全文获取类型
收费全文 | 2378篇 |
免费 | 24篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 21篇 |
综合类 | 10篇 |
化学工业 | 170篇 |
金属工艺 | 22篇 |
机械仪表 | 25篇 |
建筑科学 | 61篇 |
矿业工程 | 4篇 |
能源动力 | 16篇 |
轻工业 | 126篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 61篇 |
一般工业技术 | 98篇 |
冶金工业 | 1680篇 |
原子能技术 | 13篇 |
自动化技术 | 97篇 |
出版年
2021年 | 11篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 41篇 |
2012年 | 26篇 |
2011年 | 21篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 24篇 |
2007年 | 36篇 |
2006年 | 19篇 |
2005年 | 57篇 |
2004年 | 15篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 19篇 |
2000年 | 17篇 |
1999年 | 62篇 |
1998年 | 485篇 |
1997年 | 293篇 |
1996年 | 198篇 |
1995年 | 104篇 |
1994年 | 99篇 |
1993年 | 100篇 |
1992年 | 17篇 |
1991年 | 27篇 |
1990年 | 20篇 |
1989年 | 28篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 23篇 |
1985年 | 32篇 |
1984年 | 16篇 |
1983年 | 24篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 25篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 56篇 |
1976年 | 121篇 |
1975年 | 22篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1971年 | 6篇 |
1970年 | 5篇 |
排序方式: 共有2418条查询结果,搜索用时 62 毫秒
61.
Ahmad Jalloh Antwoine Flowers Charles Hudson Dale Chaput Jennifer Guergues Stanley M. Stevens Jr. Paula C. Bickford 《International journal of molecular sciences》2021,22(12)
Microglial activity in the aging neuroimmune system is a central player in aging-related dysfunction. Aging alters microglial function via shifts in protein signaling cascades. These shifts can propagate neurodegenerative pathology. Therapeutics require a multifaceted approach to understand and address the stochastic nature of this process. Polyphenols offer one such means of rectifying age-related decline. Our group used mass spectrometry (MS) analysis to explicate the complex nature of these aging microglial pathways. In our first experiment, we compared primary microglia isolated from young and aged rats and identified 197 significantly differentially expressed proteins between these groups. Then, we performed bioinformatic analysis to explore differences in canonical signaling cascades related to microglial homeostasis and function with age. In a second experiment, we investigated changes to these pathways in aged animals after 30-day dietary supplementation with NT-020, which is a blend of polyphenols. We identified 144 differentially expressed proteins between the NT-020 group and the control diet group via MS analysis. Bioinformatic analysis predicted an NT-020 driven reversal in the upregulation of age-related canonical pathways that control inflammation, cellular metabolism, and proteostasis. Our results highlight salient aspects of microglial aging at the level of protein interactions and demonstrate a potential role of polyphenols as therapeutics for age-associated dysfunction. 相似文献
62.
63.
T. Sadhasivam M. Sterlin Leo Hudson Sunita K. Pandey Ashish Bhatnagar Milind K. Singh K. Gurunathan O.N. Srivastava 《International Journal of Hydrogen Energy》2013
This paper reports the catalytic effects of mischmetal (Mm) and mischmetal oxide (Mm-oxide) on improving the dehydrogenation and rehydrogenation behaviour of magnesium hydride (MgH2). It has been found that 5 wt.% is the optimum catalyst (Mm/Mm-oxide) concentration for MgH2. The Mm and Mm-oxide catalyzed MgH2 exhibits hydrogen desorption at significantly lower temperature and also fast rehydrogenation kinetics compared to ball-milled MgH2 under identical conditions of temperature and pressure. The onset desorption temperature for MgH2 catalyzed with Mm and Mm-oxide are 323 °C and 305 °C, respectively. Whereas the onset desorption temperature for the ball-milled MgH2 is 381 °C. Thus, there is a lowering of onset desorption temperature by 58 °C for Mm and by 76 °C for Mm-oxide. The dehydrogenation activation energy of Mm-oxide catalyzed MgH2 is 66 kJ/mol. It is 35 kJ/mol lower than ball-milled MgH2. Additionally, the Mm-oxide catalyzed dehydrogenated Mg exhibits faster rehydrogenation kinetics. It has been noticed that in the first 10 min, the Mm-oxide catalyzed Mg (dehydrogenated MgH2) has absorbed up to 4.75 wt.% H2 at 315 °C under 15 atmosphere hydrogen pressure. The activation energy determined for the rehydrogenation of Mm-oxide catalyzed Mg is ∼62 kJ/mol, whereas that for the ball-milled Mg alone is ∼91 kJ/mol. Thus, there is a decrease in absorption activation energy by ∼29 kJ/mol for the Mm-oxide catalyzed Mg. In addition, Mm-oxide is the native mixture of CeO2 and La2O3 which makes the duo a better catalyst than CeO2, which is known to be an effective catalyst for MgH2. This takes place due to the synergistic effect of CeO2 and La2O3. It can thus be said that Mm-oxide is an effective catalyst for improving the hydrogen sorption behaviour of MgH2. 相似文献
64.
