
2007年 | 125篇 |
2006年 | 106篇 |
2005年 | 82篇 |
2004年 | 84篇 |
2003年 | 70篇 |
2002年 | 66篇 |
2001年 | 47篇 |
2000年 | 49篇 |
1999年 | 61篇 |
1998年 | 108篇 |
1997年 | 78篇 |
1996年 | 65篇 |
1995年 | 65篇 |
1994年 | 50篇 |
1993年 | 38篇 |
1992年 | 39篇 |
1991年 | 32篇 |
1990年 | 32篇 |
1989年 | 24篇 |
1988年 | 28篇 |
1987年 | 25篇 |
1986年 | 36篇 |
1985年 | 38篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 25篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 11篇 |
1974年 | 9篇 |
排序方式: 共有2836条查询结果,搜索用时 15 毫秒
21.
22.
A quantum-well-intermixing process for wavelength-agile photonic integrated circuits 总被引:1,自引:0,他引:1
Skogen E.J. Barton J.S. Denbaars S.P. Coldren L.A. 《IEEE journal of selected topics in quantum electronics》2002,8(4):863-869
Wavelength-agile photonic integrated circuits are fabricated using a one-step ion implantation quantum-well intermixing process. In this paper, we discuss, the issues in processing optimized widely tunable multisection lasers using this technique and present the results achieved using this process. This quantum-well intermixing process is general in its application and can be used to monolithically integrate a wide variety of optoelectronic components with widely tunable lasers. 相似文献
23.
Totterdell Peter; Spelten Evelien; Smith Lawrence; Barton Jane; Folkard Simon 《Canadian Metallurgical Quarterly》1995,80(1):43
Although regulations on work hours usually include a minimum weekly rest period, there is little empirical evidence concerning recovery from work. Shift-working nurses (N?=?61) used a handheld computer for 28 days to complete self-ratings, cognitive-performance tasks, and a sleep diary. Many measures were worse on rest days that followed a night shift rather than a day shift and tended to be worse on 1st rest days compared with subsequent rest days. Alertness was lowest on the 1st rest day following a night shift. Social satisfaction was better on workdays that were preceded by 2 rather than 1 rest day. Reaction time (RT) decreased over consecutive night shifts and tended to increase over rest days following night shifts. The results are interpreted as being consistent with the combined adaptive costs of fatigue and adjustment to and from a nocturnal routine. The practical implications for scheduling rest days are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
24.
A measurement technique is presented which uses narrow, fast-rise-time pulses applied to both the gate and the drain of a GaAs MESFET to obtain the drain characteristics of the device. This allows the characteristics of the device to be obtained which correspond to frequencies above those at which surface and substrate traps can respond. The resulting characteristics show significant departures from those obtained using conventional long pulse and DC measurement techniques. 相似文献
25.
26.
27.
Rainer Hauenschild 《e & i Elektrotechnik und Informationstechnik》2003,120(4):a13-a16
Ohne Zusammenfassung 相似文献
28.
29.
Embedded micromachined fiber-optic Fabry-Perot pressure sensors in aerodynamics applications 总被引:4,自引:0,他引:4
Gander M.J. MacPherson W.N. Barton J.S. Reuben R.L. Jones J.D.C. Stevens R. Chana K.S. Anderson S.J. Jones T.V. 《IEEE sensors journal》2003,3(1):102-107
Small size, high bandwidth pressure sensors are required for instrumentation of probes and test models in aerodynamic studies of complex unsteady flows. Optical-fiber pressure sensors promise potential advantages of small size and low cost in comparison with their electrical counterparts. We describe miniature Fabry-Perot cavity pressure sensors constructed by micromachining techniques in a turbine test application. The sensor bodies are 500 /spl mu/m squared, 300 /spl mu/m deep with a /spl sim/2 /spl mu/m-thick copper diaphragm electroplated on one face. The sensor cavity is formed between the diaphragm and the cleaved end of a single mode fiber sealed to the sensor by epoxy. Each sensor is addressed interferometrically in reflection by three wavelengths simultaneously, giving an unambiguous phase determination; a pressure sensitivity of 1.6 radbar/sup -1/ was measured, with a typical range of vacuum to 600 kPa. Five sensors were embedded in the trailing edge of a nozzle guide vane installed upstream of a rotor in a full-scale turbine stage transient test facility. Pressure signals in the trailing edge flow show marked structure at the 8 kHz blade passing frequency. To our knowledge, this is the first report of sensors located at the trailing edge of a normal-sized turbine blade. 相似文献
30.
PURPOSE: To evaluate factors that lead to the diagnosis of hemochromatosis probands in a community hospital, including education of physicians about hemochromatosis and iron overload, specialty of physicians, diagnostic indicators of hemochromatosis, and clinical manifestations of hemochromatosis probands. PATIENTS AND METHODS: We conducted a hemochromatosis education program for health care personnel associated with a community hospital and the public during 1990 to 1994. Data on physicians who diagnosed probands, diagnostic indicators of hemochromatosis, and manifestations of hemochromatosis and associated illnesses were tabulated. Iron grades of all hospital liver biopsy specimens obtained from Caucasian subjects during 1990 to 1994 were also analyzed. RESULTS: We identified 162 hemochromatosis probands; 66.7% were diagnosed by physicians who participated in our education program. Primary care and internal medicine subspecialty physicians diagnosed 66.7% and 29.6% of probands, respectively, based on elevated serum iron parameters and hepatic enzyme concentrations (51.9% and 36.4% of probands, respectively). Iron overload occurred in 90.7%, and was associated with clinical manifestations in most. Of 844 hospital liver biopsy specimens from Caucasians, 8.5% had increased iron grades; 4.6% represented hemochromatosis. CONCLUSIONS: Physicians with current education readily diagnose hemochromatosis probands during routine health care delivery, but most probands identified in this manner have iron overload. Our results suggest that community physicians and hospitals could contribute substantially to hemochromatosis screening programs, permitting detection of more homozygotes before the development of iron overload. 相似文献