全文获取类型
收费全文 | 725981篇 |
免费 | 20615篇 |
国内免费 | 2860篇 |
专业分类
电工技术 | 13094篇 |
技术理论 | 5篇 |
综合类 | 1441篇 |
化学工业 | 123436篇 |
金属工艺 | 30365篇 |
机械仪表 | 23110篇 |
建筑科学 | 17961篇 |
矿业工程 | 5440篇 |
能源动力 | 16104篇 |
轻工业 | 64689篇 |
水利工程 | 8450篇 |
石油天然气 | 17925篇 |
武器工业 | 280篇 |
无线电 | 77620篇 |
一般工业技术 | 150872篇 |
冶金工业 | 118390篇 |
原子能技术 | 17178篇 |
自动化技术 | 63096篇 |
出版年
2021年 | 7043篇 |
2020年 | 6534篇 |
2019年 | 9285篇 |
2018年 | 13459篇 |
2017年 | 13926篇 |
2016年 | 15231篇 |
2015年 | 11220篇 |
2014年 | 15968篇 |
2013年 | 35860篇 |
2012年 | 22652篇 |
2011年 | 28319篇 |
2010年 | 23314篇 |
2009年 | 25186篇 |
2008年 | 25825篇 |
2007年 | 25276篇 |
2006年 | 22059篇 |
2005年 | 19471篇 |
2004年 | 18395篇 |
2003年 | 17804篇 |
2002年 | 17198篇 |
2001年 | 17062篇 |
2000年 | 16057篇 |
1999年 | 15500篇 |
1998年 | 33711篇 |
1997年 | 24633篇 |
1996年 | 18703篇 |
1995年 | 14318篇 |
1994年 | 12948篇 |
1993年 | 12943篇 |
1992年 | 9876篇 |
1991年 | 9569篇 |
1990年 | 9550篇 |
1989年 | 9253篇 |
1988年 | 8903篇 |
1987年 | 7854篇 |
1986年 | 7667篇 |
1985年 | 8766篇 |
1984年 | 8289篇 |
1983年 | 7782篇 |
1982年 | 7149篇 |
1981年 | 7413篇 |
1980年 | 7057篇 |
1979年 | 7185篇 |
1978年 | 7173篇 |
1977年 | 7732篇 |
1976年 | 9698篇 |
1975年 | 6379篇 |
1974年 | 6266篇 |
1973年 | 6341篇 |
1972年 | 5411篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
de Oliveira J.C. Hosseini M. Shirmohammadi S. Malric F. Nourian S. El Saddik A. Georganas N.D. 《Multimedia, IEEE》2003,10(3):18-29
Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use. 相似文献
32.
L. Gao P. Hrter Ch. Linsmeier J. Gstttner R. Emling D. Schmitt-Landsiedel 《Materials Science in Semiconductor Processing》2004,7(4-6):331
Deposition of Ag films by direct liquid injection-metal organic chemical vapor deposition (DLI-MOCVD) was chosen because this preparation method allows precise control of precursor flow and prevents early decomposition of the precursor as compared to the bubbler-delivery. Silver(I)-2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato-triethylphosphine [Ag(fod)(PEt3)] as the precursor for Ag CVD was studied, which is liquid at 30 °C. Ag films were grown on different substrates of SiO2/Si and TiN/Si. Argon and nitrogen/hydrogen carrier gas was used in a cold wall reactor at a pressure of 50–500 Pa with deposition temperature ranging between 220 °C and 350 °C. Ag films deposited on a TiN/Si diffusion barrier layer have favorable properties over films deposited on SiO2/Si substrate. At lower temperature (220 °C), film growth is essentially reaction-limited on SiO2 substrate. Significant dependence of the surface morphology on the deposition conditions exists in our experiments. According to XPS analysis pure Ag films are deposited by DLI-MOCVD at 250 °C by using argon as carrier gas. 相似文献
33.
