全文获取类型
收费全文 | 197834篇 |
免费 | 2115篇 |
国内免费 | 633篇 |
专业分类
电工技术 | 4060篇 |
综合类 | 123篇 |
化学工业 | 26707篇 |
金属工艺 | 7507篇 |
机械仪表 | 5460篇 |
建筑科学 | 4038篇 |
矿业工程 | 747篇 |
能源动力 | 4657篇 |
轻工业 | 14383篇 |
水利工程 | 1695篇 |
石油天然气 | 2843篇 |
武器工业 | 7篇 |
无线电 | 27292篇 |
一般工业技术 | 37391篇 |
冶金工业 | 45401篇 |
原子能技术 | 3563篇 |
自动化技术 | 14708篇 |
出版年
2021年 | 1248篇 |
2019年 | 1280篇 |
2018年 | 2124篇 |
2017年 | 2105篇 |
2016年 | 2172篇 |
2015年 | 1489篇 |
2014年 | 2618篇 |
2013年 | 7951篇 |
2012年 | 4462篇 |
2011年 | 6111篇 |
2010年 | 4931篇 |
2009年 | 5776篇 |
2008年 | 6146篇 |
2007年 | 6195篇 |
2006年 | 5635篇 |
2005年 | 5304篇 |
2004年 | 5249篇 |
2003年 | 5089篇 |
2002年 | 4898篇 |
2001年 | 5305篇 |
2000年 | 4915篇 |
1999年 | 5435篇 |
1998年 | 15623篇 |
1997年 | 10317篇 |
1996年 | 7931篇 |
1995年 | 5784篇 |
1994年 | 5014篇 |
1993年 | 5023篇 |
1992年 | 3386篇 |
1991年 | 3260篇 |
1990年 | 3216篇 |
1989年 | 3041篇 |
1988年 | 2784篇 |
1987年 | 2234篇 |
1986年 | 2301篇 |
1985年 | 2607篇 |
1984年 | 2312篇 |
1983年 | 2064篇 |
1982年 | 1901篇 |
1981年 | 2043篇 |
1980年 | 1790篇 |
1979年 | 1659篇 |
1978年 | 1656篇 |
1977年 | 2023篇 |
1976年 | 2702篇 |
1975年 | 1422篇 |
1974年 | 1369篇 |
1973年 | 1316篇 |
1972年 | 1124篇 |
1971年 | 957篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
The electrochemical faceting of polycrystalline (pc) platinum yielding a (100)-preferred oriented electrode surface was accomplished in HF solutions by applying to the pc platinum electrode a square wave potential perturbation at 1 kHz in the 0.2 to 1.3 V range (vs rhe). SEM patterns of the resulting surfaces were also obtained. For HF concentrations up to 2 M no appreciable influence of the electrolyte concentration on the electrochemical faceting was noticed. Otherwise, the voltammetric response of the (100)-type preferred oriented platinum surface in the H-adatom potential range when compared to previously reported data resulted remarkably sensitive to the electrolyte composition. The discussion of results was based on the non-equilibrium adsorption conditions for anions under the periodic perturbation. 相似文献
65.
Amanda Alliband Daniel W. Lenz Laura E. Stevenson Travis Whitmer Rex Cash Dennis Burns Sarah Hall William T.K. Stevenson 《Progress in Organic Coatings》2008
A model has been proposed to explain the failure of the original BMS10-39 epoxy paint on upper vertical surfaces in B-52 fuel tanks. The model involves interaction of the paint with DIEGME, a fuel system ice inhibitor (FSII) in jet fuel, that is distilled from the liquid fuel. In this communication, distillation experiments used to support the model are refined to better match the mass transfer of vapor from fuel in a B-52 fuel tank at close to room temperature. The interaction of these lower temperature distillates with the paint affirms the earlier model. On the basis of these experiments it is proposed that paint failure may be controlled or eliminated by reducing the level of DIEGME in the fuel. Proposed changes in military jet fuel composition are detailed. 相似文献
66.
Yunlei Li Dick de Ridder Robert P.W. Duin Marcel J.T. Reinders 《Pattern recognition》2008,41(1):320-330
Samples can be measured with different precisions and reliabilities in different experiments, or even within the same experiment. These varying levels of measurement noise may deteriorate the performance of a pattern recognition system, if not treated with care. Here we seek to investigate the benefit of incorporating prior knowledge about measurement noise into system construction. We propose a kernel density classifier which integrates such prior knowledge. Instead of using an identical kernel for each sample, we transform the prior knowledge into a distinct kernel for each sample. The integration procedure is straightforward and easy to interpret. In addition, we show how to estimate the diverse measurement noise levels in a real world dataset. Compared to the basic methods, the new kernel density classifier can give a significantly better classification performance. As expected, this improvement is more obvious for small sample size datasets and large number of features. 相似文献
67.
I. D. Kashcheev T. V. Bayandina A. I. Usherov V. I. Shishkin I. V. Shishkin 《Refractories and Industrial Ceramics》2008,49(3):167-170
Secondary aluminum waste products, and processes that occur during heating and mineral formation on introducing fine periclase
powder into the composition of waste products are studied. It is demonstrated that secondary aluminum production waste may
be used as a raw material for synthesizing aluminomagnesia spinels.
Translated from Novye Ogneupory, No. 6, pp. 15–18, June 2008. 相似文献
68.
T. V. Bayandina I. D. Kasheev A. I. Usherov V. I. Shishkin 《Refractories and Industrial Ceramics》2008,49(4):255-256
On the basis of periclase powder (70%) and aluminomagnesia spinel (30%), synthesized from secondary aluminum production waste
and caustic magnesite, test objects are produced of periclase spinel composition satisfying the requirements of GOST 1579-006-00190495-98.
The articles are successfully tested in the working layer for lining tunnel furnace cars of OAO Kombinat Magnezit.
__________
Translated from Novye Ogneupory, No. 8, pp. 16–17, August 2008. 相似文献
69.
Nanosized (2–8 nm) amorphous powders of the solid solution based on zirconia and hafnia are synthesized through back coprecipitation
upon treatment of gels at temperatures from +20 to −77°C. Heat treatment of these powders at temperatures up to 1000 and above
1100°C leads to the formation of cubic (fluorite type, O
h
5 = Fm3m) and tetragonal phases of the Zr82Hf10Y3Ce5O
x
composition, respectively. It is revealed that a decrease in the synthesis temperature (from +20°C to −6°C) results in a
decrease in the size of gel agglomerates from 30 to 1 μm. Recrystallization processes in the gels prepared using cryochemical
treatment are developed very slowly in the temperature range 500–1200°C (the crystallite size does not exceed 25 nm).
Original Russian Text ? T.I. Panova, V.B. Glushkova, A.E. Lapshin, 2008, published in Fizika i Khimiya Stekla. 相似文献
70.
E. V. Golikova V. S. Grigor’ev V. I. Kuchuk T. S. Mashchenko L. P. Efimenko A. T. D’yachkova 《Glass Physics and Chemistry》2008,34(5):582-598
The aggregate stability of submicron and nanosized ZrO2 aqueous sols of different origins and different dispersities at pH 3–10 in the KCl concentration range 10?3–10?1 M is investigated by flow ultramicroscopy and photometry. The results obtained are analyzed in the framework of the extended Derjaguin-Landau-Verwey-Overbeek theory and the Muller-Martynov theory of reversible aggregation. The extension of boundary layers of water near the surface of the ZrO2 particles is estimated. 相似文献