全文获取类型
收费全文 | 728篇 |
免费 | 10篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 17篇 |
综合类 | 6篇 |
化学工业 | 127篇 |
金属工艺 | 22篇 |
机械仪表 | 29篇 |
建筑科学 | 17篇 |
矿业工程 | 1篇 |
能源动力 | 46篇 |
轻工业 | 29篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
武器工业 | 1篇 |
无线电 | 163篇 |
一般工业技术 | 137篇 |
冶金工业 | 56篇 |
原子能技术 | 3篇 |
自动化技术 | 87篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 60篇 |
2012年 | 25篇 |
2011年 | 28篇 |
2010年 | 29篇 |
2009年 | 34篇 |
2008年 | 38篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 20篇 |
2004年 | 26篇 |
2003年 | 33篇 |
2002年 | 22篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 25篇 |
1998年 | 27篇 |
1997年 | 21篇 |
1996年 | 29篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 26篇 |
1992年 | 10篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有745条查询结果,搜索用时 15 毫秒
111.
112.
Liou A.E.-L. Sivertsen K.N. Michelson D.G. 《Wireless Communications, IEEE Transactions on》2009,8(8):3975-3979
We observed temporal fading on 1.9 GHz fixed wireless channels during short-term measurements at 107 different locations in a suburban macrocell environment characterized by flat terrain and heavy foliage in order to determine how the rate of fading varies with average wind speed and distance. For each location, we estimated: (1) the Ricean K-factor using a momentbased estimator and (2) an equivalent Doppler frequency which is related to the maximum Doppler frequency by a factor that depends upon the shape of the Doppler spectrum. We did so by fitting the measured level crossing rate (LCR) and average fade duration (AFD) distributions to expressions normally justified for mobile wireless links using a method recently proposed by Feick, Valenzuela and Ahumada (2007). As has been observed at other sites, the Ricean K-factor decreased with both average wind speed and distance. However, we found that the equivalent Doppler frequency was effectively uncorrelated with wind speed and noticeably increased with distance. Similar measurements at other sites will be required to determine the extent to which these trends are affected by foliage density and tower height. 相似文献
113.
Huei Tarng Liou 《臭氧:科学与工程》2009,31(1):53-59
We report on an on-site 500 RT cooling tower ozone treatment process, in which chemicals other than ozone itself were completely eliminated. Ozone in an amount leading to less than 0.1 ppm of dissolved ozone was continuously introduced via side-stream injection into the circulating water returning from the chiller. The ozonated water was initially made to flow from the distributor to the filler in order to eliminate the growth of algae, and then to the chiller to reduce the corrosion and the fouling in the water. Positive ions such as Ca+2 and Mg+2 in the circulating water were precipitated by chelating them with carboxylic acids formed by the oxidation of organic compounds. We observed that using an ozone dosage of 0.1 ppm resulted in a colony-forming unit (CFU) less than 2 × 103 /mL. With that well-controlled CFU, corrosion controlling and scale reducing were achieved as well. 相似文献
114.
Ce0.9Gd0.1O1.95 ceramics were prepared using a simple and effective process in this study. Without any prior calcination, the mixture of raw materials was pressed and sintered directly. The reaction of the raw materials occurred during the heating up period by passing the calcination stage in the conventional solid-state reaction method. More than 99.5% of theoretical density was obtained for Ce0.9Gd0.1O1.95 sintering at 1500–1600 °C. Fine grains (<1 μm) formed in pellets sintered at 1450 °C. The homogeneity of grains increased with the sintering temperature. The grains grew to >4.5 μm in pellets sintered at 1600 °C. The reactive-sintering process is proved to be a simple and effective method in preparing Ce0.9Gd0.1O1.95 ceramics for solid electrolyte application. 相似文献
115.
Low-temperature synthesis of BiNbO4 ceramics using reaction-sintering process was investigated. Orthorhombic BiNbO4 phase together with minor triclinic BiNbO4 phase were found in the pellets. The phase transition temperature in BiNbO4 with 0.5 wt% CuO addition was lowered from 960 °C via traditional route to 880 °C when the reaction-sintering process was used. After 920 °C sintering for 4 and 6 h, densities 6.8–6.85 g/cm3 (94% of the theoretical value) were obtained. The abnormal grain growth in BiNbO4 via traditional route was not observed in this study. 相似文献
116.
This paper discusses the role of government mortgage guarantee schemes in housing policy. It explores different types of government mortgage guarantee scheme, which play different roles, in eight countries. Mortgage guarantee schemes interfere in the mortgage market in order to improve access to mortgages. Such guarantees can be shaped as self-supporting instruments or as subsidies. If the latter is the case the issue of competition and a level playing field is relevant. This paper explores the US and the Dutch guarantee models in depth in order to answer the question of whether these schemes are unsubsidised mortgage market instruments or subsidised programmes. It concludes by reflecting on the meaning of the outcomes in the context of EU competition policy. 相似文献
117.
简述了甲醇装置甲醇分离器的基本结构和技改前存在的问题,介绍了复合型高效捕沫器的基本原理以及应用于甲醇分离器的实际效果,分析了技改中有待解决的问题和原因。技改效果表明,采用复合型高效捕沫器后,甲醇分离器的分离效率由28.9%提高至94.4%;技改投资为30万元/套,投资回收期为2个月。 相似文献
118.
Pei-Yi Chen Wan-Yun Gao Je-Wen Liou Ching-Yen Lin Ming-Jiuan Wu Jui-Hung Yen 《International journal of molecular sciences》2021,22(14)
Dyslipidemia is characterized by increasing plasma levels of low-density lipoprotein-cholesterol (LDL-C), triglycerides (TGs) and TG-rich lipoproteins (TGRLs) and is a major risk factor for the development of atherosclerotic cardiovascular disorders (ASCVDs). It is important to understand the metabolic mechanisms underlying dyslipidemia to develop effective strategies against ASCVDs. Angiopoietin-like 3 (ANGPTL3), a member of the angiopoietin-like protein family exclusively synthesized in the liver, has been demonstrated to be a critical regulator of lipoprotein metabolism to inhibit lipoprotein lipase (LPL) activity. Genetic, biochemical, and clinical studies in animals and humans have shown that loss of function, inactivation, or downregulated expression of ANGPTL3 is associated with an obvious reduction in plasma levels of TGs, LDL-C, and high-density lipoprotein-cholesterol (HDL-C), atherosclerotic lesions, and the risk of cardiovascular events. Therefore, ANGPTL3 is considered an alternative target for lipid-lowering therapy. Emerging studies have focused on ANGPTL3 inhibition via antisense oligonucleotides (ASOs) and monoclonal antibody-based therapies, which have been carried out in mouse or monkey models and in human clinical studies for the management of dyslipidemia and ASCVDs. This review will summarize the current literature on the important role of ANGPTL3 in controlling lipoprotein metabolism and dyslipidemia, with an emphasis on anti-ANGPTL3 therapies as a potential strategy for the treatment of dyslipidemia and ASCVDs. 相似文献
119.
Peng JY Aston JA Gunn RN Liou CY Ashburner J 《IEEE transactions on medical imaging》2008,27(9):1356-1369
120.
Journal of Real-Time Image Processing - Due to the effect of lighting and complex background, most visual hand gesture recognition systems work only under restricted environments. Here, we propose... 相似文献