各种引气剂以及抑泡剂对混凝土经时变化状态等的影响 总被引:1,自引:0,他引:1
众所周知,采用粉煤灰制备混凝土,因粉煤灰成分中含有未燃炭等微粒子,容易造成阴离子型引气剂吸附在这些微粒子上,导致含气量经时损失.同时在混凝土的制备、运输过程中,因受采用的材料、拌和状态等物理因素影响,还会发生含气量经时增加的现象.所以在制备、管理混凝土时,如何保证出机初期一定的含气量、缓解含气量的经时损失或经时增加,是一项极其关键的技术.本文将就采用能改善上述状态的引气剂、抑泡剂拌和混凝土,对混凝土的经时变化以及抗冻融性等特征产生的影响进行论述. 相似文献
65.
We evaluated the ability of a portable ozone generating machine (Viroforce 1000) to inactivate 13 different species of environmental fungi. Samples, prepared as wet or dried films, were subjected to one or two cycles of treatment (35 ppm ozone for 20 minutes, with a short burst of?>90%?relative humidity), and measured for residual viability. Treatments could inactivate 3 log10 cfu (colony forming units) of most of the fungi, both in the laboratory and in simulated field conditions, on various surfaces. We conclude that the ozone generator would be a valuable decontamination tool for mold removal in buildings. 相似文献
66.
Brian Shelmadine Matt Cooke Thomas Buford Geoffrey Hudson Liz Redd Brian Leutholtz Darryn S Willoughby 《Journal of the International Society of Sports Nutrition》2009,6(1):16
Purpose
This study determined the effects of 28 days of heavy resistance exercise combined with the nutritional supplement, NO-Shotgun?, on body composition, muscle strength and mass, markers of satellite cell activation, and clinical safety markers. 相似文献67.
68.
Dipalmitoyl phosphatidyl ethanolamine (DPE) is a potent synergist for a wide range of primary antioxidants in edible oils
at elevated temperature, i.e., above 80 C. At lower temperatures it has very little synergistic action. At 120 C the synergistic
effect increases progressively as the concentration of synergist increases from 0.025% to 0.25%. At a given level of synergist,
its effect is proportionately greater at low rather than high levels of primary antioxidant. 相似文献
69.
The preparation of films from starch and their degradation by amylase enzymes is described. Starch acetate was prepared by acetylation of starch with a pyridine/acetic anhydride mixture. The resulting polymer was cast into films from solutions of 90% formic acid. A series of films with a range of acetyl content were then exposed to buffered amylase solutions and the retained tensile strength measured. It was found that with a sufficient acetyl content the wet strength of the films was maintained in the aqueous solutions, but that the acetyl content was sufficiently low enough to permit degradation by a mixture of alpha and beta amylases within a period of 1 h. These films could be useful as membranes in bioreactors, which could be degraded at will by the addition of enzymes to the system. © 1993 John Wiley & Sons, Inc. 相似文献
70.
Olutosin T. Odumosu Janet Sinha Bertram J. F. Hudson 《Journal of the science of food and agriculture》1979,30(5):515-520
Seven chemical methods, namely peroxide value (PV), totox value (TV), anisidine value (AV), conjugable oxidation products (COP), oxodiene value (OV), induction period (IP), iodine value (IV) and a sensory analytical procedure (flavour score, FS) have been used in evaluating the oxidation state of groundnut oil heated at 100°C for varying lengths of time up to 20 h. As oxidation progressed, PV, TV, AV, COP and OV increased. IP and IV decreased with oxidation while FS showed a progressive deterioration on a seven-point scale from bland to very rancid. On the basis of sensitivity to oxidative changes, five of the methods (PV, TV, IP, IV and FS) were found to be satisfactory. However, the best correlation with flavour scores were obtained in the case of IP, IV and OV while AV and COP correlated poorly with FS. Three methods (PV, IP and IV) best satisfied the combined criteria of sensitivity to oxidative changes and correlation with flavour. 相似文献