全文获取类型
收费全文 | 355589篇 |
免费 | 4037篇 |
国内免费 | 1234篇 |
专业分类
电工技术 | 6993篇 |
综合类 | 217篇 |
化学工业 | 51722篇 |
金属工艺 | 14465篇 |
机械仪表 | 9936篇 |
建筑科学 | 8047篇 |
矿业工程 | 1578篇 |
能源动力 | 8876篇 |
轻工业 | 28998篇 |
水利工程 | 3222篇 |
石油天然气 | 5585篇 |
武器工业 | 9篇 |
无线电 | 44386篇 |
一般工业技术 | 66790篇 |
冶金工业 | 75311篇 |
原子能技术 | 7332篇 |
自动化技术 | 27393篇 |
出版年
2021年 | 2413篇 |
2019年 | 2377篇 |
2018年 | 3943篇 |
2017年 | 3969篇 |
2016年 | 4122篇 |
2015年 | 2913篇 |
2014年 | 5002篇 |
2013年 | 14931篇 |
2012年 | 8495篇 |
2011年 | 11703篇 |
2010年 | 9428篇 |
2009年 | 11003篇 |
2008年 | 11315篇 |
2007年 | 11343篇 |
2006年 | 10012篇 |
2005年 | 9425篇 |
2004年 | 9157篇 |
2003年 | 8746篇 |
2002年 | 8525篇 |
2001年 | 8912篇 |
2000年 | 8360篇 |
1999年 | 8998篇 |
1998年 | 24750篇 |
1997年 | 16885篇 |
1996年 | 12980篇 |
1995年 | 9590篇 |
1994年 | 8211篇 |
1993年 | 8195篇 |
1992年 | 5665篇 |
1991年 | 5491篇 |
1990年 | 5357篇 |
1989年 | 5215篇 |
1988年 | 4896篇 |
1987年 | 4147篇 |
1986年 | 4171篇 |
1985年 | 4743篇 |
1984年 | 4284篇 |
1983年 | 3885篇 |
1982年 | 3625篇 |
1981年 | 3801篇 |
1980年 | 3396篇 |
1979年 | 3344篇 |
1978年 | 3287篇 |
1977年 | 3951篇 |
1976年 | 5186篇 |
1975年 | 2855篇 |
1974年 | 2786篇 |
1973年 | 2792篇 |
1972年 | 2356篇 |
1971年 | 2127篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
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
112.
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
113.
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
114.
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
115.
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
116.
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
117.
118.
A. E. Lapshin Yu. F. Shepelev Yu. I. Smolin E. A. Vasil’eva 《Glass Physics and Chemistry》2008,34(2):182-186
The distribution and structure of tellurium nanoclusters synthesized in crystal channels of the porous silica ZSM-11 are investigated
using the maximum-entropy method and the Rietveld analysis. It is shown that the intercalated tellurium atoms are arranged
in channels of the ZSM-11 zeolite not randomly but in the form of scraps of infinite chains similar to those observed in massive
tellurium. The distances between the nearest neighbor tellurium atoms vary in the range 2.53(4)–2.70(3) ?. The clusters Te4 are formed at the intersections of channels in the structure. These clusters have the form of distorted tetrahedra in which
the tellurium atoms are separated by distances of 2.53(4) and 2.90(4) ?.
Original Russian Text ? A.E. Lapshin, Yu.F. Shepelev, Yu.I. Smolin, E.A. Vasil’eva, 2008, published in Fizika i Khimiya Stekla. 相似文献
119.
To gain a better understanding of the ultra-high molecular weight polyethylene (UHMWPE) wear mechanism in the physiological environment, the effects of protein and lipid constituents of synovial fluid on the specific wear rate of UHMWPE were examined experimentally. The multidirectional sliding pin-on-plate wear tester was employed to simulate the simplified sliding condition of hip joint prostheses. Bovine serum γ-globulin and synthetic l--DPPC were used as model protein and lipid constituents of synovia, respectively. Results of the wear test indicated that the UHMWPE wear rate primarily depended on the protein concentration of the test lubricant. Lipids acted as a boundary lubricant and reduced polyethylene wear in the low protein lubricants. However, the polyethylene wear rate increased with increasing lipid concentrations if the protein concentration was within the physiological level. Increased interactions between protein and lipid molecules and lipid diffusion to polyethylene surface might be responsible for the increased wear. 相似文献
120.
Hung-da Wan F. Frank Chen 《The International Journal of Advanced Manufacturing Technology》2008,38(9-10):995-1005
A Kanban system facilitates lean principles in a simple and effective way. While reportedly successful in many manufacturing firms, the conventional Kanban systems using physical cards suffer from human errors, limited tracking capability, and so on. To make the information flow leaner, software providers add new features to their existing programs for manufacturing systems to computerize Kanban activities. As Web-based technologies advance rapidly, developing an entirely Web-based Kanban system appears to be feasible and promising. This paper presents the advantages, limitations, and challenges of Web-based Kanban systems. An experimental program has been developed based on PHP+MySQL, a popular Web programming platform. The server-executed program features cross-platform compatibility, real-time tracking and performance monitoring, and greatly enhanced information contents compared to physical Kanbans. Human errors are minimized by the automated transactions; nevertheless, the interfacing and data maintenance require further research efforts. 相似文献