全文获取类型
收费全文 | 280059篇 |
免费 | 3573篇 |
国内免费 | 1301篇 |
专业分类
电工技术 | 4819篇 |
综合类 | 519篇 |
化学工业 | 40530篇 |
金属工艺 | 11166篇 |
机械仪表 | 8451篇 |
建筑科学 | 6489篇 |
矿业工程 | 1596篇 |
能源动力 | 7070篇 |
轻工业 | 22727篇 |
水利工程 | 3044篇 |
石油天然气 | 5788篇 |
武器工业 | 43篇 |
无线电 | 33728篇 |
一般工业技术 | 56778篇 |
冶金工业 | 51548篇 |
原子能技术 | 7505篇 |
自动化技术 | 23132篇 |
出版年
2021年 | 2184篇 |
2019年 | 2084篇 |
2018年 | 3618篇 |
2017年 | 3698篇 |
2016年 | 3942篇 |
2015年 | 2521篇 |
2014年 | 4414篇 |
2013年 | 12081篇 |
2012年 | 7160篇 |
2011年 | 9821篇 |
2010年 | 7612篇 |
2009年 | 8823篇 |
2008年 | 9216篇 |
2007年 | 9235篇 |
2006年 | 7883篇 |
2005年 | 7316篇 |
2004年 | 7255篇 |
2003年 | 7033篇 |
2002年 | 6767篇 |
2001年 | 6895篇 |
2000年 | 6515篇 |
1999年 | 6817篇 |
1998年 | 16495篇 |
1997年 | 11710篇 |
1996年 | 9006篇 |
1995年 | 6903篇 |
1994年 | 6057篇 |
1993年 | 6111篇 |
1992年 | 4430篇 |
1991年 | 4210篇 |
1990年 | 4100篇 |
1989年 | 4091篇 |
1988年 | 3773篇 |
1987年 | 3419篇 |
1986年 | 3425篇 |
1985年 | 3764篇 |
1984年 | 3481篇 |
1983年 | 3242篇 |
1982年 | 3038篇 |
1981年 | 3052篇 |
1980年 | 3049篇 |
1979年 | 2837篇 |
1978年 | 2886篇 |
1977年 | 3163篇 |
1976年 | 4151篇 |
1975年 | 2429篇 |
1974年 | 2390篇 |
1973年 | 2415篇 |
1972年 | 2029篇 |
1971年 | 1787篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
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
62.
Nicole Jacqueline Jensen Helena Zander Wodschow Malin Nilsson Jrgen Rungby 《International journal of molecular sciences》2020,21(22)
Under normal physiological conditions the brain primarily utilizes glucose for ATP generation. However, in situations where glucose is sparse, e.g., during prolonged fasting, ketone bodies become an important energy source for the brain. The brain’s utilization of ketones seems to depend mainly on the concentration in the blood, thus many dietary approaches such as ketogenic diets, ingestion of ketogenic medium-chain fatty acids or exogenous ketones, facilitate significant changes in the brain’s metabolism. Therefore, these approaches may ameliorate the energy crisis in neurodegenerative diseases, which are characterized by a deterioration of the brain’s glucose metabolism, providing a therapeutic advantage in these diseases. Most clinical studies examining the neuroprotective role of ketone bodies have been conducted in patients with Alzheimer’s disease, where brain imaging studies support the notion of enhancing brain energy metabolism with ketones. Likewise, a few studies show modest functional improvements in patients with Parkinson’s disease and cognitive benefits in patients with—or at risk of—Alzheimer’s disease after ketogenic interventions. Here, we summarize current knowledge on how ketogenic interventions support brain metabolism and discuss the therapeutic role of ketones in neurodegenerative disease, emphasizing clinical data. 相似文献
63.
64.
65.
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
66.
67.
68.
69.
70.