全文获取类型
收费全文 | 287609篇 |
免费 | 3067篇 |
国内免费 | 817篇 |
专业分类
电工技术 | 5030篇 |
综合类 | 162篇 |
化学工业 | 45409篇 |
金属工艺 | 11895篇 |
机械仪表 | 8606篇 |
建筑科学 | 6846篇 |
矿业工程 | 1835篇 |
能源动力 | 6734篇 |
轻工业 | 25916篇 |
水利工程 | 3190篇 |
石油天然气 | 7087篇 |
武器工业 | 16篇 |
无线电 | 31455篇 |
一般工业技术 | 56930篇 |
冶金工业 | 51365篇 |
原子能技术 | 7532篇 |
自动化技术 | 21485篇 |
出版年
2021年 | 2099篇 |
2018年 | 3675篇 |
2017年 | 3622篇 |
2016年 | 3905篇 |
2015年 | 2466篇 |
2014年 | 4234篇 |
2013年 | 12020篇 |
2012年 | 6830篇 |
2011年 | 9214篇 |
2010年 | 7566篇 |
2009年 | 8642篇 |
2008年 | 8932篇 |
2007年 | 8813篇 |
2006年 | 7827篇 |
2005年 | 7310篇 |
2004年 | 6800篇 |
2003年 | 6553篇 |
2002年 | 6627篇 |
2001年 | 6497篇 |
2000年 | 6177篇 |
1999年 | 6229篇 |
1998年 | 14749篇 |
1997年 | 11030篇 |
1996年 | 8567篇 |
1995年 | 6523篇 |
1994年 | 5915篇 |
1993年 | 5787篇 |
1992年 | 4480篇 |
1991年 | 4440篇 |
1990年 | 4284篇 |
1989年 | 4301篇 |
1988年 | 4255篇 |
1987年 | 3598篇 |
1986年 | 3595篇 |
1985年 | 4161篇 |
1984年 | 3965篇 |
1983年 | 3620篇 |
1982年 | 3422篇 |
1981年 | 3558篇 |
1980年 | 3422篇 |
1979年 | 3365篇 |
1978年 | 3445篇 |
1977年 | 3923篇 |
1976年 | 5038篇 |
1975年 | 3158篇 |
1974年 | 3007篇 |
1973年 | 3024篇 |
1972年 | 2651篇 |
1971年 | 2473篇 |
1970年 | 2104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals. 相似文献
172.
L. M. Aksel’rod V. I. Rumyantsev N. Yu. Korableva N. V. Belykh Ya. G. Dyatlova 《Refractories and Industrial Ceramics》2008,49(2):116-119
Technology is developed for preparing refractory components made of partially stabilized zirconium dioxide using an isostatic
compaction press. Technology is provided for manufacturing dispensing nozzles using combined and separately stabilized zirconium
dioxide, and also indices of the refractories obtained and imported materials are compared.
__________
Translated from Novye Ogneupory, No. 3, pp. 127–131, March 2008. 相似文献
173.
174.
N. A. Kochetov B. S. Seplyarskii S. G. Vadchenko 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(3):206-209
Combustion of bulk density Ti powder (containing 20 wt % TiN as a diluent) in a coflow of N2-Ar mixture was investigated upon variation in the nitrogen content of the gaseous mixture. The obtained data are believed
to open up new horizons for fabrication of layered and composite ceramics by infiltration-mediated combustion.
相似文献
175.
176.
177.
Steensgaard J. Zhiqing Zhang Wenhuan Yu Sarhegyi A. Lucchese L. Dae-Ik Kim Temes G.C. 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(5):1289-1296
Incremental data converters (IDCs) are useful in instrumentation and measurement applications, where low-frequency analog signals need to be converted into digital form with high accuracy and low power dissipation. They are particularly well suited for applications where a single analog-digital converter is multiplexed between many channels. This paper proposes an exact design methodology for IDCs, which optimizes the signal-to-noise ratio of the converter under practical design constraints. The process also allows the designer to apportion the noise budget in an arbitrary manner between thermal and quantization noise. The design process is illustrated by an example which describes the optimization of a third-order multiplexed IDC. 相似文献
178.
Chaves R. Kuzmanov G. Sousa L. Vassiliadis S. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2008,16(8):999-1008
179.
It is shown that, at thermodynamic equilibrium, the release of charge carriers from the localized states of bistable amphoteric centers into quasi-free states depends on the degree of compensation. This brings about different functional dependences of the concentration of free charge carriers on temperature. It is found that, in uncompensated semiconductors, the concentration of free charge carriers follows the same dependence in the case of bistable amphoteric centers and bistable amphoteric U ? centers, although the distributions of charge carriers over the charge states and configurations are different for these types of centers. The results can be used for interpreting various experimental data insufficiently explained in the context of the traditional approach. 相似文献
180.
V. N. Jmerik A. M. Mizerov T. V. Shubina A. V. Sakharov A. A. Sitnikova P. S. Kop’ev S. V. Ivanov E. V. Lutsenko A. V. Danilchyk N. V. Rzheutskii G. P. Yablonskii 《Semiconductors》2008,42(12):1420-1426
Features of plasma-assisted molecular-beam epitaxy of AlGaN compounds at relatively low temperatures of the substrate (no higher than 740°C) and various stoichiometric conditions for growth of the nitrogen- and metal-enriched layers are studied. Discrete submonolayer epitaxy for formation of quantum wells and n-type blocking layers without varying the fluxes of components was used for the first time in the case of molecular- beam epitaxy with plasma activation of nitrogen for the nanostructures with the Al x Ga1 ? x N/Al y Ga1 ? y N quantum wells. Structural and optical properties of the Al x Ga1 ? x N layers in the entire range of compositions (x = 0–1) and nanostructures based on these layers are studied; these studies indicate that there is photoluminescence at room temperature with minimum wavelength of 230 nm. Based on the analysis of the photoluminescence spectra for bulk layers and nanoheterostructures and their temperature dependences, it is concluded that there are localized states in quantum wells. Using the metal-enriched layers grown on the c-Al2O3 substrates, heterostructures for light-emitting diodes with Al x Ga1 ? x N/Al y Ga1 ? y N quantum wells (x = 0.4–0.5, y = x + 0.15) were obtained and demonstrated electroluminescence in the ultraviolet region of the spectrum at the wavelength of 320 nm. 相似文献