Yu. I. Golovin D. V. Lopatin R. K. Nikolaev A. V. Umrikhin 《Technical Physics Letters》2004,30(5):426-428
The effect of crystal orientation on the photogeneration of free charge carriers was studied for C60 single crystals in a weak magnetic field. The photoconductivity sharply depends on the orientation of magnetic field with
respect to the crystallographic directions, showing a 5–8% increase for seven axes of the C60 crystal. 相似文献
34.
Popular biorthogonal wavelet filters via a lifting scheme and its application in image compression 总被引:2,自引:0,他引:2
Cheng L. Liang D.L. Zhang Z.H. 《Vision, Image and Signal Processing, IEE Proceedings -》2003,150(4):227-232
A technique using a lifting scheme is presented for constructing compactly supported wavelets whose coefficients are composed of free variables locating in an interval. An efficient approach-based wavelet for image compression is developed by selecting the coefficients of the 9-7 wavelet filter and associated lifting scheme. Furthermore, the rationalised coefficients wavelet filter that can be implemented with simple integer arithmetic is achieved and its characteristic is close to the well known original irrational coefficients 9-7 wavelet filters developed by A. Cohen et al. (Commun. Pure Appl. Maths., vol.45, no.1, p.485-560, 1992). To reduce the computational cost of image coding applications further, an acceleration technique is proposed for the lifting steps. Software and hardware simulations show that the new method has very low complexity, and simultaneously preserves the high quality of the compressed image. 相似文献
35.
V. G. Deibuk 《Semiconductors》2003,37(10):1151-1155
The miscibility gaps and the critical temperatures of spinodal decomposition of ternary semiconducting Ga-In-Sb, Ga-In-P, and In-As-Sb systems are calculated by taking into account the deformation energy and the effect of plastic relaxation caused by the misfit dislocations. It is shown that taking into consideration elastic energy narrows the ranges of spinodal decomposition and lowers its critical temperature. The introduction of the phenomenological parameter into Matthews-Blakeslee formula makes it possible to reach a satisfactory agreement between theoretically calculated values of critical thickness of epitaxial films and the experimental data. 相似文献
36.
Korolev I. A. Alekseenko N. N. Porodnov B. T. Sapunov V. A. Savel'ev D. V. 《Measurement Techniques》2003,46(9):865-871
The design of a sylphon bellows sensor and the basic circuits of an LC-generator and of a microprocessor unit are presented. An analytical pressure–frequency conversion function and a special method of adjusting the sensor ensure an error of less than 0.05%. The dynamic range is up to 105. The instruments developed cover the ranges 103, 104, and 105 Pa. 相似文献
37.
The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit. 相似文献
38.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
39.
Honour Index (HoI), a method to evaluate research performance within different research fields, was derived from the impact
factor (IF). It can be used to rate and compare different categories of journals. HoI was used in this study to determine
the scientific productivity of stem cell research in the Asian Four Dragons (Hong Kong, Singapore, South Korea and Taiwan)
from 1981 to 2001. The methodology applied in this study represents a synthesis of universal indicator studies and bibliometric
analyses of subfields at the micro-level. We discuss several comparisons, and conclude the developmental trend in stem cell
research for two decades.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
40.
Ciofi C. Crupi F. Pace C. Scandurra G. 《IEEE transactions on instrumentation and measurement》2003,52(5):1533-1536
Low-frequency noise measurements represent an interesting investigation technique for the characterization of the quality and reliability of microelectronic materials and devices. Performing meaningful noise measurements at low and very low (f<1 Hz) frequencies, however, may be quite challenging, particularly because of the many sources of interference that superimpose on the noise signal. For this reason, packaged samples are preferred because they allow accurate shielding from the external environment, and because keeping the sample in close proximity to the low-noise biasing system and amplifier reduces microphonic and electromagnetic disturbances. Notwithstanding this, the possibility of performing low-frequency noise measurements at wafer level would be quite interesting, both because of the ease of obtaining wafer-level samples from industries with respect to packaged samples, and because this would avoid possible packaging-process induced device degradation. The purpose of this work is to demonstrate that it is, in fact, possible to design and build a dedicated probe system for performing high-sensitivity, low-frequency noise measurements on metal-oxide-semiconductor devices at wafer level. 相似文献