全文获取类型
收费全文 | 412377篇 |
免费 | 14483篇 |
国内免费 | 6938篇 |
专业分类
电工技术 | 13382篇 |
技术理论 | 9篇 |
综合类 | 8903篇 |
化学工业 | 62243篇 |
金属工艺 | 18988篇 |
机械仪表 | 17237篇 |
建筑科学 | 15731篇 |
矿业工程 | 4717篇 |
能源动力 | 10803篇 |
轻工业 | 30349篇 |
水利工程 | 5239篇 |
石油天然气 | 12309篇 |
武器工业 | 1064篇 |
无线电 | 51023篇 |
一般工业技术 | 74875篇 |
冶金工业 | 58814篇 |
原子能技术 | 9323篇 |
自动化技术 | 38789篇 |
出版年
2023年 | 2887篇 |
2022年 | 5978篇 |
2021年 | 8279篇 |
2020年 | 6145篇 |
2019年 | 5839篇 |
2018年 | 8150篇 |
2017年 | 8630篇 |
2016年 | 8302篇 |
2015年 | 7731篇 |
2014年 | 11056篇 |
2013年 | 20100篇 |
2012年 | 15527篇 |
2011年 | 18550篇 |
2010年 | 15368篇 |
2009年 | 16169篇 |
2008年 | 16546篇 |
2007年 | 15912篇 |
2006年 | 14476篇 |
2005年 | 12570篇 |
2004年 | 10861篇 |
2003年 | 11062篇 |
2002年 | 10619篇 |
2001年 | 10695篇 |
2000年 | 9581篇 |
1999年 | 9601篇 |
1998年 | 18988篇 |
1997年 | 13517篇 |
1996年 | 10678篇 |
1995年 | 8276篇 |
1994年 | 7306篇 |
1993年 | 6996篇 |
1992年 | 5262篇 |
1991年 | 5016篇 |
1990年 | 4848篇 |
1989年 | 4564篇 |
1988年 | 4362篇 |
1987年 | 3774篇 |
1986年 | 3626篇 |
1985年 | 3834篇 |
1984年 | 3520篇 |
1983年 | 3401篇 |
1982年 | 3229篇 |
1981年 | 3118篇 |
1980年 | 3017篇 |
1979年 | 2946篇 |
1978年 | 2782篇 |
1977年 | 3259篇 |
1976年 | 4235篇 |
1975年 | 2413篇 |
1974年 | 2346篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
51.
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
52.
Yu. I. Berdyshev 《Journal of Computer and Systems Sciences International》2006,45(4):526-531
An algorithm for construction of the reachability domain by the given time instant ? for a nonlinear third order system under the condition of preliminary approach to a predefined point is proposed. All possible cases of location of this point in the motion plane of the system for different values of the time instant ? are studied. 相似文献
53.
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
54.
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
55.
56.
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
57.
58.
59.
Yu. G. Teterev 《Atomic Energy》1989,67(4):760-763
Translated from Atomnaya Énergiya, Vol. 67, No. 4, pp. 271–274, October, 1989. 相似文献
60.
A. N. Gudkov V. M. Zhivun A. V. Zvonarev V. V. Kovalenko A. B. Koldobskii Yu. F. Koleganov S. V. Krivasheev V. B. Pavlovich N. S. Piven' E. V. Semenova 《Atomic Energy》1989,66(2):115-118
Translated from Atomnaya Énergiya, Vol. 66, No. 2, pp. 100–103, February, 1989. 相似文献