全文获取类型
收费全文 | 676840篇 |
免费 | 8010篇 |
国内免费 | 2877篇 |
专业分类
电工技术 | 12728篇 |
综合类 | 1070篇 |
化学工业 | 98414篇 |
金属工艺 | 27716篇 |
机械仪表 | 20365篇 |
建筑科学 | 16396篇 |
矿业工程 | 2851篇 |
能源动力 | 16931篇 |
轻工业 | 58605篇 |
水利工程 | 6453篇 |
石油天然气 | 10083篇 |
武器工业 | 110篇 |
无线电 | 83106篇 |
一般工业技术 | 129241篇 |
冶金工业 | 131718篇 |
原子能技术 | 14230篇 |
自动化技术 | 57710篇 |
出版年
2021年 | 5000篇 |
2019年 | 4817篇 |
2018年 | 8122篇 |
2017年 | 8179篇 |
2016年 | 8691篇 |
2015年 | 5895篇 |
2014年 | 9892篇 |
2013年 | 29625篇 |
2012年 | 16328篇 |
2011年 | 22656篇 |
2010年 | 17941篇 |
2009年 | 20303篇 |
2008年 | 21462篇 |
2007年 | 21529篇 |
2006年 | 19241篇 |
2005年 | 17585篇 |
2004年 | 17189篇 |
2003年 | 16933篇 |
2002年 | 16561篇 |
2001年 | 16584篇 |
2000年 | 15549篇 |
1999年 | 16644篇 |
1998年 | 41184篇 |
1997年 | 29263篇 |
1996年 | 22600篇 |
1995年 | 17220篇 |
1994年 | 15210篇 |
1993年 | 15101篇 |
1992年 | 11212篇 |
1991年 | 10640篇 |
1990年 | 10082篇 |
1989年 | 9814篇 |
1988年 | 9405篇 |
1987年 | 8214篇 |
1986年 | 8161篇 |
1985年 | 9379篇 |
1984年 | 8617篇 |
1983年 | 7888篇 |
1982年 | 7455篇 |
1981年 | 7496篇 |
1980年 | 7268篇 |
1979年 | 6782篇 |
1978年 | 6755篇 |
1977年 | 7962篇 |
1976年 | 10681篇 |
1975年 | 5846篇 |
1974年 | 5687篇 |
1973年 | 5754篇 |
1972年 | 4740篇 |
1971年 | 4316篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Ferdinand P. Ferragu O. Lechien J.L. Lescop B. Magne S. Marty V. Rougeault S. Kotrotsios G. Neuman V. Depeursinge Y. Michel J.B. Van Uffelen M. Varelas D. Berthou H. Pierre G. Renouf C. Jarret B. Verbandt Y. Stevens W. Voet M.R.H. Toscano D. 《Lightwave Technology, Journal of》1995,13(7):1303-1313
Recent developments of stability control in mines, essentially based on Ge-doped fiber Bragg gratings (FBG) are reported including results about the different aspects of the system: accurate characterizations of FBG, sensor network topology and multiplexing method, user interface design and sensor packaging 相似文献
992.
2-D dopant profiling in VLSI devices using dopant-selectiveetching: an atomic force microscopy study
We report a detailed mapping of a 2-D dopant profile on a fully processed industrial sample with large dynamic range and high spatial resolution by utilizing a dopant-selective etching process and Atomic Force Microscopy. The experimental results show excellent agreement with those obtained from SRP and SIMS as corroborative methods. We also discuss the most critical factors which influence the applicability, reproducibility, and reliability of this method 相似文献
993.
Mineralization occurred both in fetal rat calvarial cells and UMR 106 osteoblastic cells when they were cultured in medium containing L-ascorbate and beta-glycerophosphate as evidenced by von Kóssa staining as well as deposition of calcium ions and inorganic phosphate in the cells. When compared with corresponding non-mineralized cell cultures, both the mineralized cultures of calvarial cells and UMR 106 cells did not exhibit any change in intracellular bone-specific alkaline phosphatase activities which were measured by wheatgerm lectin precipitation method. Our results support the hypothesis that mineralization may not exert any direct negative feedback on matrix protein synthesis in osteoblasts during bone formation. 相似文献
994.
995.
996.
997.
Bao X. Dhliwayo J. Heron N. Webb D.J. Jackson D.A. 《Lightwave Technology, Journal of》1995,13(7):1340-1348
Results are reported from recent research on the use of the Brillouin gain/loss mechanism for distributed sensing. A theoretical model of the interaction of the pulsed and CW beams is described and compared with experiments. Results from a system with a 51 km sensing length are presented. We finally investigate issues related to the variation within the sensing fiber of the polarizations of the two beams 相似文献
998.
Hillmer H. Grabmaier A. Zhu H.-L. Hansmann S. Burkhard A. 《Lightwave Technology, Journal of》1995,13(9):1905-1912
We have implemented and studied a new type of tunable multiple-section semiconductor distributed feedback (DFB) laser using tailored chirped DFB gratings. Arbitrarily and continuously chirped DFB gratings are defined by bent waveguides on homogeneous grating fields with ultrahigh spatial precision. The mathematical bending functions are optimized in this case to provide enlarged wavelength tuning ranges. We present the results of model calculations, the technological device realization and experimental results of the DFB laser characterization e.g. a tuning range of 5.5 nm without wavelength gaps and high side mode suppression ratio 相似文献
999.
Chun Hu Ji Zhao Li G.P. Liu P. Worley E. White J. Kjar R. 《Electron Device Letters, IEEE》1995,16(2):61-63
The effects of the plasma etching process induced gate oxide damages on device's low frequency noise behavior are investigated on MOSFET's fabricated with different field plate perimeter to gate area ratio antennas. Abnormal 1/f noise spectrum with a shoulder centered in the frequency range of 100 and to 1 kHz was frequently observed in small geometry devices, and it is attributable to a nonuniform distribution of oxide traps induced by plasma etching process 相似文献
1000.
Feng M. Scherrer D. Kruse J. Apostolakis P.J. Middleton J.R. 《Electron Device Letters, IEEE》1995,16(4):139-141
We present experimental evidence that the noise figure (NF) and associated gain equal to those achieved with GaAs pseudomorphic high electron mobility transistors (GaAs p-HEMT's) can also be accomplished by ion implanted GaAs metal-semiconductor field-effect transistors (GaAs MESFET's). These measured noise figure results as a function of low temperature for GaAs MESFET's and p-HEMT's clearly suggest that the transport properties of the two-dimensional electron gas in HEMT's and p-HEMT's do not make a significant contribution to the noise reduction at high frequency operation of these devices 相似文献