全文获取类型
收费全文 | 704314篇 |
免费 | 9160篇 |
国内免费 | 2106篇 |
专业分类
电工技术 | 12993篇 |
综合类 | 671篇 |
化学工业 | 105325篇 |
金属工艺 | 26707篇 |
机械仪表 | 20457篇 |
建筑科学 | 17379篇 |
矿业工程 | 2942篇 |
能源动力 | 19773篇 |
轻工业 | 61412篇 |
水利工程 | 6798篇 |
石油天然气 | 11415篇 |
武器工业 | 45篇 |
无线电 | 83402篇 |
一般工业技术 | 137166篇 |
冶金工业 | 136481篇 |
原子能技术 | 13872篇 |
自动化技术 | 58742篇 |
出版年
2022年 | 4170篇 |
2021年 | 6383篇 |
2020年 | 4665篇 |
2019年 | 5896篇 |
2018年 | 10044篇 |
2017年 | 9863篇 |
2016年 | 10358篇 |
2015年 | 7115篇 |
2014年 | 11930篇 |
2013年 | 32576篇 |
2012年 | 18854篇 |
2011年 | 26072篇 |
2010年 | 20636篇 |
2009年 | 23290篇 |
2008年 | 23923篇 |
2007年 | 23500篇 |
2006年 | 20651篇 |
2005年 | 18565篇 |
2004年 | 17961篇 |
2003年 | 17839篇 |
2002年 | 16892篇 |
2001年 | 17272篇 |
2000年 | 16019篇 |
1999年 | 16973篇 |
1998年 | 43433篇 |
1997年 | 30405篇 |
1996年 | 23339篇 |
1995年 | 17587篇 |
1994年 | 15367篇 |
1993年 | 15150篇 |
1992年 | 10899篇 |
1991年 | 10360篇 |
1990年 | 10107篇 |
1989年 | 9678篇 |
1988年 | 9120篇 |
1987年 | 8027篇 |
1986年 | 7874篇 |
1985年 | 8718篇 |
1984年 | 8137篇 |
1983年 | 7388篇 |
1982年 | 6920篇 |
1981年 | 6893篇 |
1980年 | 6632篇 |
1979年 | 6379篇 |
1978年 | 6047篇 |
1977年 | 7351篇 |
1976年 | 9736篇 |
1975年 | 5149篇 |
1974年 | 4904篇 |
1973年 | 4947篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone. 相似文献
122.
M. D. Korostash 《Drying Technology》1985,3(4):603-611
The paper presents the results of research in the convection drying of unidirectional glass fibre bobbins on the basis of which the relations are suggested required to calculate the process of drying in the design of drying equipment. 相似文献
123.
Nagpal R. Zambonelli F. Sirer E.G. Chaouchi H. Smirnov M. 《Intelligent Systems, IEEE》2006,21(2):50-58
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing. 相似文献
124.
Hayashi M. Tanaka H. Ohara K. Otani T. Suzuki M. 《Lightwave Technology, Journal of》2002,20(2):236-242
An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal 相似文献
125.
K. A. Abdikalikov V. K. Zadiraka O. S. Kondratenko S. S. Mel'nikova 《Cybernetics and Systems Analysis》1991,27(3):414-419
A fast algorithm is proposed for estimating the auto- and cross-correlation functions of a large signal. The algorithm is based on the sectioning method by the fast Fourier transform. We determine the optimal length of the portion of data read from external memory into RAM which achieves Tmin—a minimum processing time. An estimate of Tmin is obtained.Translated from Kibernetika, No. 3, pp. 78–81, May–June, 1991. 相似文献
126.
127.
Antoniades N. Boskovic A. Tomkos I. Madamopoulos N. Lee M. Roudas I. Pastel D. Sharma M. Yadlowsky M.J. 《Selected Areas in Communications, IEEE Journal on》2002,20(1):149-165
This paper demonstrates the use of computer simulation for topological design and performance engineering of transparent wavelength-division multiplexing metropolitan-area networks. Engineering of these networks involves the study of various transport-layer impairments such as amplifier noise, component ripple, chirp/dispersion, optical crosstalk, waveform distortion due to filter concatenation, fiber nonlinearities, and polarization effects. A computer simulation methodology composed of three main simulation steps is derived and implemented. This methodology obtains performance estimations by applying efficient wavelength-domain simulations on the entire network topology, followed by time-/frequency-domain simulations on selected paths of the network and finally Q-budgeting on an identified worst case path. The above technique provides an efficient tool for topological design and network performance engineering. Accurate simulation models are presented for each of the performance impairments, and the computer simulation methodology is used for the design and engineering of a number of actual metro network architectures 相似文献
128.
Buttari D. Chini A. Meneghesso G. Zanoni E. Moran B. Heikman S. Zhang N.Q. Shen L. Coffie R. DenBaars S.P. Mishra U.K. 《Electron Device Letters, IEEE》2002,23(2):76-78
Pre-metal-deposition reactive ion etching (RIE) was performed on an Al0.3Ga0.7N/AlN/GaN heterostructure in order to improve the metal-to-semiconductor contact resistance. An optimum AlGaN thickness for minimizing contact resistance was determined. An initial decrease in contact resistance with etching time was explained in terms of removal of an oxide surface layer and/or by an increase in tunnelling current with the decrease of the AlGaN thickness. The presence of a dissimilar surface layer was confirmed by an initial nonuniform etch depth rate. An increase in contact resistance for deeper etches was experienced. The increase was related to depletion of the two-dimensional (2-D) electron gas (2-DEG) under the ohmics. Etch depths were measured by atomic force microscopy (AFM). The contact resistance decreased from about 0.45 Ωmm for unetched ohmics to a minimum of 0.27 Ωmm for 70 Å etched ohmics. The initial thickness of the AlGaN layer was 250 Å. The decrease in contact resistance, without excessive complications on device processing, supports RIE etching as a viable solution to improve ohmic contact resistance in AlGaN/GaN HEMTs 相似文献
129.
Losada M.A. Garces I. Mateo J. Salinas I. Lou J. Zubia J. 《Lightwave Technology, Journal of》2002,20(7):1160-1164
We have studied the optical power losses due to multiple curvatures in polymethylmetacrylate (PMMA) plastic optical fibers (POFs) of different numerical apertures (NAs) and attenuation. The fibers were tested for several configurations in order to assess the influence of different types of curved-to-straight fiber transitions in the amount of power radiation. We found that losses are below the standards for all tested fiber types, and thus, they are a suitable choice for local area network (LAN) applications. In addition, our results revealed the presence of modal interactions as confirmed using an experimental procedure to estimate the mode coupling strength for the same fibers. 相似文献
130.
Integrated chaos generators 总被引:4,自引:0,他引:4
Delgado-Restituto M. Rodriguez-Vazquez A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2002,90(5):747-767
This paper surveys the different design issues, from mathematical model to silicon, involved in the design of analog CMOS integrated circuits for the generation of chaotic behavior 相似文献