全文获取类型
收费全文 | 101688篇 |
免费 | 10521篇 |
国内免费 | 6019篇 |
学科分类
工业技术 | 118228篇 |
出版年
2024年 | 578篇 |
2023年 | 1909篇 |
2022年 | 3761篇 |
2021年 | 5277篇 |
2020年 | 4036篇 |
2019年 | 3012篇 |
2018年 | 3446篇 |
2017年 | 3763篇 |
2016年 | 3343篇 |
2015年 | 4864篇 |
2014年 | 6062篇 |
2013年 | 7093篇 |
2012年 | 8187篇 |
2011年 | 8412篇 |
2010年 | 7530篇 |
2009年 | 7037篇 |
2008年 | 6616篇 |
2007年 | 6025篇 |
2006年 | 5462篇 |
2005年 | 4416篇 |
2004年 | 2864篇 |
2003年 | 2141篇 |
2002年 | 1929篇 |
2001年 | 1519篇 |
2000年 | 1423篇 |
1999年 | 1479篇 |
1998年 | 1112篇 |
1997年 | 985篇 |
1996年 | 872篇 |
1995年 | 727篇 |
1994年 | 567篇 |
1993年 | 408篇 |
1992年 | 300篇 |
1991年 | 256篇 |
1990年 | 179篇 |
1989年 | 148篇 |
1988年 | 128篇 |
1987年 | 78篇 |
1986年 | 72篇 |
1985年 | 33篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 29篇 |
1981年 | 22篇 |
1980年 | 28篇 |
1979年 | 17篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1959年 | 14篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
电站锅炉制粉系统的爆炸原因与防范对策 总被引:1,自引:0,他引:1
火力发电厂制粉系统爆炸事故时有发生 ,重大设备损坏 ,造成了严重的经济损失。本文通过分析研究 ,找出制粉系统爆炸的原因 ,从措施上、煤的质量控制上及制粉系统结构改造上提出了防范的对策。 相似文献
24.
Yu‐Qing Cao Zhan Zhang Yan‐Xin Guo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1441-1444
A new efficient method for synthesising nitriles, important organic reagents, is reported in this paper. In an environmentally benign solvent‐free system, aryl carboxylic acids were converted into the corresponding nitriles via one‐pot reactions, by amidation with ethyl carbamate followed by dehydration with thionyl chloride, in excellent yields. The results showed that the method has the advantages of lower cost, higher yield, less pollution and greater ease of work‐up. Copyright © 2008 Society of Chemical Industry 相似文献
25.
26.
Sosnowchik B.D. Azevedo R.G. Cao A. Lin L. Pisano A.P. 《Advanced Packaging, IEEE Transactions on》2005,28(4):626-634
This paper presents the rapid, low-temperature bonding between silicon and steel using the rapid thermal annealing process. Three different thin-film adhesion layer systems including silver, gold, and nickel were utilized as the intermediate bonding material to assist the eutectic Pb/Sn bonding between silicon and steel. The bonding temperature was set at 220/spl deg/C for 20 s, with a 20-s ramp-up time. Five experiments were conducted to determine the strength of the bond, including static tensile and compressive four-point bend tests, axial extension tests, tensile bending fatigue tests, and corrosion resistance tests. The test results have shown that the gold adhesion layer is the most robust, demonstrating minimal creep during fatigue tests, no delamination during the tensile or compressive four-point bend tests, and acceptable strength during the axial extension tests. Additionally, all adhesion layers have withstood four months of submersion in various high-temperature solutions and lubricants without failure. Simulations of the axial stresses and strains that developed during the four-point bend and axial extension tests were performed and showed that the presence of the silicon die provides a local reinforcement of the bond as observed in the experimental tests. 相似文献
27.
A novel ultra-wideband (UWB) bandpass filter (BPF) is presented using the hybrid microstrip and coplanar waveguide (CPW) structure. A CPW nonuniform resonator or multiple-mode resonator (MMR) is constructed to produce its first three resonant modes occurring around the lower end, center, and higher end of the UWB band. Then, a microstrip/CPW surface-to-surface coupled line is formed and modeled to allocate the enhanced coupling peak around the center of this UWB band, i.e., 6.85GHz. As such, a five-pole UWB BPF is built up and realized with the passband covering the entire UWB band (3.1-10.6GHz). A predicted frequency response is finally verified by the experiment. In addition, the designed UWB filter, with a single resonator, only occupies one full-wavelength in length or 16.9mm. 相似文献
28.
Xue‐Bing Zhao Lei Wang De‐Hua Liu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(6):950-956
Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X‐ray diffraction (XRD) analysis indicated that the crystallinity of PAA‐treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers. Copyright © 2008 Society of Chemical Industry 相似文献
29.
30.
Young Sil Jeon Jing Lei Ji-Heung Kim 《Journal of Industrial and Engineering Chemistry》2008,14(6):726-731
This study examined the removal of some basic dyes, such as Methylene Blue, Malachite Green and Methyl Orange, using alginate or alginate/polyaspartate composite gel beads. The adsorption of dyes from aqueous solutions at 25 °C was examined using a batch sorption technique. The effects of CaCl2 and the dye concentration on the adsorption were examined. Type-S adsorption isotherms were obtained, which is characteristic of a weak solute–solid interaction. The ionic interaction between the dye molecule and gel matrix appears to be responsible for the efficient adsorption of cationic dyes in this system. These results suggest that an alginate/polyaspartate gel can be used as an effective sorbent for water pollutants such as dyes, and the immobilization of these organic contaminants in the hydrogels from wastewater can solve one of the most important environmental problems in the related industry. 相似文献