全文获取类型
收费全文 | 283644篇 |
免费 | 3727篇 |
国内免费 | 1356篇 |
专业分类
电工技术 | 4863篇 |
综合类 | 528篇 |
化学工业 | 41235篇 |
金属工艺 | 11201篇 |
机械仪表 | 8585篇 |
建筑科学 | 6632篇 |
矿业工程 | 1631篇 |
能源动力 | 7096篇 |
轻工业 | 22931篇 |
水利工程 | 3119篇 |
石油天然气 | 5797篇 |
武器工业 | 43篇 |
无线电 | 33831篇 |
一般工业技术 | 57422篇 |
冶金工业 | 52344篇 |
原子能技术 | 7530篇 |
自动化技术 | 23939篇 |
出版年
2021年 | 2247篇 |
2019年 | 2145篇 |
2018年 | 3710篇 |
2017年 | 3776篇 |
2016年 | 4011篇 |
2015年 | 2606篇 |
2014年 | 4523篇 |
2013年 | 12347篇 |
2012年 | 7360篇 |
2011年 | 10075篇 |
2010年 | 7811篇 |
2009年 | 8987篇 |
2008年 | 9426篇 |
2007年 | 9454篇 |
2006年 | 8088篇 |
2005年 | 7500篇 |
2004年 | 7427篇 |
2003年 | 7163篇 |
2002年 | 6917篇 |
2001年 | 6968篇 |
2000年 | 6573篇 |
1999年 | 6879篇 |
1998年 | 16411篇 |
1997年 | 11691篇 |
1996年 | 9021篇 |
1995年 | 6939篇 |
1994年 | 6114篇 |
1993年 | 6132篇 |
1992年 | 4495篇 |
1991年 | 4231篇 |
1990年 | 4164篇 |
1989年 | 4127篇 |
1988年 | 3819篇 |
1987年 | 3469篇 |
1986年 | 3444篇 |
1985年 | 3803篇 |
1984年 | 3513篇 |
1983年 | 3278篇 |
1982年 | 3079篇 |
1981年 | 3081篇 |
1980年 | 3073篇 |
1979年 | 2870篇 |
1978年 | 2900篇 |
1977年 | 3180篇 |
1976年 | 4122篇 |
1975年 | 2449篇 |
1974年 | 2395篇 |
1973年 | 2414篇 |
1972年 | 2031篇 |
1971年 | 1787篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Madhu H. C. Edachery Vimal Lijesh K. P. Perugu Chandra Shekhar Kailas Satish V. 《Metallurgical and Materials Transactions A》2020,51(8):4086-4099
Metallurgical and Materials Transactions A - Hybrid nanocomposites have potential as wear-resistant materials. However, synthesizing these nanocomposites by conventional molten state methods result... 相似文献
62.
Zavadiuk S.V. Loboda P.I. Soloviova T.O. Trosnikova I.Iu. Karasevska O.P. 《Powder Metallurgy and Metal Ceramics》2020,59(1-2):22-28
Powder Metallurgy and Metal Ceramics - The properties of sintered and heat-treated steels produced from the Catamold 8740 material by powder injection molding were examined. Parts made of the... 相似文献
63.
64.
65.
Paul Geoerg Florian Berchtold Steven Gwynne Karen Boyce Stefan Holl Anja Hofmann 《火与材料》2019,43(7):759-781
To quantify the evacuation process, evacuation practitioners use engineering egress data describing the occupant movement characteristics. These data are typically based to young and fit populations. However, the movement abilities of occupants who might be involved in evacuations are becoming more variable—with the building populations of today typically including increasing numbers of individuals: with impairments or who are otherwise elderly or generally less mobile. Thus, there will be an increasing proportion of building occupants with reduced ability to egress. For safe evacuation, there is therefore a need to provide valid engineering egress data considering pedestrians with disabilities. Gwynne and Boyce recently compiled a series of data sets related to the evacuation process to support practitioner activities in the chapter Engineering Data in the SFPE Handbook of Fire Protection Engineering. This paper supplements these data sets by providing information on and presenting data obtained from additional research related to the premovement and horizontal movement of participants with physical‐, cognitive‐, or age‐related disabilities. The aim is to provide an overview of currently available data sets related to, and key factors affecting the egress performance of, mixed ability populations which could be used to guide fire safety engineering decisions in the context of building design. 相似文献
66.
Marcela Stoia Cornelia Păcurariu Ciprian Mihali Iosif Mălăescu Cătălin Nicolae Marin Aylin Căpraru 《Ceramics International》2019,45(2):2725-2735
Magnetic MnFe2O4 nanopowders were synthesized by an original solvothermal method in the absence and in the presence of tetra-n-butylammonium bromide (TBAB) and Tween 80 (TW) as surfactants. Manganese ferrite/polyaniline (PANI) hybrid materials were synthesized by in situ polymerization of aniline on the surface of MnFe2O4 using ammonium persulfate as oxidant. The purpose of the study was to investigate the influence of the two surfactants on the properties of the MnFe2O4 powders and of their composites with PANI. The specific surface area, the cumulative surface area of pores and the cumulative volume of pores are influenced by the nature of surfactant in case of MnFe2O4 powders and are higher by comparison to those of the MnFe2O4/PANI hybrid materials. The values of saturation magnetization in case of MnFe2O4 powders are higher than those of the hybrid materials and are not influenced by the surfactant nature. These features revealed that MnFe2O4 powders can be efficiently used as adsorbents for the purification of wastewaters. The values of the electrical conductivity of the composites exhibit a significant increase in comparison to the MnFe2O4 powders and depend on the surfactant nature. The highest value of electrical conductivity was achieved by the composite obtained using Tween 80 as surfactant (σDC = 54.5·10?5S?m?1) which was close to that of PANI (σDC = 61.2·10?5 S?m?1). The fact that the magnetic and electric properties of the synthesized MnFe2O4/PANI composites can be changed by design, demonstrate the high potential of these materials to be used in magneto-electric applications. 相似文献
67.
68.
69.
70.