全文获取类型
收费全文 | 72318篇 |
免费 | 6068篇 |
国内免费 | 3282篇 |
专业分类
电工技术 | 3603篇 |
技术理论 | 2篇 |
综合类 | 4034篇 |
化学工业 | 13573篇 |
金属工艺 | 2978篇 |
机械仪表 | 2758篇 |
建筑科学 | 5065篇 |
矿业工程 | 6139篇 |
能源动力 | 5718篇 |
轻工业 | 4551篇 |
水利工程 | 536篇 |
石油天然气 | 20005篇 |
武器工业 | 300篇 |
无线电 | 1718篇 |
一般工业技术 | 3705篇 |
冶金工业 | 3817篇 |
原子能技术 | 655篇 |
自动化技术 | 2511篇 |
出版年
2024年 | 226篇 |
2023年 | 916篇 |
2022年 | 1875篇 |
2021年 | 2507篇 |
2020年 | 2623篇 |
2019年 | 2154篇 |
2018年 | 1853篇 |
2017年 | 2040篇 |
2016年 | 2618篇 |
2015年 | 2600篇 |
2014年 | 4646篇 |
2013年 | 4279篇 |
2012年 | 5635篇 |
2011年 | 5818篇 |
2010年 | 3957篇 |
2009年 | 3850篇 |
2008年 | 3248篇 |
2007年 | 4095篇 |
2006年 | 4347篇 |
2005年 | 3635篇 |
2004年 | 3112篇 |
2003年 | 2712篇 |
2002年 | 2305篇 |
2001年 | 2070篇 |
2000年 | 1740篇 |
1999年 | 1398篇 |
1998年 | 1067篇 |
1997年 | 922篇 |
1996年 | 736篇 |
1995年 | 610篇 |
1994年 | 479篇 |
1993年 | 335篇 |
1992年 | 278篇 |
1991年 | 213篇 |
1990年 | 178篇 |
1989年 | 173篇 |
1988年 | 70篇 |
1987年 | 48篇 |
1986年 | 48篇 |
1985年 | 35篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 19篇 |
1981年 | 66篇 |
1980年 | 37篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 5篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
对动态泡沫床处理过磷酸钙含氟尾气的有关技术及费用作了说明 ,指出该方法费用高 ;提出一种新方法 ,该方法不加任何化学助剂 ,采用水作吸收剂 ,只需改变动态泡沫床一些设计参数和选用一种特殊的喷头 (喷头周围设计 1个圆锥形死角区 ,使含氟气体不可能进入该区 )避免了硅胶堵塞。该方法已在湖南浦市化工总厂运行 1年多未发现堵塞 ,同时该法投资少、能耗低、排放尾气达标 相似文献
62.
63.
我国烧碱生产技术概况 总被引:2,自引:0,他引:2
介绍了我国氯碱行业近几年来的发展情况:分析了我国烧碱生产的工艺技术现状。指出了为缩短与世界先进国家的差距需要加快开发关键设备和高性能的离子膜,加强管理。 相似文献
64.
Bubble characteristics and gas hold-up were studied in a two phase (air-aqueous CMC solution) bubble column provided with helical coils and straight tubes as internals. The effects of superficial gas velocity, rheological properties, and volume fraction covered by the internals, on gas hold-up were studied. Hold-up values determined directly and by simultaneous pressure drop measurements matched well. Enhancement of gas hold-up values up to 55 per cent was achieved in systems using internals. The gas hold-up results were also compared with the values obtained from correlations reported in the literature. 相似文献
65.
Phenolic acids and related compounds were separated by gas chromatography using three separate columns. One of these columns was coupled to a Fourier transform infrared spectrometer. The trimethylsilyl derivatives could be separated and identified by comparing the relative retention times of the three different columns. However, where there was overlap, the accompanying infrared data clearly distinguished between the questionable derivatives, thus enabling characterization of all derivatives.The use of trade, firm, or corporation names in this article is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture or the Forest Service of any product or service to the exclusion of others that may be suitable. 相似文献
66.
溴虫腈土壤和甘蓝微量残留量的气相色谱法测定 总被引:12,自引:0,他引:12
采用气相色谱法定量分析溴虫腈土壤和甘蓝微量残留量。样品经丙酮提取 ,液 液分配及氧化铝柱层析法净化后 ,以GC ECD测定 ,DB 170 1毛细管柱 ,氮气为载气 ,柱温 2 6 0℃ ,汽化室温度 2 5 0℃ ,检测器温度 2 80℃ ,外标法定量。该方法快速、准确 ,在 0 0 1~ 2 0 0mg/L范围内线性相关系数r2 =0 9999,平均回收率 90 0 %~ 10 3 6 7% ,变异系数 4 4 8%~ 5 89% ,最小检测量 2× 10 12 g ,最低检出浓度 3 3× 10 4mg/kg。 相似文献
67.
A zero dead-volume all-glass-lined stainless-steel effluent splitter with a modified thermal gradient collector was designed for preparative gas chromatography using glass capillary columns. This system gives efficient collection of extremely pure samples of the 1-ng to 10-g range for spectral analysis and biological testing.Approved as TA 15656 by the director of the Texas Agricultural Experiment Station in cooperation with ARS, USDA. Supported by the Texas Department of Agriculture interagency agreement IAC-0487 (78-79). 相似文献
68.
The solubility of H2S and CO2 in aqueous solutions of the sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), was determined at 40 and 100°C. Partial pressures of C)2 ranged from approximately 2 to 6000 kPa and of H2S from 2 to 2200 kPa. The solubility results were compared with previously reported acid gas solubilities in aqueous monoethanolamine (MEA) solutions. 相似文献
69.
A kinetic study for the one-step conversion of synthesis gas to gasoline on a ZnO–Cr2O3–ZSM-5 catalyst is described. On this catalyst, three reactions are involved in the overall transformation of synthesis gas: the methanol synthesis, the conversion of methanol to hydrocarbons and the water–gas shift reaction. Under the operating conditions selected for the study, it was found that the water–gas shift was at equilibrium and the methanol was completely converted to hydrocarbons. Consequently, it was postulated that the kinetics of the limiting reaction step, the methanol synthesis on the ZnO–Cr2O3 component, was the one that controls the overall reaction rate. Three kinetic model equations describing the rate of synthesis gas conversion on the bifunctional catalyst, were considered to fit the data of the experimental runs performed in a Berty well-mixed reactor. Those equations were derived under very special conditions where the methanol decomposition term could be neglected. It was also observed that in the kinetic equations a term involving the fugacity of CO2 was required to predict the rate properly. The catalyst deactivation was also taken into account in the analysis. 相似文献
70.
B. S. Goodrich E. R. Hesterman K. S. Shaw R. Mykytowycz 《Journal of chemical ecology》1981,7(5):817-827
A study has been made of the volatile constituents in the vapors collected from fecal pellets of wild rabbits,Oryctolagus cuniculus. Measurements of changes in the heart rates of adult male rabbits exposed to the effluent of a gas chromatographic capillary column were used to indicate the presence of compounds which may be of behavioral significance. Combined with the use of high-resolution columns in gas chromatography and gas chromatography-mass spectrometry, this approach has implicated several classes of compounds, including volatile fatty acids and phenols, which in certain absolute or relative concentrations may be involved in the formation of signals of territorial importance. 相似文献