全文获取类型
收费全文 | 179860篇 |
免费 | 20507篇 |
国内免费 | 11271篇 |
专业分类
电工技术 | 11032篇 |
技术理论 | 4篇 |
综合类 | 12788篇 |
化学工业 | 26507篇 |
金属工艺 | 4189篇 |
机械仪表 | 10308篇 |
建筑科学 | 9224篇 |
矿业工程 | 8546篇 |
能源动力 | 7127篇 |
轻工业 | 16660篇 |
水利工程 | 1251篇 |
石油天然气 | 20209篇 |
武器工业 | 1610篇 |
无线电 | 26116篇 |
一般工业技术 | 13005篇 |
冶金工业 | 4608篇 |
原子能技术 | 1336篇 |
自动化技术 | 37118篇 |
出版年
2024年 | 1025篇 |
2023年 | 3146篇 |
2022年 | 5597篇 |
2021年 | 6559篇 |
2020年 | 6688篇 |
2019年 | 5554篇 |
2018年 | 5024篇 |
2017年 | 6430篇 |
2016年 | 7078篇 |
2015年 | 7938篇 |
2014年 | 12218篇 |
2013年 | 11290篇 |
2012年 | 14401篇 |
2011年 | 14753篇 |
2010年 | 10619篇 |
2009年 | 10767篇 |
2008年 | 10000篇 |
2007年 | 11949篇 |
2006年 | 10997篇 |
2005年 | 9031篇 |
2004年 | 7246篇 |
2003年 | 6202篇 |
2002年 | 5150篇 |
2001年 | 4280篇 |
2000年 | 3541篇 |
1999年 | 2828篇 |
1998年 | 2201篇 |
1997年 | 1984篇 |
1996年 | 1512篇 |
1995年 | 1244篇 |
1994年 | 1020篇 |
1993年 | 766篇 |
1992年 | 627篇 |
1991年 | 523篇 |
1990年 | 380篇 |
1989年 | 273篇 |
1988年 | 150篇 |
1987年 | 84篇 |
1986年 | 83篇 |
1985年 | 69篇 |
1984年 | 74篇 |
1983年 | 52篇 |
1982年 | 39篇 |
1981年 | 85篇 |
1980年 | 63篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1951年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
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
122.
碳纤维(CF)表面经氧等离子、KH550和 LiAlH_4处理后,其物理和化学性能得以改善.由于提高了 CF 和树脂间的联结,使 CF 复合材料的层间剪切强度提高50%以上,在湿热下的强度保留率达94%以上.使用纤维接触角测定仪,SEM 和 XPS 等对 CF 表面的浸润性、形态和化学组成进行了研究.实验指出:CF 经等离子和 KH550处理后,其临界表面能有了提高;CF 本身仅受氧离子刻蚀,故其拉伸强度的损失小于其他处理方法. 相似文献
123.
聚丙烯纤维母粒着色生产技术 总被引:2,自引:0,他引:2
概述了聚丙烯母粒色纺的生产技术,提出了色母粒制备的质量要求:颜料粒径≤1.0μm,细且丝颜料粒径≤0.5μm;压力过滤值≤0.15MPa·cm~2/g;色母粒热稳定性280~300℃.色母粒的加入对纺丝工艺与产品质量指标有影响,喷丝板换板周期色纺丝约为本色纺的一半,纤维强力约降低10%.依据有关配色定律可优化配方工艺,降低成本,增加效益. 相似文献
124.
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
125.
126.
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
127.
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
128.
Experimental data on the kinetics of methane hydrate formation in aqueous electrolyte solutions are reported. The experiments were carried out in a semi-batch stirred tank reactor in three NaCl and two KCl solutions as well as in a solution containing a mixture of NaCl and KCl at three different nominal temperatures from 270 to 274 K and at pressures ranging from 3.78 to 7.08 MPa. The kinetic model developed by Englezos et al. (1987a) was adapted to predict the growth of hydrates. The model is based on the crystallisation theory coupled with the two-film theory for gas absorption in the liquid phase. The kinetic rate constant which appears in the model was that obtained earlier for methane hydrate formation in pure water. The effect of the electrolytes was taken into account through the computation of the three-phase equilibrium conditions and the corresponding fugacities. Overall, the model predictions match the experimental data very well with the largest prediction error being less than 10%. 相似文献
129.
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
130.
高冲击玻纤增强聚丙烯的研制与应用 总被引:2,自引:1,他引:2
利用玻璃纤维、SBS橡胶和高密度聚乙烯增韧聚丙烯。增韧后的聚丙烯冲击强度是只用玻纤增强的2倍以上,而其它性能影响较小。 相似文献