全文获取类型
收费全文 | 183055篇 |
免费 | 24210篇 |
国内免费 | 6975篇 |
专业分类
电工技术 | 10391篇 |
技术理论 | 12篇 |
综合类 | 9869篇 |
化学工业 | 39483篇 |
金属工艺 | 8414篇 |
机械仪表 | 10036篇 |
建筑科学 | 13838篇 |
矿业工程 | 3601篇 |
能源动力 | 5027篇 |
轻工业 | 16245篇 |
水利工程 | 3210篇 |
石油天然气 | 7164篇 |
武器工业 | 1174篇 |
无线电 | 24141篇 |
一般工业技术 | 27957篇 |
冶金工业 | 7371篇 |
原子能技术 | 1648篇 |
自动化技术 | 24659篇 |
出版年
2024年 | 688篇 |
2023年 | 2351篇 |
2022年 | 4386篇 |
2021年 | 6175篇 |
2020年 | 5760篇 |
2019年 | 6485篇 |
2018年 | 6693篇 |
2017年 | 7616篇 |
2016年 | 7727篇 |
2015年 | 9143篇 |
2014年 | 10744篇 |
2013年 | 13373篇 |
2012年 | 12273篇 |
2011年 | 12395篇 |
2010年 | 11627篇 |
2009年 | 11234篇 |
2008年 | 10630篇 |
2007年 | 10025篇 |
2006年 | 9783篇 |
2005年 | 8295篇 |
2004年 | 6099篇 |
2003年 | 5551篇 |
2002年 | 5497篇 |
2001年 | 4948篇 |
2000年 | 4687篇 |
1999年 | 3978篇 |
1998年 | 3068篇 |
1997年 | 2451篇 |
1996年 | 2185篇 |
1995年 | 1796篇 |
1994年 | 1484篇 |
1993年 | 1090篇 |
1992年 | 838篇 |
1991年 | 683篇 |
1990年 | 511篇 |
1989年 | 448篇 |
1988年 | 376篇 |
1987年 | 224篇 |
1986年 | 194篇 |
1985年 | 139篇 |
1984年 | 118篇 |
1983年 | 73篇 |
1982年 | 76篇 |
1981年 | 68篇 |
1980年 | 53篇 |
1979年 | 38篇 |
1978年 | 15篇 |
1977年 | 37篇 |
1976年 | 19篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
62.
63.
64.
The Synthesis of Sulfated Titanium Oxide Nanotubes 总被引:1,自引:0,他引:1
Chiu-Hsun Lin Shu-Hua Chien Jiunn-Hsing Chao Chyi-Yang Sheu Yu-Cheng Cheng Ya-Jean Huang Chih-Hsiang Tsai 《Catalysis Letters》2002,80(3-4):153-159
TiO2 nanotubes can be prepared in gram quantities by treating anatase TiO2 powder with concentrated NaOH solution. These TiO2 nanotubes acquired strong acidity after being impregnated with sulfuric acid solution and calcined at 300 °C. The anatase TiO2 powder used to prepare the nanotube did not catalyze the esterification between cyclohexanol and acetic acid, while sulfated TiO2 nanotubes were very reactive toward the esterification reaction. 相似文献
65.
66.
Chen H.H. Huang T.S. 《IEEE transactions on pattern analysis and machine intelligence》1991,13(9):872-878
The specific problem addressed by the authors is how to detect the true match of a fourth point from among candidate matches in a situation in which three points have already been matched. The two sets of points to be matched are both subject to measurement errors. The depth error is more dominant than errors in the other two coordinates; however, the exact statistical distribution of the measurement errors is not known. The authors present a new method for solving the problem. The method is based on the technique of motion analysis using orthographic views. It discards the noisy z (depth) coordinates and uses only the x and y coordinates of the points to verify the match. The effect of depth errors on the motion estimate is completely prevented. Results show that this method is substantially more effective than previous methods that use all three coordinates 相似文献
67.
Hong Jeong Jeong‐Ho Park 《International Journal of Adaptive Control and Signal Processing》2002,16(1):1-23
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
68.
Qin‐Tao Liu Malcolm R Clench Judith L Kinderlerer 《Journal of the science of food and agriculture》2002,82(5):553-558
Structural isomers of monoacylglycerols (monoglycerides, MAGs) were identified and compared after degradation of butter oil by two strains of Penicillium roquefortii and a commercial lipase from P roquefortii (EC 3.1.1.3) at pH 7.0 and 10 °C. The conditions were selected as they were comparable with those used in the manufacture of blue mould‐ripened cheese. The commercial lipase was selected to compare with the fungal strains in terms of acyl migration. Results showed that the main isomers formed by lipolysis with the commercial lipase were sn‐2 MAGs (64 mol%), whilst spores and emerging mycelia of P roquefortii produced mainly sn‐1(3) MAGs (83–90 mol%). The work reported here may lead to further assessment of different MAG structural isomers as natural preservatives in foods and dairy products. © 2002 Society of Chemical Industry 相似文献
69.
70.